JPH05220801A - Injection amount control method of injection molding machine - Google Patents

Abstract

(57) [Abstract] [Object] The present invention relates to a method for controlling an injection amount of an injection molding machine, and more particularly, to control an injection amount of an injection compression molding machine by supplying a plastic material when a mold is opened at a predetermined interval. It is about the method. [Composition] In an injection amount control method of an injection molding machine, which determines an injection amount of a molten resin into a cavity in a fixed mold and a movable mold through a valve provided at a tip of a heating cylinder by advancing a screw with a backflow prevention ring. While the valve is closed, the screw is moved forward to bring the backflow prevention ring into contact with the screw, and the pressure of the molten resin in the heating cylinder is raised to the specified pressure, and the forward position (or time) of this screw is the origin of the injection amount. Then, the injection amount of the molten resin is determined from the forward position of the screw when the screw is further advanced to inject the molten resin.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of controlling an injection amount of an injection molding machine, and more particularly to a method of controlling an injection amount of an injection compression molding machine by supplying a plastic material when a mold is opened at a predetermined interval. It is a thing.

[0002]

2. Description of the Related Art Conventionally, in an injection molding machine, when a movable mold is in contact with a fixed mold and is in a closed state, molten resin in a heating cylinder is moved in a cavity of the movable mold and the fixed mold by advancing a screw. It is injected at a high pressure of several hundreds to a few hundreds of kilograms per square centimeter. Recently, the injection amount of molten resin is made variable according to the filling amount in the cavity,
This change is adjusted by the forward speed of the screw. Further, recently, in order to improve the quality of the molded product, an injection compression molding method is adopted as in JP-A-62-268620.

[0003]

However, in the above-mentioned conventional injection molding machine, the position of the screw or the injection cylinder is measured and a variable injection amount is obtained according to the injection timing or the filling amount. The injection amount is not calculated. This is to apply a holding pressure after the injection process,
This is because the molten resin was replenished with cooling of the molded product to prevent sink marks and the like, so that it was unnecessary.

Further, in a compression molding machine, generally, the accuracy of the mass of the molten resin supplied to the cavity is inferior to the mass of the product, so that it is difficult to control the wall thickness in the pressing direction, and the wall thickness varies. On the other hand, JP-A-62-26
In 8620, in order to reduce variation in wall thickness and improve quality, a safety valve that releases excess resin into the mold when compressing and spreading while injecting molten resin into the cavity in excess of the product mass ( A pressure release section) is provided. For this reason, there is a problem that the die becomes complicated and the pressure releasing portion needs to be removed after the molded product is formed, resulting in wasting man-hours and resin.

The present invention has been made in view of the above problems, and relates to a method for controlling an injection amount of an injection molding machine, and more particularly, to controlling an injection amount of an injection compression molding machine by supplying a plastic material when a mold is opened at a predetermined interval. It is intended to provide an improvement in the method.

[0006]

In a first aspect of the present invention, a heating cylinder is provided with a valve provided at a front end thereof,
In the injection amount control method of the injection molding machine, in which the molten resin is injected into the cavity in the fixed mold and the movable mold by advancing the screw with the backflow prevention ring, the screw is advanced with the valve closed and the backflow prevention ring is used. Abutting against the screw and raising the pressure of the molten resin in the heating cylinder to a predetermined pressure, the forward position of this screw is the origin of the injection amount, and the forward position of the screw when the screw is further advanced to inject the molten resin The injection amount of molten resin is determined more.

In the second aspect of the invention, the molten resin is injected into the cavities in the fixed mold and the movable mold through the valve provided at the tip of the heating cylinder to determine the injection amount by advancing the screw with the backflow prevention ring. In the injection amount control method of the molding machine, while advancing the screw while keeping the valve closed and bringing the backflow prevention ring into contact with the screw, a predetermined time for increasing the pressure of the molten resin in the heating cylinder to a predetermined pressure is set as an origin, The amount of molten resin to be injected is determined by advancing the screw when a predetermined time elapses from that time.

