JPH0369329A - Compression-impressive molding machine - Google Patents

Abstract

PURPOSE:To enable the primary mold clamping force to be changed arbitrarily in accordance with molding conditions by providing between a mold clamping ram and a movable disc a control mechanism which serves to vary the extending rate of a tie-bar during the mold clamping period in changing the operational stroke of the mold clamping ram by means of a screw. CONSTITUTION:A control mechanism 20 for the primary mold clamping force is provided between a mold clamping 16 and a movable disc 17 and the control mechanism 20 comprises cylindrical screw materials 21, 22 screwed in each other. In these screw materials 21, 22, the inside screw material 21 is fixed to the top end of the mold clamping ram 16 and the outside screw material 22 is secured rotatably onto the back surface of the movable disc 17 by means of a stop ring 23. And, in the outer periphery of the screw material 22, graduations 24 are given which show revolution number. In the injection-compressive molding machine of this type, the movable disc side can be moved in advance and retreat through rotation of the screw material 22, and since the operational stroke of the mold clamping ram 16 varies therethrough, the tie-bar 14 is given a proper extension even at the time when each of the mold thickness, molding article configuration, material resin, temperature or the like is changed, thus enabling fine control within a cavity according to the changing of molding conditions.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application J] The present invention relates to an injection compression molding machine for synthetic resin.

[Conventional technology] In the molding of synthetic resins, such as lenses and disc plates for optical discs, which require strict shape accuracy on the submicron scale, molding of synthetic resins is difficult due to the high pressure generated within the cavity during the injection process when the cavity is filled with material. Based on the relationship between the volumetric shrinkage rate of the synthetic resin material to be molded and the mold volume, the length, thickness, and elastic modulus of the tie bars are determined so that the tie bars can be stretched by the amount predicted and the mold can be opened wide. is determined in advance, and the high-pressure energy of the injection is stored in the form of elongation of the tie bar. When gate sealing is completed, as the molded product cools down, the elastic deformation recovery force of the tie bar that has been stretched in the thickness direction of the molded product is applied to the mold. There is an injection compression molding machine that compresses the molded product and performs precision molding.

Figure 6 is an explanatory diagram of the process in the injection compression molding machine. In the figure, 1.2 is a support plate installed on the machine stand 3, 4.4 is a tie bar installed across the support plate 1.2, and both ends are supported. A movable platen 7 connected to a mold clamping ram 6 of a mold clamping cylinder 5 is movably supported by the tie bars 4.4.

Reference numeral 8 denotes a mold, which is attached to the opposing side surface of the support plate 2 and the movable plate 7. Further, the support plate 1 having the mold clamping cylinder 5 is
Although it is fixed to the machine base, the support plate 2 with the mold 8 attached is
The tie bar 4.4 is provided on the machine base so as to be movable within a range that allows extension of the tie bar 4.4.

The relationship between the elongation of the tie bars 4 and the mold clamping force during the mold clamping process, injection process, compression process, etc. in such an injection compression molding machine is as follows:
This will be explained with reference to FIGS. 6 and 7.

Mold clamping process (-next mold clamping) When the mold clamping ram 6 is moved forward and the mold 8 is closed, how much margin is there in △L0 for the movement of the mold clamping ram 6, and how much is the expansion of the tie bar 4? It has not occurred.

Let L be the tie bar length at this time.

Furthermore, when the mold clamping ram 6 is moved to the mold clamping stroke end, that is, ΔLo, at the highest pressure, the tie bar 4 is extended by ΔL due to the pressure, and the tie bar length becomes +ΔLo, and a primary mold clamping force proportional to ΔLo is generated.

When the cavity of the mold 8 is injected and filled with molten resin during the primary mold clamping state of the injection process, the resin pressure generated during the filling process becomes internal pressure and pressurizes the mold 8 outward. At this time, since the movable platen side is pushed off by hydraulic pressure, the resin pressure acts largely on the support platen 2 side, and an elongation ΔL1 of the tie bar 4 occurs there.

With this new extension of the tie bar 4, the support plate 2 moves together with the mold, so the mold 8 opens by a dimension equal to the amount of elongation ΔL1, and a mold clamping force proportional to the amount of elongation is applied to the mold 8. Acts as secondary mold clamping force.

