JP3173359B2 - Operation method for screw prepra injection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for operating a screw prepeller type injection apparatus used for injection molding of a synthetic resin.

[0002]

2. Description of the Related Art A general screw pre-plaster type injection device has a plasticizing cylinder mounted inside a screw in parallel with an injection cylinder mounted inside a plunger, and a leading end of the plasticizing cylinder and a leading end of the injection cylinder are connected by a resin path. do it,
After the resin melted and kneaded (hereinafter referred to as plasticization) in the plasticizing cylinder is filled and measured in the front portion of the injection cylinder, the injection is performed by advancing the plunger.

[0003]

In such a screw prepra injection apparatus, since the resin is plasticized by a screw rotating at a fixed position, an in-line screw type in which the plasticizing is carried out by a screw which retreats while rotating. It is said that plasticization can be performed uniformly compared to injection equipment, but it is not necessarily performed uniformly, and depending on the screw design, material condition and characteristics, etc., plasticization is likely to be uneven and temperature It may even cause unevenness.

[0004] The uneven temperature can be improved by making the resin path connecting the injection cylinder and the plasticizing cylinder a small-diameter resin path provided with a heater on the outer periphery and forcibly flowing the resin path. Although it is possible to improve the plasticized state uniformly in the course of the flow of the resin path, the optimum rotational speed of the screw differs depending on the type of the material resin and is determined by the material resin used.

Therefore, the speed of the plasticized resin which is sent out at the rotation speed determined by the material resin and passes through the small-diameter resin path is not necessarily from the viewpoint of further plasticizing the material resin and improving the temperature unevenness. It cannot be said that the speed is optimal, and it is not enough to control the state of the material resin employed therein.

The speed of the plasticized resin passing through the small-diameter resin path is proportional to the rotation speed of the screw. Therefore, if the rotation speed is increased, the passage speed is inevitably increased. It is extremely difficult to achieve optimum conditions by controlling the rotation speed because if the screw speed is high, the speed can be increased, and vice versa.

[0007] In the plasticization by a screw rotating at a fixed position, the plasticized resin is continuously discharged to the injection cylinder side, and the plunger is retracted by the discharge force to measure the resin. During the period from the start of the injection filling by the advance to the holding pressure, the rotation of the screw is stopped to stop the plasticization. Therefore, there is also a problem that it is difficult to shorten the molding cycle by performing the injection and the plasticization in parallel.

The present invention has been conceived in order to solve the above-mentioned conventional problems, and has as its object to control the rotation speed of a screw in a plasticizing apparatus to plasticize a material resin and prevent the plasticization of the resin before the plasticizing cylinder. The primary metering into the section and the control of the screw advance speed allow the plasticized resin to pass through the small-diameter resin path at the optimum speed, thereby improving plasticization of the material resin and solving temperature unevenness. Another object of the present invention is to provide a new operation method in a screw prepeller type injection apparatus capable of shortening a molding cycle.

[0009]

SUMMARY OF THE INVENTION According to the present invention, there is provided an injection apparatus having a plunger moving device at a rear portion of an injection cylinder in which an injection plunger is retractably mounted.
A screw moving device and a rotating device are provided at the rear of a plasticizing cylinder in which an L / D having a compression ratio of 1 and an L / D of 15 or less and a screw groove having a fixed depth and having no compression portion are rotatably and reciprocally mounted. And an inflow path of a part corresponding to a plunger advancement limit at the tip of the injection cylinder,
It communicates with a resin path with an open / close valve having a temperature control means on the outer circumference with a small diameter provided over the outflow path at the tip of the plasticizing cylinder, and the open / close valve is closed when the plunger retreats to the set position, and the screw is rotated. While the plasticization and retreating can be performed in parallel with the injection filling operation, the plasticizer is opened when the plasticization is stopped, and the entire amount of the resin measured and plasticized by the screw rotation and retreating and accumulated in the tip of the cylinder is released. Filling the plunger front part of the injection cylinder from the resin path by the screw advance after rotation stop,
The speed of the plasticized resin passing through the resin path is arbitrarily changed by controlling the forward speed of the screw by the screw moving device. Further, the plunger moving device of the injection device and the screw moving device of the plasticizing device are hydraulic cylinders, and the forward speed of the screw can be arbitrarily changed by controlling the flow rate of the hydraulic oil of the hydraulic cylinder. The rotating device may be an electric motor.

In the above configuration, the resin can be measured by retreating the rotation of the plasticizing screw, so that the plasticization and the measurement of the material resin can be performed even during injection filling by cutting off the small-diameter resin path. Since the resin to be measured is forcibly pressed into the resin path by the pressing force due to the forward movement of the resin, the press-fitting of the resin into the injection cylinder and the filling and measuring can be completed in a short time.

