JPH0645164B2 - Injection compression molding machine - Google Patents

Description

Detailed Description of the Invention

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection compression molding machine used for molding a synthetic resin such as a lens or a disk plate of an optical disk that requires strict shape accuracy in the submicron unit. [Prior Art] In this type of injection compression molding machine, in the process of filling the cavity of the injection process with the synthetic resin material, the volume shrinkage ratio of the material to be molded due to the high pressure generated in the cavity is lost. From the relationship of mold volume, the length of tie bar, so that the tie bar can be expanded by the required amount and the mold can be opened by the required amount.
Predetermined thickness and elastic modulus of material, high-pressure energy of injection is stored in the form of expansion of tie bar, and when the gate seal is completed, as the cooling of the molded product progresses, elasticity of the tie bar expanded in the thickness direction of the molded product. Apply the deformation recovery force to the mold,
The molded product can be compressed for precision molding. FIG. 6 is a process explanatory view of the injection compression molding machine. In the figure, reference numerals 1 and 2 are support boards installed on the machine base 3, 4 and 4 are tie bars provided over the support boards 1 and 2, and both ends are supported. Board 1,
The tie bars 4, 4 are inserted through the two corners and fastened.
A movable platen 7 connected to the mold clamping ram 6 of the mold clamping cylinder 5 is movably supported. Reference numeral 8 denotes a mold, which is attached to the opposing surfaces of the support board 2 and the movable board 7. Further, the support board 1 having the mold clamping cylinder 5 is fixed to the machine base 3, but the support board 2 to which the mold 8 is attached is
The tie bars 4 and 4 are provided on the machine base so that the tie bars 4 and 4 can be moved within an allowable range. The relationship between the elongation of the tie bar 4 and the mold clamping force in the mold clamping process, the injection process, the compression process and the like in such an injection compression molding machine will be described below with reference to FIGS. 6 and 7. Clamping Step (Primary Clamping) First, when the mold clamping ram 6 is moved back and forth and the mold 8 is closed, there is a margin of ΔL _{0 for} the mold clamping ram 6 to move, and the tie bar 4 does not stretch. The tie bar length at this time is L. Further, when the mold clamping ram 6 is moved to the mold clamping stroke end at high pressure, that is, ΔL ₀ , the tie bar 4 is pressurized to ΔL _0.
Only, the tie bar length is L + ΔL ₀ , and the primary mold clamping force proportional to ΔL ₀ is generated. Injecting process When molten resin is injected and filled into the cavity of the die 8 in the state of primary mold clamping, the resin pressure generated in the filling process becomes an internal pressure, and the die 8 is pressed outward. At this time, the movable plate side is pushed off by hydraulic pressure,
Elongation ΔL ₁ occurs in the tie bar 4 due to the pressure applied by the resin pressure. With the new extension of the tie bar 4, the support plate 2 moves together with the die 8, so that the die 8 opens by a dimension equal to the extension amount ΔL ₁ and a die clamping force proportional to the extension amount is applied to the die 8. Acts as a secondary mold clamping force. At this time, the tie bar length becomes ΔL ₀ + ΔL ₁ of L +. Compressing Step From the time when the injection filling is completed, the secondary mold clamping force due to the extension of the tie bar 4 becomes an elastic deformation recovery force in the tie bar 4 and changes into a force for compressing 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 before the mold opening becomes ΔL ₂ . The amount of compression at that time can be represented as ΔL ₁ −ΔL ₂ . Next, the behavior of the molten resin in the cavity from the flow to the solidification, that is, the way of changing the resin pressure P, the specific volume V, and the temperature T at the time of molding is P for each resin.
The change is according to the -VT curve. FIG. 8 shows a P-V-T curve and the history of the injection process. The horizontal axis represents temperature T, the vertical axis represents specific volume V, and the curve is plotted using resin pressure P as a parameter. . Usually, when considering the injection molding means, its characteristics can be considered by describing how each point on the diagram is traced. Considering the injection compression process with respect to FIG. 8, first, the temperature rises from I to II along the isobar of normal pressure (1 kg / cm ² ) by heating at room temperature. When injection begins, the pressure in the cavity rapidly increases to a certain value I to III. Further, when the resin has completely filled the cavity, a compression process is started, and while being compressed, the material shrinks by cooling and progresses from III to I. The molded product taken out after completion of the compression step is cooled to its normal temperature by itself. [Problems to be Solved by the Invention] In the case of molded products that require dimensional accuracy such as optical disks and lenses, in order to obtain molded products of high accuracy and high quality, the molding process depends on the shape, material, and molding temperature of the molded product. Differently, it is necessary to perform optimum control of the cavity internal pressure. The mold clamping force of injection compression molding depends on the elongation of the tie bar 4,
Further, for example, the mold clamping force at the time of completion of injection is ΔL ₀ + in FIG.
The [Delta] L _1, the clamping force during compression completion becomes proportional to ΔL ₁ + ΔL _2. However, in the case of performing compression molding by expanding and contracting the tie bar 4 in an injection compression molding machine equipped with a direct pressure type mold clamping device, as described above, the mold clamping device clamps to the mold clamping stroke end and performs injection compression molding. Therefore, the amount of tie bar expansion ΔL ₀ at the time of maximum stroke mold clamping in the primary mold clamping is fixedly determined by the stroke of the mold clamping device at the design stage, the mold thickness of the mold 8 attached to the groove, etc. When the shape, material resin, temperature, etc. of the product change, it becomes impossible to finely adjust the optimum cavity pressure. The present invention was conceived in order to solve the above-mentioned problems of the conventional injection compression molding machine, and its object is to change the tie bar elongation amount according to molding conditions and arbitrarily change the primary mold clamping force. An object of the present invention is to provide an injection compression molding machine provided with an adjusting mechanism capable of performing the above. [Means for Solving the Problems] The feature of the present invention according to the above-mentioned object is that a tie bar provided by fixing both ends to a pair of supporting plates extends by a mold clamping force and a cavity internal pressure, and after a gate seal is performed. In an injection compression molding machine in which the elastic deformation restoring force of the tie bar is applied to the mold as the molded product cools to compress and mold the molded product, the mold clamping ram moves forward between the mold clamping ram and the movable plate. This is to provide an adjusting mechanism with screw means for changing the movable platen position during the primary mold clamping and varying the amount of tie bar expansion during the mold clamping. Another feature is that the adjusting mechanism using the screw means is provided between the support plate and the tie bar, and the length between the support plates of the tie bar can be changed to change the amount of tie bar expansion during mold clamping. is there.

