JPS6327228A - Mold clamping apparatus of injection and compression molding machine - Google Patents

Abstract

PURPOSE:To improve a transfer property and strain by shortening a pressure raising time when an injection process is transferred to a compression process, by respectively pressurising both of the front and rear chambers of a mold clamping ram during the injection process by separate pressure sources and releasing the pressure of the mold clamping ram when the injection process is transferred to the compression process. CONSTITUTION:When a movable platen 2 reaches a set position, said platen is stopped temporarily and the hydraulic oil of a hydraulic source 34 is introduced into a chamber-B and the hydraulic oil of a hydraulic source 35 is introduced into an chamber-A and the outputs of both oil chambers are allowed to be well balanced to perform positional control. Therefore, strain due to flow resistance is reduced. When a predetermined amount of a resin is injected, the pressurizing force of the chamber-A is increased while pressurization is applied to the chamber-B to allow the movable platen to advance by difference pressure. whereupon, the lowering in the spreading speed of the leading end part of the molten resin with the advance of the molten resin is relaxed and force right-angled to the flow direction of the molten resin is applied to said resin and, therefore, the orientation of the resin in the flow direction is reduced. When the completion of mold closing and filling is detected, the pressure of the chamber-B is released and the force negated by the output of the chamber-B is added to the chamber-A to perform the raising of pressure to compression pressure rapidly and, therefore, a transfer property can be enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a mold clamping device for an injection compression molding machine suitable for use in molding bidet sub-disks, draw discs, lenses, and the like.

[Prior Art] In the Kenzan Getsu-Shin molding, which is generally used to mold the above-mentioned molded products, molten resin is injected and filled into a mold that is closed at low pressure.
The Gino method involves slightly opening the mold using injection pressure and then compressing it by applying high pressure to the movable platen, or by injecting and filling the molten resin into the mold that is slightly open in advance, and then strongly clamping the mold after filling is completed. There are ways to perform compression.

In any of the above cases, it is necessary to accurately determine the slightly open position of the mold, and therefore, in order to prevent the movable platen from retreating from the predetermined position due to indexing pressure, It can be held mechanically, or it can be held hydraulically by controlling the pressure in the chamber behind the J-shaped mold clamping shim with a →j-bo valve for position feedback control.

[Problems to be Solved by the Invention] However, in the above conventional method, the force acting on the rear chamber of the mold clamping ram during the injection process is maintained mechanically (very low, and is maintained hydraulically). If the pressure is maintained at a very low level to balance the injection pressure, it is necessary to switch from low pressure to high pressure when moving to the compression process, so it takes time to build up the back pressure, and during that time the molten resin solidifies. I did it,
There were problems with deterioration of transferability and generation of distortion due to internal stress.

This invention was made in view of the above circumstances, and is a mold clamping method for a new injection compression molding machine that can shorten the pressure increase time when transitioning from the injection process to the compression process and improve transferability and distortion. The purpose is to provide equipment.

[Means for solving the problem] The inventions of 1-1 J and Rinaru Q above have 11 molds on the fixed plate and the movable plate that can change the capacitor volume by moving one of the molds. A mold clamping device for an injection compression molding machine, comprising a high-speed moving means for moving the movable plate back and forth at high speed;
A first pressure source selectively connected to the front chamber of the mold clamping ram that moves the moving platen forward and backward, and a second pressure horn source connected to the mold clamping ram rear chamber via a servo valve. A pressure detector for detecting the pressure in the ram rear chamber and a position detector for detecting the position of the movable platen, connected to the pressure detector and the position detector,
The gist of the present invention is to include a control device that provides a command signal to a servo valve by calculating each detected value and a set value.

[Function 1] With the above configuration, both the front and rear chambers of the mold clamping ram can be pressurized by separate pressure sources during the injection process, so the rear chamber of the mold clamping ram has a force that balances the injection pressure and a mold A force is generated that balances the output of the front chamber of the tightening ram.

