JPH0369331A - Correcting method for weight of molding in injection molding machine - Google Patents

Abstract

PURPOSE:To reduce the operation time of workers, and correct the weight of a molding to a standard weight promptly and correctly by measuring the weight of the molding, and calculating the corrected weight in processing a measured effect by a computer, and then outputting it into the control unit of an injection molding machine in order to control the retraction and stopping position of a screw. CONSTITUTION:An injection molding main body made up mainly of an injection cylinder 1 works to mold a molding W in the order of clamping, injection of resin from a nozzle 2 to a mold 11, measuring of resin through the revolution and retraction of a screw 4, mold opening, removing of molding, and mold clamping. A molded article W removed from a mold 11 is carried to an electronic balance 15 by an industrial robot 14. The electronic balance 15 measures the weight of the molding W and outputs the value into a computer 16 and the computer calculates whether or not the weight of the molding is larger or smaller than the standard weight. Where the weight of the molding is larger than the standard weight, a correcting command is outputted so that the weight of the molding becomes the standard weight by decreasing the resin quantity in the measuring period, and where the molded article is smaller than the standard weight, a correcting command is outputted so that it becomes the standard weight by increasing the resin quantity in the measuring period.

Description

[Detailed description of the invention] [Industrial application field] The present invention measures the weight of a molded product molded with an injection molding machine, and if the weight is larger or smaller than the standard weight, the following The present invention relates to a method for correcting the weight of a molded product so that the weight of the molded product becomes a reference weight.

[Conventional technology]

In injection molding, especially in push-cut molding, long-term or gradual changes in the weight of the molded product occur due to external changes during continuous molding, such as changes in the quality of the resin or changes in ambient temperature. do.

In the past, when a worker measured the weight of a molded product and found that the measured weight was larger or smaller than the standard weight, the worker operated the control device of the injection molding machine to adjust the molded product to the standard weight. I'm making adjustments.

[Problem to be solved by the invention]

Workers directly measure the weight of molded products and adjust the control device, which is time-consuming and labor-saving. Furthermore, if it is necessary to stop the operation of the injection molding machine when making the correction, work efficiency will be significantly reduced.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for correcting the weight of a molded product, which does not require the labor of an operator and can quickly and accurately correct the weight of the molded product to a reference weight.

[Means to solve the problem]

In order to achieve the above object, the present invention transports the molded product taken out from the mold to an electronic balance using a conveying means to measure its weight, sends the measurement result to a computer, and uses the computer to weigh the measured product. The corrected weight is calculated by calculating the corrected weight, and the corrected weight is output from the computer to the control device of the injection molding machine to adjust the backward stop position of the screw so that the weight of the molded product becomes the reference weight. It is.

[Effect]

The molded product that has been molded and taken out from the mold is conveyed to an electronic balance by a conveying means, and its weight is measured.

The measurement results are then output from the electronic balance to the computer. The computer calculates a corrected weight by processing the measured weight, and outputs the corrected weight to the control device of the injection molding machine. The control device receives the output from the computer and adjusts the retracted position of the screw so that the weight of the molded product becomes the reference weight.

In this way, the machine performs everything from carrying out the molded product to measuring the weight, calculating, and adjusting the retracted position of the screw, so there is no need for any labor on the part of the operator.

〔Example〕

FIG. 1 shows an example of an injection molding machine that implements the correction method of the present invention, and reference numeral 1 indicates an injection cylinder. At one end of this injection cylinder l (the left end in the figure), a nozzle 2 is installed.
Furthermore, a raw material charging hopper 3 is provided at the other end, and a screw 4 is inserted inside. A rotation drive device 5 such as a hydraulic motor and a hydraulic cylinder 6 are attached to the screw 4 . The rotation drive device 5 rotates the screw 4 in the circumferential direction.
are connected to each other via a transmission mechanism 10 consisting of a drive gear 7, an intermediate gear 8, and a driven gear 9.

The driven gear 9 is attached to the screw 4 with a sliding key (not shown) or the like, and allows the screw 4 to move freely in the axial direction and transmits the rotation of the rotary drive device 5 to the screw 4.

The screw 4 is configured to plasticize the resin introduced from the hopper 3 by rotation in the circumferential direction by the rotary drive device 5, and gradually retreat while storing the plasticized resin on the nozzle 2 side. The hydraulic cylinder 6 moves the screw 4 forward to inject resin from the nozzle 2 into the mold 11, and has a piston rod 6a rotatably connected to the rear end of the screw 4.

Further, the screw 4 is attached with a screw position detection mechanism 12 using an absolute encoder or the like. The screw position detection mechanism 12 is connected to a control device 13 together with the rotary drive device 5.

The screw position detection mechanism 12 detects that the screw 4 has retreated and reached a predetermined position, and its detection signal is output to the control device 13, and the control device 13 receives the detection signal from the screw position detection mechanism 12. In response to this, the rotary drive device 5 is stopped.

