JP2000280289A - Injection molding machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the abrasion resistance of a screw and a heating barrel and especially to reduce the abrasion of the heating barrel near a resin inlet by closing the inlet before the completion of plastication/measurement. SOLUTION: By the rotation of a screw 3 in a plastication/measuring process, after a resin raw material 30 in a hopper 31 is transferred to the tip side of the screw 3, the screw is retracted by the pressure of a molten resin stored in a heating barrel 2, the screw 3 is advanced after the completion of plastication/measurement, and injection to a mold is done. Then a rigid adduct such as glass fibers and mica exists in the raw material 30, the adduct is held between the top part of a screw flight and the inner wall of the heating barrel 2 during the advance of the screw 3 in an injection process to promote the abrasion of the screw 3 and barrel 2. A space C by a resin inlet 2a is formed below a shutter 33, the shutter is closed before the completion of plastication/ measurement, the raw material 30 in the space C is transferred to the front side of the screw 3. In this way, the abrasion of the barrel 2 near the inlet 2a can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection molding machine, and more particularly to an injection molding machine capable of improving the wear resistance of a screw and a heating barrel.

[0002]

2. Description of the Related Art In general, in an injection molding machine, a screw is rotated in a plasticizing and measuring step, and a resin raw material is transferred from a resin inlet to a screw tip side by rotation of the screw. The screw is retracted by the molten resin pressure to complete the plasticization measurement. When the screw is injected into the mold, the screw is advanced without rotating the screw.

In the case where the resin raw material contains a hard additive such as glass fiber or mica (mica), when the screw is advanced in the injection step, a gap between the screw flight top and the inner wall of the heating barrel is formed. There is a problem in that the additional material is interposed between the heating barrels and wear of the inner wall of the heating barrel is accelerated.

[0004] Therefore, conventionally, by devising the base material and surface treatment of the members of the screw and the heating barrel,
A method to improve wear resistance is adopted.

[0005]

The conventional method can improve the wear resistance of the screw and the heating barrel to a certain extent, but the effect is limited to a certain extent and is not always satisfactory. is there.

[0006] The present invention has been made in view of the above points, and is capable of further improving the wear resistance of the screw and the heating barrel, and in particular, reducing the wear of the heating barrel near the resin inlet. An object is to provide a molding machine.

[0007]

In order to achieve the above-mentioned object, the present invention provides a resin raw material supplied from a resin inlet into a heating barrel, and a screw inserted into the heating barrel so as to rotate and move forward and backward. In an injection molding machine for plasticizing and measuring a resin material and injecting it into a mold, a closing mechanism for closing a resin inlet is provided just before plasticizing and measuring is completed.

[0008]

In the present invention, a closing mechanism is provided so that the resin raw material is not supplied from the resin inlet during plasticization measurement. For this reason, it is possible to prevent the wear of the heating barrel near the resin inlet.

[0009]

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows an example of an injection molding machine according to the present invention. In the drawing, reference numeral 1 denotes an injection molding machine. A screw 3 is inserted and arranged in a heating barrel 2 of the injection molding machine 1. The screw 3 is configured to be driven forward and backward by an injection stroke S in an axial direction by an injection cylinder 4 and a hydraulic pressure. The motor 5 is driven to rotate.

At the base end of the heating barrel 2, a resin inlet 2
a is provided, and on the tip side of the heating barrel 2,
A fixed mold 7 is mounted via a fixed plate 6.

A movable die plate 8 is disposed opposite to the fixed plate 6, and a movable die 9 is attached to a portion of the movable die plate 8 opposite to the fixed die 7. The movable mold 9 is moved toward and away from the fixed mold 7 by the mold clamping cylinder 10, and when the mold is clamped, the two molds 7, 9 come into contact with each other to form the cavity 11.

The screw 3 is provided with a position detecting device 12 for detecting the position of the screw 3, and the position detecting device 12 always detects the position of the screw 3 while the screw 3 moves through the injection stroke S. It has become.