[0008]

According to the above construction, since the screw is moved forward while the valve at the tip of the heating cylinder is closed and the backflow prevention ring is in contact with the screw, there is no place where the molten resin in the heating cylinder escapes, and the heating is performed quickly. The pressure of the molten resin in the cylinder can be raised to a predetermined pressure. In addition, the forward position (or time) of this screw is used as the origin of the injection amount, and the valve forward position is opened from that position to advance the screw and inject the resin. Can be obtained with high accuracy. Further, when the mass of the molded product is obtained in accordance with the forward position of the screw, the supply is stopped by closing the valve, so that the injection amount can be controlled with higher accuracy by a simple device. Further, variations in molded products are reduced and maintenance is unnecessary.

[0009]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a schematic view of an embodiment of the injection compression molding machine of the present invention, and FIG. 2 is an explanatory view of an injection amount control method.

In FIG. 1, the injection compression molding machine has a fixed die plate portion 10 for holding a fixed die, a movable die plate portion 20 for holding a movable die, and the movable die plate approaching the fixed die plate and predetermined. After reaching the position, the movable die plate advances to the fixed die plate to perform mold clamping while compressing and spreading the plastic material, which is not shown, and the plastic material is injected. An injection device 50 and a control device 90 for controlling the injection device and the start timing of compression / spreading of the plastic material. The injection device 50 includes an injection cylinder section 60 for injecting plastic material, and a flow control valve section 80 for controlling the injection flow rate of the plastic material and the start time of injection.

A fixed die plate portion 10 is fixed to a bed (not shown), and the fixed die plate portion 10 comprises a fixed die 11 and a fixed die plate 12 which holds the fixed die 11. A mold clamping device 30 is arranged on the fixed die plate portion 10. Further, at a substantially central portion of the fixed die plate 12, a cylinder 61 (hereinafter referred to as a heating cylinder 61) that heats a plastic material of an injection device 60 that injects a plastic material such as a resin into the cavity portion 5 is fixed mold 11. Is provided with a hole 12a for abutting.

A movable die plate portion 20 is slidably arranged on a tie rod (not shown). The movable die plate portion 20 is provided with a movable die 21, a movable die plate 22 that holds the movable die 21, and an ejector device 110. Further, the movable die plate portion 20 is provided with a mold opening / closing device (not shown) for quickly opening / closing the mold to a predetermined position, and the mold is opened / closed by a command from the control device.

The injection cylinder portion 60 of the injection device 50 is mounted slidably in the direction of the fixed mold 11 by a slider (not shown) fixed to the heating cylinder 61. A screw 62 is closely inserted into the heating cylinder 61 of the injection cylinder portion 60, and the screw 62 is connected to a hydraulic cylinder 63 via a bracket 64, and the screw 62 slides in the Z direction by driving the hydraulic cylinder 63. Then inject the plastic. Further, as shown in FIG. 2, a backflow prevention valve 65 is attached to the tip portion 62 a of the screw, and the backflow prevention valve 65 is attached to the screw 62 via a valve seat 66 and a ring 6
A screw head 68 in which 7 is loosely fitted is screwed.

The check valve 65 is in the measuring process (W direction).
Is opened between the ring 67 and the valve seat 66, and the molten resin is sent to the left side (arrow E) in the drawing through the skimmer (S) as the screw 62 is retracted while rotating. Next, at the time of injection, the ring 67 is pushed to the right in the figure by the reaction force of the molten resin and comes into close contact with the valve seat 66, and the skimmer is closed to prevent the reverse flow of the resin. The screw 62 is rotated by a hydraulic motor 69 that receives pressure oil from a variable pump (not shown) in response to a command from the control device 90.

Further, at the tip of the heating cylinder 61 of the injection cylinder section 60, a flow control valve section 80 for controlling the injection flow rate of the plastic material and the start of injection is disposed. The flow control valve unit 80 includes a valve 81 pivotally inserted into a spool hole provided in the heating cylinder 61, and a step motor 84 that swings the valve 81 via a rod 82 and a lever 83.

