JPS5964337A - Method and apparatus for controlling injection process of injection molding machine - Google Patents

Abstract

PURPOSE:To make it possible to set the program of a filling process with high accuracy, by enabling the arbitrary setting of an injection speed by a position detector using a potentiometer, an injection speed change-over position setting device and a flow control valve. CONSTITUTION:The moving position of a screw 1 is detected by a position detector 7 such as a potentiometer and a plurality of arbitrary positions of an injection stroke are set by injection speed change-over position setting devices 8- 11 such as potentiometers. Injection speeds corresponding to a plurality of injection speed change-over positions are set by flow control valves F1-F5. The detection value signal of the position detector 7 with the advance of the screw 1 and values set to the setting devices 8-11 are compared and the flow amount of a hydraulic drive source is changed by successively changing over the flow control valves F1-F5 when both values are coincided to each other to control the advance speed of the screw 1.

Description

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

Conventionally, a programmed injection method has been known in which the injection speed of an injection plunger or screw is varied in the injection process of an injection molding machine, but this type of control system has the following drawbacks.

In general, the injection process consists of 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 resin cools and solidifies. keep it moving forward.

It consists of both a pressure holding process that applies pressure to the molten resin.

However, in the filling process, if the molten resin is filled at low speed, the molten resin will cool down to the top of the stack, reducing fluidity and causing short shots, weld marks, and sink marks to occur, as well as increasing viscosity. As a result, the pressure transmission becomes difficult, so a vortex injection pressure is required, and the increase in internal stress causes cracks, cracks, etc. Also, if filling is performed only at high speed, at the start of filling, Jetting phenomenon is likely to occur at the gate, and after the resin flow reaches the cavity, turbulence is likely to occur in the flow of the melted resin at parts where the wall thickness suddenly changes or where the flow bends, resulting in excessive friction heat and total melting. The adiabatic compression of the air inside the mold can cause burns, and furthermore, it becomes difficult to absorb the dynamic energy when filling is completed, making burrs more likely to occur.Therefore, in this type of filling process, Programmatic control of injection speed or pressure is required in a manner appropriate to the molding process.

From this point of view, conventional program control methods in the injection process include: ■Program control of flow rate or pressure using a cam, and ■Multi-stage program control using section divisions using limit switches.

■Multi-stage program control using a combination of multiple pumps is known. However, since the 0-term control is programmed using a cam in an extensible manner, flexibility is poor and free programming is inhibited, resulting in poor operability. Also,
The control described in item (2) above directly moves the limit switch itself or the cam that operates it, so it is difficult to make fine adjustments and has poor operability and setting reproducibility.Moreover, the repeatability of each shot cannot be achieved using continuous controls such as potentiometers. It has disadvantages compared to electrical position detection methods. Furthermore, with the above-mentioned 0-term control, the flow rate obtained is limited to several stages depending on the combination of pumps, and fine adjustment is not possible. has the disadvantage of poor response to changes in flow rate.

Furthermore, a method is known in which the speed program control during the filling process is controlled by pressure, but this method generally uses pressure to control the speed in a filling process with large load fluctuations.
falJ control, and there is a problem with its control accuracy. That is, for any rapid growth τ,
It is necessary to set the pressure to a little higher than the load resistance, but
In injection molding, the p-load resistance increases over time as molten resin is filled into the mold, resulting in a pattern in which the speed gradually decreases in accordance with the load resistance. Furthermore, the load resistance varies depending on the temperature of the melted resin in the bath, the temperature of the mold, etc., and therefore the repeatability of each shot operation is poor.

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. Therefore, it is an object of the present invention to provide an injection process control method and apparatus that can finely adjust the injection speed and change the injection speed in an arbitrary pattern with high repeatability, especially in the filling process.

Next, embodiments of the present invention will be described in detail below with reference to the accompanying drawings. In this embodiment, j-stage injection speed control is performed in the filling process, and one-stage holding pressure control is performed in the pressure-holding process.

Embodiment/Explanation will be given based on FIGS. 1 to 3. / indicates a screw. d indicates an injection ram, and hydraulic pressure acts on the chamber on the right side of the figure to advance the screw/'(i-) and perform injection. 3. ≠ indicates a mold; This figure shows a rack that moves in synchronization with the reciprocating motion of the same screw.
It meshes with the screw/ and rotates due to the movement of the screw/.
This converts linear motion into rotational motion. 7 indicates a potentiometer, which is connected via a binion tK gear train, etc.
Or, it is directly connected and converts the moving distance of the system into a continuous electrical signal by rotating the pinion t.
Complete configuration of position detector. S indicates the injection stroke, and the same stroke S is divided into j stages of A, B, C, D, and E.
are configured to pass through each at different injection speeds.

