JP6528616B2 - Injection filling control method for injection molding machine - Google Patents

Description

  The present invention relates to an injection filling control method of an injection molding machine.

  A typical injection filling process of an injection molding machine consists of an injection process and a pressure holding process. The injection step is a step of advancing the screw in the injection device of the injection molding machine to fill the molten resin (molten resin) measured in the injection device into the mold cavity. In the injection process, the filling speed (filling volume per hour) of the molten resin to be filled is considered more important than the pressure applied to the molten resin to be filled, and the set injection speed, ie, the advancing speed of the screw is set to the set value. Control for maintaining (injection speed control) is performed.

  Then, in the injection process, at a timing when the inside of the mold cavity is substantially filled with the molten resin, the process proceeds to a pressure holding process for compensating the shrinkage volume due to the cooling and solidification of the molten resin in the mold cavity. In the pressure holding process, since the inside of the mold cavity is substantially filled with the molten resin, the predetermined pressure (pressure holding) applied to the molten resin in the mold cavity is more important than the filling speed (injection speed). Control is performed to maintain the set injection pressure (holding pressure), that is, the forward force of the screw at a set value (injection pressure control).

  Moreover, in the control method of the injection filling process which consists of such an injection process and a pressure holding process, the advancing position of the screw in which the control object item of a screw is switched from injection speed to injection pressure (holding pressure) / Pressure switching point (hereinafter referred to as VP switching point) or the like.

  In the present invention, since there is a difference from a general injection filling process, a holding pressure is applied after the screw of the injection device is advanced to fill the molten resin in the mold cavity (injection process). The process up to the step of filling the molten resin in the cooled and solidified shrinkage portion (pressure-holding step) is referred to as an injection filling step. Moreover, in the injection filling process, the control method performed in the injection apparatus including the behavior of a screw shall be referred to as an injection filling control method.

  In the injection filling control method of such an injection molding machine, in order to obtain a non-defective product, it is important to set the injection speed in the injection process, the VP switching point, the injection pressure (holding pressure) in the pressure holding process, and the like. Even if the setting of the VP switching point is appropriate, if the setting value of the injection speed is too high, a surge pressure as described later occurs at a timing when the inside of the mold cavity is substantially filled with the molten resin, and this surge pressure When the pressure exceeds the setting clamping force, a local mold opening force is generated, the mold mating surface opens, and the molten resin is ejected (blow blow), or the backflow of the molten resin from the mold to the injection device It will occur. Therefore, control is performed to prevent the generation of surge pressure by reducing the setting injection speed to a low set value in advance immediately before the screw reaches the VP switching point, as described in [Conventional art] in Patent Document 1 May be done.

  On the other hand, even if the setting value of the injection speed is appropriate, a problem occurs if the setting of the VP switching point is not appropriate. For example, even if the inside of the mold cavity is substantially filled with the molten resin, if the filling of the molten resin is continued while the predetermined injection speed is maintained, surge pressure is generated due to excessive resin filling, and burrs are blown And backflow of molten resin occur. In addition, if the mold cavity is shifted to the pressure holding process before the inside of the mold cavity is filled with the molten resin, the inside of the mold becomes short of resin filling (short shot), and even if the holding pressure set is appropriate, melting in the mold An appropriate mold clamping force or filling pressure can not be applied to the resin, and a molding defect such as a shape defect or a sink mark occurs.

  Further, in a general injection / filling control method, in the vicinity of the VP switching point where the inside of the mold cavity is substantially filled with the molten resin, the resistance received from the molten resin by the advancing screw is maintained, that is, the set injection speed. The injection pressure (actual injection pressure) in the state reaches approximately the maximum value. Then, at the VP switching point, the injection speed control up to that point (setting advance speed maintenance of screw) is transferred to injection pressure control (holding pressure / setting advance force maintenance of screw). In this injection pressure control, the set pressure set as the holding pressure to be applied to the molten resin is a pressure lower than the actual injection pressure which has substantially reached the apex at the VP switching point.

  At this time, the check ring (resin flow path switching valve) on the screw tip in the injection device is maintained in the closed state by the resistance (resin pressure) received from the molten resin in the storage section (forward of screw) in the injection device as well. Therefore, a continuous space including the mold cavity from the reservoir in the injection device, which ends at the closed check ring, is a closed space filled with the molten resin. Here, a preferred method for reducing the resin pressure of the molten resin that fills this closed space from the actual injection pressure which has substantially reached the apex at the VP switching point to the set pressure in injection pressure control after the VP switching point is this closing. It is to expand the volume of space. Therefore, in a general injection filling control method, not only the advancing of the screw is stopped when the screw reaches the VP switching point, but also the advancing force of the screw is released, and then the resistance force the screw receives from the molten resin Control to allow the backward movement by the resistance received by the screw until pressure is reduced to the set pressure (holding pressure), or after stopping the screw forward when the screw reaches the VP switching point, the actual injection pressure is Control is performed to retract the screw until the pressure is reduced to the set pressure.

  Then, after the actual injection pressure is reduced to the set pressure (holding pressure) by the backward movement of the screw, forward movement of the screw is resumed so that the set pressure is maintained (injection pressure control), and the molten resin is set. In the state where pressure (pressure holding pressure) is applied, a pressure holding process is performed to compensate for the contraction volume due to cooling and solidification of the molten resin in the mold cavity.

  During advancement of the screw under injection speed control, the molten resin is continuously filled into the mold cavity, and the flow thereof does not greatly change. However, during the operation switching from forward to backward movement of the screw after reaching the VP switching point as described above, the resin flow of the molten resin into the mold cavity fluctuates greatly, causing deceleration, stagnation, or reverse flow. It will On the other hand, the cooling of the molten resin proceeds also during that time, so the viscosity of the molten resin decreases, or the cooling and solidification of the molten resin from the contact portion with the mold cavity proceeds, and the flow direction of the flowable molten resin The flowability of the molten resin fluctuates greatly, for example, as the cross-sectional area decreases. After shifting to the pressure holding step due to the fluctuation of the resin flow of the molten resin into the mold cavity as described above, the advancing of the screw is resumed under the control of the injection pressure, and the molten resin in the mold cavity is Even if it is intended to apply the set pressure (holding pressure), it becomes difficult to supplement the molten resin appropriately according to the shrinkage volume of the molten resin in the mold cavity due to cooling and solidification, and molding defects such as flow marks and transfer defects It becomes a factor of

  Therefore, in the injection and filling process, the method of accurately detecting the VP switching point, and the injection speed and injection pressure are properly set and controlled to prevent burr blowing and backflow of resin, and the inside of the mold cavity is melted. Various injection filling control methods have been devised to shift to the pressure holding step in a state substantially filled with resin (full shot).

  In Patent Document 1, a plurality of factors of injection speed, injection pressure and mold opening amount are controlled sequentially as set values of upper factors according to the required characteristics of the resin immediately before the resin is full in the cavity (filling completion), There is disclosed a molding method of an injection molding machine in which the injection pressure and the injection pressure are associated with the injection pressure and the injection amount as lower factors, respectively, and the constraint conditions are given and controlled. Specifically, a molding method (claim 2) in which control is started immediately after the completion of filling, after reaching a set value determined by any one or a plurality of values of the mold opening amount, screw position and injection pressure. When controlling the injection pressure as the upper factor, set the mold opening amount that releases gas but does not generate burrs, and after the mold opening amount becomes the setting value, inject using the mold opening amount as the target value Switching to the method of controlling the pressure, but limiting the injection pressure as a subfactor to a value where local burrs do not occur (Claim 3), Furthermore, as a superfactor, control the injection speed before controlling the injection pressure And automatically switch to injection pressure control after reaching the above injection pressure setting value, but disclose a molding method (claim 4) in which the injection speed is a lower factor and the resin does not back It is done.