The speed of the plasticized resin passing through the small-diameter resin path can be arbitrarily varied by controlling the forward speed of the screw. The screw has a compression ratio of 1 and the L / D is 15 or less. Since a screw having no compression portion formed at a constant depth is employed, heat generation due to shearing force and frictional force during compression can be suppressed, and discoloration of the resin due to overheating can be prevented.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the drawings, reference numeral 1 denotes an injection device, and 2 denotes a plasticizing device. The plasticizing device 2 has a distal end portion 21 of a plasticizing cylinder 20 located behind a distal end portion 11 of an injection cylinder 10. It is juxtaposed on the injection device 1. The two devices are connected to each other by a small-diameter resin path 3 provided obliquely over the distal ends 11 and 21.

The injection device 1 includes an injection plunger 12.
The above-mentioned injection cylinder 10 in which a nozzle member 13 is extended long at the tip, and the injection cylinder 1
0, and the piston 14 is connected to the plunger 12
And an injection hydraulic cylinder 15 connected to the
A rotary opening / closing valve 16 is provided in the injection path of the nozzle member 13.

The injection cylinder 10 has an inflow path of the resin path 3 at an upper portion corresponding to a plunger advance limit of the tip section 11, and the inflow path is provided with a rotary opening / closing valve 17 having the same diameter as the resin path 3. It is. Further, a resin vent hole 18 is provided in a wall portion behind the plunger stroke of the injection cylinder 10, and a band heater 19 is provided from the nozzle tip portion to the periphery of the cylinder after the resin vent hole 18 to extend the heater zone. It has been set. As a result, the resin that has entered the periphery of the plunger is sent rearward each time the plunger 12 retreats, and is discharged to the outside through the resin removal hole 18.

The plasticizing device 2 includes a plasticizing cylinder 20
, A plasticizing screw 22 is provided so as to rotate and move forward and backward. The depth of the screw groove of this screw 22 is constant, has no compression portion, and L / D at a compression ratio of 1 is 1
5 or less, the rear end of which is a plasticizing cylinder 20
Is connected to a piston 25 of a hydraulic cylinder 24 provided on a rear holding member 23.

A hydraulic or electric motor 26 for screw rotation is attached to the rear end of the hydraulic cylinder 24. A rotary drive shaft 27 projecting from the motor 26 into the hydraulic cylinder and the piston 25 are connected to a spline or the like. Thus, the screw 22 is movably fitted in the axial direction so that the screw 22 can be rotated via the piston 25.

A band heater 28 is attached to the outer periphery of the plasticizing cylinder 20, and a hopper 29 is attached to a supply hole at the rear end of the plasticizing cylinder 20 fitted to the holding member 23.

The resin path 3 having a small diameter is made of a thin metal tube having an inner diameter of about 5 to 10 mm.
Temperature control means. Further, the resin path 3 is provided at an acute angle obliquely forward with an inclination angle of 40 ° to 50 ° over the distal end portion 11 of the injection cylinder 10 and the distal end portion 21 of the plasticizing cylinder 20.

The injection device 1 and the plasticizing device 2 are connected to a support 30 provided on the hydraulic cylinder 15 of the injection device 1.
Then, the holding member 23 of the plasticizing device 2 is placed and fixed,
A base block 4 which is constituted by an upper and lower two-stage screw pre-plastic injection device and is provided below the hydraulic cylinder 15
Are slidably mounted in the front-rear direction on the machine base 5 and mounted on the machine base 5.

The forward / backward movement of the screw prepeller type injection device is caused by the hydraulic cylinder 7 and the piston 7a extending between the rear end of the base block 4 and the receiving member 51 protruding from the upper surface of the base plate 5, and the piston 7a extends. In each case, the injection device 1 and the plasticizing device 2 move forward, and the tip of the nozzle of the injection device 1 is not shown in the drawing. The movement moves away from the sprue or the like so that material purging or maintenance of the apparatus can be performed.

Next, the injection operation will be described. First, the resin path 3 is closed by an opening / closing valve 17, and a predetermined back pressure is applied to the plunger 12 in the injection cylinder by the hydraulic cylinder 15.

After such preparation, the resin material of the pellets is fed from the hopper 29 to the plasticizing cylinder 20 while the screw 22 is rotated by the motor 26, and the resin material is transferred to the front portion of the cylinder by a screw groove having a constant depth. Is transferred. During this transfer, heating is performed from the cylinder side by the band heater 28 and a certain amount of shear heat generated by the rotation of the screw 22 is sequentially fed forward while being melted and kneaded. The screw 22 retreats due to the resin pressure generated by the plasticization, but the plasticization is continued. As the screw 22 retreats, plasticized resin is sequentially accumulated in the cylinder at the front of the screw. The amount of accumulation differs depending on the amount of screw retreat.