To explain the hydraulic circuit, M/ indicates an injection switching solenoid valve, which controls the forward and backward movement of the screw/. M3 to M7 indicate solenoid valves,
This person is responsible for controlling the hydraulic pressure to the injection ram 2, and each hydraulic circuit 20-. It is located in 2 Hiro. In addition, for each oil pressure cycle %'-20~, a flow control valve (flow control valve) (hereinafter referred to as flow control) F1~F
The amount of oil passing through each hydraulic circuit 20-2≠ is determined in advance by the same flow controllers F1 to F5, and when the screw passes through the above-mentioned section during injection, the amount of oil passing through each hydraulic circuit 20-2≠ is determined in advance.
20, similarly, the B section is a hydraulic circuit, 2/, the C section is a hydraulic circuit, the D section is a hydraulic circuit, 23, the E section is a hydraulic circuit, and the injection speed is predetermined by 2 Hiro. It is something. C1 to C5 indicate check valves, and each hydraulic circuit 20-. This is provided to prevent backflow at 24t. R+&S relief valve (pressure control valve)
(l- indicates and sets the injection pressure. Mf, 1
1' indicates a solenoid valve, and solenoid valve Mr
Controls the relief valves R2 and R3Q via the solenoid valve M. IJ IJ-7 valves R2 and R3 are used to set the full pressure that is switched during the pressure holding process.

The electric circuit shown in FIG. 2 will be explained in conjunction with FIG. 7
shows the potentiometer that converts the position of the screw / into voltage as described above, and as shown in Figure ≠, while the screw / moves between strokes S, the voltage is proportional to the distance Q-V.
The voltage up to 5 can be changed. g is a potentiometer that sets the voltage v1 indicated by potentiometer 7 when the screw advances through section A. is screw/
The voltage V indicated by the potentiometer 7 when advances through the A0B interval
2i set potentiometer, 10 is screw/
When advances to A 10B -1-C section, potentiometer 7
a potentiometer to set the voltage indicated by /
/ indicates the potentiometers that set the voltage indicated by the potentiometer 7 when the screw / has advanced by A + B 10 100. These potentiometers t~// are the injection speed switching position setters. Configure. 72 to /j indicate signal transmitters (comparators), which compare the set voltages v1 to v4 of each potentiometer g to // with the voltage of potentiometer 7, which changes every moment as the screw / moves, and determine whether both voltages are equal to each other. When a match occurs, a built-in relay (not shown) operates 1. and is configured to emit a signal. / 2 a ~ / j a, / 2 b ~ / , t
b is the signal transmitter 7.2~l! This shows the relay contacts inside the. Mj' to M P/ indicate solenoids of solenoid pulps M3 to M.

10R indicates a relay, which operates at the same time as the solenoid M7' is energized.5. It has an A contact 10R'. TR indicates a timer, which switches the holding pressure in the holding pressure process, and has an A contact TR'. 30～
3 shows an electric circuit for controlling solenoids M3' to MRI'.

Next, the operation will be explained. When the injection start signal switches the solenoid valve M/ to the forward position, as shown in FIG. 2, the solenoid M3' in the electric circuit 30 is energized, and the solenoid pulp M3 switches to the forward position. Hydraulic pressure is applied to the injected cylinder by the hydraulic circuit 20, and the screw passes through the cylinder at an injection speed iv+ (see FIG. 3) predetermined by the controller 70-con F1. Screw/
After passing through section A, the voltage of potentiometer 7 becomes equal to the predetermined voltage V1 of potentiometer ♂ (see Figure 3), and the signal from signal transmitter/2 causes contact A/2m. is closed and B+ij, point 7.2b is opened, so that solenoid M3' is de-energized and solenoid Mμ' in electric circuit 3/ is energized. Therefore, the solenoid pulp M3 is cut off, the hydraulic circuit and the solenoid pulp M with 2/VC enter the forward position, a predetermined amount of oil is applied to the injection ram λ by the flow controller F2, and the screw/ is predetermined in the B section. It moves forward at the injection speed V2 (see Figure 3). Similarly, the screw / connects sections C, D, and E to each signal transmitter /3. /lit and /j switch the p1 electric circuit 32, 33, and 3 one after another.

