JP5649233B2 - Plasticizing unit for vent type injection molding machine - Google Patents

Description

  The present invention relates to a plasticizing unit in a vent type injection molding machine. In particular, the present invention relates to a vent-type multi-strip plasticizing unit that does not have a vent-up, saves the time required for raw material replacement, and has a low raw material loss.

  Conventionally, non-vented injection molding machines have been used in injection molding, including hygroscopic materials. On the other hand, a vent type injection molding machine is also known in which an exhaust hole (vent) is provided in the cylinder portion, and volatile components such as water vapor generated when the raw resin melts are released from the exhaust hole to the outside of the system. If such a vent type injection molding machine is used, there is an advantage that preliminary drying of the raw material can be omitted because degassing drying can be performed while performing kneading and melting operations.

  However, since the exhaust hole is open to the atmosphere, there is a problem that a bent-up phenomenon occurs in which the melted raw material leaks out of the apparatus through the exhaust hole. Unlike an extrusion molding machine that has a gear pump at the tip of the cylinder and continuously supplies the molten resin, the injection molding machine injects the molten resin in the cylinder batch-wise into the injection mold. It was difficult to reliably prevent vent-up.

Further, in the vent type injection molding machine, the pressure in the cylinder is released at the vent part, so that sufficient pressure cannot be increased in the second stage after the vent part, and the operation is finished compared with a normal injection molding machine. At that time, a large amount of raw material remained on the second stage, and it was necessary to extrude the remaining raw material with compressed air or to extrude it with the raw material to be used next before proceeding to the next operation.
For this reason, it takes time to change the raw material, and there is a problem that a large amount of raw material including the residue of the previous operation, that is, so-called contamination is generated at the start of the operation, resulting in increased raw material loss, making it difficult to put it to practical use.

  In recent years, with the expansion of resin molded product applications, higher quality products have been demanded, and the generation of various gases due to the combination of raw materials has increased. A vent type injection molding machine that does not require treatment has been attracting attention, and a solution to the above-described problems has been desired.

  On the other hand, the raw material supply to the injection molding machine is supplied from the hopper to the injection molding machine via a quantitative feeder, etc., but the bridge phenomenon caused by the pelletized molding material and the overfilling generated in the injection molding machine are problematic. It was.

  As a method for solving this problem, a starvation supply method has been proposed (Non-Patent Document 1). However, in this method, the difficulty of quantitative control that occurs because the material is always supplied in a small amount, the heating cylinder and the molding material Becomes difficult to come into contact with each other, resulting in a problem that the heating efficiency is lowered.

In order to solve these problems, the present inventor has proposed a supply device in which a visual recognition means is attached and fixed in a molding machine (Patent Document 1).
However, no attempt has been made to prevent vent-up of the vent type injection molding machine using such a supply device.

Patent No. 4195404

Plastics, February 2002, page 30, Figure 2

  The present invention solves the various problems in the prior art described above, can efficiently supply raw materials, reliably prevents vent-up, saves the time required for raw material replacement, and is a bent multi-row injection molding with low raw material loss. It is an object to provide a machine.

This inventor makes the screw in the 2nd stage provided with the vent part into the multi-strip shape of 3 or more, and makes the pitch of the screw groove larger than the 1st stage, and the molten material is smoothly transferred in the 2nd stage. Vent-up in the vent part is less likely to occur, and if the raw material supplied to the vent-type injection molding machine is always adjusted to the minimum necessary, the pressure in the vent part can be stabilized without lowering the heating efficiency. Thus, since excessive pressure is not generated in the vent portion, it has been found that vent-up can be reliably prevented and the present invention has been achieved.
According to the present invention, since the screw in the second stage has a multi-strip shape of 3 or more, the volatile components in the molten raw material can be efficiently volatilized, and the amount of residue in the second stage can be greatly reduced. It is possible to reduce the time for raw material change and the raw material loss.

