JPH11227016A - Control of injection molding machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the lowering of the quality of a molded product even if a time required in a weighting process is different according to the kind of a resin. SOLUTION: When a weighting process is completed (OFF) at a timing t3 after the elapse of a time (a), the clocking by a suck-back delay time is started (ON) by the suck-back delay time setting means of a control part 51 and the counting by a plasticizing recession delay timer is started (ON). After, the clocking by the suck-back delay timer is started, the clocking by the suck-back delay timer is completed (OFF) at a timing t4 after the elapse of a suck-back delay time (b), and suck-back is started (ON) to be performed for a predetermined time. Next, the suck-back is completed (OFF) at a timing t5 and, when the clocking by the plasticizing recession delay timer is completed (OFF) at a timing t6, plasticizing recession is started (OFF) and completed (OFF) at a timing t7. Continuously, an injection device is stopped at a timing t8 and mold opening is started (ON) on the side of a mold apparatus. When mold opening is completed (OFF) at a timing t9, injection and dwelling are performed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art Conventionally, in an injection molding machine, a screw is disposed in a heating cylinder so as to be rotatable and advanceable and retractable. In a measuring step, the screw is rotated and retracted, and the resin is heated and melted. The resin is stored in front of the screw, and the resin is injected from the injection nozzle by advancing the screw in the injection step.

[0003] The injection nozzles are classified into open nozzles, shut-off nozzles (needle valve nozzles), and the like. Since the nozzle ports of the open nozzles are always open, the injection nozzles are closed when the measurement process is completed. Resin leaks from the nozzle opening and drooling occurs. Therefore, after the weighing process is completed, that is, immediately after the screw reaches the weighing end position, suckback is performed, the screw is slightly retracted, and the pressure of the resin near the nozzle port in the injection nozzle is reduced. Lower,
Drooling is prevented from occurring.

[0004]

However, in the conventional method of controlling an injection molding machine, the time required for the weighing process differs depending on the type of the resin. Is also delayed accordingly. However, after a certain period of time has elapsed after the measurement process is started, the injection process is started. Therefore, the time from when the suckback is performed until the injection process is started changes. Therefore, the state of the resin stored in front of the screw is not constant, and the quality of the molded product is reduced.

The present invention solves the above-mentioned problems of the conventional control method of an injection molding machine, so that even if the time required for the measuring process varies depending on the type of resin, the quality of the molded article is not degraded. It is an object of the present invention to provide a method of controlling a machine.

[0006]

Therefore, in the control method of the injection molding machine according to the present invention, when the weighing process is completed, time measurement by a suck back delay timer is started, and the suck back delay time elapses. When the clocking by the suckback delay timer ends, suckback is performed.

The suck back delay time is set according to the pressure of the resin. In another control method of the injection molding machine of the present invention, the pressure of the resin in front of the screw in the heating cylinder is detected. The suckback delay time is set based on a comparison result between the detected value of the pressure and a reference value.

[0008]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 2 is a schematic diagram of an injection molding machine according to the embodiment of the present invention. In the figure, reference numeral 11 denotes a mold device. The mold device 11 is disposed so as to be able to freely contact and separate from the fixed mold 31 and the fixed mold 31 when the fixed mold 31 is brought into contact therewith. And a movable mold 32 forming a cavity space 33 between them. A mold clamping device (not shown) is provided adjacent to the mold device 11, and the movable mold 32 is moved forward and backward (moves in the left and right directions in the figure) by operating the mold clamping device to close and close the mold. And mold opening can be performed.

Reference numeral 34 denotes an injection device which is disposed so as to face the mold device 11. The injection device 34 includes the heating cylinder 14 and a drive unit 35. The heating cylinder 14 has an injection nozzle 38 integrally formed in front of the cylinder main body 36 (left side in the figure), and has a hopper 15 near the rear end (right end in the figure) of the cylinder main body 36 and has an inside. , And has a screw 13 rotatably and freely retractable. A heater (not shown) for heating and melting the resin (not shown) supplied to the heating cylinder 14 is provided on the outer periphery of the cylinder body 36.