[Action]

In the above configuration, when the movable platen position at the time of the mold clamping ram is most advanced (during primary mold clamping) is moved to the support platen side (right side in the figure) by the rotation of the adjusting mechanism, or the length between the support platen of the tie bar is reduced,
The expansion of the tie bar at the time of primary mold clamping becomes large, the mold clamping force that acts secondarily on the mold also becomes large, and the compressive force due to the elastic deformation restoring force of the tie bar also increases. On the contrary, if the movable platen position at the most forward movement of the mold clamping ram is moved to the support plate side (left side in the figure) opposite to the above, or if the length between the tie bar support plates is increased, the tie bar expansion during primary mold clamping will occur. Becomes smaller, the mold clamping force that temporarily acts on the mold becomes smaller, and the compressive force due to the elastic deformation restoring force of the tie bar decreases.

【Example】

1 to 5 show some embodiments of the present invention. In the drawings, 11 and 12 are support plates installed on a machine base 13, and 14 and 14 are provided over the support plates 11 and 12. With four tie bars, both ends are inserted into and fixed to the corners of the support plate, and the tie bars 14 and 14 movably support a movable plate 17 connected to a mold clamping ram 16 of a mold clamping cylinder 15. Has been done. Reference numeral 18 denotes a pair of split molds, which are attached to the opposing side surfaces of the support plate 12 and the movable plate 17. The mold 18 is sufficiently temperature-controlled so that the thermal expansion does not change each time under the influence of the material temperature at the time of injection molding. The support board 11 having the mold clamping cylinder 15 is fixed to the machine base, but the support board 12 having the mold 18 attached thereto is
Although not shown in the drawing, the movable plate 1 is designed to move on the machine base within a range in which the tie bars 14 and 14 can be extended.
The linear bearing guide for linear motion on the machine base which is shared with 7 is provided on the machine base via the linear bearing for linear motion. The mold clamping ram 16 has sufficient rigidity to withstand high pressures during mold clamping and injection, and the high pressures during mold clamping and injection are all absorbed by the amount of expansion of the tie bars 14, 14. In order to realize injection compression molding, the tie bars 14 and 14 are stretched by a required amount due to the relationship between the volumetric shrinkage rate of the molded product to be molded and the cavity capacity, under the high pressure in the cavity of the injection process. , Part 14a, 14a
Is formed with a small diameter. First Embodiment (FIG. 1) In this embodiment, an adjusting mechanism 20 for the primary mold clamping force is provided between the mold clamping ram 16 and the movable platen 17, and the adjusting mechanisms 20 are screwed with each other. Cylindrical screw parts 21, 22 that fit together
Consists of. Of the 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 plate 17 with a stop 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 can be moved back and forth by the rotation of the screw member 22, which changes the position of the movable platen when the mold clamping ram is most advanced. Even when the temperature or the like changes, the tie bar 14 can be appropriately stretched, and the internal pressure of the cavity can be finely adjusted according to changes in the molding conditions. Second Embodiment (FIGS. 2 and 3) In this embodiment, an adjusting mechanism 20 is provided between the support board 11 and the tie bars 14 and 14, and the adjusting mechanism 20 is a screw portion provided at the tie bar end. 25 and a nut member 26 fitted into the tie bar insertion hole of the support board 11 and screwed into the screw portion 25.
And a chain 27 for rotating the nut member 26 and its drive gear 28. The chain 27 meshes with a gear in a groove provided around the nut member 26, is hung over each nut member 26, and circulates by a drive gear 28 to rotate all the nut members 26 at the same time. To work. As a result, the tie bar length between the support boards changes, so that a thrust force is generated in the tie bars 14, 14 inserted in the support board 11 in the axial direction, and this thrust force is applied to the other support board 12 (the first support board 12 connected to the tie bars 14, 14). (Refer to the drawing), the support plate 12 moves forward and backward with respect to the movable plate 17 together with the mold 18. This movement also changes the amount of elongation of the tie bars 14, 14, so that even if the molding conditions are changed, the tie bars can be given an appropriate amount of elongation as in the first embodiment. Third Embodiment (FIG. 4) In this embodiment, the adjusting mechanism 20 shown in the second embodiment is provided on the support board 12 side, and the tie bars 14 and 14 are fixed to the other support board 11. Support plate 12
Is directly pushed by the nut member 26 and moves with respect to the movable plate 17. As a result, the tie bar can be stretched according to the molding conditions. Embodiment 4 (FIG. 5) In this embodiment, an adjusting mechanism 20 is provided between the mold clamping cylinder 15 and the mold clamping ram 16, and an inner screw attached to the opening of the mold clamping cylinder 15 with a bolt 29. The adjusting ring 30 has an adjusting ring 30, and the adjusting ring 30 is screwed with an outer peripheral screw, and the adjusting cylinder 31 is interposed between the adjusting screw 30 and the mold clamping ram 16. A receiving member 33 for the piston 32 is provided inside the adjusting cylinder 31.
Are connected, and the position of this receiving member 33 is adjusted to the adjustment tube 31.
It is possible to adjust the maximum forward position of the piston 32 by moving the piston 32 back and forth. Further, the rotation of the adjusting cylinder 31 is performed by passing through the adjusting ring 30 and inserting the tip portion into the annular groove on the outer periphery of the adjusting ring.
It is regulated within a certain range by 4. In this embodiment, the most advanced position of the mold clamping ram 16 is
Since it can be determined by operating the adjusting cylinder 31,
As a result, it is possible to secure the elongation of the tie bar suitable for the molding conditions.

