JPH05192976A - Molding control method for injection molding machine and device therefor - Google Patents

Abstract

PURPOSE:To provide a control device and an injection molding machine which forcibly feed necessary resin or the like properly only to a thick wall section where a sink mark is easily generated, grasp and control the shortest and proper cooling time and make the marks generated by a resin force feeding device extremely few and inconspicuous on a product. CONSTITUTION:An ejector plate 11 for retaining an ejector pin 14 and a pressurizing pin plate 6 for retaining a pressurizing pin 5 running through the ejector plate 11 are disposed in parallel, and a return pin 10 is disposed integrally with the ejector plate 11 in a manner of positioning its end face on a parting face of a mold at the time of mold closing. A compression spring 10a is interposed between the return pin 10 or the ejector plate 11 and the pressurizing pin plate 6, and the drive of pressurizing pin 5 and the drive of ejector pin 14 are combined by one driving section.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molding control method and apparatus for an injection molding machine.

[0002]

2. Description of the Related Art Conventionally, in an injection molding machine, as a method of preventing sink marks in a thick portion, there has been a method in which a male and a female dies are made to have a staggered structure after press-fitting a resin to compress the volume. This is known as a Rollinx mold. In this mold, as shown in FIG. 8, the pressing surface 16 is almost perpendicular to the dividing surface 17. When the resin is injected into the mold with a high pressure as shown in FIG. 7, the pressure of the resin in the cavity 4 overcomes the mold clamping force to slightly open the mold (FIG. 8). Since the pressing surface 16 is almost perpendicular to the dividing surface 17, even if the mold is slightly opened, the resin does not leak out. By appropriately limiting the injection amount of resin at the injection stage, the mold can be stopped by only slightly opening it. Next, in the cooling process, the molded product is compressed and solidified by the mold clamping force due to shrinkage of the resin. When it is solidified, it is sufficient to inject just enough resin to finish the mold. However, although the product molded in this way retains its dimensions very accurately, it has the drawback that it can only be used for molded products of simple shape.

Next, it is also known to use a projecting pin to further press-fit the resin accumulated at the tip of the projecting pin.
As shown in FIG. 9, a plurality of (three in the figure) push-in pins 19 are incorporated in the movable mold 18, and the push-in pins 19 are perpendicular to the surface of the flat plate-shaped molded product being molded. It can be pushed in. And if the pin 19 is pushed into the molded product by the same volume as the sink mark (Fig. 10), the sink mark can be eliminated (NIKKEI M
ECHANICAL February 1989).

However, this method has the following drawbacks. a) Since the pushing pin 19 is stopped on the surface of the molded product at the time when the pushing pin 19 is started to be pressed, it must be on the verge of solidification of the filled resin, which is difficult to control. b) Push the push pin 19 into the molded product to push the volume of the sink mark, and then push the push pin 19 on the surface of the molded product.
In order to control the position so that the trailing edge does not remain, specifically, the step must be 20 μm or less. In the mechanism shown in FIG. 9, complicated control such as feedback control cannot be avoided. c) Since the viscosity in the cavity 4 becomes high just before solidification, the pressure transmission effect is exerted only on the portion near the push-in pin 19, so that the product shape is limited to a wide range. d) With pressing by a single plate as shown in FIG. 9, it is not possible to select and use the pressurizing portion and the non-pressurizing portion, and the push pin operates even in a fine and complicated shape portion, so that there is no burrs. There is a drawback that it becomes easy to generate.

[0005]

SUMMARY OF THE INVENTION According to the present invention, a resin or the like is press-fitted into only a thick portion where sink marks are likely to appear, and the shortest and appropriate cooling time is grasped and controlled. An object of the present invention is to provide a control method that makes the product extremely insignificant when the device is press-fitted, and makes it inconspicuous, as well as an apparatus for implementing this method.

[0006]

[Means for Solving the Problems]

1) A pressurizing pin 5 slidable back and forth in a hole communicating with the cavity 4 provided in the mold is provided, and after the molten material is injected and filled into the cavity 4, it is immediately flush with the product surface of the cavity. Alternatively, the pressure pin 5 is advanced so as to hold the tip end surface of the pressure pin 5 at a predetermined position. 2) By the method of 1), the processing pin 5 was positioned in the thick part of the product and pressed. 3) By the method of 1), the hydraulic pressure source of the pressurizing pin drive unit is branched and used at the same set pressure as the pressure holding source for the injection screw for holding pressure after injection filling. 4) Further, by the method of 1), the pressure pin 5 is gradually brought closer to the same surface as the product surface by the correlation between the pressure pin pushing force of the pressure pin drive unit and the cavity internal pressure. 5) The molten state of the resin in the cavity 4 is grasped by the relationship between the backward position of the pressure pin 5 and the time required for it or the backward speed, and the pressure pin 5 is gradually brought closer to the product surface. 6) In the method of 1), when the pressure pin plate 6 is moved by the pressure pin drive unit and comes into contact with the ejector plate 11, the pressure pin tip surface and the cavity product surface become the same surface. I did it. 7) The ejector plate 11 for holding the protruding pin and the pressure pin plate 6 for holding the pressure pin 5 penetrating the ejector plate are arranged in parallel, and the mold part is closed when the mold is closed. Ejector plate so that the tip surface is located on the operating surface.
The return pin 10 is provided integrally with the valve 11, the compression spring 10a is interposed between the return pin 10 or the ejector plate 11 and the pressure pin plate 6, and the pressure pin drive and the projecting pin drive are performed. And are driven by a single drive unit. 8) One of the ejector plate 11 and the pressure pin plate 6 is provided with a sensor 13 at a position opposite to the other, and the sensor 13 is activated when both plates approach each other. Adjust the pushing force

