JPS61177221A - Plasticating control device of injection molder - Google Patents

Abstract

PURPOSE:To lower the rejection rate in molding and consequently improve the productivity by a method wherein the rotational speed of a screw is gradually decreased throughout the whole range of the plasticating stroke of the screw so as to be able to uniformly melt and knead resin. CONSTITUTION:At the start of plastication, a screw rotates at the speed set by a rotating speed setter at the start of stroke 108. The movement of the screw is detected by a screw movement detecting device. The rotating speed of the screw is controlled by a controller (a screw rotating speed controlling device) 112 so as to become slower gradually as the movement of the screw increases. Thus, when the screw moves to the end of the plasticating stroke set by a plasticating stroke setter 104, the plasticating process completes. At this time, the rotating speed of the screw equals to the rotating speed of the screw set by a rotating speed setter at the end of stroke 110. As a result, the degree of kneading of molten resin can become uniform or the uniform degree of kneading over the whole range of plasticating stroke can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a plasticization control device for an injection molding machine.

(b) Conventional technology In a screw-type injection molding machine, resin pellets are melted and kneaded by rotation of a screw and heat transfer from a heating cylinder. The molten resin is transferred forward by the screw, and the screw is moved back by the pressure of the molten resin accumulated in front of the heating cylinder. In conventional injection molding machines, the rotational speed of the screw is always constant or varied in several steps.

(c) Problems to be solved by the invention However, such conventional injection molding machines have a problem in that molding defects may occur because the uniformity of the 1 m kneading degree of the molten resin is not sufficient. Ta. In other words, since the resin pellets are fed from a hopper installed at a predetermined position in the heating cylinder, a sufficient screw length is ensured at the initial stage of plasticization, which is effective for plasticization.
As the screw moves, the effective length of the screw becomes shorter due to softening, and in the latter half of the softening process, the degree of suspension of the plasticized and melted resin becomes lower. Therefore, temperature unevenness occurs and molding defects are likely to occur. Although it is possible to lengthen the melting time in the latter half of the plasticizing process by varying the rotational speed of the screw in several stages, there is a limit to the uniformity of the degree of kneading of the molten resin. The present invention aims to solve the problems as described below.

(d) Means for solving the problem The present invention gradually reduces the screw rotation speed from the start point to the end point of the plasticizing stroke.
Solve the above problems. That is, the plasticization and control device for an injection molding machine according to the present invention includes a screw movement amount detection device (in the embodiment described later, the first pulse generator 72, the first pulse generator 72, 2 pulse generator 73 and arithmetic unit 102), a plasticizing stroke setting device capable of setting the allowable/increasing stroke, and a stroke start point rotation speed setting device capable of setting the screw rotation speed at the plasticizing stroke start point. , a stroke end point rotation speed setting device that can set the screw rotation speed at the stroke end point, and a screw rotation speed set by the stroke end point rotation speed setting device from the screw rotation speed set by the stroke start point rotation speed setting device. and a screw rotation speed control device (controller 112) that gradually reduces the screw rotation speed over the entire range of the plasticized steel loaf according to the amount of screw movement.

(e) Operation When plasticization starts, the screw rotates at the rotational speed set by the stroke start point rotational speed setting device. Next, the screw starts moving, and the amount of movement of the screw is detected by a screw movement amount detection device. The screw rotation speed is controlled by the screw rotation speed control device in accordance with the amount of screw movement as shown in FIG. That is, the screw rotation speed gradually decreases as the amount of screw movement increases. In this way, the a plasticization process ends when the screw moves through the plasticization stroke set by the plasticization stroke setting device, but the screw rotational speed at that time is equal to the screw rotational speed set by the stroke end point rotational speed setting device. Become. Thereby, the degree of kneading of the molten resin can be made uniform. In other words, as the screw moves, the melting rate from the hopper to the tip of the screw increases.
The length of the part that is effective for the suspension wire becomes shorter, but as a result, the screw rotation speed decreases, the time for melting and kneading becomes longer, and the amount of heat received from the heating cylinder increases.
A uniform degree of kneading can be obtained over the entire range of the plasticizing stroke.

(F) Embodiments Hereinafter, embodiments of the present invention will be described based on FIGS. 1 to 4 of the accompanying drawings.