That is, the embodiment of the present invention is as follows.
(1) In a plasticizing unit for a vent type injection molding machine that includes a raw material supply unit, a first stage, a mixing unit, and a second stage, and has a vent unit immediately after the mixing unit, the second stage is provided with three or more A plasticizing unit in a vent type injection molding machine characterized by a strip shape.
(2) The pitch width of the thread groove of the second stage is larger than the pitch width of the thread groove of the first stage, and the sectional area of the thread groove of the second stage is smaller than the sectional area of the thread groove of the first stage. A plasticizing unit for a vent type injection molding machine according to (1), characterized in that
(3) The plasticizing unit for a vent type injection molding machine according to (1) or (2), wherein the raw material supply unit includes a monitoring unit of the raw material supply unit and a raw material supply amount adjusting unit.
(4) The raw material supply means in the vent type injection molding machine of (1) to (3) adjusts the supply amount of the raw material so that a small amount of raw material always stays in the cylinder of the raw material supply unit. Injection molding method.
(5) An injection molding method characterized in that the supply amount of the raw material by the raw material supply means in (4) is adjusted based on image analysis of the monitor means of the raw material supply section.

In the present invention, sufficient deaeration can be performed and vent-up can be reliably prevented for the following reason.
According to the vent type injection molding machine of the present invention, the pitch of the thread groove of the second stage can be increased by the pitch of the groove of the first stage by making the thread groove of the second stage three or more. Therefore, since the molten resin extruded from the mixing part is smoothly transferred to the second stage, the molten resin does not stay in the vent part.
In addition, since the material supply state in the heating cylinder can be visually confirmed by the monitoring means, it becomes possible to supply the minimum necessary raw material into the cylinder, and the cylinder is filled with the raw material, so the heat from the cylinder can be efficiently used. Therefore, the pressure in the cylinder in the first stage can be stabilized because the pressure fluctuation due to the raw material supply unit being filled with the raw material does not occur.

  In addition, since the second stage is composed of three or more multi-thread screws, the molten resin is divided into multi-groove grooves and the contact area with the air increases, so that volatile components from the inside of the raw material easily volatilize. Thus, deaeration is effectively performed.

Moreover, in the present invention, the time for changing the raw material is shortened and the raw material loss can be reduced for the following reason.
In order to move the molten material in the cylinder, it is essential that the friction with the inner wall of the cylinder is greater than the friction with the side wall of the thread groove. The screw cannot be moved and remains in the cylinder. However, if the screw has a multi-strip shape, the molten material moves in a distributed manner in a plurality of screw grooves, so that the cross section of each screw groove is cut off from the screw groove of the first stage. It can be made smaller than the area, and as a result, the depth of the thread groove becomes shallow and it becomes easy to contact the material and the inner peripheral surface of the cylinder, so that the movement is promoted, and the amount of residual material in the cylinder at the end of the operation It can be reduced (see FIG. 3).
Further, when another operation using another raw material is started, the screw groove is shallow, so that the residue is easily removed, and the raw material changing time and the raw material loss can be significantly reduced.

  As described above, according to the vent type injection molding machine of the present invention, the spiral groove of the second stage is formed into three or more strips, and the pitch is larger than the pitch of the grooves of the first stage. The molten resin does not stay in the part, venting up can be prevented, and further, the raw material supply amount is adjusted by the monitoring means for visually confirming the raw material supply state in the raw material supply part, and supplied to the first stage cylinder. If the raw material supply amount is made the minimum necessary, the pressure in the first stage can be stabilized, and vent-up can be reliably prevented.

  In addition, since the spiral groove of the second stage has three or more strips, the molten resin is divided into multiple strips and the contact area with the atmosphere increases, so that volatile components from the inside of the raw material are volatilized. Degassing is effectively performed, and the number of strips of three or more is reduced, so that the depth of the groove can be reduced. Therefore, at the end of the operation, the amount of resin remaining in the groove is significantly reduced. Therefore, it is possible to significantly reduce the time for changing the raw material and the raw material loss.

Overall view of plasticizing unit of vent type injection molding machine of the present invention Drawing comparing thread groove cross-sectional areas Drawing comparing the amount of residue on single and multiple threads

DESCRIPTION OF SYMBOLS 1 Raw material supply apparatus 2 Cylinder 3 Screw 4 1st stage 5 2nd stage 6 Single thread part 7 Mixing part 8 Multiple thread part 9 Vent part 10 Heater 11 Hopper 12 Screw feeder 13 Cylinder raw material supply part 14 Monitor 15 Residue

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is an overall view of a plasticizing unit in a vent type injection molding machine according to the present invention, which includes a raw material supply device 1 and a cylinder part 2, and a heater 10 is attached to the cylinder part 2.
A screw 3 is arranged in the cylinder 2, and the screw 3 has a first stage 4 composed of a single threaded portion 6 and a mixing portion 7, and a second stage composed of three or more multiple threaded portions, and the second stage Is provided with a vent portion 9 for volatilizing volatile components in the molten resin.