At this time, the tie bar length increases +Δ and becomes +ΔL1.

From the point at which the compression process injection filling is completed, the secondary mold clamping force due to the extension of the tie bars 4 becomes an elastic deformation restoring force in the tie bars 4 and turns into a force that compresses the molded product.

This compressive force acts in the direction of closing the mold 8 until the cooling of the molded product is completed, and the opening amount of the mold 8 is reduced to ΔL2. The amount of compression at that time can be expressed as ΔL - ΔL2.

Next, the behavior of the molten resin in the cavity from its flow to its assimilation, that is, how the pressure (P), specific volume (V), and temperature (T) of the resin change during molding, is determined by the P- This is a change that follows the V-7 curve.

Figure 8 shows the PVT curve and the path of the injection process.The horizontal axis is the resin temperature (T), the vertical axis is the specific volume (V), and the curve is drawn using the resin pressure (P) as a parameter. be.

Normally, when considering injection molding means, its characteristics can be considered by noting how to trace each point on the diagram.

Therefore, considering the injection compression process with reference to FIG. 8, first, by heating at room temperature, the temperature rises from 1 to 2 along the isobar line of normal pressure (1 Kg/cII).

When injection begins, the pressure rapidly increases from ■ to ■.

Further, when the resin has finished filling the cavity, a compression process begins, and cooling progresses from (1) to (1) while being compressed.

After the compression process is completed, the molded product is naturally cooled to room temperature.

For molded products that require dimensional accuracy such as optical desks and lenses, shrinkage rate becomes an issue, and in order to obtain high-precision, high-quality molded products, the molding route will vary depending on the shape of the molded product, material, and molding temperature. , it is necessary to perform optimal control of the cavity internal pressure.

Figure 9 shows various molding routes for injection compression molding of acrylic resin, and the molding routes at various molding shrinkage rates from the above molding route are as follows: Mold shrinkage ratio Specific volume Molding route (%) <c1
13/g> 0.64 0.856 0-4-8-12-
130.47 0.851 0-3-7-1
1-12-130.20 0.844 0-
2-6-10-12-130.00 0.839
0-1-5-9-12-13 The mold clamping force of an injection compression molding machine depends on the elongation of the tie bar 4, and for example, the mold clamping force at the end of indexing is Δ[0+ΔL1, and the mold clamping force at the end of compression is Δ[0+ΔL1. The clamping force is proportional to ΔL0+ΔL2, and depends on the tie bar extension amount ΔL0 of the -blow mold clamping force.

However, when performing compression molding by expanding and contracting the tie bars 4 with an injection compression molding machine equipped with a direct-pressure mold clamping device, the mold clamping device clamps the mold to the end of the clamping stroke, and the injection compression molding Therefore, the amount of tie bar extension ΔLo when the mold is clamped with the maximum stroke in the next mold clamping is fixedly determined by the stroke of the mold clamping device at the design stage and the mold thickness of the mold 8 attached thereto. If the molded product shape, resin material, or temperature changes, it becomes impossible to make fine adjustments to the optimal cavity internal pressure.

This invention was devised to solve the above problems of the conventional injection compression molding machine, and its purpose is to provide an adjustment mechanism that can arbitrarily change the primary mold clamping force according to molding conditions. Our objective is to provide an injection compression molding machine.

[1! Means for Solving the Problem] The feature of the present invention according to the above object is that the mold clamping device is configured such that a tie bar, which is provided across a pair of support plates and fixed at both ends, is expanded by the internal pressure of the cavity during the injection process. In an injection compression molding machine, the mold is opened slightly by the internal pressure of the cavity, while the elastic deformation restoring force of the tie bar is applied to the mold as the molded product cools after the gate seal, and the molded product is compressed. The length and the operating stroke of the mold clamping ram are changed by an adjustment mechanism using screw means, so that the extension amount ΔLo of the tie bar during the next mold clamping can be adjusted.

[Function] In the above configuration, if the operating stroke of the mold clamping ram is increased by rotating the adjustment mechanism, or if the length between the support plates of the tie bars is decreased, the elongation of the tie bars after the mold is closed increases, and the mold The mold clamping force that acts secondarily on the mold also increases, and the compressive force due to the elastic deformation restoring force of the tie bars also increases.