When the accumulated amount reaches a predetermined amount, the rotation of the screw 22 is stopped, the plasticization of the material resin is also stopped, and the screw stops at the retracted position. As a result, a set amount of resin is primarily measured in the cylinder at the front of the screw. Almost simultaneously with the stop, the opening / closing valve 17 is opened, and the resin path 3 communicates with the injection cylinder side. Therefore, when the screw 22 is moved forward by the hydraulic cylinder 24, the plasticized resin after measurement is forcibly pushed into the resin path 3 having a small diameter. The forward speed of the screw 22 can be arbitrarily changed by controlling the flow rate of the pressure oil supplied to the hydraulic cylinder 24.

On the side of the injection cylinder, only a predetermined back pressure is applied to the plunger 12 and there is nothing to prevent the injection of the resin, so that the total amount of the plasticized resin primarily measured at the front of the screw 22 is The resin is passed through the resin path 3 by the pressing force of the screw 22, and is filled in the front portion of the injection cylinder 10 while the plunger 12 is moved backward. On this occasion,
In the resin path 3, the plasticized resin flows into the front portion of the injection cylinder 10 while being further plasticized by the flow resistance during the passage through the narrow tube and the external heating.

The retraction of the plunger 12 causes the plasticized resin to accumulate again in the front portion of the injection cylinder 10, so that the injection amount is accurately measured. And plunger 12
Is retracted to the set position, the opening / closing valve 17 is closed to close the resin path 3, and the plunger 12
The process is switched to the injection process of the plasticized resin by the forward movement of. On the plasticizing device side, the screw 22 rotates and plasticization of the material resin is performed again.

When the plunger 12 is moved forward by the hydraulic cylinder 15 with the resin path 3 closed, the entire amount of the plasticized resin measured in the injection cylinder is injected and filled into a mold (not shown) from the nozzle tip. Is done. After the filling is completed, a predetermined pressure is applied to the plunger 12 by the hydraulic cylinder 15 to maintain the pressure of the resin. At the time when the pressure holding is completed, or in some cases, before the completion, the opening / closing valve 16 is closed to shut off the injection passage, and the process shifts to cooling.

When the opening / closing valve 17 of the small-diameter resin passage 3 is opened after the injection passage is shut off, the injection device 1 is moved from the plasticizing device 2 side of the plasticized resin measured by the opening of the resin passage 3.
Side filling is possible. When filling, screw 22
Since the rotation of the screw 22 is already stopped, the filling can be performed by the forward movement of the screw 22 regardless of the rotation of the screw. For this reason, the process in which the plasticized resin passes through the resin path 3 having a small diameter can be arbitrarily controlled by controlling the forward speed of the screw. As a result, the state of the plasticized resin can be further improved.

In the plasticizing device 2, since the plasticizing operation of the material resin is performed in parallel with the injection filling operation by the injection device 1, immediately after the completion of the injection filling and the pressure holding, the plasticizing operation is performed to the front of the injection cylinder. Since the resin to be measured can be injected and filled, and the resin previously measured on the plasticizing cylinder side can be re-measured on the injection cylinder side, the measuring accuracy can be improved and the cycle can be shortened and the cycle can be increased.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional side view of an embodiment of a screw prepra type injection device according to the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 injection device 2 plasticizing device 3 small-diameter resin path 10 injection cylinder 12 injection plunger 13 nozzle member 15 injection hydraulic cylinder 16 injection path opening / closing valve 17 resin path opening / closing valve 20 plasticizing cylinder 22 plasticizing Screw 24 Hydraulic cylinder for screw forward and backward movement 26 Motor for screw rotation

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B29C 45/00-45/84

Claims (3)

(57) [Claims] 1. An injection device having a plunger moving device at a rear portion of an injection cylinder in which an injection plunger is housed so that the plunger can move forward and backward. At the rear of the plasticizing cylinder, in which the formed screw without compression part is rotatably and retractably housed, a plasticizing device with a screw moving device and a rotating device is attached at the part of the tip of the injection cylinder that corresponds to the plunger advance limit. The inflow path is communicated with a resin path with an on-off valve provided with a temperature control means on the outer circumference, which is provided with a small diameter and is provided between the inflow path and the outflow path at the end of the plasticizing cylinder. , While plasticizing by screw rotation and weighing by retreating can be performed in parallel with injection filling work, while opening when plasticization stops, screw rotation and retreating The entire amount of metered resin that has been plasticized and accumulated in the tip of the cylinder is filled into the front of the plunger of the injection cylinder from the resin path by the screw advancement after rotation stop, and the speed of the plasticized resin passing through the resin path is An operation method in a screw prepeller-type injection device, wherein the operation is arbitrarily changed by controlling a screw advancing speed by the screw moving device. 2. A hydraulic cylinder as a plunger moving device of the injection device and a screw moving device of the plasticizing device,
2. The resin operating method according to claim 1, wherein the forward speed of the screw can be arbitrarily changed by controlling the flow rate of pressure oil of a hydraulic cylinder. 3. The operating method according to claim 1, wherein the screw rotating device of the plasticizing device comprises an electric motor.