The screw 13 comprises a screw head 12 provided at a front end (left end in the figure) and a screw body 37 provided behind the screw head 12 (right side in the figure). A spiral groove 40 is formed around the screw body 37. Reference numeral 45 denotes a check ring disposed between the screw head 12 and the screw body 37.

The driving section 35 comprises an electric motor section 41 disposed behind the screw 13 and an injection cylinder 42 disposed behind the electric motor section 41. In the injection cylinder 42, the rear end of the screw 13 and the piston 44 are connected to a servomotor that is not provided.

In the injection device 34 having the above-described configuration, when the servo motor is driven to move backward (moving to the right in the drawing) while rotating the screw 13 during the measuring process, the pellet-like resin in the hopper 15 Is dropped into the heating cylinder 14, heated and melted in the heating cylinder 14, and advanced (moved to the left in the figure) in the groove 40. As a result, the screw 13 reaches the metering end position, and the resin advanced in the groove 40 is stored in front of the screw head 12.

In the injection step, the injection cylinder 4
When the screw 2 is driven to advance without rotating the screw 13, the resin stored in front of the screw head 12 is injected from the injection nozzle 38 and is charged (balanced) into the cavity space 33. When the injection process is completed, the pressure is maintained in the mold apparatus 11. By the way, in the measuring step, when the screw 13 is retracted while rotating, the resin advanced in the groove 40 becomes:
The resin is stored in front of the screw head 12. At this time, if the resin flow path 46 in the injection nozzle 38 is open, the resin leaks from the nozzle port 39 of the injection nozzle 38 when the measurement process is completed, and A ring occurs. Therefore, after the measurement process is completed, that is, immediately after the screw 13 reaches the measurement end position, suckback is performed, and the screw 13 is slightly retracted,
The pressure of the resin in the vicinity of the nozzle port 39 in the injection nozzle 38 is reduced to prevent drooling from occurring.

[0014] Even if the time required for the weighing process differs depending on the type of resin, the time from suckback to the start of the injection process is set so that the quality of the molded product does not deteriorate. I try to keep it constant. FIG.
3 is a control block diagram of the injection molding machine according to the embodiment of the present invention, FIG. 3 is a time chart showing the operation of the injection molding machine according to the embodiment of the present invention, and FIG. It is a flowchart which shows an operation.

In the drawing, reference numeral 51 denotes a CPU (not shown),
A control unit including a storage device and the like, 52 is a heating cylinder 14
A resin pressure sensor for detecting the pressure of the resin in front of the screw 13 in (FIG. 2), 53 is a hydraulic servo valve,
By opening and closing the hydraulic servo valve 53, the injection cylinder 42 can be driven and the screw 13 can be moved forward and backward without rotating. Reference numeral 55 denotes a servo motor provided in the electric motor unit 41 for rotating the screw 13. The servo motor 55 is connected to the control unit 51 via a driver 54, and the control unit 51
Driven by

In the injection molding machine having the above-described configuration, in the previous injection step, after the injection is performed on the injection device 34 side and the holding pressure is performed on the mold device 11 side, the measurement delay of the hydraulic servo valve 53 is performed at timing t1. When the time measurement by the timer is started (ON) and the measurement is delayed, and the measurement by the measurement delay timer is ended (OFF) at the timing t2, the injection device 3 is started.
The measuring process is started (turned on) on the side 4 and cooling of the resin filled in the cavity space 33 is started on the side of the mold apparatus 11.

Subsequently, when the time a elapses and the timing t3
When the weighing process is completed (OFF), the time measurement by the suck-back delay timer is started (ON) by the suck-back delay time setting means 62 of the control unit 51, and the time measurement by the plasticizing retreat delay timer is started (ON). You. Then, when the suck-back delay time b elapses after the clocking by the suck-back delay timer is started, the timing by the suck-back delay timer ends (off) at timing t4, and the suck-back is started (on), and the predetermined time is set. Only done for hours.

Next, when the suck-back ends (off) at a timing t5 and the time measured by the plasticizing retreat delay timer ends (off) at a timing t6, the plasticizing retreat starts (on), and the plasticizing at a timing t7. Retreat is ended (off). Subsequently, at timing t8, the injection device 34 is stopped, and the mold opening is started (on) on the mold device 11 side. Then, when the mold opening is completed (off) at the timing t9, the injection and the pressure holding are performed.