As shown in FIG. 3, the control device 4 has a RAM 4
a, a ROM 4b, a CPU 4c and a CL 4d (clock), and an electromagnetic switch for switching the pressure sensor for driving the distance sensor 100 between the fixed mold 11 and the movable mold 21 and the mold clamping cylinder 30b of the mold clamping device 30. A switching valve 30a, an electromagnetic switching valve 63a that switches the pressure oil for driving the hydraulic cylinder 63 of the injection cylinder unit 60, and a distance sensor 71 that measures the stroke of the hydraulic cylinder 63 that measures the injection amount of the plastic to be injected. , A pressure sensor 73 that is mounted on a hydraulic cylinder 63 that measures the pressure of the injected plastic material and measures the pressure, a step motor 84 that drives the valve 81 of the flow control valve unit 80, and the mold clamping device 3
It is connected to the movable mold stroke setting means 120 for inputting the operating position and speed of 0, or the injection timing of the plastics, and the injection amount setting means 130 for setting the injection amount of the plastics, each of which is set to a predetermined value. It is controlled by the command.

Next, the operation of the above structure will be described. When the molds are exchanged, the molds are attached to the fixed die plate 12 or the movable die plate 22, and the molds are brought close to each other by operating the mold clamping device 30. The fixed mold 11 and the movable mold 21 are brought into close contact with each other, and the distance between the fixed mold 11 and the movable mold 21 is set to zero by the distance sensor 100. Next, the heating cylinder 71 is brought into contact with the fixed mold 11.

In order to start stamping, first in step 1, a rotation command is issued to the hydraulic motor 69, and the screw 6
2 moves backward while rotating. At this time, the molten resin is sent to the left side (arrow E) in the drawing through the gap (S). In step 2, it is determined whether or not a predetermined amount of resin has been supplied to the heating cylinder 61. When supplied (Fig. 2
It shows in (a). ), The screw rotation command is stopped in step 3, and a forward command is issued to the hydraulic cylinder 63. Whether or not the pressure of the molten resin has reached a predetermined pressure (which may be equal to or lower than the injection pressure) by moving the hydraulic cylinder 63 forward, for example,
The pressure sensor 73 attached to the hydraulic cylinder 63 makes the determination. If it does not reach, it returns to step 3 and repeats.
When it reaches, it goes to step 5 and the distance sensor 100 measures and judges whether or not the movable mold 21 reaches a predetermined position. If not, step 5
repeat. When it reaches, it goes to step 6 and issues an operation command from the control device 90 to the step motor 84,
The valve 81 is swung to open the valve 81. (Fig. 2 (b)
Shows the middle of opening the valve 81. ) At this time, the injection amount of the molten resin is measured with the position of the screw 62 as the origin.

When the valve 81 is opened in step 6, a forward command is issued again to the hydraulic cylinder 63 in step 7, and injection of the molten resin is started. At this time, the clearance between the movable mold 21 and the fixed mold 11 (the inlay slide clearance Y is determined by the thickness and size of the molded product, which is about 30 mm to 2 mm) is wide, and the cavity 10 is large. It is possible to inject at a low pressure in order to inject in a closed state.

At step 8, it is judged whether or not the hydraulic cylinder 63 has advanced by a predetermined amount, that is, whether or not the molten resin has been injected by a predetermined amount. If not, the process returns to step 7 and is repeated. If injected, step 9
To the electromagnetic control valve 3 of the mold clamping device 30 from the control device 90.
The pressure oil from a pump (not shown) is sent to the mold clamping cylinder 30b by switching the command to 0a, and the movable mold 21 is moved toward the fixed mold 11 by the mold clamping cylinder 30b.

In step 10, it is judged whether or not a predetermined amount of plastics commensurate with the molded product has been injected. If injected, in step 11, the control device 4 causes the flow control valve section 80 of the injection device 3 to operate. A command is sent to the step motor 84 to swing and close the valve 81 to stop the injection of the plastic material. In step 12, after the flow control valve section 80 is closed, the movable mold 21 is closed at a predetermined speed and pressure to compress and spread the plastic in every corner of the cavity section 10 to increase the density. In step 13, it is judged whether or not the movable die has come into contact with the fixed die, and if so, step 1
At 3, the mold clamping cylinder 30b is stopped, and the state is kept as it is until the plastic resin is cooled, so that the plastic is kept under pressure. If they do not come into contact, the process returns to step 12.

In the above embodiment, step 4 or 8
The pressure was detected and it was judged whether or not the check valve had come into contact with the screw valve seat, or whether or not a predetermined amount had been injected.The size of the molded product, the volume of the heating cylinder or the molten resin You may judge by time considering the material etc. of.