[0007]

The construction of an injection molding machine for carrying out the method of the present invention will be described with reference to the drawings. Reference numeral 1 is an injection nozzle, 2 is a sprue, 3 is a runner, and 4 is a molding cavity.
A pressure pin 5 is slidable back and forth in a hole communicating with the cavity 4 provided in the mold, and its tip 5a is always held in the same plane as the surface of the thick portion of the cavity 4. 6 is a pressure pin plate, 7 is a mold mounting plate, and 8 is an ejector.

Reference numeral 9 is a fixed mold plate, and 10 is a return pin, which is constantly urged by a spring 10a in the returning direction (to the right in the drawing). Reference numeral 11 is an ejector plate, 12 is a step provided on the ejector plate 11, and the return pin 10
Is engaged with the stepped portion 12a. 13 is a pressure pin plate 6
The position sensors 14 and 14 for detecting the displacement of are the protruding pins of the molded product a.

The molten resin injected from the nozzle 1 in FIG. 1 passes through the sprue-2 and the runner-3 and is filled into the cavity-4. The tip 5a of the pressure pin 5 is regulated so that it is flush with the surface of the molded product a, and the rear end of the pressure pin 5 is a pressure pin plate.
The mold mounting plate 7 regulates the last retracted position.

FIG. 6 is a hydraulic system diagram of the injection molding machine, in which the screw pressure holding source for holding pressure after injection and filling of the molten resin and the hydraulic source of the drive unit of the pressurizing pin 5 are set to the same set pressure. The hydraulic power source is branched and used. In the conventional hydraulic circuit, if at least one hydraulic pressure source and its flow rate / pressure regulating valve are pressurized with the same pressure as the holding pressure,
ON / O directional switching valve that simply obtains ejector forward pressure
All you have to do is FF.

Now, after the injection filling has almost reached the end and a minute time has elapsed, the surface of the resin in the cavity-4 has begun to solidify, and then the ejector 8 has the same hydraulic pressure as the holding pressure H (FIG. 7) after injection.
To move forward (a servomotor system or different pressure may be used). At this time, the mold is closed, so return pin 1
At 0, the ejector plate 11 is pushed by the pressure pin plate 6 and the step 12a provided on the return pin 10 pushes the return pin 10 leftward in the figure. At this time, the return pin 10 is prevented from advancing by the fixed-side mold plate 9 and the ejector plate 11 is fixed (FIG. 2). At that position, the tip of the pressing pin 5 is pre-machined so that it is on the same surface as the surface of the cavity-4.

Immediately before this position, the position sensor 13- (FIG. 2)
Sends an ON signal, it is switched to a holding pressure L (FIG. 7) lower than the holding pressure H. At the same time, the timer is activated. Before the timer expires, the thick part in the cavity-4 is not solidified, and the pressure pin 5 retracts, that is, the ejector plate 1
1 moves backward and the position sensor 13 is turned off (FIG. 3). The holding pressure H rises again (FIG. 7), and the pressure pin 5 is advanced (FIG. 4).

When the thick portion is solidified, the cavity-4
Even if the timer expires, the position sensor 13 does not turn off. At this time the timer
The pressure pin plate 6 is moved forward with the holding pressure H for an arbitrary time from the time when the time measurement is completed to complete the holding pressure and cooling (FIG. 4).

Thereafter, when the mold is opened, the fixed side mold plate 9 does not prevent the return pin 10 from advancing, so that the product 15, sprue-2 and runner are formed by the pressing pin 5 and the projecting pin 14 as shown in FIG. 3 and are discharged.

As the above-mentioned applied operation, the forward movement of the pressurizing pin 5 is stopped when the holding pressure timer is completed, and the normal cooling timer is pushed out as shown in FIG. 5 when the timing is completed, and the position sensor 13 is turned on, It is also possible to program the pressing force as a function of the numerical value instead of the OFF value.

[0016]

[Effect] The tip of the pressurizing pin 5 incorporated in the movable side mold is regulated on the same surface as the surface of the molded product, and separately from this, the return pin 10 which can further advance when the mold is opened is provided. By pressing the return pin 10 before it is solidified, traces of the pressure pin 5 are not left on the surface of the product, so that the resin or the like can be appropriately and appropriately pressed into the thick portion where sink marks are likely to appear.

