JP4024742B2 - Calculation method of holding pressure switching position of injection molding machine and computer-readable recording medium recording a calculation program for executing the calculation method - Google Patents

Description

  The present invention relates to a method for calculating a holding pressure switching position of an injection molding machine, and a computer-readable recording medium on which a calculation program for executing the calculation method is recorded. And in particular, a calculation method for a holding pressure switching position of an injection molding machine that can calculate a set value used for initial setting of the holding pressure switching position with a small number of input items, and a calculation program for executing the calculation method. The present invention relates to a recorded computer-readable recording medium.

  The injection conditions of the injection molding machine are determined in consideration of various factors such as the type of resin, the shape of the mold, and the volume of the cavity. When setting the injection conditions, in order to avoid burrs due to overfilling of the resin in the cavity and damage to the mold, enter values that allow for safety, such as the holding pressure switching position. Thus, by adjusting a so-called short shot molded product and bringing it close to a complete molded product, the setting of injection conditions such as the holding pressure switching position has been adjusted. However, the method for setting the injection conditions such as the holding pressure switching position largely depends on the experience of a skilled worker, and the working time and the loss of the test resin are also problematic.

  As described in Patent Document 1, it is known that the above-mentioned problems can be solved, initial operation conditions of mold opening / closing, injection, and plasticization can be automatically set by simple input, and the operator's input operation becomes easy. Yes. According to Patent Document 1, initial operating conditions of an injection molding machine are set by inputting initial input items of a mold closing start position, a protruding forward position, a mold thickness, a resin name, a molded product thickness, and a molded product weight. It is described. However, Patent Document 1 discloses a calculation formula for the measurement completion position LS8, but there is a description that an experience value is set in (0019) for the holding pressure switching position LS6, and LS6 is shown in (FIG. 4). = Β is only described, and no specific calculation formula is disclosed.

  On the other hand, what is described in Patent Document 2 is known as an injection condition for setting a measured value, a minimum cushion amount, a VP switching position (holding pressure switching position), and a speed command value. However, in Patent Document 2, the calculation formula is disclosed in (0036) and (FIG. 5) for the VP switching position, and there is a description that it is multiplied by a predetermined coefficient r [for example, 5%]. The grounds are not described. Even if the VP switching position is calculated by uniformly setting r to 5% as in the calculation formula of (0036), there is a difference in the volume change rate when solidified from the molten state by the resin used. In some cases, it was not possible to calculate the correct VP switching position.

JP-A-6-114907 (Abstract, 0008, 0019, FIG. 4) JP-A-7-232356 (Claims 1, 0032, 0036, FIG. 5)

  As described above, the theoretical calculation method is not disclosed for the initial setting value of the holding pressure switching position of the injection molding machine, and the molded product is almost filled with respect to the cavity volume by calculation from the beginning of molding. Could not be molded. Accordingly, in the present invention, the holding pressure switching position can be calculated almost accurately with a small number of input items, and by setting the holding pressure switching position as an initial set value, the degree of filling with respect to the cavity volume from the beginning of the molding. It is an object of the present invention to provide a calculation method of a holding pressure switching position of an injection molding machine capable of molding the molded product, and a computer-readable recording medium recording a calculation program for executing the calculation method.

According to a first aspect of the present invention, there is provided a method for calculating a holding pressure switching position, which is a switching position from a filling process to a pressure holding process in an injection process of an injection molding machine, in which molten resin is filled into a cavity volume in the filling process. that calculates the virtual loading, calculates the amount of shrinkage of the molten resin in the virtual loading, the amount of shrinkage as a replenishing loading in the filling process, molten in the filling process by adding and a replenishment loading the virtual loading Calculate the total filling amount of resin, calculate the filling stroke in the filling process by dividing the total filling amount by either the screw pressing area or the heated cylinder cross-sectional area, and subtract the filling stroke from the metering stroke to switch the holding pressure. The position is calculated.

  The method for calculating the holding pressure switching position of the injection molding machine according to claim 2 of the present invention is the calculation method according to claim 1, wherein the virtual filling amount is calculated by multiplying the cavity volume by a predetermined cavity filling coefficient, The replenishment filling amount is obtained by multiplying the virtual filling amount by a predetermined solidification coefficient to calculate the resin solidification amount, and multiplying the resin solidification amount by the volume change rate when the resin is solidified from the molten state. It is characterized by.

