JPS60154028A - Control on injection process of injecting molding machine - Google Patents

Abstract

PURPOSE:To obtain a highly accurate molding free of a stress by a method in which a brake device is actuated at the same time switching is made to a pressure maintainer process, and the blade device is locked by the detection of the positions of a screw or a plunger or of the internal pressure of the mold cacity. CONSTITUTION:In injecting a molten resin into the mold cavity 13, a screw 16 is advanced for high-speed packing. When the pressure of molten resin injected is detected by a pressure sensor 18 and the internal pressure of the cavity 13 reaches a set value by a pressure setter 26, a relay R1 is operated. Return oil from a cushion chamber is backed to a tank, the contact-A is connected to R1, and thereby the amount of oil to an injection cylinder 19 is controlled on a set value by a flow rate setter 30 by means of an electromagnetic flow cone 25. When the internal pressure of the cavity 13 coincides with a set value by a pressure setter 27, a relay R2 is operated, an electromagnetic switch valve 24 is set to neutral position, and return oil from the cylinder 19 is blocked. The flow cone 25 is controlled by signals from an arithmetic unit 33b to keep the stop position of the screw 16.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] The present invention relates to an injection process control method for an injection molding machine that performs precision molding.

[Prior art]

In precision molding, injection process control K “accurate filling and holding pressure control”
is required. That is, in the filling process, in order to minimize the viscosity difference between the leading and trailing ends of the molten resin flowing into the mold cavity, filling must be performed in as short a time as possible, and the holding pressure following the filling process must be In the process, it is important to compensate for the shrinkage of the molten resin filled in the mold cavity as it cools, in just the right amount, and the switching point from the filling process to the pressure holding process, which is the contact point between the two processes, is important. Another important factor is to move from filling to pressure holding process in a short time while maintaining accurate positioning and repeatability.

Here, when observing the behavior of the molten resin in the mold cavity through the filling and pressure holding processes, the degree of skin layer formation is determined as a result of the following thermal balance.

1. Heat supply by molten resin, heat generation due to internal friction, and heat generation due to compression.

2 Heat loss due to thermal conduction and thermal expansion.

Therefore, if the temperature of the molten resin and the temperature of the cavity surface are the same, the growth of the skin layer slows down as the flow rate increases. On the other hand, the flow resistance is expressed by the following formula, taking polycarbonate as an example.

where ΔP: dynamic pressure drop, v: average flow rate, L: flow
H: Height of cavity cross section As can be understood from the above equation, when the flow velocity is low and the growth of the skin layer is large, the force of the flow stagnation becomes large, thus giving unnecessary stress to the skin layer.

This improves general dimensional accuracy, geometrical accuracy, physical strength, etc., but defects such as flow marks and rhubarb streaks tend to appear on the surface of the product, and the transition from the filling process to the packing process increases. Programmed injector is not recommended as it may cause disadvantages such as unstable switching.

In order to minimize the influence of kuzoyon etc., the injection stroke is divided into several stages of filling speed during injection.

However, although it is possible to perform filling by varying the filling speed during the filling process, after switching to the pressure holding process, it is difficult to control the process to compensate for the shrinkage caused by the cooling of the molten resin filled in the cavity.

In the pressure holding process, the flow of the molten resin is almost zero, the amount of heat lost overwhelmingly exceeds the amount of heat generated, and the skin layer becomes thicker rapidly. At this time, if there is flow in the molten resin, stress will be applied to the skin layer being formed, making it impossible to ensure accuracy.

As a result of various researches, we wondered if there was a way to completely stop the axial movement of the scree or plunger that directly flows the molten resin during the pressure holding process, and to compensate for the shrinkage of the molten resin. is a compressible fluid when melted, and varies depending on the type of p1 resin, but 600
Kr/cd: 4-5, 10001φ/cd: 8-1
After filling the cavity with molten resin at precisely controlled pressure, it quickly shuts off external pressure, and the shrinkage of the molded product absorbs the compressed pressure. The conclusion was that it is sufficient to supply the molded product from within the molded product itself by releasing it, that is, to release the stress of the molded product itself while applying a constant holding pressure in the trench where the molded product itself is formed and the gate knoll is completed. The present invention has been achieved.

[Structure of the invention]

In order to achieve the object of the present invention, the present invention performs high-speed filling during injection filling of a resin material, and performs quick filling of the resin material.

Or, at the same time as switching to the pressure holding process by detecting the position of the plunger, etc. or detecting the internal pressure of the mold cavity, a brake device that mechanically automatically stops the scree or plunger, etc. is activated, and then the position of the screw or plunger, etc. is detected or This is an injection process control that uses the detection of the internal pressure of the mold cavity to activate the brake device and continue to apply a constant force to the screw until the timer has elapsed until the gate roll is completed.

