JPS5964336A - Method and apparatus for controlling injection process of injection molding machine - Google Patents

Abstract

PURPOSE:To obtain a molded product free from deformation, a shrink mark cavity, air bubbles and the irregularity of dimensional preciseness caused by residual stress, by respectively performing the program controls of a filling process and a pressure holding process according to a method suitable for a molding process. CONSTITUTION:A filling process is completed by passing a screw through A-E sections at injection speeds V1-V5 and pressure to be held is changed to holding pressure P3 from holding pressure R2 in a pressure holding process. When the surface part of a cavity is held under a sufficient flowable state, the holding pressure is made low to prevent the generation of a burr and, when a skin layer is properly cooled, high pressure P3 is applied to prepare a molded product free from a shrink mark. In this case, residual stress can be reduced by lowering pressure corresponding to a cooling progress state.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an injection process control method and apparatus for an injection molding machine.

Conventionally, programmed injection methods have been known in which the injection speed of the injection plunger or screw is changed in the injection process of injection molding machines, but in this type of method, the molten resin reaches the end of the cavity from the start of injection. The filling pressure or filling speed used for so-called dynamic injection was changed until filling was completed. However, in general, the injection process involves a filling process from the start of injection until the molten resin reaches the end of the cavity, and then a hydraulic pressure applied to the injection ram to compensate for the volume change that occurs as the molten resin progresses as it cools and solidifies. It consists of both a pressure holding process in which the plunger or screw is kept movable and pressure is applied to the molten resin, and control of the pressure holding process also has an important influence on quality.

However, there has been no technology to apply program control to the pressure holding process. As conventional maintenance/positive pressure control means, there are the following systems, each of which has the following drawbacks.

That is, ■A method that controls the entire injection process with one pressure setting.

This method does not make a clear distinction between filling and holding pressure, but according to this method, (1) if the pressure is set high so as not to reduce the filling speed, the pressure after filling the mold will increase. It got too high and I was disappointed.

Residual stresses arise. .

(2) After filling the mold, if the pressure is set low to remove paris and residual stress, slow filling (low speed filling), short shots, and sink marks will occur.

(6) Above +1), (21) Setting that satisfies both conditions is difficult (4) The pressure during filling and the pressure after filling the mold are the same pressure, which will not cause the above disadvantages. When controlling at the same pressure, no distinction can be made between filling and holding pressure.

The problem is that the pressure level after filling the mold cannot be adjusted arbitrarily.

L Next, according to the method in which the filling pressure and holding pressure are set separately but the holding pressure is not programmed, (1) If a high holding pressure is set to prevent sink marks and air bubbles from occurring, burrs may occur. ), the residual stress is high and deformation occurs.

(2) If the holding pressure is set low to prevent deformation due to cracks and residual stress, sink holes and bubbles are likely to occur, and variations in dimensional accuracy are likely to occur.

(3) Settings that satisfy both conditions (1) and (21) above are difficult.

(4) The drawbacks of (11 and (2+) described above cannot be solved because of the control that can arbitrarily adjust the pressure level of only one stage during the pressure holding process).

Therefore, in the present invention, in order to program the most suitable injection process for each molded product of various shapes and materials, the filling process and the holding pressure process are each programmed and controlled using a method suitable for the molding process. It is an object of the present invention to provide an injection process control method and apparatus that can change the holding pressure in an arbitrary pattern, especially in the holding pressure process.

Next, embodiments of the present invention will be described in detail below with reference to the accompanying drawings. In addition, in this example, injection speed control is performed in 5 stages in the filling process, and 2 stages in the holding pressure process.
It is configured to perform holding pressure control in stages.

Example 1 This will be explained based on FIGS. 1 to 4. 1 indicates a screw. A two-piece injection ram is shown, and hydraulic pressure acts on the chamber on the right side of the figure to advance the screw 1 and perform injection. 6
, 4 indicate molds, and 5 indicates a rack that is attached to the screw 1 and moves in synchronization with the reciprocating motion of the screw 1. Reference numeral 6 indicates a pinion, which meshes with the rack 5 and rotates many times as the screw 1 moves, converting the linear motion of the screw 1 into rotational motion. Reference numeral 7 indicates a potentiometer, which is connected to the pinion A through a gear train or the like or directly, and converts the moving distance of the screw 1 into a continuous electrical signal by the rotation of the pinion 6, and constitutes a position detector. do. S indicates the injection stroke, and the same stroke is divided into 5 l-i A, B, C, D, BO5 gJ. During injection, the screw 1 moves in the same section A, B, C, D, B at different injection speeds. configured to pass.