  The method for calculating the holding pressure switching position of the injection molding machine according to claim 3 of the present invention is the holding pressure switching position which is the switching position from the filling process to the holding pressure process in the injection process of the injection molding machine. In this calculation method, the cushion distance from the screw advance limit position to the cushion position is calculated by multiplying the screw diameter by the predetermined cushion coefficient, and the molded product weight is divided by the specific gravity of the resin solid. Multiply the volume change rate when the resin is solidified from the molten state, or divide the weight of the molded product by the specific gravity at the time of melting of the molten resin, and add the filling process and pressure holding process, and the total injection amount of the molten resin The total injection stroke is calculated by dividing the total injection amount by either the screw pressing area or the heating cylinder cross-sectional area, and adding the filling process and pressure holding process. The metering stroke is calculated by adding the mark and the total filling amount calculated in claim 1 is divided by either the screw pressing area or the heating cylinder cross-sectional area to calculate the filling stroke in the filling process. The holding pressure switching position is calculated by subtracting the stroke.

According to a fourth aspect of the present invention, the pressure holding switching position calculation method for the injection molding machine calculates a cushion distance from the screw advance limit position to the cushion position by multiplying the screw diameter by a predetermined cushion coefficient, Calculates the virtual filling amount by which the molten resin is filled with respect to the cavity volume in the filling process, multiplies the virtual filling amount by a predetermined non-solidification coefficient, and the non-solidified amount of the molten resin until the end of the filling step in the virtual filling amount To calculate the shrinkage amount of the molten resin in the non-solidified amount of the molten resin, subtract the virtual filling amount from the cavity volume to calculate the non-filling volume, and the shrinkage amount and non-filling volume in the non-solidified amount of the molten resin Is added to calculate the filling amount in the pressure-holding process, and the pressure-holding stroke is calculated by dividing the filling amount in the pressure-holding process by either the screw pressing area or the heating cylinder cross-sectional area. Characterized by calculating the hold pressure switching position by adding the holding pressure stroke and cushion distance.

According to a fifth aspect of the present invention, there is provided the method for calculating the holding pressure switching position of the injection molding machine according to the second aspect, wherein the predetermined cavity filling factor is 0.95 to 1.00, and the predetermined solidification factor is 0. .25 to 0.35 .

  According to a sixth aspect of the present invention, there is provided a computer-readable recording medium on which an arithmetic program for executing the arithmetic method according to any one of the first to fifth aspects is recorded.

  The calculation method of the holding pressure switching position of the injection molding machine according to the present invention calculates a virtual filling amount in which the molten resin is substantially filled with respect to the cavity volume in the filling step, and calculates a shrinkage amount of the molten resin in the virtual filling amount. The shrinkage amount is used as the replenishment filling amount in the filling step, the virtual filling amount and the replenishing filling amount are added to calculate the total filling amount of the molten resin in the filling step, and the total amount of either the screw pressing area or the heating cylinder cross-sectional area is calculated. Since the holding pressure switching position is calculated using the filling amount, the holding pressure switching position can be calculated almost accurately with a small number of input items. By setting the holding pressure switching position as an initial set value, Since it is possible to mold a molded product that is almost filled with the cavity volume from the beginning of molding, anyone can easily set the holding pressure switching position and complete the setting of the holding pressure switching position. Leading to savings in time and the test resin.

  An embodiment of the present invention will be described with reference to FIGS. FIG. 1 is an explanatory view of an injection position of an injection molding machine for carrying out the present invention, and shows a state where a screw is in a metering position. FIG. 2 is an explanatory view of the injection position of the injection molding machine for carrying out the present invention and is a view showing a state in which the screw is at the holding pressure switching position. FIG. 3 is a diagram showing an input screen used in the method for calculating the holding pressure switching position according to the present invention.

The configuration of an injection molding machine 1 used in the present invention will be described with reference to FIG. The injection molding machine 1 includes an injection device 2 and molding dies 3 attached to a movable platen and a fixed platen (not shown). The injection device 2 is provided with a heating cylinder 4 whose temperature is controlled by a heater (not shown), and a screw 6 with a backflow prevention valve 5 attached to the tip is provided in the heating cylinder 4a. It is attached so that it can be rotated and moved forward and backward by a screw driving means comprising a motor. An encoder is attached to each of the servo motors. From the rotation speed of the servo motor, the screw rotation speed in the measuring process, the position of the screw 6 such as the measuring position Iq ₁ and the holding pressure switching position Iq ₂ , and the injection in the filling process. Speed etc. can be detected. The injection device 2 is provided with a load cell for detecting the injection pressure or a heating in-cylinder resin sensor. The screw driving means may use hydraulic pressure, and the pressure sensor in that case may be a hydraulic pressure sensor.

