JPH02182366A - Method for discriminating quality of forming product in injection molding apparatus - Google Patents

Abstract

PURPOSE:To discriminate the quality of a forming product during casting by comparing difference between additional stroke of an injection plunger advanced from completion of filling up molten material into cavity to completion of solidified shrinkage with the normal advancing stroke. CONSTITUTION:The molten metal 12 is supplied into an injection sleeve 5 from a pouring sprue 5a, and after filling up the molten metal 12 into the cavity 4 with a plunger tip 11 by advancing the injection plunger 9, further the molten metal 12 is pushed to make the molten metal 12 close with feeder head action of an injection cylinder 7. In the casting process, a forming product quality discriminating device 20 is attached in an injection forming apparatus, and magnetic scale 21 is advanced together with coupling 10, and the additional stroke of the magnetic scale 21 from the completion of filling up the molten material to the completion of the solidified shrinkage detected with a position detector 22 is transmitted to a computing element 25 through an amplifier 23. The computing element 25 compares the difference between the measured additional stroke with the normal additional stroke decided previously with X-ray inspection at the time of trial before working mass-production, and in the case the measured additional stroke is smaller than the normal additional stroke, this is decided as the deteriorated product.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for determining the quality of a molded product during the injection process in an injection molding apparatus such as a die casting machine or a plastic injection molding machine. It is.

[Prior Art] In injection molding equipment such as die casting machines and plastic injection IH molding machines, molten metal or molten resin is injected into the cavity of a clamped mold, and as the molten material solidifies, A molded product is obtained.

In such injection operations, when the molten material is extruded by a plunger, air may be drawn in and enter the cavity, where it may be mixed in with the molten material, resulting in the formation of cavities in the molded product. There was a problem in that the quality deteriorated.

Conventionally, X-ray inspection has been used to examine the presence or absence of cavities by exposing the molded product to X-rays and checking the difference in transmission and absorption of X-rays depending on the density, or by sending ultrasonic waves to the molded product and receiving the reflected sound. Ultrasonic testing and other methods were used to determine the quality of molded products.

[Problems to be Solved by the Invention] However, in such conventional molding quality determination methods, it is not always possible to expect a satisfactory determination result, and since the inspection is performed in a process after the injection process, it is possible to There were problems in that countermeasures were delayed in the event of a large number of non-defective products, and it was difficult to grasp the incidence of defective products by manufacturing loft.

[Means for Solving the Problems] In order to solve the above problems, in the present invention, as a method for determining the quality of a molded product in an injection molding apparatus, after filling the melt into the cavity is completed, the above-mentioned The stroke increment of the injection plunger advanced during the time until the molten material completes solidification and contraction is converted into a normal stroke increment obtained from the X-ray test results during a trial before mass production operation or a stroke of the solidification number lil amount with respect to the cavity weight. The quality of the molded product was determined by comparing the size with the normal stroke increment obtained.

[Function] Comparing the stroke increment of the injection plunger for each shot with the normal stroke increment when injecting a predetermined normal molded product, it is found that during normal injection, it is almost the same as or more than the normal stroke increment. In contrast,
If the stroke increment is clearly smaller than the normal stroke increment, casting defects such as shrinkage holes will be discovered by X-ray inspection or ultrasonic inspection after the product is taken out. therefore,
There is a clear correlation between the quality of the molded product and the stroke increment, and by controlling the operation using this value as a control value during operation, online quality control can be performed.

[Example] FIGS. 1 to 3 are diagrams shown to explain the molding quality determination method according to the present invention, in which FIG. 1 is a schematic configuration diagram of a die casting machine, a flowchart of a molding quality determination device, and Figure 2 shows a relationship diagram between the injection time of the injection plunger and the pressure and stroke of the injection cylinder in a die-casting machine. These are stroke relationship diagrams, and both of them show normal values during a trial (test run) before mass production operation.On the other hand, Figure 3 shows a relationship diagram during actual operation, and Figure 3 ( a) is a time-pressure relationship diagram, Figure 3 (
b) shows a time-stroke relationship diagram when forming a good or bad product, and FIG. 3(c) shows a time-stroke relationship diagram when molding a defective product. (a) and (b) in FIGS. 2 and 3 or (a)
, (b), and (c) are all behaviors with respect to the same time axis.

In the figure, the die casting machine includes a fixed mold 1a mounted on a fixed platen 1, and a movable mold 2a mounted on a movable platen 2, which is clamped and opened by moving forward and backward with respect to the fixed mold 1a. It is equipped with.

Cavities 4 are formed on both sides of the dividing surface 3 of the clamped molds 1a and 2a. An injection sleeve 5 having a pouring port 5a is inserted into the sleeve hole of the fixed fil, and the inner hole thereof and the cavity 4 are communicated through a gate 6 and a sleeve lb provided in the molds 1a and 2a. There is. Reference numeral 7 denotes an injection cylinder disposed concentrically with the injection sleeve 5, and an injection plunger 9 is connected to the piston rod 8, which moves back and forth using hydraulic pressure, via a coupling 10. The plunger tip 11 is fitted into the inner hole of the injection sleeve 5 so that it can move forward and backward.

