JPS6360505A - Controlling method for degaussing of magnetic injection molding machine - Google Patents

Abstract

PURPOSE:To achieve sufficient degaussing in a magnetic injection molding machine by stopping the energization of a magnetic field generating coil to supply a small current in the opposite direction to the previous current when the absolute value of a detected voltage value is lower than a set voltage value, and then repeating the similar operation predetermined times or for a predetermined time. CONSTITUTION:A movable board 16 is advanced toward a stationary board 14 to bring a movable metal mold 24 into contact with a stationary metal mold 22, a magnetizing current is supplied to coils 28 and 30 for generating a magnetic field, and an injection is carried out when a predetermined magnetic field is established in a cavity 26. When the machine 12 is moved forward, melted resin which contains magnetic particles is injected through a nozzle 42 into a cavity 26, and magnetizing current value I0 is maintained for a predetermined time. A degaussing step is then started, and a predetermined current value I1 is supplied to the coils 28 and 30. The direction of the value I1 is opposite to the direction of the current in the magnetizing step, and smaller than the value I0. Then, similar process is repeated to finish the degaussing step when the set current value of an alternating current conductor 40 becomes sufficiently small. Thus, it can be effectively and rapidly degaussed.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a demagnetization control method for a magnetic field injection molding machine.

(B) Prior Art A conventional demagnetization control method for a magnetic field injection molding machine is disclosed in, for example, Japanese Patent Laid-Open No. 60-79920. That is, the molded product is demagnetized by supplying an alternating damping current to the Shimaba generation coil when the molded product is taken out from the magnetic field injection molding machine.

(c) Problems to be Solved by the Invention However, there is a problem in that even if an alternating attenuating current is passed through the magnetic field generating coil, a desired alternating attenuating magnetic field cannot be obtained. In other words, an eddy current is generated in the magnetic circuit at the start of energization, and a magnetic field opposite to the rise of the magnetic field due to the flow of the magnetic field generating coil is generated, making it impossible to obtain the desired alternating attenuation magnetic field.The molded product is not sufficiently demagnetized. In some cases, the molded product adheres to the mold and becomes difficult to remove when taking it out.Furthermore, since the mold also remains magnetic, the magnetic material adheres to the mold as a foreign substance that reduces the quality of the molded product. Furthermore, when magnetizing a molded product with multiple poles after taking it out, if magnetism remains, there will be a difference in magnetic properties between the front & F! and rear magnetic poles, resulting in either multi-pole magnetization or incomplete magnetization. Become something.

When molded products and Sublu runners are crushed and reused for molding, the crushed pieces adhere to the crusher, molding machine, etc., requiring extra cleaning work, and the pieces also adhere to each other and form large clumps. This may prevent the screw from penetrating. Therefore, after the molded product and sprue runner are removed from the mold, it is necessary to demagnetize them again using another demagnetizer. The present invention aims to solve these problems.

(d) Means for Solving the Problems The present invention does not supply a normal alternating current during demagnetization, but instead supplies a current in one direction, thereby attenuating the influence of the reverse magnetic field caused by the eddy current and producing a predetermined result. The above problem is solved by flowing a current in the opposite direction after magnetic flux is generated. That is, the magnetic field injection molding machine according to the present invention? i! 1 Magnetic control method generates a magnetic field when the absolute value of the detected voltage value detected by the detection coil installed in the tie bar becomes less than the preset voltage value after the power supply for magnetization is stopped. Demagnetization is performed by applying a current with a small absolute value to the coil for a predetermined period of time in the opposite direction to the current direction immediately before it, and then repeating the same operation a predetermined number of times or for a predetermined period of time.

(E) Function First, while a magnetic field is generated in the cavity of the mold, molten resin mixed with a magnetic material is injected from an injection device and magnetized. Next, after magnetization is completed, the molded product is cooled and solidified, and at the same time, the magnetic field generating coil is energized for demagnetization. First, a current smaller than the magnetizing current is applied for a predetermined period of time in the opposite direction to that for magnetization. The voltage detected by the detection coil increases rapidly at the start of energization, and decreases as 7 hours pass. When the absolute value of the voltage value detected by the detection coil decreases to a predetermined value, the direction of energization to the magnetic field generation coil is reversed, and the current value is set to a value smaller than the value immediately before that. When the absolute value of the voltage detected by the detection coil becomes smaller than a predetermined value, the magnetic flux generated in the molded product is in a stable state, and a predetermined magnetic field can be generated. Next, the same operation as above is repeated a predetermined number of times or for a predetermined time until the applied current becomes sufficiently small. Next, the mold is opened and the molded product is taken out. The above operation makes it possible to apply a desired alternating attenuating magnetic field to the molded product in the mold, thereby making it possible to sufficiently demagnetize the molded product.