When moving to the compression process, the pressurization of the mold clamping ram front chamber is stopped and released to the oil tank.

As a result, the pressure in the rear chamber of the mold clamping ram is instantaneously added to the pressure that was canceled by the output of the front chamber, and the differential pressure from that pressure to a predetermined pressure becomes the second pressure. The pressure is boosted by the source.

1 Implementation Example 1 The "possible Iυ" board 2 has a step 41 that can freely slide back and forth on a tie bar 5 that is horizontally suspended between the fixed board 1 and the mold clamping cylinder 3, and the back side is inserted into the mold clamping cylinder. The mold clamp 114 is connected to the mold clamp 114.

The tightening ram 4 has a small diameter cylinder part inside, and a rear J-shaped booster ram 6 is inserted into the cylinder part, and the large diameter part of the tip of the booster ram 6 pushes the cylinder part 2. It is divided into two oil chambers, C chamber and D chamber.

Furthermore, the mold clamping ram 4 divides the interior of the mold clamping cylinder 3 into two oil chambers, a Δ chamber and a B chamber.

The C chamber and D chamber form a differential circuit with switching valves 26 and 27, and together with a pressure source 34 consisting of a pump 20, a motor 21, a relief valve 24, a flow valve 25, an oil tank 33, and an oil tank. 33, the A chamber is connected via the servo valve 28 to another pressure source 3 () consisting of an oil tank 33, a pump 22, and a motor 23, and is also connected to the oil tank 33, and the B chamber is connected to the oil tank 33. is connected to the hydraulic power source 34 and the air tank 33 via a switching valve 31 and a relief valve 32.

The rear portions of the prefill valves 10.11 are connected to each other and to the oil tank 33, and the opening oil chambers E and F of each prefill valve 10.11 are connected to pressure horns via switching valves 29.30, respectively. source a34 and oil tank 3
Connected to 3.

Further, a pressure detector 40 for detecting the pressure in the A chamber and a position detector for detecting the position of the movable platen 2 include an amplifier 40° 43, an analog switch 44, a comparator 45, and a characteristic compensator 46.
, amplifier 47, controller 48, setting devices 49a to 49
n, and is connected to a control device 50 that provides a signal to the servo valve 28.

Movable! A movable mold 7 is provided on the mold mounting surface of I42, which is equipped with a stamper (not shown in the drawing) and a cavity surface, and is integrally formed with a flange that protrudes outside the cavity surface. On the opposite surface of the movable mold 7, there is provided a fixed mold having an outer part and a stamper that fit into the inner circumferential surface of the flange, and a sprue hole communicating with the cavity surface.

Further, the movable mold 7 and the fixed mold 8 have a temperature control circuit, although not shown in the drawing. The temperature control circuit heats the mold with pressure-controlled steam to a temperature two times higher than the softening point of the material resin before injection starts, and heats the mold to a temperature lower than the softening point of the material resin with cooling water after injection filling. Adjust the temperature.

Setting values for the mold closing method stop position, mold clamping filling speed, and compression pressure (multistage) are set in the setting devices 49a, 49b to 49n.

The relief valve 24, the flow valve 25, and the switching valves 26, 27, 29, 30, and 31 are connected to an oil control device equipped with a separate setter group (not shown).

Next, the operation will be explained.

[High-speed mold closing]

In the mold open state shown in FIGS. 1 and 2, each switching valve 26
Set r127 to 0129 to r, 30 to r, 31 to n14, and turn off the novo valve 28.

Thereby, pressure oil from the pressure source a34 is supplied to the D chamber, and the movable platen 2 moves forward at high speed. Further, the oil in the C chamber, which is reduced as the movable platen 2 moves forward, is transferred to the D chamber via the switching valves 26 and 27, thereby operating the movable platen 2 at a higher speed.