  The raw material supply apparatus 1 of the present invention includes a hopper 11, a screw feeder 12 capable of adjusting the supply amount, and a monitor 14 capable of visually checking the raw material supply state of the raw material supply unit 13 in the cylinder. 1 indicates a screen on which the monitor 14 displays the raw material supply state of the raw material supply unit 13 in the cylinder.

  The raw material resin pellets in the hopper 11 are dropped into the raw material supply unit 13 of the cylinder 2 with the supply amount controlled by the screw feeder 12. The supply state of the raw material pellets in the raw material supply unit 13 is photographed by an imaging means provided in the supply device, and can always be visually recognized by the monitor 14.

  The supply amount of the raw material pellets is adjusted so that the pellets dropped on the screw 3 of the raw material supply unit 13 are always kept in a small amount in the raw material supply unit 13 so that the monitor screen in the round frame is displayed. To do. By adjusting the supply amount of the raw material pellets in this way, the minimum necessary raw material is always present in the cylinder, and the pressure in the first stage of the cylinder is stabilized.

  The adjustment of the supply amount of the raw material pellets can be manually performed while the operator visually recognizes the monitor, but it is also possible to automatically adjust the supply amount using analysis software on the monitor screen.

  The single threaded portion 6 of the first stage 4 may have a conventional screw design, and the mixing portion 7 may adopt a conventionally known dalmage type, barrier type, subflight type, wave type or the like.

  The screw 3 of the second stage 5 has three or more multi-thread screw portions 8. In Article 2, the effect of the present invention cannot be sufficiently exhibited, and even if the number of threads is excessively large, individual screw grooves become narrow, and problems such as increase in the frictional resistance of the resin with the groove sidewalls occur. Is 5 or less.

By making the pitch width of the screw part of the second stage 5 larger than the pitch width of the screw part of the first stage 4, the molten resin from the first stage 4 can be smoothly transferred without being retained in the vent part. it can.
The pitch width of the screw portion of the second stage 5 is preferably 1.1 to 1.3 of the diameter D of the screw shaft, and is about 1.2 to 1.6 of the pitch width of the screw portion of the first stage 4. Is preferred. If it exceeds 1.6 times, the friction between the side wall of the thread groove and the molten resin is undesirably increased.

Moreover, since the screw part of the 2nd stage 5 was made into the multi-threaded thread part 8 of 3 or more, the cross-sectional area of 1 groove | channel can be made small. As a guide, the total cross-sectional area of each groove per pitch is approximately the same as the cross-sectional area of the first stage groove (see FIG. 2).
As a result, the molten resin from the first stage 4 comes into contact with the atmosphere while being distributed to the plurality of screw grooves in the vent portion, so that the volatile components inside the resin are also efficiently evaporated. Further, since the depth of the thread groove can be reduced, as shown in FIG. 3, the resin residue 15 in the cylinder can be remarkably reduced at the end of the operation.

  If the plasticizing unit of the vent type injection molding machine of the present invention is used, the preliminary drying of the raw material can be omitted, and a high-quality molded product can be produced at a low cost.

Claims (4)

A single thread groove is formed on the first stage adjacent to the raw material supply section of the screw, a multi-thread thread is formed on the second stage located downstream of the first stage and the mixing section, and a vent section is provided immediately after the mixing section. In the plasticizing unit for a vent type injection molding machine provided, the second stage has a multi-strip shape of three or more, and the pitch width of the thread groove of the second stage is larger than the pitch width of the thread groove of the first stage. A plasticizing unit for a vent type injection molding machine, wherein the sectional area of the thread groove of the second stage is smaller than the sectional area of the thread groove of the first stage . Raw material supply unit, according to claim 1 Symbol placement of the vent type injection molding machine plasticizing unit, characterized in that it comprises adjusting means of the monitoring means and the raw material supply amount of the raw material supply unit. 3. The injection molding method according to claim 1, wherein the raw material supply means in the vent type injection molding machine adjusts the supply amount of the raw material so that a small amount of the raw material always stays in the cylinder of the raw material supply unit. 4. An injection molding method according to claim 3 , wherein the supply amount of the raw material by the raw material supply means is adjusted based on an image analysis of the monitor means of the raw material supply section.

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