  Further, a nozzle 7 having a resin passage 7 a communicating with the inside of the heating cylinder 4 a is attached to the tip of the heating cylinder 4, and the tip 7 b of the nozzle 7 contacts the sprue bush 8 a of the fixed mold 8 of the molding die 3. It is provided so that it can touch. In the molding die 3, a cavity 10 is formed by matching the fixed die 8 and the movable die 9. The cavity 10 can communicate with the nozzle 7 of the injection device 2. Note that the concept of the cavity 10 in the description of the calculation by the calculation program according to the present invention, which will be described later, includes a part that forms a surplus part such as a runner part or a sprue part. The molding die 3 is provided with a temperature control means (not shown) so that the molten resin injected into the cavity 10 is cooled and solidified.

In the measuring step of the injection molding machine 1, the resin pellets fed from the hopper 11 are melted by rotating the screw 6 in the heating cylinder 4a, and the melted resin is subjected to a predetermined back pressure. The screw 6 is retracted and stored in the front portion of the heating cylinder 4a. When the screw 6 is moved backward to a predetermined measuring position Iq _1, rotation of the screw 6 is stopped, the metering step is completed. Further, when the nozzle 7 is retracted from the sprue bush 8a of the molding die 3, a suck back process for slightly retracting the screw position may be performed after the completion of the measuring process. In any case, in the next injection step, the screw 6 is advanced in a state where the nozzle 7 is in contact with the sprue bush 8a of the molding die 3 which is re-clamped after the molded product is taken out. An injection process for injecting molten resin into the cavity 10 of the molding die 3 is performed.

Injection process is composed of the filling process and pressure holding process, the switching position is hold pressure switching position Iq _2. First, in the filling step, the screw 6 is advanced by speed control until immediately before the cavity 10 is completely filled with the molten resin, and the cavity 10 is filled with the molten resin. At that time, as shown in FIG. 2, the molten resin that has touched the cavity forming surface of the cooled molding die 3 is solidified to form a skin layer M1, and the center layer M2 of the cavity 10 is still molten. Is in a state. When the molten resin is almost completely filled into the cavity 10, the filling process is terminated, and at the holding pressure switching position Iq ₂ , the control of the screw 6 is switched to the pressure control, and the pressure holding process is started. Then, in the pressure holding process, a predetermined pressure is applied to the resin in the cavity 10 by the screw 6 of the injection device 2 to compensate for the shrinkage of the molten resin due to cooling. The screw 6 is advanced completed cushion position Iqc, as can exert pressure to the cavity 10 within the dwelling step, a position leaving the cushion distance S1 from the screw forward limit position Iq ₀ to cushion position Iqc Is set to

Note the relationship molding hold pressure switching position Iq ₂ is injection speed and injection pressure of the filling process, the set pressure of the pressure holding process, and depending on the molded article thickness such as from the filling process to the pressure-holding step If the switching is accelerated (switching is performed when the screw 6 is located at the right side in FIG. 2), the injection speed and the injection pressure when the molten resin is injected and filled into the cavity 10 are not accompanied, and the portion far from the gate is reached. In many cases, the resin is not completely filled. Further, if the switching from the filling process to the pressure holding process is delayed (switching is performed when the screw 6 is located on the left side in FIG. 2), the molten resin in the cavity 10 becomes extremely high pressure, and the party of the molding die 3 is increased. It is easy to cause a so-called overpack in which burrs are generated from the sealing surface 3a. Therefore hold pressure switching position Iq ₂ needs to be set in position. But of the conventional pressure-holding switch position Iq ₂ set has a large place to rely on skilled worker's experience, loss of work time and the test for the resin has been a problem.

Next, a calculation program for easily calculating the initial setting positions of the measurement position Iq ₁ , the holding pressure switching position Iq ₂ , and the cushion position Iqc at the time of injection in the injection molding machine 1 for solving the above problem. A computer equipped with a computer-readable recording medium on which the arithmetic program is recorded will be described. In the present embodiment, the calculation program is created by commercially available calculation software used in a commercially available personal computer, and the calculation result for the initial setting position such as the holding pressure switching position Iq ₂ is displayed on the screen of the personal computer. The Then, the operator views the screen and inputs an initial setting position on the setting screen of the injection molding machine 1. However, the calculation program of the present invention may be a dedicated program installed in the control device of the injection molding machine 1, and the injection molding machine 1 may be controlled based on the calculation result of the dedicated program. Note that the arithmetic program may be recorded on a recording medium such as a flexible disk or an optical disk in addition to those recorded on the hard disk of the personal computer or the control device.