  In Patent Document 2, a detection unit that detects information on the mold clamping state of the mold clamping unit, and information from the detection unit during the injection process are monitored, and a numerical value obtained from the information is set in advance as a threshold. Control means for controlling the injection pressure of the injection device when the pressure exceeds the threshold value (claim 1), and the control means controls the value when the value exceeds the threshold value. A molding machine (claim 2) is disclosed which controls the injection pressure so as to decrease below. As information on the state of this mold clamping, a mold clamping force (claim 8), an inter-mold distance between the fixed mold and the movable mold (movable mold) (claim 9) and the like are mentioned.

  The patent document 1 (paragraph 0017 et al.) And the patent document 2 (paragraphs 0052 and 0053 et al.) Both describe solving burr blowing and molding defects caused by short shots.

Japanese Patent Application Laid-Open No. 05-309713 JP 2012-250360 A

  However, both the molding method of the injection molding machine of Patent Document 1 and the injection control method of Patent Document 2 relate to the opening (mold open amount) of the parting surface (mold split surface) of the mold and the mold clamping force. Starting from reaching the threshold value set for information (the amount of extension of tie bar, etc.), the control of the injection pressure (decompression) prevents the blow of burrs, and the following problems arise.

  First, in the molding method of the injection molding machine of Patent Document 1, before the screw reaches the VP switching point, that is, when the mold opening amount reaches the threshold during the injection process under injection speed control, It switches to injection pressure control in the state of the short shot in which the inside of a mold cavity is not filled with molten resin. Under injection pressure control, the advancing speed of the screw is decelerated from the set injection speed that has been controlled (maintained) until that time to the actual injection speed in the state where the set injection pressure is maintained, or as described above In some cases, the screw may be retracted, so the filling amount of the molten resin in the mold cavity is insufficient, and the cooling and solidification of the molten resin in the mold cavity proceeds in a short shot state, and molding such as filling failure Defects occur.

  Burr blowing also occurs in the injection process before the screw reaches the VP switching point. In a general injection filling control method, since cooling and solidification of the molten resin filled in the mold cavity proceeds, in the injection step, the injection speed control gives priority to the filling of the molten resin in the mold cavity. To be done. On the other hand, since the mold cavity including the overflow portion and the resin flow path to the mold cavity have various cross-sectional areas orthogonal to the flow direction of the molten resin, the resin flow speed and filling resistance of the molten resin are not constant. . The resin flow rate is high and the filling resistance is large with respect to a large cross-sectional area. In addition, since the cooling and solidification speed is also fast due to heat removal from the mold cavity surface, the filling completion of such a small cross-sectional area is faster than the large part, and the resin pressure by resin flow force is also rapidly raised. The timing is also different at each of these sites within the mold cavity.

  Therefore, even if the setting of injection speed and the amount of measurement resin are appropriate, depending on the product shape, there may be a region where the resin pressure rises during the injection process due to the restriction of the mold cavity shape (resin pressure deviation) . The same resin pressure deviation is also caused by an improper resin flow path design such as a runner of the mold cavity, an improper adjustment of clamping force (uneven clamping state) for each tie bar of an injection molding machine, or the like. When the local high resin pressure generated by such a resin pressure deviation exceeds the mold clamping force substantially applied in the vicinity, the resin which is large relative to other parts of the part where the resin pressure rises Due to the synergetic effect of kinetic energy with the flow velocity, even during the injection process, a local mold opening force acts on the vicinity of the part of the mold to open the mold and cause burr blow. Such a blow of the burr not only causes molding failure of the part but also promotes the short shot state in the mold cavity by the amount of resin lost by the blow of the burr, and the shape defect and sink mark of the other part. It becomes a factor of molding defects such as. That is, in the molding method of the injection molding machine of Patent Document 1, there is a problem that even if suppression of burring becomes possible, the occurrence of short shots can not be solved.

  Next, in the injection control method of Patent Document 2, injection pressure control is performed from the start to the end of the injection filling process. If there is no resin pressure deviation that causes burr blowing as described above while the screw reaches the VP switching point from the start of the injection filling process, information on the clamping force (the amount of elongation of the tie bar) Etc. never reach the threshold. In addition, the molten resin is filled into the mold cavity while receiving a filling resistance which slightly fluctuates as the filling rate of the molten resin in the mold cavity increases. However, in the injection pressure control performed during this time, while the advancing force of the screw is controlled so that the injection pressure is maintained at the set pressure against the slightly fluctuating filling resistance of the molten resin, the advancing speed of the screw (actual injection Speed is uncontrolled and fluctuates. In the injection process of the general injection filling control method, in view of the fact that injection speed control is performed with priority given to filling of the molten resin into the mold cavity, the inside of the mold cavity is filled with the molten resin as soon as possible. In addition to being unable to set a suitable injection speed (the advancing speed of the screw), there is a problem that the speed fluctuates in a non-controlled manner, and it is difficult to form a non-defective product.

  In addition, when information on the mold clamping force (e.g., the amount of extension of the tie bar) reaches a threshold value, injection pressure control is performed to reduce the injection pressure in order to prevent burr blowing. Therefore, as in the molding method of the injection molding machine of Patent Document 1, there is a problem that the occurrence of short shots can not be solved.

  The next problem is the response of the control switching at the time of transition from the injection speed control to the injection pressure control, and the response of the injection pressure control itself. The former is a problem of the molding method of the injection molding machine of Patent Document 1 which has a transition from injection speed control to injection pressure control, and the latter both have patents for preventing burr blowing by injection pressure control to reduce injection pressure. It is a problem of Document 1 and Patent Document 2.

  In the molding method of the injection molding machine of Patent Document 1, the advancing speed (actual injection speed) of the screw at the VP switching point is substantially the same speed as the set injection speed immediately before reaching the same point. As described above, when advancing the screw at the VP switching point is stopped, and the actual injection pressure is reduced to the set pressure (holding pressure) by the screw retraction operation to shift to the injection pressure control (pressure holding process), VP It is difficult to immediately stop the advancing of the screw at the switching point, and the advancing of the screw is continued even after the VP switching point until the advancing of the screw is stopped and the reverse operation is started. Therefore, the inertia weight and kinetic energy by forward movement (forward speed) of the screw during this time, and kinetic energy by the mass and flow velocity of the molten resin flowed to the mold cavity side by forward movement of the screw The pressure is converted to the resin pressure of the filled molten resin, and the resin pressure is transmitted to the molten resin in the mold cavity, and the resin pressure in the mold cavity rapidly rises. This is the aforementioned surge pressure.

  In the molding method of the injection molding machine of Patent Document 1, a threshold is provided for the mold opening amount as a factor related to burr blowing, and when the factor reaches or exceeds the same threshold, the resin pressure of the molten resin in the mold cavity It is stated that it is effective to prevent the blow of the burr by reducing the pressure quickly. However, when the injection speed control is switched to the injection pressure control when the factor reaches the same threshold, it takes a predetermined time (response time 1) to switch the screw operation as described above. The surge pressure can not be sufficiently reduced because the resin pressure of the molten resin continues to increase at least until the advancing of the screw is stopped within the response time 1.