In FIG. 1, reference numerals 13 to 16 denote position setting devices, and these position setting devices 13 to 16
An arbitrary position between the injection strokes S can be set. The detected values detected by the position detecting device 12 and the values set in the position setting devices 13 to 16 are compared by comparators 17 to 20, respectively, and when the detected values match the set values, Are designed so that a match signal is output from the comparators 17 to 20 to the speed setting devices 21a to 24a.

Each of the speed setting units 21a to 24a is capable of setting an injection speed (screw moving speed) to an arbitrary value, and the injection speed set by the input of a coincidence signal from each of the comparators 17 to 20. The screw 3 is controlled so as to achieve the speed. That is, the injection stroke S
For example, when the screw 3 has passed a position set in the position setting device 13, the screw 3 is moved to the speed setting device 21.
The injection speed is controlled to be set to a.

Output signals from the speed setting devices 21a to 24a are input to signal switching devices 25a and 25b, respectively.
The output signals from the signal switching devices 25a and 25b control the electromagnetic flow control valves 26 and 27, respectively. The two electromagnetic flow control valves 26 and 27 are held at the opening corresponding to the previous signal until the next signal is input.

The electromagnetic flow control valve 26 controls the flow rate of the pressure oil acting on the injection cylinder 4 to control the injection speed of the screw 3. The electromagnetic flow control valve 27 is a hydraulic motor. The rotation speed of the screw 3 is controlled by controlling the flow rate of the pressure oil acting on the screw 5.

On the other hand, a converter 28 is set on the input side of the signal switching device 25b. The converter 28 is a screw rotation speed corresponding to the injection speed set value from the speed setters 21a to 24a. Is calculated, and the calculation result is sent to the electromagnetic flow control valve 27 via the signal switching device 25b.

The electromagnetic flow control valve 27 is adapted to receive a signal from a screw rotation speed setting device 29 instead of a signal from the signal switching device 25b. Is input to the electromagnetic flow control valve 27, the screw rotation speed is controlled regardless of the injection speed of the screw 3.

On the other hand, as shown in FIG. 2, a hopper 31 for accommodating a resin raw material 30 is connected to the resin input port 2a of the heating barrel 2, and the resin input port 2a is driven by an actuator 32. Shutter 33 is provided.

The actuator 32 includes a switching valve 34
The pressure fluid source 35 is connected via the control valve 36, and the switching valve 34 is controlled to be switched by a command signal from a controller 36. The shutter 33 is normally open, and closes just before the completion of the plasticization measurement.

Next, the operation of this embodiment will be described.
In the plasticizing and measuring step, the screw 3 is driven to rotate, and this rotation causes the resin material 30 from the hopper 31 to rotate.
Is transferred to the tip side of the screw 3. Thereafter, the screw 3 is retreated by the pressure of the molten resin accumulated in the heating barrel 2 by this transfer, and the plasticization measurement is completed. After that, the screw 3 advances and injection into the dies 7 and 9 is performed.

However, when the resin raw material 30 contains a hard additive such as glass fiber or mica,
When the screw is advanced in the injection step, the additional material is sandwiched between the flight top of the screw 3 and the inner wall of the heating barrel 2, and the wear of the screw 3 and the heating barrel 2 is accelerated.

However, in this embodiment, when the screw is advanced in the injection step, the screw 3 is rotated at a rotation speed corresponding to the injection speed.
Are rotated, so that the wear resistance of the screw 3 and the heating barrel 2 can be greatly improved. This will be described below.

When the screw 3 is rotated in the direction of arrow A when the screw is advanced in the injection step, as shown in FIGS. 3 (a) and 3 (b), the resin material 30 in the groove 37 of the screw 3 becomes
It is transported in the direction indicated by arrow B. When the transfer speed matches the forward speed of the screw 3, no force acts on the resin raw material 30 so as to get over the top of the flight 38 of the screw 3.