Then calculation method of hold pressure switching position Iq ₂ of the injection molding machine 1 by the calculation program of the present embodiment will be described. The calculation program of the present embodiment is configured to input an input value from the screen of “Measuring position / holding pressure switching position / cushion position calculation sheet” shown in FIG. In the present embodiment, the only required input items are “screw diameter (mm)”, “resin type”, “molded product weight (g) or cavity volume (cc)”. The screw diameter (mm) is used when calculating the filling stroke at the time of filling by dividing the screw pressing area from the total filling amount (volume) of the molten resin, which will be described later, and numerical values are entered. ing. When the arithmetic program is used only for a specific model, a fixed value may be registered in advance for the screw diameter (mm), and the input of the screw diameter (mm) may be omitted.

  With respect to “type of resin”, when the ▽ button on the right side is clicked, a list of resins such as PP, PC, and ABS is displayed, and a resin to be used is selected and input. In this embodiment, when the resin type is input, the heating cylinder temperature corresponding to the previously input resin type is automatically read out. Then, the specific gravity γ when the resin is melted at the heating cylinder temperature and the specific gravity γf at the time of solid are read out for the calculation of the present invention in a state where a predetermined back pressure is applied. In addition, about the kind of resin, you may subdivide further according to molecular weight, a filler, etc. The numerical value of the specific gravity and the like may be corrected manually, and the specific gravity γ at the time of melting may be a fixed value for each type of resin.

  The molded product weight (g) or cavity volume (cc) can be switched to either by inputting the right ▽ button. Therefore, if a molded product already exists or if the weight of the molded product is known from the design drawing, the “molded product weight (g)” is selected and input. If the volume of the cavity 10 is known from the design drawing of the molding die 3, etc., “cavity volume (cc)” is set and inputted. Then, as shown in FIG. 3, when “molded product weight (g)” is selected, the description column on the left side of the next stage shows “weight of one molded product (g)”, “number of molded products taken”. , “Weight of sprue and runner (g)”, “total weight (g)”. Therefore, if you enter a single-byte number in the right-hand side of the “weight of one molded product (g)”, “number of molded products”, and “weight of sprue and runner (g)”, The total weight (g) in one molding is calculated and displayed in the numerical value display column on the right side of the “weight (g)” column. In addition, when the cavity volume (cc) is selected, the description column on the left side of the next stage includes “volume of one molded article (cc)”, “number of molded articles”, and “volume of sprue and runner (cc ) ”, And the total volume (cc) in one molding can be calculated and displayed by inputting a numerical value as in the case of the weight (g). Therefore, the weight (g) or cavity volume (cc) of the molded product in the present invention is obtained by multiplying the weight or volume per molded product by the number of molded products, and adding the weight or volume of surplus parts such as sprues and runners. The total weight (g) and the total volume (cc) are used for the calculation. The total weight (g) or the total capacity (cc) may be input manually.

An arithmetic expression by the following arithmetic program will be described. First, the cushion position Iqc (= cushion distance S1): (mm) is calculated by the following equation.

The cushion position Iqc is obtained by multiplying the screw diameter d by a predetermined cushion coefficient c (0.10 to 0.20), and an optimal position where excessive resin stagnation does not occur is calculated. In the present embodiment, the predetermined cushion coefficient c is set to 0.15, where 0 is a position where the screw 6 is at the screw advance limit position Iq ₀ and there is no cushion amount. For the predetermined cushion coefficient c, the coefficient value can be changed within the above range in accordance with changes in the type of resin, temperature, injection pressure, injection speed, and the like.

Next, the measurement position Iq ₁ (= measurement stroke S2): (mm) is calculated by the following equation.

