JPH0825435A - Control of electromotive injection molding machine - Google Patents

Abstract

PURPOSE:To perform stable weighing while minimizing spring back quantity in a process transferring a dwelling process to a weighing process. CONSTITUTION:At the time of the transfer from a dwelling process (C) to a weighing process (D), a speed limit is applied in a weighing direction by a spring back time (t) preset after the completion of a dwelling time to suppress spring back quantity in the weighing direction.

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 electric injection molding machine, and more particularly, in a step of shifting from a pressure holding step to a weighing step through a weighing waiting step or a step of directly shifting from the pressure holding step to the weighing step. The present invention relates to a new improvement for minimizing the amount of springback in which the screw is returned to the measuring direction by the resin pressure when the pressure holding time expires when the resin accumulated at the tip of the cylinder becomes sufficiently high pressure.

[0002]

2. Description of the Related Art In the case of the control method of this type of electric injection molding machine which has been conventionally used, the pressure-holding step is followed by the weighing waiting step to enter the weighing step, or the pressure-holding step is directly entered into the weighing step. As a control method at this time, generally, as shown in FIG. 4, since the pressure control is pressure control in the pressure holding process, the speed upper limit value is set in the injection direction at the time of pressure holding. In the weighing waiting process and the back pressure process, the pressure is controlled in the back pressure process, so that the speed limit is set as the speed upper limit value to the injection side during back pressure, as in the pressure holding process described above. The value B is set and controlled,
No speed limit value was set as the speed upper limit value in the weighing direction.

[0003]

Since the conventional control method for the electric injection molding machine is configured as described above, the following problems exist. That is, since the negative speed limit value in the metering direction was not set, when the pressure holding time expires when the resin accumulated at the cylinder tip in the pressure holding process becomes sufficiently high, the repulsion of the resin The force caused the screw to retract in the metering direction in an uncontrolled state (hereinafter this phenomenon is called springback). This causes air to be entrained in the cylinder in the measuring process and causes variations in the resin kneading amount. In particular, this phenomenon remarkably appeared under molding conditions where the measurement was short stroke and the holding pressure was high. Further, due to this springback, the screw reaches the measurement completion position without rotating, and there is a problem that the next shot becomes a short shot.

The present invention has been made to solve the above problems, and in particular, a step of shifting from a pressure holding step to a weighing step through a weighing waiting step or a step of directly shifting from the pressure holding step to the weighing step. When the holding pressure time expires at the time when the resin accumulated at the tip of the cylinder becomes sufficiently high in pressure, the electric injection molding machine that minimizes the springback amount of the screw returned to the measuring direction by the resin pressure. It aims at providing the control method of.

[0005]

According to the method of controlling an electric injection molding machine of the present invention, the rotation of an injection motor is converted into a linear motion by a ball screw mechanism to move a screw forward in a cylinder, and an injection step and a pressure holding step. In the control method of the electric injection molding machine, wherein the resin is stored in the cylinder by rotating the plasticizing motor and plasticizing is performed, in the weighing step from the pressure holding step to the weighing waiting step. Or when the pressure-holding step is directly transferred to the measuring step, the screw speed is preset in the metering direction with respect to the injection motor for a preset springback prevention time after the pressure-holding time of the pressure-holding step expires. This is a method of suppressing the amount of springback of the screw in the measuring direction so as not to become higher than the speed.

More specifically, a speed limit value in the injection direction of the injection motor is set, and a speed limit value in the metering direction is set for a preset springback prevention time t for limiting the springback amount. Is the way to do it.

[0007]

In the control method of the electric injection molding machine according to the present invention, after the holding pressure time has expired, as shown in FIG. 2, the springback is prevented by using the speed limit value preset in the controller for the injection motor. The negative speed is limited in the metering direction for the time t to limit the springback amount of the screw, and the springback amount is minimized. As a result, it is possible to eliminate the measurement instability phenomenon due to the short stroke measurement caused by the spring back, and it is possible to perform stable and highly accurate electric injection molding even under molding conditions of short stroke and high holding pressure.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of a control method for an electric injection molding machine according to the present invention will be described in detail below with reference to the drawings.
1 to 3 show a control method of an electric injection molding machine according to the present invention, in which FIG. 1 is a configuration diagram including a cross section, and FIG.
Is a process diagram showing control from the pressure maintaining process to the measuring process, and FIG. 3 is a flow chart. A reference numeral 1 in FIG. 1 denotes a heating type cylinder of an electric injection molding machine, and a screw 2 movably and rotatably fitted into the cylinder 1 includes:
The drive shaft 4 is connected via the connecting shaft 3. At the rear end of the drive shaft 4, a ball screw mechanism 8 having a structure in which a ball screw 7 is screwed into a ball nut 6 axially slidably supported in a housing (not shown)
Are connected via a slide bearing 5, and a first end such as an encoder is attached to the rear end of the ball screw 7.
The output shaft 10 of the injection motor 9 having the rotation detector 12 is connected. The injection motor 9 includes a control device 13
It is configured to be driven by an injection driver amplifier 14 for servo connected to the. A waveform display device 21 is connected to the control device 13.