With this configuration, in the state shown in FIG.
When the piston rod 8 is advanced by the hydraulic pressure of the injection cylinder 7, the plunger tip 11 moves into the injection sleeve 5.
The molten metal 12 is pushed out and injected into the cavity 4 through the gate 6. Once the molten metal 12 has been filled into the cavity 4, the molten metal in the cavity 4 is further pushed by the pressing force caused by the action of the injection cylinder 7, which continues to push, and is subjected to a feeder action, so that the molten metal in the cavity 4 becomes more dense. Filling is completed. Thereafter, the molten metal is allowed to solidify and cool, and then the mold is opened and the solidified cast product is taken out from the cavity 4.

Die casting machines configured and operated in this way include:
A molding quality determination device, generally designated by the reference numeral 20, is attached.

That is, a magnetic scale 21 is fixed to the coupling 10, which is parallel to the piston rod 8 and moves forward and backward integrally therewith.
A position detecting detector 22 electrically connected to the computing unit 25 via 3 and provided with a pulse transmitter is fixed to and facing the machine base side. Then, the position detection detector 22
However, each time the magnetic scale 21 moves by 1 mm, that is, each stroke (st) imm of the plunger tip 11, a signal is generated and transmitted to the computing unit 25. Further, a crystal oscillator 24 that emits a signal at a natural frequency by passing an electric current is electrically connected to the calculator 25, and a monitor device 26 that displays the injection stroke is electrically connected to the calculator 25. . The monitor device 26 is configured to digitally display the position of the injection stroke, that is, the position of the plunger tip 11 when the pressure on the head end side or the rod end side of the injection cylinder 8 suddenly increases.

On the other hand, electric signals from a pressure sensor 31 that keeps the head pressure PH of the injection cylinder constant M and a pressure sensor 32 that measures the rod pressure PR are input to the calculator 25 via an amplifier 33.

With the configuration as described above, the plunger tip 11 can be used to inject the molten metal 12 into the cavity 4.
When the magnetic scale 21 is advanced, the magnetic scale 21 is connected to the magnetic scale 21.
moves, and the position detecting detector 22 facing it issues a signal every 1 mm movement of the magnetic scale 21, and inputs the stroke (St) of the plunger tip 11 every 1 mm to the arithmetic unit 25 via the amplifier 23. Therefore, the im advance movement position of the plunger tip 11 of the injection cylinder 7 from the start position is determined as the movement distance,
A position signal is sent to the arithmetic unit 25 via the amplifier 23.

Further, when a current is passed to the crystal oscillator 24, it is transmitted at a natural frequency and inputted to the calculator 25, so that the time required to pass between two positions of the stroke and the passing speed between the two positions can also be obtained. As a result, in the computing unit 25, the plunger chip 11
The time it takes for the stroke to move 1 mm is calculated, and the monitor device 26 can digitally display the stroke position and passing speed at each point on the display surface 26a.

In the present invention, as a result of the so-called curing time (curing time) from the completion of filling the molten material into the cavity until the completion of solidification shrinkage, solidification shrinkage and mixing into the molten material within the cavity occur due to the injection cylinder being pressed at high pressure. We focused on the fact that the stroke increment of the plunger tip 11 of the injection cylinder due to the discharge of the gas that had been used is different between a defective molded product and a good molded product, and the stroke increment of a defective molded product is smaller than that of a good molded product. The aim is to use this stroke increment as an index to determine the quality of the molded product.

By the way, the inventor of the present invention has experimented with various injection conditions and found that in every case, the rise position where the oil pressure on the head end side and the rod end side of the injection cylinder 7 suddenly increases, and the transition from low speed injection to high speed injection. We have confirmed the phenomenon that the switching position always coincides within a practically acceptable range.

That is, during injection in a die-casting machine, at the initial stage of injection, the amount of hydraulic oil supplied from the hydraulic pump to the injection cylinder is small, so the piston of the injection cylinder moves at a low speed of, for example, 0.1 to 0.2 m/sec. It moves forward, but during that slow forward movement.

When the piston moves forward, the pressure does not increase much because there is little frictional resistance between the outer peripheral surface of the piston S and the inner peripheral surface of the cylinder. Normal injection cylinder is 15-20kg/cm"
That's about it.

However, in the middle of injection, based on a command to switch to high-speed injection, a large amount of hydraulic oil that had been stored in the accumulator at a high pressure of, for example, 140 kg/crn' or 210 kg/c, suddenly flows from the accumulator into the injection cylinder. When the piston is pushed in, the piston begins to move forward at a high speed of 1 to 5 m/sec. At this time, as the piston attempts to move forward at high speed, the frictional resistance between the outer circumferential surface of the piston and the inner circumferential surface of the cylinder increases, and the hydraulic oil that has been stored at high pressure in the accumulator is transferred to the injection cylinder. The pressure in the injection cylinder increases rapidly. Of course, at this time, a peak pressure of, for example, 40 to 60 kg/crn' is generated due to the water hammer phenomenon accompanying the rapid supply of high-pressure hydraulic oil into the injection cylinder.