For the weighing position Iq ₁ , as described above, first, the molded product weight Wa (g) is divided by the specific gravity γ when the resin is melted, and the total injection amount of the molten resin is the sum of the filling step and the pressure holding step. determine the V _1. Then, the total injection amount V ₁ of the molten resin corresponding to the addition of the filling step and the pressure holding step is divided by the screw pressing area (π ÷ 4 × d ² ) to obtain the total injection stroke S3 (from the measurement position Iq ₁ to the cushion position). The injection stroke (mm) up to Iqc is calculated. At this time, the total injection amount V ₁ of the molten resin added to the filling step and the holding step is multiplied by 10 ^{3 because} the total injection amount of the molten resin added to the filling step and the holding step is added. The unit of V ₁ is cc, whereas the unit of the required measurement position Iq ₁ is mm. Therefore, the unit of the total injection amount V ₁ of the molten resin obtained by adding the filling step and the pressure holding step is mm ^3. It is to make it. Then, the cushion distance S1 (mm) obtained above is added to the total injection stroke S3 (mm) to obtain the measurement position Iq ₁ (= measurement stroke S2) (mm). Note that the total injection amount V ₁ of the minute of the molten resin was added filling process and pressure holding process are moldings weight Wa (g) of was divided by the specific gravity γf during resin solid sought solid upon gravity, it You may obtain | require by multiplying the volume change rate Vt at the time of resin solidifying from a molten state.

Next, the holding pressure switching position Iq ₂ : (mm) is calculated by the following equation.

In the above, the predetermined cavity filling coefficient C ₁ is a coefficient value for calculating a virtual filling amount (C ₁ × Vf) in which the molten resin is substantially filled with respect to the cavity volume Vf in the filling step, and is 0.95. A coefficient value between 1.00 and 1.00 is desirable. In this embodiment the predetermined cavity filling coefficient C ₁ is set to 0.97. The predetermined solidification coefficient C ₂ are coefficients for virtual filling amount of the molten resin (C ₁ × Vf) is computed the resin solidified quantity which has already been solidified upon being substantially filled into the cavity 10, 0. A coefficient value between 25 and 0.35 is desirable. In the present embodiment, the predetermined hardening coefficient C ₂ is set to 0.30. In the present invention, the predetermined cavity filling factor C ₁ and the predetermined solidification factor C ₂ are changed according to changes in resin type, injection pressure, injection speed, molding die shape, cooling temperature, and the like. Thus, the setting can be changed within the above numerical range. Further, the predetermined cavity filling coefficient C ₁ and the predetermined solidification coefficient C ₂ are coefficients found from a lot of test data, and the filling and solidification of the molten resin in the filling process to be actually performed are not necessarily described above. It is not necessarily within the coefficient.

In the present invention, first, the cavity volume Vf is multiplied by a predetermined cavity filling coefficient C ₁ to calculate the virtual filling amount (C ₁ × Vf) of the molten resin in the filling step. Then by subtracting the cavity volume Vf from the total injection amount V ₁ of the minute of the molten resin by adding the filling process and pressure holding process, shrinkage of the molten resin to the total injection amount (V 1 _-Vf) determined, The molten resin shrinkage amount (V ₁ −Vf) with respect to the total injection amount is multiplied by the predetermined cavity filling coefficient C ₁ and the predetermined solidification coefficient C ₂ , respectively, to obtain a virtual filling amount (C ₁ × Vf) of the molten resin. ) To calculate the shrinkage amount (C ₁ × C ₂ × Vs) of the molten resin. The amount of shrinkage of the molten resin (C ₁ × C ₂ × Vs) is a volume that needs to be filled by adding molten resin further into the cavity 10 by the volume due to the resin shrinkage in the filling step, and the melting The shrinkage amount of the resin (C ₁ × C ₂ × Vs) corresponds to the replenishment filling amount of the molten resin. Then the by adding the virtual filling amount of the molten resin (C ₁ × Vf) and replenishing filling amount of the molten resin _{(= C 1 × C 2 ×} Vs), the total filling amount of the molten resin in the filling step (C ₁ × Vf + C ₁ × C ₂ × Vs) is calculated.

In the calculation of the total molten resin filling amount (C ₁ × Vf + C ₁ × C ₂ × Vs) in this filling step, the molten resin virtual filling amount (C ₁ × Vf) and the molten resin replenishing filling amount (= C ₁ × C ₂ × Vs) is calculated separately, but in the actual filling step, the volume reduction due to the shrinkage of the molten resin by the virtual filling amount (C ₁ × Vf) of the molten resin, and the molten resin Since the replenishment of the resin for the replenishment filling amount (= C ₁ × C ₂ × Vs) is simultaneously performed in parallel, there is no distinction.