With the forward and reverse rotation of the ball screw 7 that is normally and reversely rotated by the injection motor 9, the ball nut 6 advances or retracts in the axial direction, and the screw 2 causes the drive shaft 4 to move.
And is advanced or retracted via the connecting shaft 3. On the other hand, a plasticizing motor 1 having a rotary shaft 18 at a position parallel to the drive shaft 4 and having a second rotation detector 19 such as an encoder.
1 is installed side by side, and the rotary shaft 18 is provided with a flanged gear 16 having a pair of flanges 15 at both ends thereof via a ball spline 17, and the flanged gear 16 is fixed to the drive shaft 4. The gear 22 is engaged with each other while being sandwiched between the collars 15. Further, the plasticizing motor 1
1 is connected to a plasticizing driver amplifier 20 for servo which is connected to the control device 13.

The rotation of the plasticizing motor 11 is performed by rotating the drive shaft 4 through the rotary shaft 18, the spur gear 16 and the gear 22.
And the screw 2 is rotated via the connecting shaft 3 and the drive shaft 4 and the gear 22 are moved in the axial direction when the screw 2 is advanced or retracted, and the ribs are provided via the ball spline 17 along with the axial movement. The gear 16 is configured to be able to slide back and forth on the rotating shaft 18. As a result, the rotation of the plasticizing motor 11 is configured to be transmitted to the gear 22 by the spur gear 16 regardless of the position of the screw 2 when the screw 2 is moved forward or backward.

Next, the step of shifting from the pressure holding step C to the weighing step D in the control method for the electric injection molding machine according to the present invention will be described with reference to FIG. Control device 13 shown in FIG.
The torque (pressure) in the injection driver amplifier 14 of the injection motor 9 is controlled on the basis of the preset values set in multiple stages. At this time, since the control of the injection motor 9 is pressure control, of course, speed limitation, that is,
The speed limit value A is set so that it does not become overspeed, but this is the direction in which torque (pressure) is applied (injection direction).
It is a speed limit value to. Then, when the holding pressure time set by the operator expires, the process shifts to the measuring process D or the measuring waiting process E, but the speed is limited in the measuring direction for the springback prevention time t set in advance by the control device 13, and the cylinder is stopped. Limits (prevents) the springback amount due to the tip resin pressure. As a result, when the set pressure at the last stage of pressure holding is high, the resin pressure at the tip of the cylinder 1 also becomes high, and as the pressure holding time expires, the screw 2 will spring back at a very fast speed due to the resin pressure at the tip of the cylinder 1. However, since the speed limit value F in the metering direction is set, if the screw speed tries to move back in the metering direction because the screw speed is less than the speed limit value F by springback, the preset springback prevention time t Only, the injection motor torque is output in the injection direction so that the screw 2 is within the speed upper limit set as the speed limit value in the metering direction. Then, when the screw speed falls within the speed limit speed in the metering direction, or when the preset springback prevention time t expires, torque output in the injection direction for holding the screw 2 within the speed limit value F is output. Then, the process shifts to the normal measuring process C or the measuring waiting process D. That is, by restraining the screw 2 within the speed limit value F described above, the speed limit value F in the measurement direction for preventing springback is set for the screw 2.

The above-mentioned steps are shown in a flow chart as follows:
As shown in FIG. 3, the control device 13 sets the speed limit value B in the injection direction via the injection driver amplifier 14 (a), the speed limit value F in the metering direction (b), and the springback prevention time. Setting and expiration (t) of t, cancellation of the limit value of the speed in the weighing direction (d), and setting and expiration of the waiting time for weighing (e), screw rotation stop (f), screw through the plasticizing driver amplifier 20. The start of rotation (g) can be controlled.

[0013]

Since the control method for the electric injection molding machine according to the present invention is configured as described above, the following effects can be obtained. In other words, by setting the speed limit in the metering direction after the pressure holding time has expired, the amount of screw springback of the screw caused by the resin whose pressure has increased at the tip of the cylinder at the time of pressure holding can be suppressed to the minimum, and the metering short It is possible to perform stable measurement even in the case of forming by stroke and even under the forming condition of high holding pressure.

[Brief description of drawings]

FIG. 1 is a configuration diagram including a cross section applied to a control method of an electric injection molding machine according to the present invention.

FIG. 2 is a process diagram showing control from a pressure holding process to a measuring process.

FIG. 3 is a flowchart.

FIG. 4 is a process diagram showing control from a conventional pressure holding process to a measuring process.

[Explanation of symbols] 1 cylinder 2 screw 8 ball screw mechanism 9 injection motor 11 plasticizing motor B speed limit value in injection direction C pressure holding process D measurement process E measurement waiting process F speed limit value in measurement direction

Claims (2)

[Claims] 1. A screw (2) is converted into a cylinder by converting the rotation of an injection motor (9) into a linear motion by a ball screw mechanism (8).
An electric injection in which the resin is stored in the cylinder (1) and plasticized by rotating the plasticizing motor (11) while advancing in (1) to perform the injection step and the pressure holding step. In the control method of the molding machine, the pressure holding step (C) to the weighing waiting step (E) are followed by the weighing step.
At the time of shifting to (D) or directly from the pressure maintaining step (C) to the measuring step (D), the injection is performed for a preset springback prevention time t after the pressure maintaining time of the pressure maintaining step (C) has expired. An electric injection molding machine characterized in that the amount of springback of the screw (2) in the metering direction is suppressed so that the screw speed in the metering direction with respect to the motor (9) does not become higher than a preset speed. Control method. 2. A speed limit value (B) in the injection direction of the injection motor (9) is set, and a speed limit in the metering direction is set for a predetermined springback prevention time t for limiting the springback amount. The method for controlling an electric injection molding machine according to claim 1, wherein the value (F) is set.