〔Example〕

Next, one embodiment of the present invention will be explained with reference to FIG.
1 is an injection molding machine, 12 is a mold, and a cavity 13 formed by a fixed mold and a movable mold is provided inside. The cavity 13 is connected to a heating cylinder 15 via a gate 14.
The molten resin accumulated in front of the screw 16 flows into the screw 16 when the screw 16 moves forward (to the left in the figure) during the filling process. 17 is a position detection device that detects the screw position, and 18 is a pressure sensor that detects the pressure inside the mold. Reference numeral 19 is actuated by an injection/sudder, and the injection piston 20 is moved forward and backward by pressure oil, thereby causing the screw 16 to move forward and backward in the axial direction. The injection/cylinder 17 is provided with a cushion chamber 19b having a smaller diameter than the inner diameter of the forward oil chamber 19a so that the injection piston 20 is decelerated near its forward limit. The cushion chamber 19
The return oil from the injection cylinder 19 is discharged from the discharge port 21 until the injection piston 20 is fitted into the cushion chamber 19b. Since the inner diameter of the cushion chamber 19b is much smaller than the oil chamber 19a, the piston 20 is braked suddenly. . Reference numeral 24 controls the flow rate of pressure oil acting on the electromagnetic injection cylinder 19. 26 and 27 are pressure setting devices for setting a predetermined pressure inside the cavity 13. Comparators 28 and 29 compare the pressure inside the cavity 13 detected by the pressure sensor 18 with the pressure values set in the pressure setting devices 26 and 27, and when they match, output a signal, and relays R1 and R2 respectively. The wick is designed to operate.

30, a flow rate setting device 31 for controlling the electromagnetic flow controller 25 is an amplifier. Reference numeral 32 denotes a screw stop position detection circuit which determines whether or not the screw is stopped at a predetermined position based on a screw position detection instruction signal from a controller (not shown) and a detection value from the screw position detection device 17. . Reference numeral 33 denotes an arithmetic device which includes a position latch section 33a, a calculation section 33b, and a stop signal transmission section 33C, and the value detected by the position detection device 17 always matches the value calculated by the arithmetic section 33b via the position latch section 33a. The abutting section 34 compares the two, and applies a feed signal to the electromagnetic flow controller 25 for control.

The structure is as explained above. Next, the operation of the present invention will be explained. When injecting molten resin into the mold cavity, pressure oil is applied to the injection cylinder 19, and the screw 16 is moved to the backward limit position. Move forward to fill faster. On the other hand, the melt and grease injected into the cavity 13 are detected by the in-mold pressure sensor 18, and when the pressure in the cavity 13 reaches a certain value set in the pressure setting device 26, the relay R1 is activated. , its A contact R1 is connected, and the A contact R3 of the injection signal relay (not shown) is connected at the start of the injection process, so the electromagnetic switching valve 24 switches from the illustrated position a to the b position, and the cushion chamber 19b The return oil passes through the choke throttle 23 and returns to the tack. At the same time, by connecting the A contact Rx, the electromagnetic flowco/25 controls the amount of oil to the injection/cylinder 19 according to the value set by the flow rate setting device 30VC. When the pressure in the cavity 13 matches the set value of the pressure setting device 27, the relay R2 is activated, the B contact R2 is cut off, the electromagnetic switching valve 24 is placed in the neutral position, and the return oil from the injection/cylinder 19 is blocked. On the other hand, the tortoise flowco/25 has a calculation unit that maintains the stop position at the -I- position so that the screw 16 does not stop moving and is moved backward by the hydraulic pressure in the /yon chamber 191. It is controlled by the feed signal from 33b.

〔Effect of the invention〕

Even if high-speed filling is performed using the structure explained above, the machine has a mechanical brake device that cushions the impact caused by the flow of inertia and sudden stops. It is possible to accurately stop at a predetermined position without giving any yoke to the device, fill the cavity with molten resin at a predetermined pressure, switch to the pressure holding process, and quickly close the cavity. In order to cut off communication with the outside, the axial movement of the screw, etc. is stopped at the stop position until the gate seal is completed, and the molten resin is sealed in the cavity in a compressed state, so during the pressure holding process. The filled resin may not move, and the shrinkage of the molded product due to cooling and solidification can be compensated for by supplying it from inside by gradually releasing the compressive force of the aoh itself. There is no stress and it is possible to obtain precise molded products.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing one embodiment of the present invention. 12... Mold, 13... Cavity, 16... Screw, 17... Screw position detection device, 1B... Pressure sensor, 19... Injection cylinder, 24... Solenoid switching valve, 25...・・Electromagnetic 70-con, 26. 27・Pressure setting device, 30・・Flow rate setting device, 32・・Screw stop position detection circuit, 33・・Calculating device, Procedure amendment (method) May 1980 2J Japanese Patent Application No. 9640, filed in 1982, 2, Title of invention: Injection process control method for injection molding machine 3, Person making amendments Relationship with Kasuri Patent applicant address: No. 11 Homare, 4-2 Ginza, Chuo-ku, Tokyo 1982 April 4, 2017 (Shipping date: April 24, 1982) 5. Subject of amendment: “Application”, “Full text of the specification” and 1 drawing” 6. Contents

Claims (1)

[Claims] When filling the material resin in the injection process of an injection molding machine, which consists of the filling process and the subsequent pressure holding process, filling is performed at high speed during the filling process, and then the pressure holding process is performed by detecting the position of a scree or plunger, etc., or by detecting the internal pressure of the mold cavity. At the same time, the brake device is operated to mechanically automatically stop the screw or plunger, etc., and then the brake device is activated by detecting the position of the screw or plunger, etc. or the internal pressure of the mold cavity, and the gate seal is closed. A method for controlling an injection process of an injection molding machine, characterized in that a constant force is continued to be applied to a scree or a planojar at a time when the time until completion elapses.