Therefore, the hydraulic circuits are also sequentially switched to 2J, 2J, and 24t, and the screw / is provided in each hydraulic circuit.
Injection speed V5 + of each section C, D, E determined by the amount of oil passing through 0-con F3, F4, Fs
It will pass at V4 + v5 (see Figure 3). Contact AI! At the same time that b is switched to /la, the screw / enters section E at injection speed v5, completing the filling process and proceeding with the holding process. Also, contact points/! When b switches to /ja, solenoid.

M7' (% air circuit 3≠) and electric circuit 3! It heals.

Relay/(7R is activated, its human contact lOR' (electric circuit 37) is closed, solenoid Ml' is energized, solenoid pulp M♂ enters, and the injection pressure is set to the predetermined value of IJ IJ-7 pulp R2. The holding pressure P2 (
(See Figure 3). On the other hand, timer TR is activated at the same time as solenoid M♂′ is excited! When the timing starts and the predetermined time t times out, the contact TR' closes and the solenoid M' is energized. The pressure becomes P3 (see Figure 3).When the gate part of the mold 3.Hiroshi solidifies at the holding pressure P5 and a certain period of time for sealing has elapsed, the injection process photon timer (not shown) is activated.
works and injection is completed.

Example λ No. ! This will be explained with reference to the drawings and FIG. 10/ indicates a screw. 10.2 shows the entire injection ram, in which oil pressure acts on the injection side to advance the screw /θ/ to perform injection. 103, 10≠ indicates a mold, and 103 indicates a rack attached to the screw 10/ and synchronized with the reciprocating movement In of the screw. Showing 1otB binion, 8116r2 easy 10! The screw i
It rotates due to the movement of oi and converts the linear motion of the screw 10/ into rotational motion. Reference numeral 107 indicates a potentiometer, which is connected to the pinion 10t via a gear train or the like or directly and converts the movement of the screw 10 into a continuous electric signal in response to the rotation of the pinion 106, Configure the detector. S' indicates the injection stroke, and the same stroke S/ is AZ B/, C/,
Dl, E/'s! It is divided into stages, and during injection, the screw 10/ is in the same section A', B/, C1, Dl, E.
/ are configured to pass through each at different injection speeds.

To explain the hydraulic circuit, m/ indicates an injection switching solenoid valve, which controls the injection ram 102. fl is an electromagnetic flow control valve (flow control valve) (hereinafter referred to as electromagnetic flow controller), and the throttle opens and closes in proportion to the strength of voltage or current (hereinafter referred to as voltage), and when the voltage is high, the throttle opens and closes. The smaller the flow rate, the higher the flow rate. Furthermore, when the voltage is low, the aperture is large and the flow rate is therefore small. PF2 indicates a pump. r indicates an electromagnetic relief valve (pressure control valve), and the set pressure changes depending on the strength of the voltage.

To explain the electric circuit, 107 indicates a potentiometer that converts and indicates the position of the screw 10/ into a voltage, and while the screw 10/ moves between the straws 287, the voltage is changed to O in proportion to the distance. Continuously change the voltage from the beginning to a certain voltage. 10♂ is screw 10/
This figure shows a potentiometer that sets the voltage indicated by the potentiometer 107 when the section A' progresses. Similarly, 10 to /// indicates a potentiometer, and screw 70 to 1. A'10B/, A'+B'10C', A,
'10 B'10' + D' advanced potentiometer/θ7
These potentiometers 101 to /// constitute an injection speed switching position setter. //-~//J' indicates a signal transmitter (comparator), which compares the set voltage of each potentiometer 10~/// with the voltage of potentiometer 107 that changes every moment as the screw 10/ moves. When the two voltages match, a built-in relay (not shown) is activated to issue a signal. //2a~//G a is the A contact of the relay in the signal transmitter, //, 2b~//! b indicates a B contact.

//l and //7 indicate amplifiers, which amplify the voltages set in potentiometers iv to koj, which will be described later.
It operates the electromagnetic flow controller f1 and the electromagnetic relief pulp r. Potentiometers iir~/, 22 each have a voltage set in advance, and a signal transmitter //λ~
//! When the electric circuit (10-71) is switched by the No. 16 issued by
0.2 to form a group of electrical quantity setting devices that control the injection speed. Similarly, potentiometer/
KO3~/2jt sets a predetermined voltage and applies this to the electromagnetic +717-7 pulser to control the injection pressure during the filling process and the holding pressure during the holding process. It constitutes a group of instruments. 100TR indicates a timer, which switches the holding pressure during the holding pressure process, and has a positive contact /00TR'.