Further, the molten state of the resin in the cavity is detected by the retreating speed of the pressure pin 5, and the speed and the compression pattern of the return pin 10 and the cooling time are controlled in association with each other. As a result, it is possible to grasp and control the proper cooling time in the shortest time, and it is possible to minimize the protrusion to the product.

In particular, the push pin type known in the prior art was pushed just before solidification, but in the present invention, since it is possible to raise the internal pressure in the die by projecting in a molten state, it is separated from the inside of the die. It is possible to effectively raise the internal pressure even in the part.

Further, since the internal pressure in the mold can be raised in the molten state, not just before solidification, the patterning of molding becomes easy. Further, since it can be stopped on the same surface as the cavity, it can be applied to marking on a product if a mark is previously formed on the end surface of the pressure pin.

When solidification begins, the resin pressure in the cavity decreases and sink marks occur. A pressure holding step is provided to prevent this, but since the resin is pressed by the pressure pin at the same time during the pressure holding step, the resin is pressed while it is soft, so that the internal pressure can be kept even and high, and the mold opening In this case, it is possible to reliably obtain a product without sink marks.

Further, since the position sensor is provided on either plate as described above, the predetermined close positional relationship between both plates can be accurately grasped, and pressing is started by interposing a timer or the like. The time point can be set arbitrarily.

[Brief description of drawings]

FIG. 1 shows an operating state of the present invention.

FIG. 2 shows an operating state of the present invention.

FIG. 3 shows an operating state of the present invention.

FIG. 4 shows an operating state of the present invention.

FIG. 5 shows an operating state of the present invention.

FIG. 6 is a hydraulic system diagram of the injection molding machine.

FIG. 7 is a diagram showing a relationship between time, ejection pressure, and ejector pushing amount according to the present invention.

FIG. 8 shows a comparison diagram of eject timing with a conventional method.

FIG. 9 is an explanatory diagram of a roll-links mold.

FIG. 10 is an explanatory diagram of a roll-links mold.

FIG. 11 is a molding machine using a sink prevention method using a push pin.

FIG. 12 is an explanatory diagram of a sink mark prevention method using a push pin.

[Explanation of symbols]

a Molded product 1 Nozzle 2 Sprue-3 Runner-4 Cavity-5 Pressure pin 5a (of pressure pin)
Tip surface 6 Pressure pin plate 7 Mold mounting plate 8 Ejector 9 Fixed side mold plate 10 Return pin 11 Ejector plate 12 Step 12a (return pin) step 13 Position sensor 14 Projection pin 15 Product 16 Push-off Surface 17 Split surface 18 (Movable side) Mold 19 Push pin

Claims (8)

[Claims] 1. A pressure pin (5) slidable back and forth in a hole communicating with a cavity (4) provided in a mold is provided, and after the molten material is injected and filled into the cavity, the cavity is quickly Pressure pin on the same surface as the product surface or in a predetermined position
A molding control method characterized in that the pressure pin (5) is moved forward so as to hold the front end surface (5a) of (5). 2. The molding control method according to claim 1, wherein the processing pin is located in a thick portion of the product. 3. The hydraulic pressure source of the pressurizing pin drive unit is branched and used at the same set pressure as the pressure holding source for the injection screw for holding pressure after injection filling. The molding control method according to claim 2. 4. The pressure pin is gradually brought closer to the same surface as the product surface or a predetermined position according to the correlation between the pressure pin pushing force of the pressure pin drive unit and the cavity internal pressure. Molding control method. 5. The molten state of the resin in the cavity (4) is grasped in relation to the backward position of the pressure pin (5) and the time required for it, or to the retreat speed, and the pressure pin (5) is gradually increased. The molding control method according to claim 1, wherein the molding control method is to bring the molding surface closer to the surface. 6. When the pressure pin plate (6) is moved by the pressure pin drive section and comes into contact with the ejector plate (11), the tip surface of the pressure pin and the product surface of the cavity (4) are separated from each other. The molding control method according to claim 5, wherein the same surface or a predetermined positional relationship is established. 7. An ejector plate for holding a protruding pin.
(11) and a pressure pin penetrating the ejector plate (11)
The pressure pin plate (6) that holds (5) is placed in parallel with the ejector plate (11) so that the tip surface is positioned on the parting surface of the mold when the mold is closed. Install a return pin (10) or ejector plate (1).
Molding control, characterized in that a compression spring (10a) is interposed between 1) and the pressure pin plate (6), and the pressure pin drive and the projecting pin drive are combined by one drive unit. apparatus. 8. A sensor (13) is provided on one of the ejector plate (11) and the pressure pin plate (6) at a position facing the other, and operates when both plates approach each other. Let
The molding control device according to claim 7, wherein the pushing force of the pressure pin is adjusted by the signal.