  Further, in the molding method of Patent Document 1 and the injection control method of Patent Document 2, the driving force of a drive source (a hydraulic cylinder, a hydraulic motor, an electric motor, etc.) for advancing the screw, which is a direct source of injection pressure. It is assumed that hydraulic oil pressure, rotational torque and the like are controlled, and the resin pressure of the molten resin on the screw front side is reduced to a set pressure (holding pressure) after the response time 1 has elapsed. However, since the molten resin filling the inside of the mold cavity is a visco-elastic body, the resisting force during screw advancement received from the molten resin on the front side of the screw, that is, the reduced pressure of the actual injection pressure is within the mold cavity. It takes more time to propagate to the site of increased resin pressure (response time 2). During this response time 2 as well, resin flow with kinetic energy to the vicinity of the site of increase in resin pressure in the mold cavity is continued, and the increase in resin pressure of the molten resin at the same site is also continued. Can not be reduced enough.

  As described above, in the molding method of the injection molding machine of Patent Document 1 and the injection control method of Patent Document 2, after the increase in resin pressure of the molten resin in the mold cavity is detected by reaching the threshold of each factor In order to control and reduce pressure to a set injection pressure (set holding pressure) capable of preventing burr blowing, response time 1 + 2 in Patent Document 1 and response time 2 in Patent Document 2 are required. These response times do not become long, if at all, in the case where the setting injection speed which is inappropriately high or the viscoelastic coefficient of the molten resin as a viscoelastic body is high. Then, even after the pressure control (pressure reduction) required for preventing burr blowing is performed by such response time 1 and response time 2, the resin at the site where the resin pressure in the mold cavity increases Resin flow with increased pressure and kinetic energy is continued. As a result, a part where the resin pressure (surge pressure) increased in this response time exceeds the set clamping force is generated, and there is a problem that it is not possible to prevent burr blowing that occurs locally or in many ranges of the mold division surface. is there.

  The present invention has been made in view of the problems as described above. Specifically, after the screw of the injection device is advanced to fill the molten resin in the mold cavity, a holding pressure is applied. It is an object of the present invention to provide an injection filling control method of an injection molding machine capable of preventing short shots and burrs blowing in an injection filling step of compensating and filling the molten resin for the cooling solidification shrinkage in a fixed state.

In the injection filling step, the above object is achieved by advancing the screw of the injection device to fill the molten resin in the mold cavity and then filling the molten resin for the cooling and solidification shrinkage in a state where the holding pressure is applied. The injection speed control is performed based on the injection speed set in advance, and the point at which the expansion amount of at least one tie bar reaches the upper limit value A set in advance is the injection speed correction point, and at the injection speed correction point , wherein the extension of the tie bars correction control to decelerate the injection speed to exceed a Kunar so the upper limit value a is performed, is achieved by the injection filling method of controlling an injection molding machine.

  That is, in order to grasp the opening of the mold which is a direct factor of the burr blowing, the extension amount of the tie bar during the injection and filling process is used as a monitoring item, and the upper limit value A of the extension amount of this tie bar is obtained beforehand Keep it. The upper limit value A of the amount of extension of the tie bar means that the mold in a state in which a regular clamping force is applied is caused by the resin pressure in the mold cavity and the resin pressure deviation, the mold mating surface is entirely or locally Amount of tie bar equivalent to the amount of mold opening where burr blow does not occur even if the valve is opened, a regular mold clamping force is applied to the mold, and the state of being stretched by an amount corresponding to the same mold clamping force The tie bar is the amount stretched further. Therefore, it is preferable to set for each mold (product), and it is further preferable to set for each tie bar in order to cope with the local burr blowing due to the resin pressure deviation as described above.

Then, to perform the injection speed control based on the injection speed obtained by preset as an injection velocity correction point that the amount of stretching to reach the upper limit value A of the tie bar, the tie bar stretch amount exceeds the upper limit value A is such Kunar so Reduce the setting injection speed, not the setting injection pressure. As described above, since the injection speed is reduced during injection speed control to prevent burr blowing, the amount of extension of the tie bar reaches the upper limit value A before the screw reaches the VP switching point, and the injection speed is reduced. Even when correction control is performed, the decelerated injection speed is controlled to be maintained until the next "injection speed correction point" occurs, so screw advancement continues and the mold The filling of the molten resin into the cavity can be continued. Therefore, the short shot can be prevented from occurring with respect to Patent Document 1 and Patent Document 2 in which the injection pressure is reduced to prevent burr blowing.

  In addition, it is possible to prevent burr blowing also in the step corresponding to the VP switching point and the pressure holding step thereafter. Because, in the injection filling control method according to the present invention, the injection control based on the injection speed set in advance is performed, and the correction control for reducing the injection speed described above is the completion of the injection filling process (cooling step Until the start of the That is, it is not necessary to set the VP switching point. Even in the case of setting, there is no possibility that the accuracy will affect the effect of preventing burring.

  As described above, since there is no switching of the control system from the injection pressure control to the injection speed control, first, there is no need to retract the screw after reaching the VP switching point, which occurs in a general injection filling control method. Molding defects such as flow marks and transfer defects can be prevented. Next, the response time 1 does not occur in the case of shifting from injection speed control to injection pressure control as in Patent Document 1.

  Next, since the kinetic energy due to the advancing speed of the screw, which causes the surge pressure, can be directly reduced by the reduction of the injection speed, the surge pressure can be reduced in a shorter time. This decrease in kinetic energy is kinetic energy due to the forward speed of the screw that causes surge pressure, and resin flow velocity that is higher than other locations at the site where resin pressure rises, which causes burr blowing along with surge pressure. And kinetic energy can both be reduced directly. Therefore, it is possible to reduce the surge pressure in a shorter time and to reduce the response time 2 with respect to the injection pressure control which indirectly reduces the surge pressure by the retraction of the screw and the pressure reduction of the forward force of the screw. Contributes to further suppression of the peak value of the surge pressure.

  As described above, the correction control for reducing the injection speed can suppress the peak value of the surge pressure and can reduce the surge pressure in a shorter time. In addition, even with such correction control for reducing the injection speed, the injection pressure (the advancing force / holding pressure of the screw) is controlled in a general injection filling control method, and the holding pressure after reaching the VP switching point In the step corresponding to the step, it is possible to continuously apply an appropriate pressure (holding pressure) to the molten resin in the mold cavity while preventing burr blowing.

  That is, when the screw reaches the VP switching point, the resin pressure applied to the molten resin by the advancement of the screw causes the mold opening force to be generated in the mold in proportion to the projected area of the mold cavity. The amount of extension of the tie bar is further increased from the state where the clamping force is applied.

Then, the screw reaches the VP switching point, the extension of the tie bar reaches the upper limit value A, set injection speed to exceed a Kunar so the upper limit value A (already injection speed correction point occurs and extension of the tie bar If it is, the injection speed decelerated at the injection speed correction point just before that is decelerated, so the molten resin in the mold cavity has the screw at the injection speed under the speed control (the advancing speed of the screw) A holding pressure according to kinetic energy is applied. In contrast to the pressure holding step in a general injection filling control method, in the injection filling control method according to the present invention, the resulting holding pressure applied under this injection speed control prevents the occurrence of burr blowing. And maintain the flow of the molten resin in response to the cooling and solidification shrinkage of the molten resin in the mold cavity, and prevent short shots (insufficient filling), and become a suitable holding pressure applied to the molten resin in the mold cavity The molten resin is complemented into the mold cavity as the molten resin shrinks and solidifies.

