JPH0749213B2 - Method of distinguishing molded products from injection molding machines - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molded product non-defective method for an injection molding machine.

2. Description of the Related Art A non-defective molded product of an injection molding machine is determined based on variations in cushion amount (position of screw or plunger at the end of holding pressure), variations in injection time, measuring time, or the like.

The problem to be solved by the invention is, however, that in the method for determining the good product of the molded product based on the variation of the cushion amount, the injection time, the measurement time, etc., each of the molded products has a good product only based on a certain one point of information during molding. Make a distinction. Factors that cause variations in the precision of molded products include variations in resin temperature, variations in resin pressure, variations in injection speed, variations in measured values, etc. All of these are subtly entangled and the precision of molded products varies. Therefore, when a non-defective product is discriminated based on only one discriminating criterion, there is a possibility that even if each element varies, the discriminant criterion falls within the criterion. On the contrary, there is a possibility that the product is a non-defective product although it is out of the discrimination standard.

For example, when a non-defective product is discriminated based on the variation of the cushion amount, and the measured value varies, the cushion amount varies by an amount corresponding to it. However, variations in precision of molded products due to variations in measured values are quite small. On the other hand, if the resin pressure, resin temperature, injection speed, etc. vary, the precision of the molded product will vary greatly, but the variation in the cushion amount due to it will be small, and the cushioning amount will vary to some extent in the molding machine. The method of discriminating the non-defective product based on the variation in the quantity has low reliability.

In view of the above conventional problems, it is an object of the present invention to provide a method for determining a non-defective product of a molded product with high reliability by using the total information when the resin is filled in the mold for the non-defective product determination. .

Means for Solving the Problems In order to achieve the above object, the present invention provides (1) a predetermined resin pressure or injection output, that is, a force received by a screw or a plunger in an injection step of injecting a resin into a mold. Of the resin pressure or ejection force after a predetermined time has passed after reaching the value of, or the resin pressure or ejection force after the screw or plunger has moved by a prescribed amount after the resin pressure or ejection force reaches a prescribed value. The non-defective product of the molded product is determined based on the output variation. (2) In the injection process of injecting the resin into the mold, from the time when the resin pressure or the ejection force, that is, the force received by the screw or the plunger, reaches a certain value, and when it reaches a certain value larger than that. The non-defective product is identified by the variation in the distance the screw or plunger has moved. (3) In the injection process of injecting resin into the mold,
The non-defective product of the molded product is determined by the variation of the integral value of the waveform of the resin pressure or the ejection force, that is, the force received by the screw or the plunger. (4) In the pressure-holding step of keeping the resin pressure constant, there are variations in the difference in the position of the screw or the plunger at the start and the end of the pressure-holding, or at the start of the pressure-holding and after a predetermined time has passed. The non-defective product of the molded product is determined by the variation in the difference in the position of the plunger.
(5) In the pressure-holding step of keeping the resin pressure constant, the quality of the molded product is determined by the variation in the average value of the moving speed of the screw or the plunger for a certain time Δt from the start of the pressure-holding. To do.

Effect According to the present invention, the reproducibility within a section having a sufficient width during the injection process or the pressure holding process is used to determine the good product of the molded product. By performing the non-defective product determination, accidental misjudgment can be eliminated, and the non-defective product of the molded product can be determined with high reliability.

EXAMPLES Examples of the present invention will be described below with reference to FIGS. 1 to 7.

In FIG. 1, reference numeral 1 is a cylinder of a pre-plastic injection molding machine, and a plunger 2 which is movable back and forth is disposed inside the cylinder. A ball screw nut 5 guided by a guide 6 so as not to rotate is fixed to a rear portion of the plunger 2 by a connecting member 3, and a ball screw 4 which can be rotationally driven by a servomotor 7 is attached to the ball screw nut 5.
Are screwed together. Further, a cone-shaped plunger head 8 is provided at the front end portion of the plunger 2, and a check valve 9 is arranged at the rear portion thereof. A nozzle 11 for injecting resin into a cavity 17 formed inside a mold 16 is formed in the front portion of the resin storage space 10 in the front portion of the cylinder 1.
Reference numeral 12 is a resin supply port through which the resin plasticized by a plasticizing screw (not shown) is supplied into the cylinder 1.

Reference numeral 13 is a control device for the servo motor 7,
A position signal from an encoder 14 connected to the rotating shaft of the above and a resin pressure signal in the storage space 10 from a pressure sensor 15 attached to the front part of the cylinder 1 are input. This control device 13, the resin pressure detected by the pressure sensor 15,
The servo motor 7 is drive-controlled so that the position and the moving speed of the plunger 2 calculated from the position signal detected by the encoder 14 have predetermined values.