At the same time, chambers E and F are pressurized, and the prefill valve 10.
11 is open, the pressure is negative, and the oil discharged from chamber B and the oil in the oil tank 33 are sucked into the chamber.

[Mold closing method stop: Injection start]

The position where the movable platen 2 is set in advance by high-speed mold closing (the position where the fixed mold 8 and the movable mold 7 are fitted as shown in Fig. 3)
When the position is reached, the switching valves 26, 27 are set to n, 29° 30, 31 are set to 1, the servo valve 28 is turned on to temporarily stop the movable platen 2, and injection is started while maintaining the position by position feedback control.

That is, the B chamber is pressurized by introducing pressure oil from the hydraulic source 34 through the switching valve 31, and the △ chamber is pressurized by the pressure oil from the hydraulic source 35 introduced through the servo valve 28. The position is controlled by rebalancing the output between the arm chambers using the servo valve 28.

In this state, as shown in FIG. 3, the volume of the cavity 51 is larger than the final dimensional state shown in FIG. 5 and the dimensional state taking into account the compression allowance shown in FIG.
Better fluidity can be obtained than with conventional injection compression molding, and since injection can be performed at high speed and low pressure, distortion due to flow resistance is reduced.

[Mold clamping filling]

As shown in Fig. 3, when a predetermined amount of molten resin 52 that does not fill the cavity has been injected, the movable platen is switched to speed feedback control (when the screw advances to a predetermined position) and is moved forward again at a predetermined speed. .

That is, while the B chamber is pressurized by the pressure source a34, the pressurizing force of the Δ chamber is increased, the output of the B chamber is made larger than the output of the B chamber, and the pressure difference is used to advance.

At this time, the pressure in chamber B is increased, and one minute of the pressure increase is discharged to the re-oil tank 33 by the relief valve 32.

In this state, the cavity volume is reduced as the mold closes, and the molten resin in the cavity 51 is spread out, so that the decrease in the spreading speed of the molten resin tip as injection filling progresses is alleviated, and the molten resin 52 is subjected to a force perpendicular to the flow direction, thereby reducing orientation in the flow direction.

Further, the spreading speed of the resin in this state is controlled by controlling the forward speed of the movable platen.

Then, the injection is completed just before the cavity is completely filled, and the movable plate then moves forward, causing the fourth
As shown in the figure, the mold has a cavity volume that takes into account the amount of compression, and the inside of the mold is filled with molten resin 52.

[Compression]

When the completion of mold clamping filling is detected by monitoring the mover position, chamber pressure, etc., the servo valve 2B is switched to pressure feedback control, controlled by the compression force command signal, and the switching valve 31 is moved to the r side. Switch.

As a result, the pressure of the movable platen is controlled, so the molten resin 52 in the cracker is compressed under pressure, and as in the compression process in normal injection compression molding, the P-V-T curve (the property of the plastic material is This diagram shows the relationship between volume and temperature, with temperature on the horizontal axis and specific volume on the combined axis, and plotting the volume at a given pressure for each 7i1M degree.It depends on each. As the temperature is lowered under pressure, you can see how the specific volume decreases accordingly.) The compression force is controlled in multiple stages to cool and solidify. As a result, distortion due to residual stress is further reduced, cooling shrinkage and orientation are alleviated, and a molded product 53 with improved transferability is molded.
Fig. 5 state).

In addition, when moving to the compression process, A, 8
Both chambers were pressurized, and chamber A was under a specified pressure, so chamber B was treated as pressure, and the force that was canceled out by the output of chamber 13 was instantly applied to chamber A. Since the decoration is applied, the compression pressure can be applied quickly, and the transferability can be further improved.

[Pressure release]

Upon completion of cooling and solidification, control device 50J sends a zero pressure command to relief valve 28 to relieve pressure in chamber A.

[Strong mold]

Next, turn off the power valve 28 and turn the switching valve 29 to r13.
Switch 1 to 9.

