JPS6183016A - Injection and compression molding machine - Google Patents

Abstract

PURPOSE:To permit to manufacture a molded product excellent in transfer property by a method wherein the machine is constituted so that a plurality of pressure setters are provided to select hydraulic pressure supplied to a hydraulic cylinder so as to be capable of controlling a compression force applied on molten resin in the molding machine in multiple stages. CONSTITUTION:Molds 1, 3 are closed by a mold closing plate 5 strongly and, thereafter, the molten resin is injected by touching the nozzle of an injection device 15 while the hydraulic cylinder 11 is operated when loading of the resin is finished and plungers 6 are pushed against the loaded resin 16. In this case, the pressure of the hydraulic cylinder 7 is controlled while dividing the pressure into A area, from the finish of loading to the finish of gate seal, B area, from the gate seal to a time whereat the resin is solidified to about 70%, and C area wherein the resin is solidified perfectly. A pressure in the degree of discharging the strain of gate is applied in the area A, a high pressure, capable of compensating void, fin or the like due to thermal shrinkage, is applied in the area b and a pressure in the degree of preventing remaining internal stress is applied in the area C. According to this method, the injection molded product, excellent in the transfer properties, may be manufactured.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) This invention relates to an injection compression molding machine used for molding synthetic resin.

(Prior Art) In injection molding using normal means, large stress during injection remains in the molded product as residual internal strain around the gate portion. As a means for reducing this distortion, a method of applying compressive force to the resin filled in the mold is already known. One method is to close the mold at a slightly low pressure, apply a small amount of KtA to the mold using the filling pressure, and then increase the clamping pressure to completely close the mold. At that time, compressive force is applied to the filled resin. and when injection is carried out in the usual way, and then a blanker that also serves as an ejector pin is press-fitted into the filled resin.・It was only.

(Problems to be Solved by the Invention) In the above method, pressure is applied to the resin while it is still in a molten state after injection and filling. It is said that the y-t stress (internal stress) is discharged from the f-1 part, and after the gate sealing, sink marks, voids, etc. due to heat shrinkage are eliminated in the pressure-receiving area of the molded product.

However, during actual molding, if excessive pressure is applied before the r-gate seal, not only the dart strain will be discharged from the dart, but also the resin for compression will be discharged, and the heat after the gate seal will be discharged. It becomes impossible to compensate for shrinkage. If the pressure before gate sealing is too low, the gate sealing will be performed too quickly and the stress of the gate will not be completely discharged, resulting in insufficient pressure in the compression after gate sealing and compensation for heat shrinkage. It becomes difficult to do.

In addition, the proper pressure for sealing the gate and the proper pressure for compression almost never match, and if the compression force is kept at a certain level even during the compression process, pressure will be applied to the molded product after solidification, which will cause internal stress. may remain.

As described above, in injection compression molding, it is difficult to set the compression force, so the excellent effects of injection compression molding cannot be fully utilized, which has been a problem.

(Means for solving the problem) This invention was conceived in view of the above circumstances, and includes:
The objective is to provide an injection compression molding machine that can optimally control compression force during injection compression molding.

The present invention according to the above object includes a hydraulic cylinder that applies compressive force to the molten resin injected and filled into the mold cavity by moving a mold cavity part, and a plurality of pressures that set the hydraulic pressure supplied to the hydraulic cylinder. a setting device, a signal generator that sequentially selects a plurality of set pressures set in the pressure setting device and issues a pressure command signal corresponding to the set pressure for an appropriate time, and a supply oil pressure that is supplied to the hydraulic cylinder according to the pressure command signal. It has an electromagnetic pressure regulating valve to control.

(Function) In the above configuration, the compressive force determined by the shape and material of the molded product is applied to ff from the time of injection filling until the completion of gate sealing.
-) Divide the compression pressure into multiple stages, such as from the completion of sealing to the middle of solidification, and from the middle of solidification to the completion of solidification, set the most suitable compression force for each process, and change the compression pressure sequentially according to the process. can be changed.

(Example) The present invention will be explained in detail below using illustrated examples.

l is the fixed mold attached to the fixed platen 2, 3 is the tie bar 4, 4
The movable mold is attached to a mold clamping plate 5 that slides and moves, and the center of the cavity is a movable cavity with a silane gloss 6. This movable cavity is used for molded products (particularly large areas where precision or low internal distortion is required)
It is preferable that

7 is a hydraulic cylinder of the movable cavity, and a gland is attached to a plate 9 connected to a ram 8. 10
is a knockout pin, which is operated by a ram 12 of a hydraulic cylinder 11 installed in the mold clamping plate 5.

Figure 2 shows the circuit of the hydraulic cylinder 7.
l is a switching valve, V2 is a pressing force adjustment valve, and v3 is an electromagnetic relief valve that changes the pressing force by a control signal.The pressure is set by three pressure setting devices (not shown), and the set pressure is sequentially changed by a signal generator (not shown). Select to send a signal to the electromagnetic relief valve.