R8 indicates a relay, and A contact 1'lS1. It has R8x and B contact R82.

Next, the operation will be explained. When the injection start signal switches the injection valve m/ to the forward position R, the electromagnetic flow controller f1 controls the injection ram 1 to control the predetermined flow rate by the voltage set in the potentiometer //g in the electric circuit 1.
0λ and screw 1 at a predetermined injection speed.
0/ moves forward in section A' during stroke 87. During that time, the injection pressure is controlled by an electric circuit! Potentiometer located at j/, 2
The set pressure of the electromagnetic IJ IJ-7 valve determined by j is maintained. When the screw 10/ completes passing through the A' section, the potentiometer 70 matches the voltage and the believer transmitter //, 2 A signal is generated and the contact //2b switches to the contact //2aVC, so the electric circuit !0 is switched to the electric circuit -5'/, which is now determined by the set voltage of the potentiometers //2 and 2a. P screw ioi moves forward in section B' at a predetermined injection speed.Similarly, section Q/ is controlled by potentiometer/20 to
The flow rate of the electromagnetic flow controller f1 is controlled by the potentiometer /2/ in the / section, and the potentiometer /22 in the E' section, and the screw 10/ is controlled at a predetermined injection speed.
moves forward. After the screw 10/ has passed through the D′ section, the signal transmitter //! Signal contact //! b is //!
When switching to A, relay R8 is simultaneously excited and closes A contact R81, and timer 10OT is activated to switch the holding pressure.
R starts timing. At the same time, A contact R8s
(Since the electric circuit jQ is also closed, the injection pressure is determined by the potentiometer/24t)
Once the set pressure is reached, the process moves on to pressure control during the pressure holding process after the filling process is completed.

When the timer 10OTR times out, the contact 10
OTR' is switched from the electric circuit Jz to the electric (ro) path j7, so the set pressure of the electromagnetic IJ re-7 pulp r is determined by the potentiometer /231/i:
The holding pressure will change.

As is clear from the embodiments described above, in the present invention, the multi-stage program control of the speed according to the position of the injection plunger or screw in the filling process is performed by electrically dividing the filling stroke using a potentiometer or the like, and by using an electrically controlled screwdriver using a potentiometer or the like. By using a position detector, the following excellent effects can be obtained.

(1) The position detector using a potentiometer and the injection speed switching position setter can increase flexibility in speed program control by dividing into arbitrary sections. For example, since the filling stroke can be divided arbitrarily with high accuracy in units of θ, 1lI3+ using a potentiometer, the setting accuracy can be dramatically improved. Moreover, it has high operability, allows free programming, and makes fine adjustment of the pattern easy.

Furthermore, the reproducibility of program settings is also significantly superior to conventional devices.

(2) A position detector using a potentiometer allows highly accurate screw position detection.

For this reason, set the injection plunger or screw position to 0,
1w, because it can still be detected accurately at the nest position.

Speed programs can be repeated accurately and high precision reproducibility can be maintained.

(3) Accurate control of the filling process completion point can be achieved. In other words, in the filling process where molten resin flows into the mold,
It is important to accurately grasp the point at which filling is completed, complete the control of the filling process, and switch to the pressure holding process, but as mentioned above, the filling process program can be set to a high degree, so it is possible to By making the speed sufficiently low to reduce dynamic energy and stabilize the switching operation, it is possible to accurately determine the point at which to switch to the pressure holding process.

Therefore, by using the injection process control device jk according to the present invention, which has the excellent features described above, the molded products molded thereby will also be free from defects in the surface condition of the molded products caused by the molten resin during filling. It can improve certain flow marks, jet staining, weld marks, spiders, rough skin, gas burns, silver streaks, etc.

For example, if you fill the cylinder at a high speed, fill the parts where defective marks appear on the surface at a low speed, and fill the other parts as fast as possible, so that the molten resin is filled into the mold with sufficient fluidity. It can eliminate jet ink, discoloration, silver streaks, etc., and improve the surface quality of molded products. In addition, since it is now possible to precisely control the filling amount, it is possible to reduce the speed just before filling is completed, making it less likely that fluctuations will occur in the control of the timing of switching from filling to holding pressure, and preventing the occurrence of paris. can.