FIG. 2 shows an operation timing chart of the injection shaft of the first embodiment. The horizontal axis indicates time, and the vertical axis indicates step (a),
(B) Injection speed, (c) resin pressure, (d) plunger position are shown. In the injection step of injecting the resin into the mold, the controller 13 drives and controls the servo motor 7 so that the moving speed of the plunger 2 becomes a predetermined value. At this time,
The resin pressure increases due to flow resistance when passing through the nozzle 11 and the cavity 17, an increase in resin viscosity due to a temperature decrease, a resin compression and the like. The time when the resin pressure reaches a predetermined value P ₀ is defined as t _0, and the resin pressure when Δt ₁ elapses from that time is P ₁
And Further, the resin pressure when the plunger moves ΔX ₂ from the plunger position X _{0 at} t ₀ is P ₂ . When this P ₁ or P ₂ is detected by the pressure sensor 15 and compared with a preset target value P ₁₀ or P _20, and the difference is larger than a preset allowable value δP ₁ or δP _2. The controller
13 outputs a defective signal. When the resin temperature or the mold temperature fluctuates, P ₁ and P ₂ fluctuate due to fluctuations in shearing force due to shearing speed, fluctuations in pressure loss, and the like. If P ₁ and P ₂ fluctuate while the injection speed is stable, there is a high possibility that the resin flow in the mold has fluctuated, and the molded product is likely to be defective. Further, since the judgment is made by the relative pressure, the reliability of the non-defective product judgment is high.

FIG. 3 is a timing chart of the injection axis of the second embodiment, in which the horizontal axis indicates all time, the vertical axis indicates step (a),
(B) Injection speed, (c) resin pressure, (d) plunger position are shown.

And position x _vp of the plunger when the resin pressure has reached a hold pressure switching pressure P _p increases (V / P switching device), the plunger position x ₀ when the resin pressure has reached the predetermined value P ₀ Difference from V /
Set to P switching relative position Δx _vp . This V / P switching relative position Δx _vp
Is detected by the encoder 14 and the preset target value Δx
Compared with _vp0 , if the difference is larger than a preset allowable value Δx _vp , the controller 13 outputs a defect signal. If the resin temperature or mold temperature fluctuates, Δx _vp due to fluctuations in shear force and pressure loss due to shear rate.
Fluctuates. If Δx _vp fluctuates while the injection speed is stable, there is a high possibility that the resin flow in the mold has fluctuated, and the molded product is likely to be defective. Also, since the judgment is made based on the relative position, the reliability of the non-defective judgment is high.

FIG. 4 is a timing chart of the injection axis of the third embodiment, in which the abscissa indicates the time and the ordinate indicates the step (a),
(B) Injection speed, (c) resin pressure, (d) plunger position are shown.

The difference between the integral value ΣP of the resin pressure until the resin pressure reaches the above P ₀ to P _p and the target value ΣP ₀ is compared, and when the difference is larger than a preset allowable value δΣP, The controller 13 outputs a defect signal. When the resin temperature or the mold temperature fluctuates, ΣP fluctuates due to fluctuations in shearing force due to shearing speed, fluctuations in pressure loss, and the like. If ΣP fluctuates while the injection speed is stable, there is a high possibility that the resin flow in the mold has fluctuated, and the molded product is likely to be defective. Further, since the total pressure is used for the determination, the reliability of the non-defective product determination is high.

FIG. 5 is a timing chart of the injection axis of the fourth embodiment, in which the horizontal axis indicates time and the vertical axis indicates step (a),
(B) Injection speed, (c) resin pressure, (d) plunger position are shown.

When the resin pressure reaches P _p , the control device 13 terminates the speed control, and shifts to a pressure holding step in which pressure control is performed to keep the pressure constant. The encoder 14 detects the distance Δx _p that the plunger has moved in the first step of holding the resin pressure at P _p during this pressure-holding step, and compares it with the target value Δx _p0. When it is larger than the set allowable value ΔΔx _p , the controller 13 outputs a defect signal. In the injection process, when the resin temperature, the mold temperature, the injection output, the measured value, and the like change, the filling amount of the resin and the resin temperature at the start of the pressure holding process change and Δx _p changes. If Δx _p fluctuates while the resin pressure is stable, it is highly possible that the molded product is defective. Further, since the determination is made based on the relative position, the reliability of the non-defective product determination is high.

FIG. 6 is a timing chart of the injection axis of the fifth embodiment, in which the horizontal axis shows all time, the vertical axis shows (a) stroke,
(B) Injection speed, (c) resin pressure, (d) plunger position are shown.

