JPH0155980B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a quality determination device for molded products in an injection molding machine that can easily determine whether a molded product is a good product or not.

(Prior Art) In injection molding using thermoplastic resin, various quality determination devices have been proposed for determining defective molded products that occur during molding.

Typical examples include those that monitor the resin pressure in an injection cylinder or mold cavity, or those that monitor the oil pressure of a hydraulic circuit that drives an injection plunger.

The principle of such determination devices is to monitor the pressure change and determine whether the product is good or defective, considering that molding defects will occur if the pressure at a predetermined location is out of the appropriate range. Normally, pressure is detected by placing a pressure sensor directly facing the area where pressure is to be detected.

(Problems to be Solved by the Invention) However, all conventional quality determination devices including this device monitor the resin pressure or oil pressure during the injection filling process. It is necessary to monitor constantly changing pressures in an extremely short period of time. For this reason, accurate monitoring is difficult and requires particularly advanced molding knowledge.

In addition, only the pressure during the injection filling process can be monitored, and it is not possible to comprehensively and accurately monitor the effects of other factors that affect quality, such as resin temperature, mold temperature, and injection speed. Can not.

Furthermore, a pressure sensor with high sensitivity and precision is required, and the structure for mounting the sensor becomes complicated, and its operation becomes difficult, resulting in a significant increase in cost and a negative impact on the appearance of the molded product. The reality is that it is difficult to generalize.

Therefore, the present invention eliminates the above-mentioned problems and makes it possible to make accurate and appropriate judgments.
The present invention provides a quality determination device for molded products in an injection molding machine that can be easily implemented at low cost.

(Means for Solving the Problems) The present invention is applied to an injection molding machine M in which a molded product 3 is released from an opened mold 4 by a protruding means 2 as shown in FIG. The determining device 1 is characterized by detecting means 6 and 7 for detecting the moving position between the two points P1 and P2 of the protruding part 5 in the protruding means 2, a time measuring means 8 for measuring the moving time (detection time To) of the protrusion 5;
Travel time corresponding to the quality of molded product 3 (reference time:
a reference time setting means 9 for setting an upper limit time Tu and a lower limit time TL; and a reference time setting means 9 for setting the detection time To and the reference time.
The present invention is provided with a comparison processing means 10 for comparing Tu and TL and outputting a comparison result.

(effect) Next, the operation of the present invention will be explained.

First, during the mold release process, the following happens. The mold 4 into which the material has been injected and filled is moved to a movable mold 12 as shown in FIG.
Move and open the mold. The protruding means 2 is then moved by the hydraulic circuit 13. The protruding portion 5 gradually protrudes from this, and the molded product 3 is released from the mold.

By the way, the magnitude of the injection filling pressure greatly affects the quality of the molded product.If the pressure is too low, molding defects such as insufficient filling (shortage) in which the mold cavity is not completely filled with the molding material will occur; It is known that if the amount is too large, molding defects such as overpacking and burrs may occur due to overfilling of the molding material.

On the other hand, the magnitude of the injection filling pressure also has a correlation with the mold release resistance. That is, as shown in FIG. 3 (characteristic diagram of injection filling pressure versus ejection force), when the filling pressure increases, the adhesion force of the molded product 3 into the cavity increases approximately in proportion, and the mold release resistance also increases. As a result, the moving time for the predetermined period when the protruding portion 5 is protruded also increases. Note that the filling pressure also changes the quality of the molded product 3, such as its weight and dimensions. Therefore, the quality of the molded product 3 can be determined by detecting the moving (detection) time To of the protruding portion 5 in the ejecting means 2 when the protruding portion 5 is protruded.

Therefore, the moving time To between the moving positions P1 and P2 of the protrusion 5 is measured by the time measuring means 8, and the reference time is determined from the reference time setting means 9.
Tu and TL are compared by comparison processing means 10, and TL
If ≦To≦Tu, it is a good product, TL>To, or Tu<
If it is To, it is determined that the product is defective, and a determination signal corresponding to a non-defective product is output.

(Example) Below, preferred examples according to the present invention will be described in detail with reference to the drawings.