On the other hand, if you reduce the operating stroke of the mold clamping ram or increase the length between the support plates of the tie bars, the elongation of the tie bars after the mold is closed will become smaller, and the mold clamping force acting on the mold will also become smaller. The compressive force due to the elastic deformation restoring force of the tie bar decreases.

[Embodiments] FIGS. 1 to 5 show some embodiments of the present invention. In the figures, 11.12 is a support plate installed on the machine base 13, and 14.14 is a support plate 11.12. Four tie bars are installed across the area, and both ends are inserted into the corners of the support plate and fixed thereto, and the movable plate 17 connected to the mold clamping ram 16 of the mold clamping cylinder 15 is moved to the tie bars 14 and 14. freely supported.

A pair of split molds 18 are attached to opposing sides of the support plate 12 and the movable plate 17. This mold 18 is sufficiently WAw4 so that the thermal expansion does not vary depending on the temperature of the material during injection molding.

Further, the support plate 11 with the mold clamping cylinder 15 is fixed to the machine base, but the support plate 12 with the mold 18 attached is
Although omitted in the drawing, the movable platen 1 is designed to move on the machine base within a range that allows the extension of the tie bars 14 and 14.
The linear bearing guide for linear motion on the machine base, which is shared with 7, is provided on the machine base via a linear bearing for linear motion.

Furthermore, the mold clamping ram 16 has sufficient rigidity to withstand high pressures during mold clamping and injection, and all high pressures during mold clamping and injection are absorbed by the amount of extension of the tie bars 14 and 14.

In order to realize injection compression molding, the tie bars 14 and 14 are stretched by an amount predicted from the relationship between the volumetric shrinkage rate of the molded product and the cavity capacity due to the high pressure inside the cavity during the injection process. As in, some 148.
14a is formed to have a small diameter.

Embodiment 1 (Fig. 1) In this embodiment, a primary mold clamping force adjustment mechanism 20 is provided between the mold clamping ram 16 and the movable platen 17, and the adjustment mechanism 20 is screwed together. A cylindrical screw member 21.2
It consists of 2. Of these screw members 21 and 22, the inner screw member 21 is fixed to the tip of the mold clamping ram 16, and the outer screw member 22 is rotatably attached to the back surface of the movable platen 17 with a retaining ring 23.

Further, a scale 24 indicating the amount of rotation is provided on the outer periphery of the screw member 22.

In such an injection compression molding machine, the movable platen side can be moved forward and backward by rotating the screw member 22, which allows the mold clamping ram 16 to move forward and backward.
Since the operating stroke of the
Even when the material resin, temperature, etc. change, the tie bar 1
4 can be given appropriate elongation, and the cavity internal pressure can be delicately adjusted according to changes in molding conditions.

Embodiment 2 (FIGS. 2 and 3) In this embodiment, an adjustment mechanism 20 is provided between the support plate 11 and the tie bar 14°14.

The adjustment mechanism 20 includes a threaded portion 25 provided at the tie bar end,
The threaded portion 2 is fitted into a part of the tie bar insertion hole of the support plate 11.
5, a chain 27 that rotates the nut member 26, and a drive gear 28 thereof.

The chain 27 meshes with a gear in a groove provided around the nut member 26, is passed around each nut member 26, and is circulated by a driving gear 28 so as to rotate all the nut members 26 at the same time. It acts on As a result, the length of the tie bar between the support plates changes, so a thrust force is generated in the axial direction on the tie bar 14.14 inserted into the support plate 11, and this thrust force is applied to the other support plate 12 connected to the tie bar 14.14 (see Fig. 1). See above>, the support plate 12 is moved together with the mold 18 into the movable plate 1.
Move forward and backward relative to 7. This movement causes the tie bar 14.
Since the amount of elongation of the tie bar 14 also changes, even if the molding conditions are changed, it is possible to give the tie bar an appropriate elongation as in the above embodiment.

Embodiment 3 (FIG. 4) In this embodiment, the adjustment mechanism 20 shown in Embodiment 2 is attached to the support plate 1.
In this case, since the tie bars 14 and 14 are fixed to the other support plate 11, the support plate 1
2 is directly pushed by the nut member 26 and moves relative to the movable platen 17. As a result, the elongation of the tie bar can be obtained in accordance with the molding conditions.