To explain the hydraulic circuit, Ml indicates an injection switching solenoid pulp, which controls the forward and backward movement of the screw 1. M3 to M7 indicate solenoid pulp,
This person is responsible for controlling the hydraulic pressure to the injection ram 2, and is provided in each hydraulic circuit 20-24. Also, each hydraulic side 1! ! 520 to 24 are 70-control valves [flow rate adjustment valves] (hereinafter referred to as flow controllers) F1 to F5
The amount of oil passing through each of the hydraulic circuits 20 to 24 is determined in advance, and when the screw 1 passes through the section A during injection, the amount of oil passing through each hydraulic circuit 20 to 24 is determined in advance.
Similarly, the injection speed is advanced at a predetermined injection speed by the hydraulic circuit 21 in the 9th section 1IJ1, the hydraulic circuit 22 in the C section, the hydraulic circuit 26 in the D section, and the hydraulic circuit 24 in the E section. C1 to C5 indicate check pulps, which are provided to prevent backflow in each hydraulic circuit 20 to 24. 6M8.R1 indicates a relief pulp (pressure control valve), which sets the injection pressure. M9 indicates a solenoid valve, and the solenoid pulp M8 fully controls the relief pulp R2 and IIL s via the solenoid pulp M9. Relief pulps R2 and R5 are used to set the pressure to be switched during the pressure holding process.

The electric circuit shown in FIG. 2 will be explained in conjunction with FIG. 4. 7
indicates a potentiometer that converts the position of the screw 1 into voltage as described above, and as shown in FIG.
The voltage up to is changed. 8 is the voltage V1 indicated by the potentiometer 7 when the screw 1 advances in section A
9 is the voltage indicated by potentiometer 7 when screw 1 advances to A/B section 1.
Set the potency yometer to 2, and 10 to the screen IJ.
A potentiometer that sets the voltage indicated by potentiometer 7 when U1 advances to A10B+C section 1, and 11.
indicate the potentiometers that set the voltage indicated by the potentiometer 7 when the screw 1 advances through the A-1-B10-)-D section, and these potentiometers 8 to 11 are used to set the injection speed switching position. Configure the vessel.

Reference numerals 12 to 15 indicate signal transmitters (comparators), which compare the set voltages 1 to 1 of each potentiometer 8 to 11 with the voltage of potentiometer 7, which changes every moment as the screw 1 moves, and find that both mold pressures match. When this occurs, a built-in relay (not shown) is activated to issue a signal. 12
a to 15a and 12b to 15b indicate relay contacts inside the signal transmitters 12 to 15. M3~M9
indicates the solenoids of solenoid valves M3 to M9. 1
几 designates a relay, which operates when the solenoid M7 is energized and facing upward, and has an A contact 10R. T
R indicates a timer, which switches the holding pressure in the holding pressure process, and has an A contact TR. 30-68
shows an electric circuit for controlling solenoids M3' to M9.

Next, the operation will be explained. When the solenoid valve M1 is switched to the forward position by the injection start signal, the solenoid M3 in the electric circuit 30 is energized, as shown in FIG. 2, and the solenoid valve M3 is switched to the forward position.
Hydraulic pressure is applied to the injection ram 2 by the hydraulic circuit 20, and the screw 1 reaches the injection speed V predetermined by the flow controller F1.
, (see Figure 3) to pass through section A. When the screw 1 has passed through the section, the voltage of the potentiometer 7 becomes equal to the predetermined voltage V1 of the potentiometer 8 (see FIG. 4), and the A contact 1 is closed by the signal from the signal transmitter 12.
2a closes and B contact 12b opens, solenoid M6
Solenoid M4 in E'-air circuit 31 where ' is not energized.
is excited. Therefore, solenoid valve M6 is disconnected,
The solenoid valve M4 in the hydraulic circuit 21 enters the forward position, a predetermined amount of oil is applied to the injection ram 2 by the 70-controller F2, and the screw 1 moves in section B at a predetermined injection speed v2 (see Fig. 3). (see) to move forward. Similarly, the screw 1 connects sections C, D, and E to respective signal transmitters 13, 14, and 15, and electrical circuits 32, 33, and 3.
4 and switches one after another. Therefore, the hydraulic circuit is also 22,2
6.24, and the screw 1 injects each section C, D, EO injection speed v5)v41v5 determined by the amount of oil passing through the flow controllers F3F4 and Fs provided in each hydraulic circuit (see Figure 6). It will pass through. At the same time as the contact point 15b switches to 15a, the screw 1 enters the E section at the injection speed v5, completing the filling process and entering the pressure holding process. When contact 15b switches to 15a, solenoid M7 (electric circuit 64) and electric circuit 6
Relay 10 in 5 operates, its contact 10R (electric circuit 67) closes, solenoid M8 is energized, solenoid valve M8 is turned on, and the injection pressure is reduced to relief valve R.
The predetermined holding pressure P2 (see FIG. 6) is set to 2. On the other hand, simultaneously with the excitation of solenoid M8, timer TR starts timing, and a predetermined time t is reached.
times out, its contact 'r R' closes and solenoid M9 is energized, thus solenoid valve M
9 is input, and the holding pressure becomes P5 (see Fig. 3), which was set in advance in IJ-7 valve and R5. When the gate portions of the molds 6 and 4 are solidified by the holding pressure P3 and a certain period of time for sealing has elapsed, a timer (not shown) indicating the completion of the injection process is activated.
moves and injection is completed.