FIG. 1 is a longitudinal sectional view of an injection molding machine including a quality determination device according to the present invention.

First, in order to clarify the present invention, the overall configuration of an injection molding machine will be described. The injection molding machine M is an in-line screw type molding machine, and includes an injection cylinder 20 and a screw 21 inserted into the injection cylinder 20 so as to be rotatable and movable back and forth. The injection cylinder 20 has a nozzle 22 at its tip, and a fixed mold 14 fixed to a fixed platen 23 is received in the nozzle 22 . The movable mold 12 is disposed opposite to the fixed mold 14, and the movable mold 12 moves forward and backward relative to the fixed mold 14 on tie bars (not shown) by means of an integral movable platen 24. Fixed type 14 and movable type 12
constitutes mold 4, cavity 15, gate 1
6. A known injection mold having a runner 17 and a sprue 18 is constructed.

On the other hand, the movable mold 12 is provided with a protruding pin 30 facing each cavity, and this pin 30 is moved forward and backward by a protruding plate 31 integrated at its rear end. The protruding plate 31 and the protruding pin 30 constitute the protruding portion 5.

The projecting plate 31 further includes a projecting piston 3 inserted into a projecting cylinder 32 integral with the movable platen 24.
3 is integrally connected.

In addition, a hydraulic power source 41 is connected to the front oil chamber 34 and rear oil chamber 35 of the protruding cylinder 32 via a switching valve 40, whereby pressurized oil is selectively supplied to the front oil chamber 34 or the rear oil chamber 35. A hydraulic circuit 13 that can be constructed.

Therefore, in the mold release process, by supplying pressure oil to the rear oil chamber 35, the ejection piston 33 moves forward in the ejection direction, and the ejection plate 31 and the ejection pin 30
also moves in the protruding direction. As a result, when the mold is opened, the molded product 3 is released from the mold by the ejecting action of the ejecting pin 30 as shown in FIG.

The cycle process of such an injection molding machine M is as follows.

First, after the mold release process is completed, the movable mold 12 and the fixed mold 14 are closed by the operation of the mold clamping ram 25. Next, the process moves to an injection filling process. In this process, the screw 21 is moved forward by a predetermined pressure, and the material W accumulated in front of the screw 21 is charged into the cavity 12. Thereafter, the material W is accumulated in front of it by the rotation of the screw 21, and after a required cooling time, the mold is opened as shown in FIG.
At this time, the molded product 3 is attached to the movable mold 12 side and the fixed mold 1
It is taken out from cavity 4. Therefore, after the mold opening is completed or during the mold opening, the ejecting means 2 may be operated to perform the above-mentioned mold release process, and one cycle process is thus completed.

Next, the molded product quality determination device 1 will be specifically explained. The device 1 first includes the protruding plate 31
The detection rod 50 is integrally attached to the detection rod 50.
Therefore, the rod 50 is displaced following the displacement of the protruding plate 31, and has a detection dog 51 at its end. On the other hand, proximity switches 52 and 53 are disposed opposite to each other at two different positions on the movement trajectory of the detection dog 51. This proximity switch 52,
53 is turned on when the detection dog 51 is located at the position of each switch 52, 53.

Thereby, two moving positions of the protrusion plate 31 can be detected. Note that it is desirable that the proximity switch 52, which is first detected when the mold is opened, detects the initial position of the protrusion plate 31 as much as possible. For this reason, it is usually preferable to provide it at the forward movement start position of the protruding plate 31, and in this case, it can also be used as a position detector for the backward limit of the protruding plate 31.
In addition, at this time, the measurement of the moving time is started by a signal of a command to start moving the protruding part (switching signal of the switching valve 13, etc.)
It is done by.

Further, the proximity switches 52 and 53 are each connected to a time measuring device 54. The measuring device 54 has a built-in timer, and this timer is activated by the first proximity switch 52.
Start with ON, then turn on proximity switch 53
Stop with . This causes both switches 52,5
The moving time of the detection dog 51 during the three periods is measured and set as the detection time To. This detection time To is converted into a voltage value and given to the comparator 55, for example.