Although the preferred embodiments of the present invention have been described above, it is of course possible to make changes in the design without departing from the spirit of the present invention.

[Brief explanation of drawings]

7 is a vertical cross-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. 1, and FIG. The figure is a graph showing the relationship between the injection speed and the screw stroke position ffl during the injection process by the device of the present invention, and a graph showing the relationship between the injection pressure and the injection process time. A graph showing the relationship with the generated voltage, Fig. 5 is a schematic diagram of the hydraulic side i@1 system showing the second embodiment of the present invention, and Fig. 6 is an electrical control circuit diagram of the control system shown in Fig. S. be. / , 10/... screw 2, 10.2...
・Injection ram 3, ≠I/θ3, 104t...mold,,
z, ios...Rack B, /θ B...Binion 7, 107...Potentiometer (position detector)/
2~/! , //2~//j...Signal transmitter (comparator)
20~Details...Hydraulic circuit 30~34t...Electric enclosure M/, m/...Injection switching solenoid pulp M3~
Mri... Solenoid valve M3' to Mri'... Solenoid p+ to F,... Flow control valve (flow rate adjustment valve) fl... Electromagnetic flow control pulp (flow rate adjustment valve) R1-R5...・Relief valve (pressure control valve) r...
・Electromagnetic relief valve (pressure control valve) 10R, R8...
・Relay #) R', R81...Relay A contact TR, 100T
R...Timer TR', #)OTR'...A contact C1 to C5 of timer
...Check valve PF+, -PFz...Pump patent applicant Toshiba Machine Co., Ltd.

Claims (2)

[Claims] (1) A method for controlling the injection process of an injection molding machine, which includes a filling process in which a cavity is filled with molten resin, and a pressure holding process in which pressure is applied to compensate for shrinkage caused by cooling and solidification of the molten resin filled in the cavity. , the movement position of the injection plunger or screw is detected and released using a position detector such as a potentiometer attached to the injection plunger or screw. A plurality of arbitrary positions of the injection stroke during the filling process are set by an injection speed switching position setter consisting of a plurality of potentiometers, etc., and seven flow Jt14 regulating valves are provided in each of the plurality of flow path circuits arranged in parallel. Alternatively, by using a flow rate regulating valve that controls the flow rate depending on the magnitude of the amount of electricity and a group of multiple electricity amount setting devices for controlling this valve, it is possible to arbitrarily set the injection speed corresponding to the plurality of injection speed switching positions. A comparator compares a detection value signal detected by a position detector attached to the plunger or screw with the value set in the injection speed switching position setter as the injection granger or screw moves forward. When both match, one flow i is provided in each of the plurality of flow path circuits provided in parallel.
During the filling process, the amount of electricity set in the flow 'Jt regulating valve that controls the flow rate depending on the magnitude of the amount of electricity or the amount of electricity set in a group of multiple electricity setting devices for controlling this valve is sequentially changed. An injection process control method for an injection molding machine, characterized in that the flow rate of a hydraulic drive source is changed according to an output signal of a comparator, and the advancing speed of an injection plunger or screw is controlled according to a preset program. (2) An injection molding machine that controls a filling process in which the cavity is filled with molten resin, and a pressure holding process in which the molten resin filled in the cavity is pressed to compensate for shrinkage caused by cooling and solidification. In an injection process control device configured to sequentially change the flow rate of a hydraulic drive source during the filling process and control the forward speed of the injection pusher or screw according to a preset program, a potentiometer or the like attached to the injection plunger or screw is used. a position detector for detecting the movement position; an injection speed switching position setter including a plurality of potentiometers capable of setting arbitrary plural positions t of the injection stroke during the filling process; Seven flow rate adjustment valves are installed in each of six parallel wave path circuits so that the corresponding injection speed can be arbitrarily set, or flow rate adjustment valves that control the flow lid depending on the amount of electricity A group of multiple electrical quantity setting devices for valve control. When the detection value signal detected by the position detector attached to the plunger or screw as the injection plunger or screw advances matches the value set on the injection speed switching position fixture, the flow irA regulating valve is provided. An injection process control device for an injection molding machine, comprising a comparator that issues a switching signal to sequentially switch a plurality of flow path circuits or to sequentially switch to an electrical quantity set in a group of electrical quantity setting devices.