  Further, in the injection filling control method of an injection molding machine according to the present invention, when the injection speed correction point occurs a plurality of times during the injection filling process, the correction control is performed for each of the injection speed correction points. preferable.

  As described above, even before the inside of the mold cavity is substantially filled with the molten resin, a resin pressure deviation may occur in the mold cavity and an injection speed correction point may occur. In addition, after the inside of the mold cavity is filled with the molten resin, the resin pressure applied to the molten resin is likely to increase due to the kinetic energy of the screw advancing, and the amount of extension of the tie bar increases with the increase in the mold opening force. And an injection speed correction point tends to occur. As described above, even when the injection speed correction point occurs a plurality of times during the injection filling process, burrs in these injection filling processes are repeated by repeatedly decelerating the set injection speed as described above each time the injection speed correction point occurs. The screw can be advanced while preventing blowing. Then, in the state where the resultant holding pressure is also continuously applied, the filling of the molten resin for the cooling and solidification shrinkage is continued, and short shots (insufficient filling) can be prevented, so injection filling closer to a full shot state The process can be performed.

  Further, in the injection filling control method of an injection molding machine according to the present invention, the point at which the actual injection speed under the correction control reaches the cooling step transfer injection speed C set in advance is taken as the injection speed correction end point. It is preferable to shift from the injection filling process to the cooling process at the injection speed correction end point. On the other hand, under the correction control, after the actual injection speed is decelerated to substantially the same value with respect to the newly set injection speed, the actual injection speed is preset to the new setting injection speed. When the time can not be maintained, or when the actual injection speed is separated from the new set injection speed by a predetermined value or more set in advance, the injection filling process may be shifted to the cooling process.

  Here, even if the molten resin in the mold cavity receives the suitable filling of the molten resin in accordance with the cooling solidification shrinkage and reaches the ideal filling state, the correction performed at the injection speed correction point immediately before Control to maintain the injection speed (advancing speed of the screw) set by the control is continued, and the driving source for advancing the screw is operating. Moreover, in order to shape | mold continuously, an injection apparatus is heated by the heating means arrange | positioned at injection apparatus outer periphery, and the molten resin remaining in the storage part ahead of a screw is maintained a molten state as it is. Therefore, if the correction control is continued as it is, unnecessary pressure acts on the resin of the gate portion of the mold cavity and the molten resin of the storage portion of the injection device. The time during which this unnecessary pressure is acting and the energy consumed by the pressure source not only contribute to the molding of good products and the operation of the injection molding machine, but also the molding cycle time and molding quality of moldings, and the mold It is a factor that adversely affects the maintenance of the device.

  Therefore, under correction control to reduce the injection speed at the injection speed correction point, not the injection speed as the set value to be decelerated but the actual injection speed (the actual advancing speed of the screw) as a result of the correction control is monitored The advancing of the screw is stopped with the point in time when the actual injection speed reaches the cooling step transition injection speed C set in advance as the injection speed correction end point. The cooling process transfer injection speed C is such that the advancing speed of the screw in a state in which the screw does not physically advance, ie, 0 (zero), when the cooling solidification rate of the molten resin in the mold cavity approaches 100%. Based on the elasticity of the resin whose cooling solidification rate has progressed and the elasticity of the molten resin of the reservoir immediately before the screw that does not solidify cooling, the advancing speed (approximately 0: zero) of the screw that has become extremely low speed It is preferable from the point of the cooling solidification rate of the molten resin in the mold cavity.

  On the other hand, regardless of the cooling solidification rate of the molten resin in the mold cavity, the gate portion which is an inlet of the molten resin to the mold cavity is cooled and solidified (gate seal state), for example, the screw is continued to advance However, it may be set as the actual advancing speed of the screw in a state where the molten resin can not be refilled into the mold cavity. The advancing speed of the screw in this state can be determined in advance by performing solidification analysis or preforming of the molten resin in the mold cavity. As described above, in consideration of the quality of the resin molded product and the molding cycle time, a suitable actual injection speed (the actual advance speed of the screw) may be set as the cooling process transfer injection speed C.

  In addition, since the speed control to maintain the injection speed (the advancing speed of the screw) set by the correction control performed at the injection speed correction point immediately before is continued, the increase in the forward resistance of the screw as described above When it is not possible to control the actual injection speed of the screw to the set injection speed, if the drive source for advancing the screw is an electric motor such as a servomotor, the rotational torque is increased to control the injection speed, and in the case of a hydraulic cylinder , The pressure in the hydraulic line on the side of advancing the screw increases. When such a situation occurs, an overload condition of the electric motor may occur to trip or a safety valve of the hydraulic line may be actuated to forcibly stop the molding.

  Therefore, after the actual injection speed is reduced to substantially the same value with respect to the newly set injection speed under the correction control, the predetermined time set in advance to the new set injection speed is set as the actual injection speed. If it can not be maintained, or if the actual injection speed is separated from the new set injection speed by a predetermined value or more set in advance, the injection filling process may be shifted to the cooling process. This control is performed separately from or separately from the control of shifting to the cooling step with reaching the cooling step transition injection speed C of the screw actual injection speed described above, or the same control. It may be performed in combination with

  In the injection filling control method of an injection molding machine according to the present invention, injection pressure control is not performed in the injection filling process, and injection speed control is performed from beginning to end. Therefore, in this case, by defining the timing for stopping the advancing of the screw and shifting to the cooling process in relation to the actual advancing speed of the screw, the same transition timing is indirectly defined from other monitoring items. In contrast, the transition time lag can be minimized. As a result, it is possible to reduce the time during which unnecessary pressure is acting on the resin of the gate portion of the mold cavity and the molten resin of the storage portion of the injection device, and the energy consumed by the pressure source. Adverse effects can also be minimized on the molding cycle time and molding quality of the molded product due to the application of unnecessary pressure, and also the maintenance of the mold and equipment.

  Furthermore, the injection filling control method of the injection molding machine according to the present invention is suitable when the mold clamping unit of the injection molding machine is a toggle type mold clamping mechanism.

The injection filling control method of an injection molding machine according to the present invention includes at least one tie bar elongation amount in an injection filling step including an injection step in which injection speed control is performed and a pressure holding step in which injection pressure control is performed. , and a point to reach the upper limit value a set in advance and the injection velocity correction point in the injection speed correction point, since the correction control tie bar stretch amount slowing the injection speed to exceed a Kunar so the upper limit value a is performed , Short shot and burr blow can be prevented.

It is a schematic sectional drawing which shows the state which the molten resin inject | poured from the injection device is filled in a mold cavity in an injection | pouring filling process. It is a graph explaining the filling process into the mold cavity shown in FIG. 1 of the molten resin injected from the injection apparatus by the general injection filling control method. It is a graph explaining the filling process into the mold cavity shown in FIG. 1 of the molten resin injected from the injection apparatus by the injection filling control method which concerns on Example 1 of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings.