Example 2 This will be explained with reference to FIGS. 5 and 6. 101 indicates a screw. 102 indicates an injection ram, and injection 11t! Hydraulic pressure acts on l to move the screw 101 forward and perform injection. 103 and 104 indicate molds, 1°C
5 indicates a rack attached to the screw 101 and synchronized with the reciprocating movement of the screw. Reference numeral 106 indicates a pinion, which meshes with the rack 105 and rotates the screw 10.
The screw 101 rotates when the screw 101 moves, converting the linear motion of the screw 101 into a rotational motion. Reference numeral 107 indicates a potentiometer 1-, which is connected to the pinion 106 via a gear train or the like, either directly or directly, and converts the amount of movement of the screw 101 into a continuous electrical signal in response to the rotation of the pinion 106. 1. Configure a position detector.

S indicates the injection stroke, and the same stroke S is A, B
Divided into 5 stages: ', C', D', E'.
During injection, the screw 101 moves in the same sections A', B', d,
D'.

They are configured to pass through E' at different injection speeds.

To explain the hydraulic circuit, ml indicates an injection switching solenoid valve, which controls the injection ram 102. ! 1 is an electromagnetic flow control valve (hereinafter referred to as an electromagnetic flow control valve), which adjusts the throttle valve in proportion to the strength of voltage or current (hereinafter referred to as voltage).
:] Closed and when the voltage is high, the restriction is small and the flow rate is therefore large. Furthermore, when the voltage is low, the throttling is large and the flow rate is therefore small. P F2 indicates a pump. r indicates all electromagnetic IJ IJ-7 valves (pressure control valves), and the set pressure changes depending on the strength of the voltage.

To explain the electric circuit, numeral 107 indicates a potentiometer that converts and indicates the position of the screw 101 into a voltage as described above, and while the screw 1Q1 moves between the stroke and the loaf S, the voltage starts from 0 in proportion to the distance. Continuously change the voltage up to a certain voltage. Reference numeral 108 indicates a potentiometer that sets the voltage indicated by the potentiometer 107 when the screw 101 advances through the forward section. Similarly, 1
09-111 indicate potentiometers, screw 10
These potentiometers 108 to 111 constitute an injection speed switching position setter. 112 to 115 indicate signal transmitters (comparators), and each potentiometer 108 to 1
11 is compared with the voltage of a potentiometer 107 that changes every moment as the screw 101 moves, and when the pressures of both chambers match, a built-in relay (not shown) is activated to issue a signal. . 112a-115a
are the A contacts of the relay in the signal transmitter, 112b to 11
5b indicates a B contact. Amplifiers 116 and 117 amplify voltages set in potentiometers 118 to 125, which will be described later, to operate the electromagnetic flow controller f and the electromagnetic relief pulp r. The voltages of the potentiometers 118 to 122 are set in advance, and when the switching of the circuits (50 to 54) is performed, each voltage is determined to be less than the voltage. is applied to the electromagnetic flow controller f1, and a predetermined amount of oil is applied to the injection ram 102, thereby forming a group of electrical quantity setting devices that control the injection speed.Similarly, the potentiometers 126 to 125 are Set a predetermined voltage and apply it to the electromagnetic
This constitutes a group of electrical quantity setting devices that control the injection pressure during the filling process and the holding pressure during the holding process. 100T indicates a timer, which switches the holding pressure during the holding pressure process, and has a contact point 100T1. R and S indicate relays, which have A contacts R81 and R85 and B contacts R and 82.