【The invention's effect】

As described above, according to the present invention, the tie bar is stretched to temporarily clamp the mold, and the tie bar is further stretched by the cavity internal pressure to secondarily clamp the mold. In an injection compression molding machine in which the elastic deformation recovery force of the expanded tie bar is applied to the molded product as it cools, and the molded product is compression molded, the movable platen position during primary mold clamping and the tie bar inter-plate length can be adjusted. Since it is configured so that the amount of tie bar expansion during mold clamping can be adjusted by changing the adjustment mechanism using screw means, it is possible to obtain the primary mold clamping force due to proper tie bar elongation even when molding conditions change. Molding can be performed under a compressive force due to an appropriate elastic deformation restoring force of the tie bar. Further, since the screw means is used as the adjusting mechanism, the structure does not become particularly complicated, and there is a feature that delicate adjustment can be easily performed by rotating.

[Brief description of drawings]

The drawing shows an injection compression molding machine according to the present invention, and FIG. 1 is a cross-sectional plan view of a main portion of a first embodiment. FIG. 2 is a cross-sectional plan view of essential parts of the second embodiment. FIG. 3 is a front view of the support board. FIG. 4 is a cross-sectional plan view of essential parts of the third embodiment. FIG. 5 is a cross-sectional plan view of essential parts of the fourth embodiment. FIG. 6 is an explanatory view of the operation of the injection compression molding machine. FIG. 7 is a relationship diagram between the mold clamping force and the amount of extension of the tie bar. FIG. 8 is a molding path diagram on the PVT curve. 11, 12 ... Supporting board 11, 12 ... Supporting board, 13 ... Machine stand 14 ... Tie bar 15 ... Mold clamping cylinder, 16 ... Mold clamping ram 17 ... Movable board, 18 ... Mold 20 ... … Adjustment mechanism 21,22 …… Screw member 23 …… Stop ring, 24 …… Scale 25 …… Screw part, 26 …… Nut member 27 …… Chain, 28 …… Driving gear 29 …… Bolt, 30 …… Adjustment Ring 31 …… Adjustment tube, 32 …… Piston 33 …… Receiving member, 34 …… Set pin

Claims (2)

[Claims] 1. A tie bar provided by fixing both ends to a pair of support plates extends by mold clamping force and cavity internal pressure, and elastic deformation restoring force of the tie bar is accompanied by cooling of a molded product after gate sealing. In the injection compression molding machine that compresses and molds the molded product by acting on the mold, by changing the movable platen position between the mold clamping ram and the movable platen during the primary mold clamping by advancing the mold clamping ram, An injection compression molding machine characterized in that an adjustment mechanism is provided by means of screw means for varying the amount of tie bar expansion during tightening. 2. A tie bar provided by fixing both ends to a pair of supporting plates extends by a mold clamping force and a cavity internal pressure, and elastic deformation restoring force of the tie bar is accompanied by cooling of a molded product after gate sealing. In the injection compression molding machine that applies pressure to the mold to perform compression molding of the molded product, the length between the support plate of the tie bar at the time of the primary mold clamping is changed between the support plate and the tie bar. An injection compression molding machine characterized in that an adjusting mechanism by means of screw means for varying the amount of tie bar expansion is provided.