  Before describing the injection filling control method of the injection molding machine according to the first embodiment of the present invention, referring to FIG. 1, a mold cavity serving as a premise of the following description and a molten resin injected from an injection device Describes the resin flow as it is filled into the mold cavity. Further, an injection and filling process according to a general injection and filling control method for injecting and filling a molten resin into a mold cavity shown in FIG. 1 will be described with reference to FIG.

  FIG. 1 is a schematic cross-sectional view showing a state where molten resin injected from an injection device is filled into a mold cavity in an injection and filling process. Fig.1 (a) is side sectional drawing, FIG.1 (b) is XX arrow line view in Fig.1 (a). In the injection device 10 of the in-line screw type injection molding machine, a resin material such as a resin pellet supplied from the material supply portion is rotated by the screw 12 so that the inner peripheral surface of the heating barrel 11 of the injection device 10 and the screw 12 Plasticizing (melting) continuously in the resin flow path formed between the outer peripheral surface of and the plasticizing state of the amount necessary for one injection filling process in the reservoir 13 inside the tip of the heating barrel 12 The measurement process of storing the molten resin of In this measurement process, with an increase in the amount of molten resin stored in the storage portion 13, retraction of the screw 12 is allowed in a state in which a retraction resistance (back pressure) is applied to the screw 12. Then, after the measurement process is completed, the screw 12 is advanced to form the resin of the storage portion 13 between the fixed mold 21 and the movable mold 22 in a clamped state via the tip of the heating barrel 11 (injection nozzle). An injection step of injection filling the mold cavity 31 is performed.

  At this time, the check ring 12b (resin flow path switching valve) at the tip of the screw 12 in the heating barrel 11 is maintained in the closed state by the pressure received from the molten resin in the storage section 13. Therefore, the closed check ring 12b The continuous space including the mold cavity 31 from the reservoir 13 in the heating barrel 11 is a closed space filled with the molten resin. In FIG. 1 (a), the molten resin of the reservoir 13 passes through the resin flow path in the fixed mold 21 by the forward movement of the screw 12 in the injection and filling process, and the gate 21a (mold cavity 31 of resin flow path end) It is shown starting to be filled into the mold cavity 31 via the side opening).

  In reality, a mold cavity that simulates the product shape is a somewhat complicated three-dimensional shape. However, to simplify the description, it is assumed that the mold cavity 31 is composed of five partial cavities. First, the central cavity 31a (cross section A1 / the end of the gate flow direction orthogonal to the resin flow direction) extending coaxially with the gate 21a on the movable platen side (left side in FIG. 1A) (flow length L1 of molten resin from end) The same applies hereinafter, the upper cavity 31b extending upward (cross sectional area A2 / flow length L1) and the lower cavity 31c extending downward (cross sectional area A3 / flow length L1), and then the right cavity 31d extending rightward Cross sectional area A2 / flow length L2) and left side cavity 31e (cross sectional area A2 / flow length L3) extending to the left side. As shown in FIG. 1, in the relationship between the cross-sectional area and the flow length, the cross-sectional area is A1> A2> A3, and the flow length is L2> L1> L3.

  Here, the filling resistance of the molten resin to each partial cavity extends coaxially with the gate 21a, and the central cavity 31a having the largest cross-sectional area orthogonal to the resin flow direction is the smallest. The partial cavities whose filling resistance is larger than this are the three partial cavities of the upper cavity 31b, the right side cavity 31d and the left side cavity 31e whose cross-sectional area is A2 and the resin flow from the gate 21a is redirected at a right angle once. The largest filling resistance is the lower cavity 31c having the smallest cross-sectional area. When arranged, the filling resistance of the molten resin to each partial cavity is: lower cavity 31c> upper cavity 31b = right cavity 31d = left cavity 31e> central cavity 31a. On the other hand, since it is assumed that the volume of each partial cavity is the cross-sectional area x flow length, the molten resin is filled in the ideal resin flow that satisfies each cross-sectional area into each partial cavity, melting each partial cavity The time required to fill with resin is proportional to the flow length of the molten resin in each partial cavity. Therefore, the time required to fill each partial cavity with the molten resin is, in order of time, right side cavity 31d (L2)> center cavity 31a = upper cavity 31b = lower cavity 31c (all L1)> left cavity 31e (L3) ).

  Thus, the molten resin filled in the mold cavity 31 through the gate 21a receives different filling resistance when flowing into each partial cavity, and the timing at which each partial cavity is filled with the molten resin is also It is different. Also, the resin does not flow to the other partial cavities until the central cavity 31a having the lowest filling resistance is filled with the molten resin, and the molten resin begins to flow into the central cavity 31a to receive the filling resistance. If the pressure rises even a little, then the resin flow to the partial cavity where the filling resistance is low occurs, and the diversion of the resin flow changes (decreases) the amount of molten resin flowing into the central cavity 31a. Furthermore, in view of the fact that the cooling / solidifying speed distribution of the molten resin in each partial cavity is uneven due to the difference in the temperature control of the mold (the mold temperature control), the resin of the molten resin in the mold cavity 31 The flow is very complicated, and as described above, the resin pressure deviation may occur at any timing during the injection and filling process regardless of the filling rate of the molten resin in the mold cavity 31.

  FIG. 2 is a graph for explaining the filling of the molten resin injected from the injection device 10 into the mold cavity 31 shown in FIG. 1 by a general injection filling control method. The origin is the start of screw advancement, and the time t when the horizontal axis has elapsed, and the vertical axis indicates the injection speed (screw advancing speed) and the injection pressure (screw advancing force). As described above, the pressure distribution of the molten resin in the continuous closed space including the mold cavity 31 from the reservoir 13 in the heating barrel 11 is not uniform, with the closed check ring 12b as an end. Therefore, the resin pressure of the molten resin at the specific portion in the same closed space and the actual injection pressure shown in the graph of FIG. 2 are not the same. Therefore, the actual injection pressure shown in the graph of FIG. 2 is not only the resisting force that the screw 12 receives when advancing but also the advancing force applied to the screw 12 substantially equal to this advancing resistance.

  The ideal VP switching point (a state where the mold cavity is filled with the molten resin without the occurrence of surge pressure) is reached after time t1 since the screw 12 starts to advance. During time 0 (zero) to time t1, injection speed control (solid line) is performed to maintain the forward speed of the screw 12 at the set injection speed V1. The actual advancing speed (actual injection speed) of the screw 12 requires a rise time to reach the set injection speed V1 from the injection speed 0 (zero), but the display of the actual injection speed is omitted. As the screw 12 advances, the molten resin of the reservoir 13 is filled into the mold cavity 31 and the actual injection pressure (the actual forward force applied to the screw 12 = the forward resistance to which the screw 12 is subjected Power) also rises.

  However, even before the screw 12 reaches the VP switching point, a resin pressure deviation occurs in the mold cavity 31. For example, while the filling of molten resin into the central cavity 31a having the smallest filling resistance and then the upper cavity 31b, the right side cavity 31d and the left cavity 31e having the smallest filling resistance proceeds, the central cavity 31a having the smallest filling resistance or As soon as the filling of the left cavity 31e with the smallest flow length is completed in the filling partial cavity, the resin flow of the molten resin is concentrated in the partial cavity where filling is not complete, and then the filling resistance is low. , And the forward resistance to which the screw 12 is subjected temporarily rises rapidly. Then, when the resin flow to the partial cavity is stabilized, the forward resistance to which the screw 12 is subjected decreases. Such a sharp increase in the filling resistance occurs as a partial peak value of the actual injection pressure such as the point X.

