JPS6364286B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an injection control device for an injection molding machine and a control method thereof.

The injection process of an injection molding machine consists of a filling process in which the mold cavity is filled with resin when the injection plunger moves at high speed, and a pressure holding process in which holding pressure is applied to the mold cavity after the filling process is completed.

In such an injection process, it is extremely difficult to reliably stop the filling operation by the injection plunger when the resin filling into the mold cavity is completed because the inertia of the injection plunger must be completely absorbed. Further, if the injection plunger is not reliably stopped when the filling operation is completed, the injection plunger will come into contact with the end face of the injection cylinder, which will not only cause a large shock but also lead to damage to the machine. In addition, excess resin was packed into the mold cavity, causing an overpack phenomenon, which became a cause of burrs.

The present invention was conceived in view of these points,
The present invention provides an injection device and a control method thereof, in which the switching position from the filling process to the pressure holding process is always constant by reliably stopping the injection plunger at the completion of the filling process.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings showing a heating cylinder, 6 a screw, 7 an injection cylinder, and 8 an injection piston slidably inserted into the injection cylinder 7. A hydraulic motor 9 rotates the screw 6, is fixed to the injection piston 8, and cooperates with the injection piston 8.

Reference numeral 10 denotes a switching valve that controls pressure oil from a hydraulic source (not shown) that acts on the injection cylinder 7 and moves the injection piston 8 forward and backward (left and right in the figure). 11
is a positioning cylinder fixed to the injection cylinder 7, and a positioning piston 12 protruding toward the injection cylinder 7 side is slidably fitted into the cylinder 11, and pressure oil is applied to the head side of the positioning piston 12 (in the figure). When the piston 1 acts on the left side)
2 moves forward (to the right in the figure), but it collides with a mechanical stopper (not shown) and the amount of advancement is regulated, and the amount of advancement can be adjusted as appropriate by the mechanical stopper. . Reference numeral 13 denotes a switching valve that acts on the positioning cylinder 11 and controls pressure oil from a hydraulic source (not shown) to move the positioning piston 12 forward and backward.

Next, the operation of the present invention will be explained with reference to the drawings. In order to perform a pressure holding operation during high-speed injection (filling) of the injection piston 8 in the figure, the solenoid a of the switching valve 10 is switched to energization, and the injection piston 8 is advanced to the position where high-speed injection (filling) is completed (as shown in the figure). left), then the solenoid a of the switching valve 10 is de-energized (the state shown).

When the switching valve 13 is switched to a non-excited state, the positioning piston 12 starts moving forward (rightward in the figure), and the tip of the piston 12 protrudes toward the injection cylinder 7 side and comes into contact with the injection piston 8. In this state, the positioning piston 12 is
If the amount of movement of the injection piston 8 is regulated, the forward stroke position of the injection piston 8 during high-speed injection (advance) will be determined by coming into contact with the positioning piston 12.

Since the configuration is as described above, the switching valve 1
0 is in the neutral position, the screw 6 is rotated by the hydraulic motor 9, and when the metering of the resin (not shown) is completed, the injection piston 8 is advanced by the excitation of the solenoid a of the switching valve 10, and the resin is released into the mold. The cavity (not shown) is sequentially filled, and when the timer (not shown) activated at the same time as the injection piston 8 moves forward, the injection piston 8 butts against the positioning piston 12 and the high-speed injection (filling) ends at the same time. By energizing the switching valve 13, the pressure oil in the positioning cylinder 11 is drained to the tank boat, and the positioning piston 12 is freed to switch to pressure holding.

As explained above, in the present invention, the position where the holding pressure is applied after high-speed injection can be adjusted appropriately depending on the shape of the mold cavity, the wall thickness of the molded product, etc., so the holding pressure switching position can be set accurately. Therefore, it is possible to eliminate molding defects such as dimensional defects due to resin sink marks and shrinkage, and it is possible to stably mold good products.

[Brief explanation of drawings]

The figure is a schematic diagram of a pressure holding device showing this embodiment. 5... Heating cylinder, 6... Screw, 7...
... Injection cylinder, 8 ... Injection piston, 9 ... Hydraulic motor, 10, 13 ... Switching valve, 11 ... Positioning cylinder, 12 ... Positioning piston.

Claims (1)

[Claims] 1. A heating cylinder for heating material resin;
An injection plunger or screw installed in the heating cylinder so that it can move forward and backward, an injection cylinder that moves the injection plunger and the like back and forth, and a positioning piston that is installed in the injection cylinder and can freely project into the injection cylinder are slidably inserted into the heating cylinder. An injection control device for an injection molding machine, comprising a positioning cylinder and a switching valve that controls pressure oil to maintain a positioning piston of the positioning cylinder at a predetermined position. 2. A heating cylinder for heating the material resin;
An injection plunger or screw mounted movably in the heating cylinder, an injection cylinder for advancing and retracting the injection plunger, etc., a positioning cylinder in which a positioning piston that can project freely is slidably inserted into the injection cylinder, and the positioning cylinder. Using an injection control device of an injection molding machine consisting of a switching valve that controls pressure oil to keep the positioning piston of the cylinder at a predetermined position, the pressure oil of the positioning cylinder is removed immediately after injection filling is completed or at a certain timing. A method for controlling an injection control device for an injection molding machine, comprising controlling the positioning piston to be free and proceeding to a pressure holding process.