On the other hand, a reference time setting device 56 is provided, and this setting device 56 sets a reference time corresponding to the quality of the molded product 3. The reference time is converted into a corresponding voltage value and set, and the upper limit time Tu and lower limit time TL are set. Note that the times Tu and TL can be arbitrarily set variably depending on the type of molded product, such as size, shape, material, etc.

The detection time To and the reference times Tu and TL are respectively supplied to the comparator 55, and as described above, the comparator 55 satisfies the condition of TL≦To≦Tu and determines whether the product is good (for example, a high level signal) or To>TL. , or Tu＜To
A determination signal indicating that the product is defective (for example, a low level signal) is output. This judgment signal may be amplified by an amplifier 57 and directly supplied to the alarm means to be used as an activation signal for activating an alarm by sound or light means, or alternatively, it may be supplied to a sorting device to distinguish defective products from non-defective products. It may also be used as a control signal for automatic selection.

FIG. 2 is a flowchart illustrating the functions of the quality determination device 1 according to the above embodiment.

Although the embodiments have been described above, the present invention is not limited to these embodiments. For example, the proximity switches 52 and 53 can use any detection means capable of detecting position, such as a detector such as an encoder or an optical detector. Furthermore, the comparator 55 may be any electrical circuit, or may use a microcomputer. Furthermore, the detection means and the measurement means are not limited to the examples shown above, and any means capable of detecting the moving time of the protrusion may be used. Furthermore, the ejection cylinder 32 serving as the driving source for the ejection means 2 may be of a hydraulic type or a pneumatic type. Note that when using a hydraulic cylinder, the detection accuracy can be further improved by using a hydraulic power source with an accumulator function. Any other changes in the shape, structure, arrangement, quantity, etc. of details that do not depart from the gist of the present invention are permitted within the scope of the present invention.

(Effects of the Invention) As described above, the quality determination device for a molded article in an injection molding machine according to the present invention is provided in an injection molding machine in which a molded article is released from an opened mold by an ejecting means. Part 2
A position detection means for detecting the movement position between points, a time measurement means for measuring the movement time (detection time) of the protrusion between each movement position, and a movement time (reference time) corresponding to the quality of the molded product. Since the present invention includes a reference time setting means for setting, and a comparison processing means for comparing the detection time and the reference time and outputting a comparison result, the following effects are achieved.

Since the time to be detected is the movement time of the protruding portion, it is possible to monitor the quality of the molded product, which is the result including all the various factors during molding, so comprehensive and accurate monitoring can be performed.

Overall structure is simplified, ease of assembly is improved,
Significant cost reductions can be achieved, and it is also excellent in practicality and versatility, as it can be installed on existing molding machines.

Since it does not affect the molding cavity, injection cylinder, etc. at all, it is possible to eliminate damage such as sensor marks remaining on the molded product.

[Brief explanation of drawings]

Fig. 1 is a vertical cross-sectional side view of an injection molding machine including a quality judgment device according to the present invention, Fig. 2 is a flowchart showing the functions of the quality judgment device of Fig. 1, and Fig. 3 is injection filling pressure versus ejection force. Characteristic diagram. In the drawing, 1...a quality determination device for molded products, 2...
...Extrusion means, 3... Molded product, 4... Mold, 5...
...Protruding portion, 6, 7...Position detecting means, 8...Time measuring means, 9...Reference time setting means, 10...
Comparison processing means, M... Injection molding machine, P1, P2...
...Movement position, To...Detection time, Tu...Upper limit time (reference time), TL...Lower limit time (reference time).

Claims (1)

[Scope of Claims] 1. In an injection molding machine in which a molded product is released from an opened mold by an ejecting means, a position detecting means for detecting a moving position between two points of a protrusion in the ejecting means; a time measuring means for measuring the moving time (detection time) of the protrusion between each moving position; a reference time setting means for setting the moving time (reference time) corresponding to the quality of the molded product; and the detection time and the reference time. A quality determination device for a molded product in an injection molding machine, comprising a comparison processing means for comparing times and outputting a comparison result. 2. The quality determination device for a molded product in an injection molding machine according to claim 1, wherein the reference time is set to an upper limit time and a lower limit time.