  Also, the moment the filling of the partial cavities other than the lower cavity 31c having the largest filling resistance is completed, the resin flow of the molten resin is concentrated in the lower cavity 31c, so the forward resistance force received by the screw 12 rises sharply again. Reappear as a partial peak value of the actual injection pressure like. The partial peak value of the actual injection pressure such as the point X and the point Y propagates the molten resin in the closed space from the portion where the partial peak value is actually generated, and is delayed by the propagation time as the advancing resistance force of the screw 12 It is detected. Then, in order to maintain the set injection speed (the advancing speed of the screw) against the advancing resistance, the advancing force of the screw is increased to at least the same magnitude as the advancing resistance.

  Even if a partial peak value of the actual injection pressure such as the point X and the point Y is detected as the forward resistance of the screw, due to the propagation time (propagation distance) described above and the viscoelasticity of the molten resin May differ from the peak value actually generated. In such a case, when the generated peak value is particularly large, if the actually generated peak value exceeds the mold clamping force acting in the vicinity of the generated site, burrs will be generated at that site. .

  Next, when the screw 12 reaches the VP switching point at time t1, the injection speed control up to that point is switched to the injection pressure control. The actual injection pressure reaches the maximum value P 'at the VP switching point. Therefore, in injection pressure control after the VP switching point, it is necessary to reduce the maximum value P 'of the actual injection pressure to a set injection pressure P1 (set holding pressure) lower than this. As a result, since the retraction operation of the screw 12 is allowed or control is performed to positively retract, molding defects such as flow marks are generated, or the maximum value P 'of the actual injection pressure becomes surge pressure and the burr is blown again. Is as described above. In order to facilitate the description, such a retracting operation of the screw 12 at the VP switching point is not reflected in the graph of FIG.

  After the VP switching point, after the actual injection pressure P 'is reduced to the set injection pressure P1 (set holding pressure), injection pressure control is performed to maintain the set injection pressure P1. The molten resin filled in the mold cavity 31 cools and solidifies, and the volume contraction associated with this progresses, but the set holding pressure P1 applied to the molten resin in the storage portion 13 of the heating barrel 11 and the resin in the mold cavity 31 The molten resin in the storage section 13 is complementarily filled into the mold cavity 31 according to the remaining fluidity (pressure holding process). The mold cavity 31 is already substantially filled with resin, and the screw 12 can only advance the volume for compensating for the cooling solidification shrinkage at a low speed according to the cooling solidification shrinkage speed of the molten resin. Therefore, the actual injection speed (two-dot chain line) under injection pressure control after the VP switching point is gradually decelerated from a low speed and becomes approximately 0 at time t2.

  Here, since the advancing of the screw 12 to which the setting injection pressure (holding pressure) is applied is continued for at least the time t1 to the time t2 after the VP switching point, the molten resin is replenished in the mold cavity 31. The holding pressure is transmitted to the entire molten resin in progress of cooling and solidification in the mold cavity 31 through the filled and refilled molten resin. Therefore, although not shown in FIG. 2, the actual injection pressure fluctuates in the process of maintaining the set injection pressure (set holding pressure) as the forward force of the screw 12, and the resin pressure deviation or the like in the mold cavity 31 Although partial resin flow is generated and the possibility is low with respect to the state of high flowability of the molten resin before the VP switching point, burr blowing may also occur in the pressure holding step.

  In addition, although it can be considered that filling of the molten resin into the mold cavity 31 taking into account the cooling solidification shrinkage of the molten resin was completed at time t 2, in the general injection filling control method, the time t 2 is In many cases, injection pressure control for maintaining the forward force of the screw 12 is continued until time t3 to complete the pressure holding process and shift to the cooling process. Therefore, unnecessary pressure acts on the resin of the gate portion of the mold cavity 31 and the molten resin of the storage portion 13 of the heating barrel 11 by maintaining the forward force of the screw 12 continued from time t2 to time t3. The time during which this unnecessary pressure is acting and the energy consumed by the pressure source not only contribute to the molding of good products and the operation of the injection molding machine, but also the molding cycle time and molding quality of moldings, and the mold It is a factor that adversely affects the maintenance of the device.

  The mold cavity 31 (FIG. 1), which is the premise of the description, and the process of filling the mold cavity 31 with the molten resin injected from the injection apparatus by the general injection filling control method (FIG. 2) are described. . Continuously, referring to FIG. 3, the injection filling control method of the injection molding machine according to the first embodiment of the present invention will be described.

  FIG. 3 is a graph for explaining the process of filling molten resin injected from the injection device 10 into the mold cavity 31 shown in FIG. 1 by the injection filling control method according to the first embodiment of the present invention. The premise of the origin, the horizontal axis, the vertical axis and the pressure of the graph of FIG. 3 is the same as that of the graph of FIG. The difference from FIG. 2 in FIG. 3 is that changes in tie bar extension amount (practice) and upper limit value A and speed correction limit value B (both broken lines) related to the change are described. The upper limit value A is, as described above, that the mold in a state in which the regular clamping force is applied is the entire mold mating surface due to the resin pressure in the mold cavity 31 and the resin pressure deviation thereof. Or, it is the amount of extension of the tie bar in the mold open state in which burr blowing does not occur even if it opens locally.

  On the other hand, the speed correction limit value B is a limit value at which further expansion of the tie bar generates burr blow. The upper limit value A is preferably set for each mold (product), and more preferably for each tie bar in order to cope with local burring due to resin pressure deviation. Also, during the injection filling process, if even one tie bar reaches the speed correction limit value B, an alarm is issued or the injection filling process is stopped at the completion of the molding cycle, and the next cycle is not started. It is preferable to perform control such as. The amount of extension of tie bars shown in FIG. 3 is described as a representative of the change in amount of extension for all tie bars, and it is assumed that the change in amount of extension of one or two specific tie bars is also reflected.

  Also in the injection filling control method according to the first embodiment of the present invention, the injection speed control (solid line) in which the set injection speed is V1 is performed from time 0 (zero). Here, it is assumed that a resin pressure deviation occurs at the same timing as the graph of FIG. 2, and a partial peak value of the actual injection pressure such as a point X is generated at a portion of the mold cavity 31 near a certain tie bar. As a result, it is assumed that a local mold opening force is generated at the portion of the mold cavity 31 where the partial peak value is generated, and the extension amount of the tie bar exceeds the upper limit value A. As a result, the injection speed correction point H1 is recognized, and correction control to reduce the set injection speed V1 to V2 is immediately performed. Due to the deceleration control of the injection speed, the expansion amount of the tie bar starts to decrease before reaching the speed correction limit value B, and the actual injection pressure (dashed dotted line) is also reduced once. In this way, while the burr blowing at the point X is prevented and decelerated from the original setting injection speed V1, the advancement of the screw 12 at the setting injection speed V2 is continued, and melting into the mold cavity 31 Resin filling continues.

  Next, while injection speed control is being performed at the set injection speed V2, a resin pressure deviation occurs at the same timing as the graph of FIG. 2 and a point Y like in the portion of the mold cavity 31 near another tie bar It is assumed that a partial peak value of the actual injection pressure occurs and the extension amount of the tie bar exceeds the upper limit value A. As a result, the next injection speed correction point H2 is newly recognized, and correction control is immediately performed to reduce the setting injection speed V2 to V3, and burr blowing from the vicinity of the tie bar is prevented, and at the setting injection speed V3. The forward movement of the screw 12 is continued.

