JPS6410171B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Technical field to which the invention pertains> The present invention relates to a method and apparatus for changing resin in an injection molding machine.

<Prior art and its drawbacks> When replacing resin, a method of purging is used by repeating the measuring and injection operations to remove the resin that has adhered to the inside of the screw, heating cylinder, and nozzle. There is.

However, in the method described above, the resin adhering to the metering part of the screw tends to remain as it is without generating any extrusion force unless the resin is fed from the feed part side. In this case, the adhesion of residual resin as described above can be prevented by supplying the resin to be used next from the feed side, but if the resin to be used next has the same properties, there will be no problem, but if the resin to be used next is of the same nature, In the case of resin, the set temperature must be changed depending on the type and physical properties of the resin. If this temperature setting is changed during purging, it will deviate from the purge temperature setting of the resin that has been used up until now, making it difficult to change the resin.

When such a different type of resin is used, complete purging is not performed, and the screw is pulled out and cleaned before molding with the next resin. Therefore, removing the screw requires considerable effort and time.

<Object of the Invention> An object of the present invention is to provide a resin replacement method that does not require removing the screw and does not leave any residual resin in the metering portion of the screw.

<Summary of the Invention> In order to achieve the above-mentioned object, a suction device is provided that is normally installed in a molding machine and that slightly retracts the screw in the barrel in order to prevent the drooling that occurs when resin comes out from the tip of the nozzle after the metering operation is completed. This is a method to effectively change the resin by using the screw, and after repeating metering and injection, at the end of the purge operation, the hole at the tip of the nozzle is closed and sealed, and then the screw is moved back at high speed to remove the inside of the barrel. This method is characterized by repeatedly generating negative pressure at the tip and drawing out the resin remaining in the screw to the tip inside the barrel.

<Example> An example of the present invention will be described with reference to FIG.
A barrel 11 has a plurality of heaters 12 attached to its outer periphery, and a screw 13 that can rotate and move back and forth in the axial direction is inserted into the barrel. 14 is a hopper for supplying the resin material into the barrel 11, and 15 is an injection cylinder for advancing and retracting the screw 13. Pressure oil from the hydraulic pump 16 acts on the oil chambers 15a and 15b, causing the piston 17 connected to the screw 13 to move forward and backward. It is designed to advance and retreat. Also, 23
The screw 13 is rotationally driven by a hydraulic motor via a gear mechanism 24. Reference numeral 25 denotes an electromagnetic switching valve that switches and controls rotational driving and stopping of the hydraulic motor 23. A flow control valve 26 controls the rotational speed of the hydraulic motor 23. Reference numeral 18 denotes an electromagnetic switching valve that connects the hydraulic pump 16 to the oil chamber 15a or 1 of the injection cylinder 15.
5b is used to switch the pressure oil acting on the pressure oil. 2
7 is a position detector for detecting the position of the screw 13, and the electromagnetic switching valve 18 is controlled based on the signal from the detector.
The screw 13 is moved forward and backward by switching. Reference numeral 19 is an electromagnetic flow control valve that adjusts the amount of oil acting on the injection cylinder 15. 20 is an electromagnetic pressure regulating valve that regulates the pressure of hydraulic oil discharged from the hydraulic pump 16. Reference numeral 21 denotes a nozzle touch plate that abuts the nozzle hole of the nozzle 22 attached to the tip of the barrel, completely cutting off the inside and outside of the barrel.

The structure is as described above, and its operation will be explained next. When the screw 13 is at the forward limit, that is, when the piston 17 is on the left side of the injection cylinder 15 (in the position shown), the nozzle touch plate 21 blocks the nozzle part 22, and with the electromagnetic switching valve 25 in a non-excited state (as shown in the figure), when the directional switching valve 18 is set to the b position and the pressure oil of the hydraulic pump 16 is applied to the oil chamber 15a of the injection cylinder 15, The screw 13 is forcibly moved backward (moves to the right in the figure) and the screw 13 inside the barrel 11
Negative pressure is generated at the tip of the screw 13, and the resin remaining in the groove of the screw 13 is drawn out to the negative pressure section at the tip inside the barrel. Next, when the nozzle plate 21 is removed and the directional control valve 18 is switched to the a position, and the pressure oil from the hydraulic pump 16 is applied to the oil chamber 15b of the injection cylinder 15, the screw 13 moves to the left in the figure, and the barrel 1
The resin remaining in the barrel 11 is discharged from the barrel 11.
After the discharge operation is completed, the nozzle 22 is again closed with the nozzle touch plate 21, and by repeating the above-described operation, it is now possible to completely replace the resin.

<Effects> As explained above, resin can be easily and inexpensively replaced using the backing device conventionally equipped with injection molding machines.

[Brief explanation of drawings]

FIG. 1 is a diagram showing one embodiment of the present invention. 11... Barrel, 13... Skrill, 15...
Injection cylinder, 16...hydraulic pump, 18...directional switching valve, 19...electromagnetic flow control valve, 21...nozzle touch plate, 22...nozzle.

Claims (1)

[Claims] 1. In a resin replacement method for an injection molding machine that purges by repeating metering and injection operations, the nozzle hole at the nozzle tip is closed and sealed after the injection operation in the final stage of the purge operation is completed, and then the screw is retreated at high speed. A method for replacing resin in an injection molding machine, characterized by repeatedly drawing out residual resin from a screw by generating negative pressure at the tip inside the barrel.