As shown in FIG. 3, a screw 12 is inserted into a cylinder 10 of an injection molding machine. The rear end side of the cylinder 10 (
A casing 14 is attached to the upstream side in the flow direction of the resin. The casing 14 includes a housing 16 and a cover 18, which define a chamber 20. A rotatable and axially movable intermediate shaft 22 is provided in this chamber 20 . The intermediate shaft 22 has a small diameter shaft portion 24 and a large diameter shaft portion 26 . Small diameter shaft part 2
The distal end of the screw 4 is connected to the screw 12 by a spline. The small diameter shaft portion 24 is rotatably and axially movably supported by sliding bearings 36 and 38 attached to the housing 16. On the large diameter shaft portion 26 side of the intermediate shaft 22, there is a nut member 5 having a female thread, which constitutes a pole screw mechanism 52 together with a male thread 50 provided on the shaft 48.
4 is fixed. A shaft 48 provided with a male thread 50 is rotatably supported with respect to the cover 18 by a thrust bearing 56 and a bearing 58. The shaft 48 is connected to a first electric motor 70 outside the casing 14 . The first electric motor 70 is provided with a first pulse generator 72 . The end of the shaft 48 inside the housing 14 is supported by a linear motion bearing 75 against the inner diameter of the intermediate +1122. A key 81 is provided on the outer periphery of the large diameter shaft portion 26 of the intermediate shaft 22.
The driven gear 82 is attached to rotate together with the intermediate shaft 22. The driven gear 82 meshes with a drive gear 83 with a collar 83a;
3 is connected to the shaft 84 by a sliding key 85. @84 is rotatably supported by bearings 86 and 87 relative to the housing 16 and cover 18.

A portion of the shaft 84 that protrudes to the outside of the casing 14 is connected to the second electric motor 71 . The second electric motor 71 is provided with an electromagnetic brake 74 and a second pulse generator 73.

Figure 81 shows a control device that controls the injection molding machine.

The control device includes an operation unit 102 to which signals from the first pulse generator 72 and the second pulse generator 73 are input, and is capable of setting the movement limit of the screw for plasticization, that is, the plasticization flow rate. A plasticizing stroke setter 104, a comparator 106 that compares signals from the calculator 102 and the plasticizing stroke setter 104, a stroke start point rotation speed setter 108 that can set the screw rotation speed at the stroke start point, and a stroke end point. a stroke end point rotational speed setting device 110 that can set the screw rotational speed; a controller 112 (screw rotational speed control device) constituted by, for example, a microcomputer to which signals from the above-mentioned devices are input; It has drive circuits 114 and 116 that supply current to the first electric motor 70 and the second electric motor 71, respectively, based on the signals.

Next, the operation of this embodiment will be explained. FIG. 3 shows the injection completed state. When the injection is completed, the first electric motor 70 becomes freely rotating, and the second electric motor 71 starts rotating. The rotation speed of the second electric motor 71 immediately after the start of rotation becomes a predetermined rotation speed set by the stroke start point rotation speed setter 108 (screw rotation speed R+ at the stroke start point S in FIG. 2). When the shaft 84 is rotated by the second electric motor 7■, the driving gear 83 and the driven gear 8
2, the intermediate shaft 22 rotates. When the intermediate shaft 22 rotates, the screw 12 connected to it through a spline rotates within the cylinder 10, melting and melting the resin pellets supplied into the cylinder 10 from the material supply port 10a provided with a hopper. It is plasticized and transferred to the front of the cylinder 10 (to the left in FIG. 3). As the molten resin transferred to the front of the cylinder 10 increases, the screw 1
2 is pushed back by the resin pressure (moves to the right in FIG. 1). Therefore, the intermediate shaft 22 similarly moves to the right in FIG. 3. ! Since the NI 48 is connected to the intermediate shaft 22 by the ball screw mechanism 52, it rotates in the same direction as the intermediate shaft 22 rotates at a rotation speed that is somewhat slower than the rotation speed of the intermediate shaft 22. As a result, the nut member 5
4 rotates relative to the male screw 50 and moves to the right in FIG. As the intermediate shaft 22 moves, the driving gear 83 moves along the sliding key 85 to follow the intermediate shaft 22 while being engaged with the driven gear 82 due to the action of the collar 83a. As the screw 12 moves, the rotational speed of the screw 12 is controlled to have the characteristics shown in FIG. 2.