Then the peak pressure subsides and the piston moves, e.g.
It continues to move forward at high speed at a pressure of 0 to 50 kg/cm'', and when the mold cavity is filled with molten metal and the injection operation is completed, the piston stops moving forward and the pressure in the injection cylinder is 140 kg/crn' or 210 kg. The set pressure of the hydraulic pump becomes approximately /crn', and the feeder action is performed.

In this way, just as the oil pressure in the injection cylinder rises rapidly when transitioning from low-speed forward movement to high-speed forward movement, it also increases when high-speed injection is completed, the piston stops moving forward, and the riser action begins. Pressure rises rapidly.

That is, as shown in FIG. 2 (and the same applies to FIG. 3), the time T1 when filling the cavity is completed is the time when high-speed injection is completed, that is, when the pressure in the injection cylinder reaches a position where it rapidly increases. On the other hand, the solidification and shrinkage completion time T2 is selected as the curing time completion time or an arbitrarily set time, and the stroke increment of the plunger tip 11 of the injection cylinder from time T1 to time T2 is set as ΔS.

Then, the stroke increment ΔS when a normal, non-defective molded product is obtained is determined in advance by a required number of trial strokes during a trial run before mass production operation, and this value is set as the normal stroke increment ΔS. . This normal stroke increment Δ
In addition to the above experimental results, S may be determined from the stroke conversion value of the solidification shrinkage amount with respect to the cavity weight.

On the other hand, the stroke increment during actual operation is measured as follows. That is, during actual operation, when the plunger tip 11 reaches the high-speed injection speed switching position,
A signal from a pressure sensor 31 that detects the pressure (PH) on the head side of the injection cylinder 7 is sent to a computing unit 25 via an amplifier 33.
, this time T, and the above-mentioned solidification and contraction completion time T
The stroke increment is determined from the digital signal from the magnetic scale 21 at 2 and 2. The stroke increment ΔS1 in FIG. 3(b) shows the stroke increment when forming a good product, and the stroke increment ΔS2 in FIG. 3(c) shows the stroke increment when forming a defective product. The stroke increment ΔS2 during defective product molding is generally equal to or greater than Δs2.
Since <ΔS, it is possible to perform online determination of non-defective products even during operation based on the display during operation by the monitor device 26.

Regarding actual examples, - To give an example, for curing time ΔT of T1 to T2 = 1.2 seconds, normal stroke increment ΔS = 2.4 mm, good product stroke increment Δ51 = 2
．． 5 mm, the defective stroke increment Δs2 = i during molding of defective products was 5 mm, and a significant difference was clearly observed.

[Effects of the Invention] As described above, the present invention is a method for determining the quality of a molded product of an injection molding apparatus, by determining the stroke increment from the time when the filling of the molten material into the cavity is completed until the time when the solidification and shrinkage is completed, using a predetermined normal control method. Since it uses a simple and easy method of comparing stroke increments and sizes, it is possible to immediately determine whether a good product is good or not good online during casting, and the wasteful non-destructive testing process after casting can be omitted.

[Brief explanation of the drawing]

1 to 3 are diagrams shown to explain the molding quality determination method according to the present invention, in which FIG. 1 is a schematic configuration diagram of a die casting machine, a flowchart of a molding quality determination device, and ), (b) shows a relationship diagram between the pressure and stroke of the injection cylinder during the trial, Figure 2 (L) shows a time-pressure relationship diagram, and Figure 2 (b) shows a time-stroke relationship diagram. , Figure 3 (a), (b)
, (c) shows the relationship diagram between the pressure and stroke of the injection cylinder during actual operation, Figure 3 (a) shows the time-pressure relationship diagram, and Figure 3 (b) shows the time-pressure relationship diagram during molding of a good product
Stroke relationship diagram. FIG. 3(C) is a time-stroke relationship diagram during molding of defective products. l...Fixed plate, 2...Movable plate, 3...Divided surface, 4...Cavity hole 5...Injection sleeve, 6 ...Gate 7 ... Injection cylinder, 8 ... Piston rod, 9 ... Injection plunger, 1 ... Plunger tip, 0 ... ... Molding quality determination device. ■... Magnetic scale, 2... Position detection detector, 3... Amplifier, 24... Crystal oscillator, 5... Arithmetic unit , 26...
Monitor device, 1.32...Pressure sensor 3...Amplifier. Patent applicant: Ube Industries Co., Ltd. Draft procedure amendment (method) May z, 1999

Claims (1)

[Claims] (1) The stroke increment of the injection plunger advanced during the period from when the filling of the molten material in the cavity is completed until the solidification and contraction of the molten material in the cavity is completed is determined in advance by X-ray inspection results during a trial period before mass production operation. The quality of the molded product in an injection molding apparatus is determined by comparing the normal stroke increment obtained from the normal stroke increment or the normal stroke increment obtained from the stroke conversion of the solidification shrinkage amount with respect to the cavity weight to determine the quality of the molded product. Discrimination method.