In this embodiment, the calculation is performed by setting the predetermined cavity filling factor C ₁ to 0.97. However, when the predetermined cavity filling factor C ₁ = 1, the virtual resin filling amount (C ₁ × Vf) Needless to say, the cavity volume Vf is used as it is in subsequent calculations. Further, in the present embodiment, the shrinkage amount (C ₁ × C ₂ × Vs) of the molten resin in the virtual filling amount (C ₁ × Vf) of the molten resin is calculated as described above. C ₁ × Vf) is multiplied by a predetermined solidification coefficient C ₂ to calculate the resin solidification amount, and the resin solidification amount is further multiplied by the volume change rate Vt when solidified in advance for each type of resin. Then, the replenishment filling amount (= C ₁ × C ₂ × Vs) of the molten resin may be calculated. Furthermore, a coefficient that takes into account both the volume change rate Vt (or the specific gravity γf at the time of melting and the specific gravity γf at the time of solidification) when the resin is solidified from the molten state and the resin solidification ratio in the cavity 10 is determined in advance. The shrinkage amount of the molten resin (= the replenishment filling amount of the molten resin) may be calculated by setting and multiplying the virtual filling amount (C ₁ × Vf) by the one coefficient.

The value obtained by subtracting the total filling amount of the molten resin _{(C 1 × Vf + C 1} × C 2 × Vs) in the filling process from the total injection amount V ₁ of the minute of the molten resin was added the filling process and pressure holding process are, It becomes the amount of molten resin filled in the cavity 10 after the holding pressure is switched.

When the total filling amount (C ₁ × Vf + C ₁ × C ₂ × Vs) of the molten resin in the filling step is calculated, the value is calculated as the screw pressing area (π ÷ 4 × d ² ) or the screw pressing area (π ÷ 4 ×). d ²⁾ filling stroke in the filling process by dividing by either heating cylinder cross-sectional area that approximates (filling stroke from the metering position Iq ₁ to hold pressure switching position Iq ₂₎ S4 is calculated. And if the filling stroke S4 are calculated by the, from said computed metering position Iq 1 ₍₌ metering stroke S2) at by subtracting the filling stroke S4, calculates a hold pressure switching position Iq _2.

When the initial setting values of the measurement position Iq ₁ , the holding pressure switching position Iq ₂ , and the cushion position Iqc are calculated and displayed on the screen of the personal computer by the above calculation formula of the calculation program, the operator inputs the values into the injection molding machine Input from 1 setting screen. Then, the molten resin is injected from the injection device 2 of the injection molding machine 1 into the cavity 10 in the molding die 3 to perform test molding. The initial setting holding pressure switching position Iq ₂ calculated by the calculation program is slightly underfilled in anticipation of safety. Therefore, in test molding, sink marks, weld lines, etc. remain in the molded product. There are many cases. However, a complete molded product can be easily obtained by slightly correcting the set value by looking at the molded product by test molding.

In the calculation program of this embodiment, by setting the type of resin, the specific gravity γ at the time of melting and the specific gravity γf at the time of solid corresponding to the type of resin are read out and used to calculate the holding pressure switching position Iq _2. However, it may be calculated from any one of the following values (1) to (3).
(1) Specific gravity γ at the time of melting of the resin and specific gravity γf at the time of solid, the volume change rate Vt when the resin is solidified from the molten state, and the weight of the molded product (g)
(2) Specific gravity γ when the resin is melted, specific gravity γf when the resin is solid, and cavity volume (cc)
(3) Volume change rate Vt and cavity volume (cc) when the resin is solidified from the molten state

前記の数式によれば、充填工程と保圧工程を加えた分の溶融樹脂の総射出量Ｖ_１から、充填工程における溶融樹脂の総充填量（Ｃ_１×Ｖｆ＋Ｃ_１×Ｃ_２×Ｖｓ）を減算して、保圧切換後にキャビティ１０に補充される溶融樹脂量｛Ｖ_１−（Ｃ_１×Ｖｆ＋Ｃ_１×Ｃ_２×Ｖｓ）｝を求める。そしてそれをスクリュ押圧面積（π÷４×ｄ^２）で除算して、保圧ストロークＳ５を求める。次にそれにクッション位置Ｉｑｃを加算して保圧切換位置Ｉｑ_２を求める。この演算方法は、上記の実施形態の数式と手順こそ相違するものの、スクリュ押圧面積（π÷４×ｄ^２）と前記総充填量（Ｃ_１×Ｖｆ＋Ｃ_１×Ｃ_２×Ｖｓ）を用いるという技術思想については同じである。 The calculation of the holding pressure switching position Iq ₂ : (mm) may be performed as follows.