Next, the operation will be explained. When the solenoid pulp m1 is switched to the forward position p by the injection start signal, the stain magnetic flow controller f1 transfers the predetermined flow rate to the injection ram 1 by the voltage set in the potentiometer 118 in the electric circuit 50.
02 and screw 1 at a predetermined injection speed.
01 moves forward in section A during stroke S. During this time, the injection pressure is maintained at the set pressure of the electromagnetic relief valve (r) determined by the potentiometer 125 in the electric circuit 55. When the screw 101 has passed through the relief section, the voltage matches the voltage of the potentiometer 108, and a signal is emitted. A signal is emitted by the device 112 and the contact 112b is switched to the contact 112a, so the electric circuit 50 is switched to the electric circuit 51,
This time, the screw 101 moves forward in section B at a predetermined injection speed according to the flow rate determined by the set voltage of the potentiometer 119. Similarly, the section C' is operated by the potentiometer 120, and the section D is operated by the potentiometer 1.
21, and the E' section is connected to the potentiometer 122.

The flow rate of the screw 10 is controlled, and the screw 10 is
1 moves forward. After the screw 101 has passed through section D, the contact 115b is set to 115 by the signal from the signal transmitter 115.
When aK switches, relay 1tS is energized at the same time, A contact 1 (, 81 is closed, and timer 1 for switching the holding pressure is activated.
00'I"几 starts the timing. At the same time, A
Since the contact R85 (electric circuit 56) is also closed, the injection pressure is kept at the set pressure of the electromagnetic relief pulp r determined by the potentiometer 124, and the pressure control is started during the pressure holding process after the filling process is completed.゛Papa said timer f00'T1
% times out, contact 100TR is connected to electrical circuit 5.
6, the stain detection circuit 57 is switched, and therefore the electromagnetic IJ
The set pressure of -7 valve r is determined by the potentiometer 126, and the holding pressure changes.

Example 6 ^ (18) In Examples 1 and 2, racks 5 and 105 are provided for the screws 1 and 101 to move in synchronization with the reciprocating motion of the screws 1 and 101, and the racks 5 and 105 are engaged with the screws 1 and 101. Pinions 6 and 106 are provided for converting the linear motion of 101 into rotational motion, and a potentiometer 7 is further connected to the pinions 6 and 106.
A control method has been shown in which the light filling process is switched from the light filling process to the pressure holding process by connecting the molds 1JL1 and 107 and detecting the positions of the molds 1JL1 and 101.
, 4 and 106. A pressure sensor is placed inside the cavity through a part of 104, or an oil pressure sensor is placed inside the injection cylinder. Using the control system shown in FIG. 2, FIG. 6, and FIG. 7, it is possible to realize program control that combines the filling process and the pressure holding process similar to those in the first and second embodiments described above. can.

As is clear from the embodiments described above, in the present invention, the following excellent effects can be obtained by performing multi-stage program control based on the holding pressure time.

(1) In the pressure holding process, when the cavity surface is in a sufficiently fluid state, the pressure can be controlled to be low for the corresponding time to prevent the occurrence of paris.

(2) After the skin layer has cooled down to an appropriate level and there is no need to worry about flaking, high pressure can be applied to form a high-density, sink-free molded product.

(6) To prevent excessive pressure from being applied, the pressure can be lowered after a predetermined period of time depending on the progress of cooling to reduce residual stress.

Therefore, in the pressure holding process control of the present invention, you can freely
Since the pressure can be programmed in multiple stages over time, molded products can be molded without deformation due to residual stress, sinkholes, bubbles, or variations in dimensional sheath jM.

Moreover, this program control of holding pressure is particularly required to be able to be programmed arbitrarily, as the optimal holding pressure program pattern varies depending on the thickness distribution of the molded product, the gate method, and the properties of the resin used. Ru. In this respect, according to the time-based pressure holding multi-stage program control of the present invention, since the movement amount of the screw is small in the pressure holding process that only replenishes the shrinkage of the molded product, a timer is used to control the period outside the period of 9 hours. Accuracy can be increased, and the effectiveness of program control can be further improved.

Although a preferred embodiment of the present invention has been described above, in the injection process control device of the present invention, the program control of the filling process is not limited to the speed control method, but it is also possible to adopt a pressure control method, so that it is possible to When controlling the switch from the process to the pressure holding process, it is possible to adopt not only the method of detecting the position of the injection plunger or screw, but also the method of detecting the pressure in the cavity or the oil pressure in the injection/cylinder.
Of course, changes in the design of the fences may be made within the scope of the spirit of the thin ice invention.