  As described above, in the injection filling control method according to the first embodiment of the present invention, the molding method of Patent Document 1 or the molding machine of Patent Document 2 is performed to perform correction control for reducing the injection speed under injection speed control. Unlike the injection filling control method in the above, even in the short shot state before the mold cavity 31 is filled with the molten resin, the filling of the molten resin in the mold cavity is continued at the injection speed reduced from the initial setting injection speed. It is possible to prevent short shots while preventing burr blowing.

  Then, although the speed is reduced, the forward movement of the screw 12 at the set injection speed V3 is continued, and as the filling rate of the molten resin into the mold cavity 31 increases, the actual injection pressure (resistance force when the screw 12 advances) The dashed line also rises. Then, when the advancing position of the screw 12 reaches the VP switching point after time t1 after the start of injection filling, the actual injection pressure reaches the maximum value P ′ ′. In the injection filling control method according to the first embodiment of the present invention Since the set injection speed V1 is actually decelerated to V3, the screw 12 reaches the ideal VP switching point in the graph of FIG. 3 at time t1 + α after the screw 12 starts to advance. Although it is later, in order to facilitate comparison with the graph of Fig. 2, it is assumed that the time is reached after time t1 also in Fig. 3. Further, in the injection filling control method according to the first embodiment of the present invention, the VP switching point However, in order to facilitate comparison with FIG. 2, the VP switching point is simply set to a state in which the inside of the mold cavity is filled with the molten resin without the occurrence of a surge pressure. And those described in the graph as the forward position.

  As a matter of course, also in the injection filling control method according to the first embodiment of the present invention, the actual injection pressure (the alternate long and short dash line) becomes the maximum value P ′ ′ (P ′ ′ <P ′) at the VP switching point. A surge pressure is generated in the molten resin in the cavity 31 to generate a local or overall mold opening force, and the extension amount of all tie bars, including a specific tie bar or a plurality of tie bars, has an upper limit value A. There is a high possibility of exceeding. Even in such a case, the next injection speed correction point H3 is newly recognized, and correction control to reduce the set injection speed V3 to V4 is immediately performed. On the other hand, as described above, after the VP switching point (full point), since the advancement of the screw 12 to which the actual injection pressure (actual holding pressure) is applied is continued, the molten resin is in the mold cavity 31. The maintenance pressure is transmitted to the entire molten resin in progress of cooling and solidification in the mold cavity 31 through the refilled and refilled molten resin. Therefore, resin pressure deviation or partial resin flow is generated in the mold cavity 31, and local mold opening force is easily generated. As a result, as shown in FIG. 3, the amount of extension of the tie bar tends to increase. .

  However, in the injection filling control method according to the first embodiment of the present invention, the VP switching point is not set, the injection speed control is continued, and a new injection speed correction is performed each time the tie bar extension amount exceeds the upper limit value A. The points are recognized one after another from H3 to H6, and each time the same point is recognized, the set injection speed is decelerated from V4 to V7. By repeating such correction control to reduce the injection speed, application of the actual injection pressure (dashed-dotted line) is continued although the pressure is gradually reduced, and forward movement of the screw 31 is continued also after the VP switching point. The injection filling process is continued while the mold cavity is filled with the molten resin (full shot) and an appropriate holding pressure (actual injection pressure) is applied. The actual screw advance speed (actual injection speed) from the injection speed 0 (zero) to the setting injection speed V7 requires the rise time and the deceleration time, but the setting injection speed V1 to V7 The display of these actual injection speeds corresponding to the deceleration control is omitted.

  As described above, in the injection filling control method according to the first embodiment of the present invention, the setting of the VP switching point is not essential, and there is no switching from the injection speed control to the injection pressure control. 1 is unnecessary. Thus, unlike a general injection filling control method or a molding method of the injection molding machine of Patent Document 1, not only can it be possible to suppress the surge pressure which should originally increase during the response time 1, but also the screw advancing As a result, since the backward movement of the screw does not occur at the time of control switching, molding defects such as flow marks can be suppressed.

  Also, unlike the molding method of Patent Document 1 and the injection filling control method of the molding machine of Patent Document 2 that prevent burr blowing by reducing the injection pressure after the VP switching point, the injection speed control is continued, so As described above, the superiority of the response of injection speed control to injection pressure control, namely, the advancing speed of the screw that causes the surge pressure and the kinetic energy due to the resin flow speed of the molten resin are directly reduced by the reduction of the injection speed. It is possible to shorten the response time 2 due to the problem. This makes it possible to follow the pressure reduction of the actual injection pressure (actual holding pressure) in the deceleration correction control of the injection speed (injection speed correction points H3 to H6) subsequent to the original VP switching point, so that the original The advance of the screw can be continued without requiring a large pressure reduction before and after the VP switching point. As described above, also in the supplementary filling of the molten resin corresponding to the original pressure holding step after the VP switching point, the injection into the mold cavity is performed with the appropriate actual holding pressure being applied while preventing burr blowing. The refilling of the molten resin can be continued.

  Furthermore, the injection filling control method according to the first embodiment of the present invention can continue the refilling of the molten resin into the mold cavity while preventing burr blowing only by the injection filling control on the injection device side. Therefore, as long as the mold clamping device is of a form in which the mold clamping force is applied by extending the tie bar by the mold clamping means, any injection molding machine having any mold clamping device can be applied. It is. Specifically, the present invention can be applied to an injection molding machine having a toggle type clamping device and a direct pressure type clamping device.

  Here, for the deceleration of the injection speed at the injection speed correction point, the amount of deceleration from the speed before deceleration and the deceleration rate may be set as fixed values. In addition, the amount of deceleration or the rate of deceleration from the speed before deceleration may be changed according to the expansion rate of the tie bar (the amount of expansion of the tie bar per unit time) when the expansion amount of the tie bar exceeds the upper limit value A. For example, with respect to the injection speed correction point where the tie bar is rapidly expanded and the injection speed correction point where slow expansion is performed, the amount of deceleration and the speed reduction ratio proportional to the expansion rate of the tie bar at each correction point are adopted. Also good. Deceleration of the injection speed at such an injection speed correction point is combined with the value of the upper limit value A by test molding, analysis on a desk, etc. because the suitable amount of deceleration and deceleration rate differ depending on the mold and molding conditions. It is preferable to obtain suitable deceleration amount and deceleration rate in advance.

  After the setting injection speed is reduced from V6 to V7 at the injection speed correction point H6, the actual injection pressure (dashed dotted line) is once reduced and then slightly raised as the screw 12 advances. However, at this time, it is assumed that the cooling and solidification of the inside of the mold cavity 31 or the gate 21 a proceeds and the filling of the molten resin into the mold cavity 31 can not be performed. The elasticity of the cooled and solidified resin in the mold cavity 31 and the gate 21a and the elasticity of the molten resin of the reservoir 13 of the injection device 10 allow the screw 12 to move slightly in this state, but setting injection Even under injection speed control by the speed V7, the actual screw 12 physically becomes difficult to advance, and the actual injection speed of the screw 12 (actual advance speed of the screw 12/2 dotted line) is approximately 0 (time t2) It becomes zero. In order to explain the behavior of the screw 12 after the last injection speed correction point H6, the actual injection speed of the screw 12 is indicated by a two-dot chain line only after the injection speed correction point H6.