According to the above formula, the total amount of molten resin injected in the filling step (C ₁ × Vf + C ₁ × C ₂ × Vs) is calculated from the total injection amount V ₁ of the molten resin added to the filling step and the pressure holding step. By subtracting, the amount of molten resin {V ₁ − (C ₁ × Vf + C ₁ × C ₂ × Vs)} to be replenished in the cavity 10 after switching the holding pressure is obtained. Then, it is divided by the screw pressing area (π ÷ 4 × d ² ) to obtain the pressure holding stroke S5. Then it adds the cushion position Iqc Request hold pressure switching position Iq _2. This calculation method uses a screw pressing area (π ÷ 4 × d ² ) and the total filling amount (C ₁ × Vf + C ₁ × C ₂ × Vs) although the procedure is different from the formula of the above embodiment. The idea is the same.

In addition to the calculation method for obtaining the holding pressure switching position after obtaining the total filling amount of the molten resin in the filling step as described above, the present invention switches the holding pressure after obtaining the filling amount in the direct holding step. It is also possible by a calculation method for obtaining the position. The following calculation method corresponds to claim 4 . The formula of the calculation method for obtaining the holding pressure switching position after obtaining the filling amount in the direct holding process is as follows:

A virtual filling amount (C ₁ × Vf) in which the molten resin is substantially filled with respect to the cavity volume in the filling step is calculated, and a predetermined non-solidification coefficient (1-C ₂ ) is calculated as the virtual filling amount (C ₁ × Vf). _First, a non-solidified amount of the molten resin (C ₁ × Vf × (1−C ₂ )) until the end of the filling process is calculated. The predetermined non-solidification coefficient (1-C ₂ ) is 0.65 to 0.75 because the predetermined solidification coefficient is 0.25 to 0.35. Next, the unsolidified amount of the molten resin (C ₁ × Vf × (1−C ₂ )) is multiplied by the volume change rate Vt, and the shrinkage amount (C ₁ × Vf ×) of the molten resin in the pressure-holding step after the filling step. (1-C ₂ ) × Vt) is calculated.

The virtual filling amount (C ₁ × Vf) is calculated with respect to the cavity volume Vf because there is still an unfilled volume (Vf−C ₁ × Vf). The unfilled volume (Vf−C ₁ × Vf) and the shrinkage amount (C ₁ × Vf × (1−C ₂ ) × Vt) of the molten resin in the pressure-holding step are added to fill the amount in the pressure-holding step. calculates the _{{(C 1 × Vf × (} 1-C 2) × Vt) + (Vf-C 1 × Vf)}. Then, the pressure holding stroke S5 is calculated by multiplying it by 10 ³ to obtain a unit mm ³ and dividing by either the screw pressing area (π ÷ 4 × d ² ) or the heating cylinder cross-sectional area. And calculating a hold pressure switching position Iq ₂ by adding the pressure holding stroke S5 and the cushion distance S1.

  In addition, Formula 4 and Formula 5 are only examples of modifications of the present invention, and other than that, in order to obtain the same or approximated calculation results, switching before and after the calculation formula, switching between multiplication and division Alternatively, the present invention includes those in which addition and subtraction are interchanged, specific gravity and volume change rate are interchanged, solidification rate and non-solidification rate, and input item are changed.

In this embodiment, the inline screw type injection molding machine 1 in which the metering process and the filling process are performed by one screw 6 is described. However, the metering process is performed by a screw, and the filling process has an injection device that is performed by a plunger. The present invention can also be applied to a pre-plastic injection molding machine. Furthermore, the present invention can also be applied to a case where a suck back process is performed after the weighing process. Originally, when the suck back process is performed, the sum of the measuring stroke S2 and the suck back stroke is the filling start position. However, the calculation formula of the present invention calculates the filling stroke S4 and the like based on the measuring stroke S2, calculating a hold pressure switching position Iq _2. Further, in the case of performing the suck-back process, it may be performed by an arithmetic expression using another coefficient separately from the above.

  The present invention is not enumerated one by one, but is not limited to the above-described embodiment, and it goes without saying that the present invention can be applied to those modified by a person skilled in the art based on the gist of the present invention.