Embodiment 4 (Fig. 5) In this embodiment, an adjustment mechanism 20 is provided between the mold clamping cylinder 15 and the mold clamping ram 16. It consists of an adjusting ring 30 having a diameter of 30 mm, and an adjusting cylinder 31 interposed between the adjusting screw 30 and the mold clamping ram 16 by screwing a screw on the outer periphery of the adjusting ring 30. A member 33 is connected to the inner end of the adjustment cylinder 31 as a receiver for the piston 32, and the position of the member 33 can be moved back and forth by rotation of the adjustment cylinder 31 to adjust the maximum stroke. It is. Further, the rotation of the adjustment cylinder 31 is regulated within a certain range by a set pin 34 that passes through the adjustment ring 30 and inserts its tip into an annular groove on the outer periphery of the adjustment ring.

In this embodiment, the maximum forward movement position of the mold clamping ram 16 can be determined by operating the adjustment tube 31, so that it is possible to ensure the extension of the tie bar in accordance with the molding conditions.

[Effects of the Invention] As described above, the present invention extends the tie bars to temporarily clamp the mold, and further extends the tie bars by the cavity internal pressure to secondarily clamp the mold, thereby sealing the gate. In an injection compression molding machine that compresses and molds a molded product by applying the elastic deformation recovery force of the elongated tie bar to the molded product as the molded product cools down, the length of the tie bar and the operating stroke of the mold clamping ram are controlled by the screw means. By changing the adjustment mechanism, the amount of elongation of the tie bars during the next mold clamping can be adjusted, so even if the molding conditions change, it is possible to obtain the appropriate primary mold clamping force due to the elongation of the tie bars. This allows molding to be carried out under appropriate compressive force due to the elastic deformation and restoring force of the tie bar.

Further, since a screw means is used as the adjustment mechanism, the structure is not particularly complicated, and delicate adjustments can be easily made by rotation.

[Brief explanation of drawings]

1 to 5 show embodiments of an injection compression molding machine according to the present invention. FIG. 1 is a cross-sectional plan view of the main part of the first embodiment, and FIG. FIG. 3 is a front view of the support plate, FIG. 4 is a cross-sectional plan view of the main part of the third embodiment, and FIG. 5 is a cross-sectional plan view of the main part of the fourth embodiment. Figure 6 is an explanatory diagram of the operation of an injection compression molding machine, Figure 7 is a diagram of the relationship between mold clamping force and tie bar elongation, Figure 8 is a diagram of the molding path on the PVT curve, and Figure 9 is a diagram of the molding path on the PVT curve. It is various molding path diagrams. 11.12... Support plate 14... Tie bar 15... Mold clamping cylinder 17... Movable plate 20... ...Adjustment mechanism 21.22...Screw member 23...Retaining ring 25...Threaded portion 27...Chain 29... Bolt 31... Adjustment barrel 33... Receiver is member 13... Machine base 16... Mold clamping ram 18... ... Mold 24 ... Scale 26 ... Nut member 28 ... Drive gear 30 ... Adjustment ring 32 ... Piston 34...Set bin

Claims (2)

[Claims] (1) A tie bar, which is fixed at both ends across a pair of support plates, expands due to mold clamping force and cavity internal pressure, and as the molded product cools after gate sealing, the elastic deformation restoring force of the tie bar is reduced. In an injection compression molding machine that compressively molds a molded product by acting on the mold, the operating stroke of the clamping ram is changed by a screw means between the mold clamping ram and the movable platen, and the amount of tie bar extension during mold clamping is adjusted. An injection compression molding machine characterized by being provided with an adjustment mechanism for varying the. (2) A tie bar, which is fixed at both ends across a pair of support plates, expands due to mold clamping force and cavity internal pressure, and as the molded product cools after gate sealing, the elastic deformation restoring force of the tie bar is reduced. In an injection compression molding machine that compressively molds a molded product by acting on a mold, an adjustment mechanism is installed between the support plate and the tie bar to change the length of the tie bar using screw means to vary the amount of tie bar extension during mold clamping. An injection compression molding machine characterized by being provided with.