[Brief explanation of drawings]

1 is a vertical sectional view of an injection device of an injection molding machine showing a first embodiment of the present invention and a schematic diagram of a hydraulic control system; FIG. 2 is an electrical control circuit diagram of the control system shown in FIG. Figure 6 is a graph showing the relationship between injection speed and screw stroke position during the injection process by the device of the present invention, and a graph showing the relationship between injection pressure and injection process time. Figure 4 is a graph showing the relationship between the screw stroke S and the potentiometer. FIG. 5 is a schematic diagram of a hydraulic control system showing a second embodiment of the present invention, and FIG. 6 is an electrical control circuit diagram of the control system shown in FIG. 1.101...Screw 2,102...Injection ram 3.4,103. ．． 104..., mold 5,105 river rack 6.106... pinion 7.107... potentiometer (position detector) 8
~11,108~111... Potentiometer (
Injection speed switching position setter) 12-15, 112-11m...Signal transmitter (comparator) 12a-15a, 112a-115a...Relay contact 20-24...Hydraulic circuit 30-64...・Electric circuit M1, ml...Solenoid valve M for injection switching
3-M9... Solenoid valve output ~ M9... Solenoid F1-F5... F4-Control valve (flow 1a
14 valve control) fl...electromagnetic flow control pulp (
Flow rate adjustment valve) fL1~几5... Relief pulp (pressure control valve) r... Solenoid IJ jJ-7 valve (pressure control valve) 10R,) υS... Re -1o
m, assistant 1... Relay A contact T, 100T... Timer Tig, 1ooTi-ff... Timer A contact C1-
c5... Check pulp PFl, PF2. -3. Pumps 118 to 125... Potentiometer (electrical sound setting device group) Patent applicant Toshiba Machine Co., Ltd. Applicant agent Patent attorney Hama 1) Haruo FIG,
2

Claims (2)

[Claims] (1) A filling process of filling the cavity with molten resin,
In the method for controlling the injection process of an injection molding machine, which includes a pressure holding process to compensate for the shrinkage of the molten resin filled in the cavity as it cools and solidifies, the position of the injection plunger or screw during the filling process is determined by a position detector. detects the position, compares the detection signal detected by the position detector with a preset position setting value by a comparator, and outputs a signal instructing the completion of the filling process and the start of the pressure holding process; The control circuit switches from the filling process to the pressure holding process based on the output signal, and there are multiple pressure control valves in the hydraulic circuit or pressure control valves that adjust the pressure based on the magnitude of the amount of electricity, and multiple settings for the amount of electricity used to control these valves. A group of devices is provided so that the holding pressure during the holding pressure process can be arbitrarily set in multiple stages. Pressure control that divides the pressure holding process from the output signal of the comparator to the completion of the injection process into a plurality of sections using a plurality of timers, and adjusts the pressure depending on the hydraulic circuit of the plurality of pressure control valves or the magnitude of the amount of electricity. During the pressure holding process, the pressure of the hydraulic drive source is changed to control the holding pressure according to a preset program by sequentially switching a plurality of electric quantity setting device groups for controlling the valves. Features: Injection process control method for injection molding machines. (2) An injection molding machine that performs filling process control for filling a molten resin into a cavity, and pressure holding process control for pressing to compensate for shrinkage accompanying cooling and solidification of the molten resin filled in the cavity, During the pressure holding process, the injection process control device is configured to control the holding pressure according to a preset program by changing the pressure of the hydraulic drive source. A position detector for detection, a comparator for outputting a signal instructing the start of the pressure holding process based on the detection signal of the position detector, and a control circuit for switching from the filling process to the pressure holding process based on the output signal of the comparator. and a plurality of pressure control valves installed in the hydraulic circuit so that the holding pressure during the pressure holding process can be arbitrarily set, or a pressure control valve that adjusts the pressure depending on the amount of electricity, and a plurality of pressure control valves for controlling this valve. a group of electric quantity setting devices, and a hydraulic circuit or electric circuit that divides the pressure holding process from the output signal of the comparator to the completion of the injection process into a plurality of parts, and sequentially controls the plurality of divisions in the pressure holding process with the pressure control valve. 1. An injection process control device for an injection molding machine, comprising: a plurality of timers that output signals for switching to an electric quantity set in a quantity setter group.