It is explanatory drawing about the injection position of the injection molding machine which implements this invention, Comprising: It is a figure which shows the state which has a screw in a measurement position. It is explanatory drawing about the injection position of the injection molding machine which implements this invention, Comprising: It is a figure which shows the state which has a screw in a holding pressure switching position. It is a figure which shows the input screen used for the calculation method of the holding pressure switching position of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Injection molding machine 2 Injection apparatus 3 Molding die 3a Parting surface 4 Heating cylinder 4a Inside heating cylinder 5 Backflow prevention valve 6 Screw 7 Nozzle 7a Resin passage 7b Tip 8 Fixed mold 8a Sprue bush 9 Movable mold 10 Cavity Iq ₀ Screw advance limit position Iq ₁ Measurement position Iq ₂ Holding pressure switching position Iqc Cushion position M1 Skin layer M2 Center layer S1 Cushion distance S2 Measurement stroke S3 Total injection stroke (injection stroke from the measurement position to the cushion position)
S4 Filling stroke (filling stroke from weighing position to holding pressure switching position)
S5 Holding pressure stroke

Claims (6)

In the calculation method of the holding pressure switching position, which is the switching position from the filling process to the holding pressure process in the injection process of the injection molding machine,
Calculate the virtual filling amount that is filled with the molten resin to the cavity volume in the filling process,
Calculate the shrinkage amount of the molten resin in the virtual filling amount,
The amount of shrinkage is the replenishment filling amount in the filling step,
Calculate the total filling amount of the molten resin in the filling step by adding the virtual filling amount and the replenishment filling amount,
The filling stroke in the filling process is calculated by dividing the total filling amount by either the screw pressing area or the heating cylinder cross-sectional area, and the holding pressure switching position is calculated by subtracting the filling stroke from the measuring stroke. Of calculating the holding pressure switching position of an injection molding machine. The virtual filling amount is calculated by multiplying the cavity volume by a predetermined cavity filling factor,
The replenishment filling amount is obtained by multiplying the virtual filling amount by a predetermined solidification coefficient to calculate a resin solidification amount, and multiplying the resin solidification amount by a volume change rate when the resin is solidified from a molten state. The calculation method of the holding pressure switching position of the injection molding machine according to claim 1. In the calculation method of the holding pressure switching position, which is the switching position from the filling process to the holding pressure process in the injection process of the injection molding machine,
Multiply the screw diameter by a predetermined cushion coefficient to calculate the cushion distance from the screw advance limit position to the cushion position,
Multiply the molded product weight by the specific gravity at the time of solidification of the resin and multiply the solid volume by the volume change rate when the resin solidifies from the molten state, or divide the molded product weight by the specific gravity at the time of melting of the molten resin, Calculate the total injection amount of the molten resin for the filling process and pressure holding process,
By dividing the total injection amount by either the screw pressing area or the heating cylinder cross-sectional area, the total injection stroke is calculated by adding the filling step and the pressure holding step,
Calculate the measuring stroke by adding the cushion distance and the total injection stroke,
The filling stroke in the filling process is calculated by dividing the total filling amount calculated in claim 1 by either the screw pressing area or the heating cylinder cross-sectional area,
The calculation method of the holding pressure switching position of the injection molding machine according to claim 1, wherein the holding pressure switching position is calculated by subtracting the filling stroke from the metering stroke. In the calculation method of the holding pressure switching position, which is the switching position from the filling process to the holding pressure process in the injection process of the injection molding machine,
Multiply the screw diameter by a predetermined cushion coefficient to calculate the cushion distance from the screw advance limit position to the cushion position,
Calculate the virtual filling amount that is filled with the molten resin to the cavity volume in the filling process,
Multiplying the virtual filling amount by a predetermined non-solidification coefficient to calculate the non-solidification amount of the molten resin up to the end of the filling step in the virtual filling amount,
Calculate the amount of shrinkage of the molten resin in the non-solidified amount of the molten resin,
Subtract the virtual filling amount from the cavity volume to calculate the unfilled volume,
The amount of shrinkage in the non-solidified amount of the molten resin and the unfilled volume are added to calculate the amount of filling in the pressure holding step,
The pressure holding stroke is calculated by dividing the filling amount in the pressure holding step by either the screw pressing area or the heating cylinder cross-sectional area,
A method for calculating a holding pressure switching position of an injection molding machine, wherein the holding pressure switching position is calculated by adding the holding pressure stroke and the cushion distance. The predetermined cavity filling factor is 0.95 to 1.00;
The method for calculating a holding pressure switching position of an injection molding machine according to claim 2 , wherein the predetermined solidification coefficient is 0.25 to 0.35 . A computer-readable recording medium recording an arithmetic program for executing the arithmetic method according to any one of claims 1 to 5.

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