Here, since the time a required for the weighing process differs depending on the type of the resin, for example, if the timing t3 at which the weighing process is completed is delayed and the timing t4 at which the suckback is started is also delayed by that amount, the suckback will occur. After that, the time c until the next injection step is started at the timing t10 changes. Therefore, since the state of the resin stored in front of the screw 13 is not constant, the quality of the molded product is reduced.

Therefore, the time c from when the suck back is performed to when the injection step is started is made constant. Therefore, when the measuring step is completed, the pressure of the resin in front of the screw 13 is detected by the resin pressure sensor 52, and the detected value is sent to the control unit 51. The control unit 5
The first comparing means 61 compares the detected value with a reference value,
The comparison result is sent to the suckback delay time setting means 62. The suckback delay time setting means 62 sets an optimum suckback delay time b for suckback based on the comparison result, and turns on the suckback delay timer.

In the embodiment of the present invention, when the pressure of the resin is high, the time a required for the measuring step is short, so that the suck-back delay time b is increased, and when the pressure of the resin is low, the time required for the measuring step is required. Since the time a becomes longer, the suckback delay time b is made shorter. Then, the control unit 51
When the time measurement by the suck-back delay timer is completed, the suck-back means 63 drives the injection cylinder 42 via the hydraulic servo valve 53 to perform suck-back.

Therefore, even if the time a required for the weighing process differs depending on the type of the resin, the suck back delay time b from the start of the time measurement by the suck back delay timer to the end thereof is controlled in accordance with the detected value. can do. Then, the time c from when the suck back is performed to when the injection process is started can be kept constant, so that the state of the resin stored in front of the screw 13 can be kept constant. As a result, the quality of the molded product does not deteriorate.

Next, the flowchart will be described. Step S1 The weighing process is completed. Step S2 The resin pressure sensor 52 detects the pressure of the resin. Step S3: The suckback delay time setting means 62 sets the suckback delay time b. Step S4: The suck-back means 63 waits for the timing to end (time-up). Step S5: Perform suck back.

It should be noted that the present invention is not limited to the above-described embodiment, but can be variously modified based on the gist of the present invention, and they are not excluded from the scope of the present invention.

[0025]

As described above in detail, according to the present invention, in the control method of the injection molding machine, when the weighing process is completed, time measurement by the suck back delay timer is started, and the suck back delay time is started. When the time measurement by the suckback delay timer ends after the elapse of the period, suckback is performed.

The suck back delay time is set in accordance with the pressure of the resin. In this case, even if the time required for the weighing process varies depending on the type of resin, the suckback delay time from when the time is measured by the suckback delay timer to when it ends can be controlled in accordance with the pressure of the resin. . Therefore, the time from when the suck back is performed until the start of the injection process can be made constant, so that the state of the resin stored in front of the screw can be made constant. As a result, the quality of the molded product does not deteriorate.

[Brief description of the drawings]

FIG. 1 is a control block diagram of an injection molding machine according to an embodiment of the present invention.

FIG. 2 is a schematic diagram of an injection molding machine according to an embodiment of the present invention.

FIG. 3 is a time chart illustrating an operation of the injection molding machine according to the embodiment of the present invention.

FIG. 4 is a flowchart showing an operation of the injection molding machine according to the embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 13 Screw 14 Heating cylinder 51 Control part 52 Resin pressure sensor 61 Comparison means 62 Suck back delay time setting means b Suck back delay time

Claims (2)

[Claims] (A) When the measuring step is completed, timing by the suckback delay timer is started. (B) When the timing of the suckback delay timer ends after the suckback delay time has elapsed, suckback is performed. And (c) the suck back delay time is set in accordance with the pressure of the resin. (A) detecting the pressure of the resin in front of the screw in the heating cylinder; and (b) setting the suck back delay time based on a comparison result between the detected value of the pressure and a reference value. The control method for an injection molding machine according to claim 1, wherein