That is, as the screw 12 moves, the screw rotation speed gradually decreases. The amount of movement of the screw 12 is determined by the first pulse generator 72 and the second pulse generator 73.
The calculation is performed by the calculation unit 102 based on the signal from. The calculator 102 calculates the amount of movement of the screw 12 by calculating the difference between the cumulative number of pulses of the second pulse generator 73 and the cumulative number of pulses of the first pulse generator 72. The signal calculated by the calculator 102 is input to the controller 112. The controller 112 controls the screw rotation speed R1 set by the stroke start point rotation speed setter 108, the screw rotation speed R2 (stroke end point F in FIG. 2) set by the stroke end point rotation speed setter 110, and Based on the plasticizing stroke L set by the plasticizing stroke setting device 104, the degree of decrease in the screw rotational speed per unit movement of the screw 12 is calculated (that is, the slope of the straight line S-F in FIG. A signal is output to the drive circuit 116 to reduce the rotational speed of the screw 12 by a minute movement amount of 4σ or every minute distance according to the movement amount of the screw 12 inputted from the njJ calculator 102, The rotational speed of the second electric motor 71 is gradually reduced. When the moving part of the screw 2 reaches L (ie, point F), the rotational speed of the screw 12 becomes R2. The movement amount of the screw 12 has reached L because the signal input from the calculator 102 to the comparator 10'6 becomes equal to the plasticizing stroke L set by the plasticizing stroke setting device 104. In this case, the comparator 106 outputs a signal to the controller 112 to stop the supply of current from the drive circuit 116 to the second electric motor 71 and actuate the electromagnetic brake 74 to stop the screw 12. This completes the plasticizing process. After all, during the plasticizing process, screw 12
As the screw 12 moves, the rotation speed gradually decreases as shown in FIG. The molten material that is plasticized and melted near the end of the plasticizing process takes a longer heat transfer time and is sufficiently melted and kneaded. Therefore, the molten resin melted at any stage of the plasticizing process is uniformly kneaded, and a good molded product can be obtained. The control interval of the screw rotational speed may be very small as in this embodiment, or the interval may be increased to some extent and changed stepwise as shown in FIG.

(g) Effects of the invention - As explained above, according to the present invention, the screw rotation speed is gradually reduced as the screw moves during the plasticizing process, so that the resin can be uniformly melted by +1 It can be kneaded, reduce the molding defect rate, and improve productivity. Further, the operation is simple because the screw rotation speed is automatically determined by simply setting the screw rotation speed at the plasticization stroke start point, the rotation speed at the stroke end point, and the plasticization stroke.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the plasticization control device for an injection molding machine according to the present invention, FIG. 2 is a diagram showing changes in rotational speed with respect to the amount of screw movement, FIG. 3 is a diagram showing the injection molding machine, and FIG. FIG. 3 is a diagram showing changes in rotational speed with respect to the amount of movement of another screw. 12. Working music screw, 70 s11 first electric motor, 71
-ψ・Second electric motor, 72...ΦFirst pulse generator, 73
...Second pulse generator, 102...-Arithmetic unit, 104
...Plasticization stroke setting device, 108...Φ Stroke end point rotation speed setting device, 110-φ Stroke end point rotation speed setting device, 112-...Controller (Screw rotation speed patent applicant Hiki Co., Ltd. Steelworks agent Patent attorney Toshiyuki Miyauchi
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11-Kuchi Danba ct ri Behe:>dai-Return song seal

Claims (1)

[Claims] A screw movement detection device that can detect the axial movement of the screw in the plasticization process, a plasticization stroke setting device that can set the plasticization stroke, and a stroke start that can set the screw rotation speed at the plasticization stroke start point. A point rotation speed setting device, a stroke end point rotation speed setting device that can set the screw rotation speed at the stroke end point, and a stroke end point rotation speed setting device from the screw rotation speed set by the stroke start point rotation speed setting device. and a screw rotation speed control device that gradually reduces the screw rotation speed over the entire range of the plasticization stroke according to the screw movement amount detected by the screw movement amount detection device up to a set screw rotation speed. Control device.