As described above, the distance L (or time) from the completion of the measurement of the plastic material in FIG. 2 (a) to the position of the injection amount measurement start in FIG. 2 (b) is determined by the ring 67 of the check valve. It is the distance that the plastic material leaks from the skimmer S to the screw 62 side and the screw 62 moves forward until it abuts on the valve seat 66, whereby the resin pressure in the heating cylinder inner chamber 61a rises early and the leakage portion Disappears and stabilizes.
By measuring the distance (M) from this state to the end of injection of the plastic material shown in FIG. 2C, the injection amount of the resin can be accurately measured for this volume.

At this time, the movable mold 21 is closed at a predetermined speed and pressure while injecting the plastic material, and the plastic material is compressed and spread in every corner of the cavity 5. Complete the injection of molten resin before contacting the mold,
By closing the valve, the heating cylinder does not have a high pressure, the injection pressure becomes constant, and the precision of the injection amount of the molten resin is particularly improved. Further, although the above-mentioned embodiment has been described with reference to the injection compression molding method, it goes without saying that the above-mentioned embodiment is used for an ordinary injection molding machine.

[0025]

As described above, according to the present invention,
With the valve at the tip of the heating cylinder closed, the screw is advanced and the backflow prevention ring is in contact with the screw.Therefore, there is no place for the molten resin in the heating cylinder to escape, and the pressure of the molten resin in the heating cylinder can be set quickly. Can be raised to pressure. In addition, the forward position (or time) of this screw is used as the origin of the injection amount, and by opening the valve from that position and advancing the screw to inject the resin, the forward position of the screw is determined to determine the injection amount of the molten resin. Can be obtained with high accuracy. Also, when the mass of the molded product is obtained according to the forward position of the screw, the supply is stopped by closing the valve, so with a simple device,
It is possible to control the injection amount with better accuracy. Further, it is possible to obtain excellent effects that the variation of the molded product is reduced and the maintenance is unnecessary.

[Brief description of drawings]

FIG. 1 is a schematic view of an embodiment of an injection compression molding machine of the present invention.

FIG. 2 is an explanatory diagram of an injection amount control method.

FIG. 3 is a block diagram of a control device unit.

FIG. 4 is a flowchart of the injection compression molding method of the present invention.

[Explanation of symbols]

 5 Cavity Part 10 Fixed Die Plate Part 11 Fixed Die 12 Fixed Die Plate 20 Movable Die Plate Part 21 Movable Die 22 Movable Die Plate 30 Mold Clamping Device 30b Clamping Cylinder 50 Injection Device 60 Injection Cylinder Part 65 Backflow Prevention Valve 66 Valve Seat 67 Ring 69 Hydraulic motor 71 Distance sensor 80 Flow control valve unit 90 Control device 100 Distance sensor 120 Movable mold stroke setting means 130 Injection amount setting means

Claims (2)

[Claims] 1. An injection amount control of an injection molding machine, which determines an injection amount of a molten resin into a cavity in a fixed mold and a movable mold through a valve provided at a tip portion of a heating cylinder and by advancing a screw with a backflow prevention ring. In the method, while advancing the screw with the valve closed and bringing the backflow prevention ring into contact with the screw, the pressure of the molten resin in the heating cylinder is increased to a predetermined pressure, and the forward position of this screw is the origin of the injection amount, An injection amount control method for an injection molding machine, characterized in that the injection amount of the molten resin is determined from the forward position of the screw when the screw is further advanced to inject the molten resin. 2. An injection amount control of an injection molding machine which determines an injection amount of a molten resin into a cavity in a fixed mold and a movable mold through a valve provided at a tip of a heating cylinder to advance the screw with a backflow prevention ring. In the method, while advancing the screw with the valve closed and bringing the backflow prevention ring into contact with the screw, the predetermined time for increasing the pressure of the molten resin in the heating cylinder to a predetermined pressure is set as an origin, and a predetermined time from that time. A method for controlling the injection amount of an injection molding machine, characterized in that the amount of injection of the molten resin is determined by determining the forward movement of the screw according to the progress of.