  Thus, it can be considered that the filling of the molten resin into the mold cavity 31 in consideration of the cooling solidification shrinkage of the molten resin is completed at time t2. Therefore, in the injection filling control method according to the present invention, under the injection speed control, the actual injection speed which is the actual injection speed (the actual advancing speed of the screw) is monitored, and the cooling step in which the actual injection speed is preset. The advancing of the screw 12 may be stopped with the transition injection speed C, for example, the time when it reaches speed 0 (zero), as the injection speed correction end point. As a result, unnecessary pressure can be prevented from acting on the resin of the gate 21 a portion of the mold cavity 31 and the molten resin of the storage portion 13 of the injection device 10, and the process can be shifted to the cooling step. Molding cycle time can be shortened.

  Further, regardless of the cooling solidification ratio of the molten resin in the mold cavity 31, the gate 21a portion which is an inlet of the molten resin to the mold cavity 31 is cooled and solidified (gate seal state), for example, The actual advancing speed of the screw 12 in a state in which the molten resin can not be refilled into the mold cavity 31 even if the advancing is continued, for example, at time t2 'at which the advancing of the screw 12 is still continuing. The actual forward speed may be the cooling process transfer injection speed C.

  Furthermore, as described above, after the actual injection speed is reduced to substantially the same value with respect to the newly set injection speed under correction control, the actual injection speed is set to the new set injection speed. Even if it can not be maintained for a predetermined time set in advance, or when the actual injection speed is separated from the new set injection speed or more by a predetermined value or more set in advance, the injection filling process is shifted to the cooling process. good.

  Example 1 is an example for explaining the injection filling control method according to the present invention in an easy-to-understand manner, and it goes without saying that the present invention can be implemented in various forms without being limited to the above embodiment. For example, it is preferable that the upper limit value A of the amount of extension of the tie bar is set for each mold (product), and further, it is preferable that the upper limit value A be set for each tie bar in order to cope with local burr blowing. If the location where burr blowing is likely to occur due to resin pressure deviation can be specified in advance by a specific mold (product), specify the upper limit value A of the amount of extension of the tie bar together with the target tie bar, It may be set as a burr blowing situation.

  In addition, local mold opening due to resin pressure deviation before the inside of the mold cavity is filled with molten resin, and the entire projected area due to resin pressure after the inside of the mold cavity is filled with molten resin The amount of expansion of tie bars and the distribution (number) of tie bars to be expanded differ from the overall mold opening. Therefore, if the latter overall die opening is obtained in advance by test molding or analysis on a desk, it is possible to confirm the arrival of the VP switching point by monitoring the amount of extension of the tie bar. In the injection filling control method according to the present invention, although setting of the VP switching point is not necessary, deceleration of the injection speed at the injection speed correction point before and after the VP switching point that can be confirmed in this way The amount of deceleration or the rate of deceleration may be changed.

Furthermore, in Example 1, the upper limit value A of the amount of extension of the tie bar can be obtained even if the mold in a state in which a regular clamping force is applied has the mold mating surface open entirely or locally. as extension of the tie bar burr blowing corresponds to the amount of mold opening is not generated, also, the upper limit value a as one value, the form in which to perform correction control to decelerate the injection speed in Kunar so exceed this description did. However, this upper limit value A corresponds to a mold opening amount in which burr blowing does not occur even when the mold mating surface is opened as a whole or locally, with the mold applied with a regular mold clamping force. It is not necessary to set it to a value that is driven down to the amount of expansion of the tie bar. In addition, the upper limit value A does not have to be a single value throughout the injection filling process including the injection process and the pressure holding process.

  For example, in the case of a molded product having a complicated shape, local mold opening is likely to occur due to resin pressure deviation before the inside of the mold cavity is filled with the molten resin, while the inside of the mold cavity is filled with the molten resin The overall mold opening that propagates over the entire projected area due to the resin pressure after being applied is unlikely to occur because solidification contraction is in progress. In such a case, the upper limit value A before the VP switching point temporarily set by the method described above may be set smaller than the upper limit value A thereafter. On the contrary, in the case of a molded article having a simple shape, local mold opening due to resin pressure deviation is unlikely to occur before the inside of the mold cavity is filled with the molten resin, but the inside of the mold cavity is molten resin. Immediately after being filled, surge pressure is also generated, and overall or local mold opening is likely to occur. In such a case, the upper limit value A in the vicinity of the VP switching point is set lower than the value obtained by driving the mold opening amount at which burr blowing does not occur, and the occurrence frequency of the injection speed correction points is intentionally increased. Alternatively, the actual injection pressure and the actual injection speed may be reduced more smoothly by increasing the number of deceleration corrections of the injection speed.

10 injection device 12 screw 31 mold cavity

Claims (5)

The screw of the injection device is advanced to fill the molten resin in the mold cavity, and then it is preset in the injection filling step of complementing the molten resin for the cooling and solidification shrinkage in the state where the holding pressure is applied. The injection speed control based on the injection speed is performed, and the point at which the expansion amount of at least one tie bar reaches the preset upper limit value A is the injection speed correction point, and the injection speed correction point correction control amount stretching is slowing the injection speed to exceed a Kunar so the upper limit value a is performed,
The upper limit value A corresponds to a mold opening amount at which burr blowing does not occur even if at least a part of the mold mating surfaces of the mold in a state where a regular mold clamping force is applied is open, for each tie bar The amount of tie bar extension to be set,
The point at which the actual injection speed under the correction control reaches the cooling process shift injection speed C set in advance is the injection speed correction end point, and the injection filling process is shifted to the cooling process at the injection speed correction end point. Injection filling control method for injection molding machines.   The injection filling control method of an injection molding machine according to claim 1, wherein when the injection speed correction point occurs a plurality of times during the injection filling process, the correction control is performed for each of the injection speed correction points. The screw of the injection device is advanced to fill the molten resin in the mold cavity, and then it is preset in the injection filling step of complementing the molten resin for the cooling and solidification shrinkage in the state where the holding pressure is applied. The injection speed control based on the injection speed is performed, and the point at which the expansion amount of at least one tie bar reaches the preset upper limit value A is the injection speed correction point, and the injection speed correction point Correction control is performed to reduce the injection speed so that the expansion amount does not exceed the upper limit value A.
The upper limit value A corresponds to a mold opening amount at which burr blowing does not occur even if at least a part of the mold mating surfaces of the mold in a state where a regular mold clamping force is applied is open, for each tie bar The amount of tie bar extension to be set,
Under the correction control, after the actual injection speed is reduced to substantially the same value with respect to the newly set injection speed, the actual injection speed is maintained at the new set injection speed for a predetermined time that has been preset. If not, or, from said actual injection speed the new setting injection speed, when spaced preset allowed a predetermined value or more, the shifting from the injection filling process in the cooling step, I De injection filling method of controlling a molding machine . The injection filling control method of an injection molding machine according to claim 3, wherein, when the injection speed correction point occurs a plurality of times during the injection filling process, the correction control is performed for each of the injection speed correction points.   The injection filling control method of an injection molding machine according to any one of claims 1 to 4, wherein a mold clamping unit of the injection molding machine is a toggle type mold clamping mechanism.

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