The non-defective product may be determined by the integral value Σv or the average value of the injection speeds from the start of the pressure holding process to the passage of a minute time Δt _p . Σv or is detected by the encoder 14, and the difference between them and their respective target values Σv ₀ or is compared. If the difference is larger than a preset allowable value δΣv or δ, the control device 13 outputs a defective signal. Output. In the injection process, when the resin temperature, the mold temperature, the injection pressure, the measured value, etc. fluctuate, the filling amount of the resin and the resin temperature at the start of the pressure holding process fluctuate and Σv or fluctuates. If Σv or fluctuates while the resin pressure is stable, the molded product is likely to be defective. Further, since the judgment is made by the total speed in the section having the width, the reliability of the non-defective product judgment is high.

FIG. 7 is an actual measurement of the relationship between the resin flow amount Δx _p and the weight of the molded product in the fourth embodiment. The horizontal axis represents the weight of the molded product, and the vertical axis represents the resin flow rate. It can be seen that the weight of the molded product decreases as the resin flow rate increases.

The present invention is not limited to the above embodiment,
For example, although the above-mentioned embodiment shows an example applied to a pre-plastic injection molding machine, it goes without saying that the invention can be similarly applied to a plunger type or in-line screw injection molding machine.

EFFECTS OF THE INVENTION As is apparent from the above description, according to the molded product non-defective method of the present invention, the reproducibility of the molded product can be improved within a section having a sufficient width during the injection process or the pressure holding process. Since it is used for the non-defective product discrimination, by performing the non-defective product discrimination by the reproducibility of only one point, there is no accidental misjudgment, and the non-defective product discrimination can be performed with high reliability.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an injection molding machine, FIGS. 2 to 6 are timing charts of steps, injection speed, resin pressure, and plunger position in the injection / pressure-holding process of each embodiment of the present invention. The figure shows the relationship between the resin flow rate and the weight of the molded product. 1 ... Cylinder, 2 ... Plunger, 3 ... Connecting member, 4 ... Ball screw, 5 ... Ball screw nut, 6 ...
… Guide, 7 …… Servo motor, 8 …… Plunger head, 9 …… Check valve, 10 …… Reservoir space, 11 …… Nozzle,
12 ... Resin supply port, 13 ... Control device, 14 ... Encoder, 15 ... Pressure sensor, 16 ... Mold, 17 ... Cavity.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takeshi Okumura 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Masayuki Ida 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co. 56) References JP-A-2-182366 (JP, A) JP-A-62-151259 (JP, A) JP-A-55-25388 (JP, A) JP-A-63-4925 (JP, A)

Claims (5)

[Claims] 1. An injection molding machine for injecting a preplasticized resin into a mold with a screw or a plunger, injecting the resin into the mold, and in the injection step with a constant injection speed, resin pressure or injection The output, that is, the force received by the screw or the plunger, reaches the predetermined value, and the resin pressure or the ejection output fluctuates after the elapse of a predetermined time, or the screw or the plan is reached after the resin pressure or the ejection output reaches the predetermined value. A method for determining a non-defective product of an injection molding machine, which comprises determining a non-defective product of a molded product based on a variation in resin pressure or injection output after the jar has moved by a predetermined amount. 2. An injection molding machine for injecting a pre-plasticized resin into a mold with a screw or a plunger, injecting the resin into the mold, in the injection step with a constant injection speed, resin pressure or injection It is possible to determine whether a molded product is a good product by the variation in the distance that the screw or plunger moves after the output, that is, the force received by the screw or plunger, reaches a predetermined value that is larger than that. A method for distinguishing the non-defective product of the injection molding machine. 3. An injection molding machine for injecting a pre-plasticized resin into a mold with a screw or a plunger, injecting the resin into the mold, in an injection step with a constant injection speed, resin pressure or injection A non-defective product discrimination method for an injection molding machine, characterized in that a non-defective product is discriminated based on a variation in an integrated value of a waveform of an output, that is, a force received by a screw or a plunger. 4. An injection molding machine for injecting a preplasticized resin into a mold with a screw or a plunger, in a pressure-holding step of holding the resin pressure at an arbitrary constant value, at the start of pressure-holding and at the end of pressure-holding. Injection molding characterized in that the product is judged to be non-defective according to the variation in the difference in the position of the screw or the plunger at the time or the variation in the difference in the position of the screw or the plunger at the start of holding pressure and after the lapse of a predetermined time. How to discriminate molded products from machines. 5. An injection molding machine for injecting a preplasticized resin into a mold with a screw or a plunger, in a pressure-holding step for holding the resin pressure at an arbitrary constant value, for a fixed time from the start of the pressure-holding. A method for discriminating a non-defective product of an injection molding machine, which comprises discriminating a non-defective product of a molded product based on a variation in an average value of moving speeds of a screw or a plunger between Δt.