Reference numeral 13 denotes an abnormal advance detector consisting of a limit switch or a photoelectronic switch, which prevents the silane gloss 6 of the movable cavity from advancing beyond a set value and unduly pressing the filled resin.

The method of the present invention will be described below using the molding of the optical component 14 shown in FIG. 3 as an example. Note that in the optical component 14, pressure by the movable cavity is applied to the light transmitting part 141) in the center part rather than the periphery 14a.

First, the nozzle of the injection device 15 is brought into contact with the dirt of the mold l to inject molten resin. At this time, the molds 1 and 3 are mounted on the mold clamping plate 5.
to completely and strongly close the planter 6, and set it to the retracted position (.

Next, when filling is completed, the hydraulic cylinder 11 is operated while the nozzle of the injection device 5 is kept in contact with the injection device 5 to push out the plunger 6 into the filled resin 16 and apply pressure to the filled resin 16 before it hardens. Note that the output of the hydraulic cylinder 7 at this time may be about 1/10 to 1/20 of the mold clamping force, and the extrusion stroke of the silant gloss 6 varies depending on the molds 1 and 3, the material resin, and the molding conditions. Usually 0.01~
It is about 0.2 wn.

In addition, in this example, the pressure settings are set in the interval from the completion of injection filling to the completion of the gate sealing (section A), and the interval from the completion of the gate sealing until 70% solidification (section B).
There are three stages from 70% solidification to completion of solidification (section C), and in section A, pressure is applied to the extent that only the strain on the gate is discharged from the gate and the gate is sealed. In section A, set a higher pressure than section A to compensate for cracks, sink marks, etc. due to heat shrinkage after gate sealing, and in section C, set a lower pressure than section B to the extent that no internal stress due to compressive force remains in the cooled and solidified molded product. It is.

Furthermore, the hydraulic cylinder 7 is operated by timing based on the injection pressure holding pressure switching signal. The holding pressure switching signal is transmitted when the position of the injection plunger or the injection pressure reaches the set pressure of the Zoresha monitor, or when the mold internal pressure sensor senses the set pressure.

When the above-mentioned pressure holding switching signal is input to the signal generator, the signal generator sequentially selects the set pressure for the A section, B section, and C section, and sets the pressurization time for each section separately. Generates a pressure signal for each set time on the setting device. This signal sets the pressure of electromagnetic IJ IJ-7 pulp ■3,
The pressure of oil supplied to the hydraulic cylinder 7 is adjusted.

If the granger 6 abnormally advances beyond the set position during operation and presses the filled resin 16 more than necessary, the detector 1
3 works to automatically stop the operation of the hydraulic cylinder 7.

As described above (in the filled resin 16 applied with pressure,
Since the dart and the injection cylinder 15& of the injection device 15 are in communication with each other by the nozzle touch, the internal pressure escapes from the dart to the injection cylinder side. The release of pressure from the dart is controlled by the pressing force in the movable cavity and the holding force of the injection cylinder 1511, and the pressing force in the movable cavity is appropriately adjusted by changing the oil pressure of the hydraulic cylinder 7 in multiple stages.

The optical part □ product 14 formed by reducing the internal pressure as described above has high precision because the residual pressure that causes distortion is removed, and in particular, no distortion occurs in the light transmitting part 14b.

In this embodiment, the compressive force was changed in three stages, with low sections in the F section and C section, and high in the B section, but the finer the division of the compressive force, the better. However, if it is divided into too many parts, the machine cost will increase, the number of settings will increase, and the operation will become troublesome, so it is better to decide appropriately depending on the properties of the molded product.

(Effects of the Invention) As described above, this invention is configured so that the compression force in injection compression molding can be controlled in multiple stages, so molding can be performed at the pressure most suitable for each condition during the compression process, making it suitable for injection filling. The accompanying case stress can be removed, molded products with little orientation distortion, voids, sink marks, etc. and good transferability can be easily obtained, and injection compression molding can be carried out more effectively.

[Brief explanation of the drawing]

The drawings illustrate an apparatus capable of carrying out the injection molding method of the present invention, and FIG. 1 is a longitudinal sectional plan view when molding is completed;
FIG. 2 is a circuit diagram of the suppression hydraulic cylinder, and FIG. 3 is a perspective view of the molded product. l...Fixed mold 3...Movable mold 5...Mold clamping plate 6...Plant holder 7...Hydraulic cylinder for pressing 8...
... Ram for pressing 14 ... Optical parts 15
... Injection device 15a ... Injection cylinder 16 ... Filling resin vl ... Switching pulp

Claims (1)

[Claims] A hydraulic cylinder that applies compressive force to the molten resin injected and filled into the mold cavity by moving the mold cavity, a plurality of pressure setting devices that set the hydraulic pressure supplied to the hydraulic cylinders, and a pressure setting device. a signal generator that sequentially selects a plurality of set pressures and issues a pressure command signal corresponding to the set pressure for an appropriate time; and an electromagnetic pressure that controls the hydraulic pressure supplied to the hydraulic cylinder based on the pressure command signal. An injection compression molding machine characterized by having a regulating valve.