As a result, the B chamber is pressurized by the pressure of the hydraulic power source a34, and a strong mold is formed. At this time, as the mold clamping ram 4 retreats, the oil in the chamber is removed by the prefill valve 1 which is opened by the pressurization of the chamber E.
0 to the oil tank 33. Also room C, D
Since the chamber and the oil tank 33 are connected, oil is discharged from the D chamber, and the C chamber sucks oil from the D chamber and the oil tank 33.

As a result, the molded disk is released from the fixed mold 8.

(Between high-speed molds) Once the movable platen 2 has retreated to the predetermined position by powerful mold opening,
Turn off the switching valve 26, turn off the switching valve 27, turn off the servo valve 28, turn off the switching valve 29, turn off the switching valve 30, turn off the switching valve 30.
Switch 1 to n.

As a result, the C chamber is pressurized by the hydraulic power source a34, so the movable platen 2 moves back at high speed, and the oil in the D chamber is returned to the oil tank 33 via the switching valves 26 and 27.

In addition, the E chamber and F chamber are pressurized, and the prefill valves 10 and 1
As the mold clamping ram 4 retreats, the oil in the chamber (1) is transferred to the B chamber via the prefill valve 10, 11 and returned to the tank.

〔take out〕

When the movable platen 2 reaches the predetermined mold opening stop position, the switching valve 26
．． '27 to n1 servo valve 28 to 0'F1 switching valve 2
9 and 30, set the 01 switching valve 31 to n to stop the mold opening,
The molded product is taken out from inside the movable mold 7.

Thereafter, the above steps are repeated to continuously perform molding.

In this example, we used a device like the one shown in Figure 1.
= is not limited to each, and may be any value as long as the method according to the present invention can be implemented.

Also, since the temperature of the mold is controlled by heating and cooling, the formation of a skin layer can be suppressed, which is better, but this can also be done by cooling only.

Furthermore, it is preferable to perform injection process control on the injection device 9 side in the same manner as usual to ensure suitable molding conditions, and to modify the structure to enable high-speed injection.

= 12 - [Effect of the Invention 1 According to the present invention, since the pressure can be quickly increased during the transition from the injection process to the compression process, it is possible to prevent deterioration of transferability and distortion due to progress of cooling and solidification. This improves the quality of molded products.

[Brief explanation of the drawing]

The drawings illustrate a mold clamping device for an injection compression molding machine according to the present invention, and FIG. 1 is a schematic cross-sectional view thereof, and FIGS.
The figures are cross-sectional views of a mold sequentially showing the injection compression process. 1... Fixed plate 2... Movable plate 3... Mold clamping cylinder 4... Mold clamping ram 5... Tie bar
6... Booster ram 7... Movable type
8...Fixed type 9...Injection device 10, 11...Prefill valve 20.22...Pump 21.23...Motor 24, 32...Relief valve 25...Flow rate valve 26 , 27.29.31...Switching valve 28...Servo valve 34.35...Pressure source 40...Pressure detector 41...Position detector 4
2, 43.47... Amplifier 44... Analog switch 45... Comparator 46... Characteristic compensation section 48... Controller 49a, 49b, 49n -... Setting device 50.
··Control device

Claims (1)

[Scope of Claims] A mold clamping device for an injection compression molding machine, which is equipped with a fixed plate and a movable plate whose cavity volume can be varied by moving one of the molds, the movable plate being moved back and forth at high speed. A high-speed moving means, a first pressure source selectively connected to the front chamber of the clamping ram that moves the movable platen forward and backward, and a second pressure source connected to the rear chamber of the clamping ram via a servo valve. A pressure detector that detects the pressure in the rear chamber of the mold clamping ram, a position detector that detects the position of the movable platen, and are connected to the above pressure detector and position detector, and are A mold clamping device for an injection compression molding machine, comprising a control device that gives a command signal to a servo valve.