As a result, a certain amount of resin is stored at the front end of the screw 4.

Further, reference numeral 14 is an industrial robot serving as a means for transporting molded products, and the molded product W, which has been molded as described above and taken out from the mold 11 by a take-out machine (not shown), is transferred to an electronic balance 15. The industrial robot 14 and the electronic balance 15 are connected to a computer 16, and the industrial robot 14 operates according to instructions from the computer 16 to transport the molded product W to the electronic balance 15, and also transports the molded product W to the electronic balance 15. 15 measures the weight of the molded product W and outputs the measured weight to the computer 16.

The computer 16 has a display 17 and a keyboard 18.
It is connected to the control device 13, receives the measured weight output from the electronic balance 15, compares it with a pre-stored reference weight, and outputs a correction value to the control device 13.

In addition to the above functions, the computer 16 has calculation functions such as data processing and statistical processing of molded product weight, and man-machine functions such as inputting reference weight and displaying measured data.

The control device 13 not only controls the rotary drive device 5 as described above, but also receives a correction signal from the computer 16, and
The structure is such that the retraction stop position of the screw 4 (the position at which the resin measurement is completed) is corrected so that the weight of the molded product becomes the reference weight.

FIGS. 2 and 3 show the actual operation of the injection molding machine shown in FIG. Injection of resin from 2 to mold 11) → Measuring (rotation of screw 4,
The molded product W is molded by operating in the order of (measuring the resin by retreating) → mold opening → molded product removal → mold clamping. The molded product W taken out from the mold 11 by the take-out machine is conveyed to an electronic balance 15 by an industrial robot 14. The electronic balance 15 that receives the molded product W measures the weight of the molded product W and outputs the value to the computer 16, and the computer 16 calculates whether the weight of the molded product is larger or smaller than the reference weight, and If the weight is larger than the standard weight, the amount of resin at the time of measurement is decreased so that the weight of the molded product becomes the standard weight, and if the weight of the molded product is smaller than the standard weight, the amount of resin at the time of measurement is increased. A correction command is output so that the weight becomes the reference weight.

Note that the electronic balance 15 performs origin alignment (09 reset) after the molded product is removed from the electronic balance 15 in order to eliminate measurement errors due to molding burrs and the like.

Here, a typical method of calculating the weight correction amount will be explained as follows.

(a) A method in which an appropriate control range is set for the reference weight, and the difference between the actual molded product weight and the reference weight is used as the corrected weight at the point when the control range is exceeded.

(b) A method in which the difference between the average weight of several shots and the reference weight is used as the corrected weight.

(c) A method of applying correction based on the tendency of weight changes over several shots. In other words, a method that detects trends in weight increase or decrease and performs backward correction for a constant weight.

These calculation methods are selected depending on the type of molded product, operating environment, etc.

By the way, in an injection molding machine, the measured value of the resin is generally not set directly by the weight (9), but by the measuring completion position (or the retracted position) of the screw 4. In this embodiment, the computer 16 calculates the following equation (1) (correction conversion equation) and outputs it to the control device 13.

ΔQ=ΔX/ρ・η×4/φ1π ・Old... (1) However, Δ12 (mm)...Weight value correction amount Δx(9)...Correction weight ρ(9/cc)...Used Resin specific gravity η: Specific volume of resin used.

φ (am)...Screw diameter π...Pi [Effects of the invention] As explained above, the molded product weight correction method of the present invention applies to the molded product taken out from the mold. is carried to an electronic balance by a conveying means, its weight is measured, the measurement result is sent to a computer, the computer processes the measured weight to calculate a corrected weight, and the corrected weight is sent from the computer to the injection coin forming machine. Since the output is output to the control device and the screw retraction stop position is adjusted so that the weight of the molded product becomes the reference weight, the weight of the molded product can be determined quickly and accurately without requiring any labor from the operator. It can be corrected to the reference weight.

Therefore, according to the present invention, it is possible to stabilize the weight of molded products during long-term continuous molding, and to prevent the occurrence of defects by automatically correcting continuous defects caused by changes in weight in an unmanned system. Furthermore, it becomes possible to obtain molded products of uniform quality.

[Brief explanation of drawings]

Fig. 1 is a Bronok diagram of an injection molding machine that implements the correction method of molded product weight according to the present invention, Fig. 2 is a system flow of the injection molding machine of Fig. 1, and Fig. 3 is the same operation flow. . 4...Screw 11...Mold, 13...Control device, 14...Industrial roboto, 15...Electronic balance, 16...Computer.

Claims (1)

[Claims] The molded product taken out from the mold is transported to an electronic balance using a conveying means, its weight is measured, and the measurement result is sent to a computer, where the computer processes the measured weight to calculate a corrected weight, and the corrected weight is calculated. A method for correcting the weight of a molded product in an injection molding machine, comprising outputting the weight from a computer to a control device of the injection molding machine and adjusting a retraction stop position of a screw so that the weight of the molded product becomes a reference weight.