Next, the relationship between the injection speed and the corresponding screw rotation speed will be described. Generally, screw 3
(Pitch P) is P = D (screw diameter). Here, in order to facilitate understanding, assuming that the injection speed is 1 m / min = 1000 mm / min and the screw diameter is D = 50 mm, the required rotation speed N is

(Equation 1) Becomes

The commonly used injection speed is 3 to 6 m / m
In, the rotation speed N of the screw 3 at that time is:
From the above equation, 20 × (3 to 6) = 60 to 120 (rpm).

Therefore, the injection speed is set to 3 to 6 m / min.
In the case of the screw 3 having a diameter of 50 mm, the rotational speed N may be changed between 60 and 120 rpm.

Incidentally, in FIG. 1, the signal switching device 2
When the rotation speed of the screw 3 is controlled by a signal from the screw rotation speed setting device 29 instead of the signal from the screw 5b, the screw rotation speed may not match the injection speed. When the screw rotation speed is lower than the injection speed, for example, some% of the resin material 30 gets over the top of the flight 38 as the screw 3 moves forward, and the worn resin material 30 causes a little wear. It becomes a problem. However, compared with the case where the screw 3 is not rotated, the wear is extremely small, and the expected effect can be sufficiently expected.

Further, in the above embodiment, as shown in FIG. 2, the shutter 33 is closed just before the completion of the plasticization measurement. Therefore, abrasion of the heating barrel 2 near the resin inlet 2a can be prevented. This will be described below.

When the shutter 33 is provided in the resin inlet 2a, it is structurally difficult to provide the shutter 33 close to the screw 3, so that a space C is formed below the shutter 33 by the resin inlet 2a. Will be done.

If the shutter 33 is closed after the plasticization measurement is completed, the unmelted resin material 30 in the space C falls into the groove 37 of the screw 3 at the time of injection. The heating barrel 2 near the resin inlet 2a may be worn by the raw material 30.

However, in this embodiment, the shutter 33 closes just before the completion of the plasticization measurement, and the resin material 30 in the space C is
Since it is transferred to the front side of the screw 3 before the plasticization measurement is completed, there is no problem as described above.

The inventor of the present invention has proposed the injection molding machine 1 of the above embodiment.
The resin containing PP (polypropylene) mica, which is a resin raw material in which abrasion of the screw 3 and the heating barrel 2 is particularly severely generated, was injection-molded, and the degree of abrasion was measured.

As a result, it has been confirmed that what had been unstable in measurement in three months in the past was able to sufficiently withstand long-term use, and it was found that the abrasion resistance could be greatly improved.

[0036]

As described above, according to the present invention, since the resin inlet is closed shortly before the completion of the plasticization measurement, the wear of the heating barrel near the resin inlet can be prevented.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram showing an injection molding machine according to one embodiment of the present invention.

FIG. 2 is an explanatory view showing details of a resin inlet around a shutter;

FIGS. 3A and 3B are explanatory diagrams showing a relationship between an injection speed and a screw rotation speed.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Injection molding machine 2 Heating barrel 2a Resin inlet 3 Screw 4 Injection cylinder 5 Hydraulic motor 7 Fixed mold 9 Moving mold 12 Position detecting device 13, 14, 15, 16 Position setting device 17, 18, 19, 20 Comparator 21a, 22a, 23a, 24a Speed setting device 25a, 25b Signal switching device 26, 27 Electromagnetic flow control valve 28 Converter 29 Screw rotation speed setting device 30 Resin raw material 31 Hopper 33 Shutter 36 Controller 37 Groove 38 Flight

Claims (1)

[Claims] 1. A resin raw material is supplied from a resin inlet into a heating barrel, and the resin raw material is plasticized and measured by a screw inserted into the heating barrel so as to rotate and move forward and backward, and is injected into a mold. An injection molding machine characterized in that a closing mechanism for closing a resin inlet is provided just before plasticization measurement is completed.