(F) Embodiments Hereinafter, embodiments of the present invention will be described based on FIGS. 1 and 2 of the accompanying drawings.

FIG. 1 shows an embodiment of the present invention. This magnetic field injection molding machine has a mold clamping device 10 and an injection device 12. The mold clamping device 10 has a fixed platen 14 and a movable platen 16, and the movable platen 16 has four parts fixed to the fixed platen 14 with nuts 18.
It is supported movably in the axial direction by wooden tie bars 20. A fixed mold 22 is attached to the fixed platen 14, a movable mold 24 is attached to the movable platen 16, and a cavity 26 is formed by both molds. A magnetic field generating coil 28 is provided on the outer periphery of the cylindrical convex portion 14a of the fixed plate 14, and a magnetic field generating coil 30 is also provided on the outer periphery of the cylindrical convex portion 16a of the movable plate 16. 1 tie bar 2
A detection coil 32 is wound around the outer circumference of the sensor. A detection signal from the detection coil 32 is input to a comparator 34 . A setting signal from an attenuation value setter 36 is also input to the comparator 34 . Comparator 34 outputs a signal to sequencer 38 which controls the operation of the entire magnetic field injection molding machine. Based on this signal, the sequencer 38 outputs a signal for controlling the operation of the alternating current energizer 40.

The injection device 12 is capable of injecting molten resin containing magnetic particles from a nozzle 42 into a cavity 26 formed by a fixed mold 22 and a movable mold 24 .

Next, the operation of this embodiment will be explained with reference to FIG. 2 as well. First, the movable platen 16 moves forward in the direction of the fixed platen 14, the movable mold 24 comes into close contact with the fixed mold 22, and a mold clamping force acts between them. Next, a magnetizing current is applied to the magnetic field generating coils 28 and 30, and injection is performed while a predetermined magnetic field is generated in the cavity 26. That is, the injection device 12 moves forward, and molten E&resin containing magnetic particles is injected from the nozzle 42 into the cavity 26. Predetermined time magnetizing current value I.

After holding , the demagnetization process is started. That is, in response to a command from the sequencer 38, the alternating current energizer 40 causes the magnetic field generation coil 28 and the magnetic field generation coil 30 to receive a predetermined current value 1. energize. The direction of the current value 11 is opposite to the direction of the current in the magnetization process,
Further, the value is smaller than the magnetizing current value IO. The detection voltage value detected by the detection coil 32 increases at the same time as this energization starts, and gradually decreases as the magnetic flux changes become stable. As the stiffness increases, the eddy current in the magnetic path also decreases.

When the absolute value of the voltage value detected by this detection coil 32 becomes smaller than a predetermined small set voltage value ΔV set by the attenuation value setter 36, the comparator 34
Outputs a signal to. The sequencer 38 determines whether or not the demagnetizing process is in progress, and outputs a command signal to the alternating current energizer 40 if the demagnetizing process is in progress. Sending a signal to the alternating current energizer 40 through the sequencer 38 in this way is as follows:
Since the detection voltage value of the detection coil 32 is always 0 except in the case of the magnetization process and the demagnetization process, the comparator 34 outputs a signal, but the sequencer 38 outputs the alternating current energizer 40 only in the case of the demagnetization process. This is to output the number.

When a command signal is output from the sequencer 38 to the alternating current energizer 40, the alternating current energizer 40 sets the next set current value ■2
The magnetic field generating coil 28 and the magnetic field generating coil 30 are energized. The current value I2 is in the opposite direction to the current value ■1, and is also smaller than 11. Thereafter, the same process is repeated to apply current values 3, I4, etc., and when the set current value of the alternating current energizer 40 becomes sufficiently small, the degaussing step is completed. Note that the degaussing process can also be ended after a predetermined period of time has elapsed from the start.

As mentioned above, after the absolute value of the voltage value detected by the detection coil 32 becomes sufficiently small in the degaussing step 1, that is, after the magnetic field generated in the cavity 26 becomes sufficiently stable, the magnetic field generation coils 28 and 30 are energized. Since the direction of current flow is switched, an alternating magnetic field can be reliably applied to the molded product, and sufficient demagnetization can be performed. In addition, as mentioned above, since the current direction is switched at the most appropriate time, problems such as switching the current direction too early and not being able to perform sufficient demagnetization, or unnecessarily passing current in the same direction may occur. The occurrence of dead time is prevented, and the demagnetization process can be performed efficiently and quickly.

(g) As described in detail, according to the present invention, the direction of the current is switched as soon as the detection coil detects whether the magnetic field has become sufficiently stable during demagnetization, so that the direction of the current is switched reliably and Demagnetization can be performed quickly.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an embodiment of the present invention, FIG. 2 is a diagram showing the characteristics of the current flowing to the magnetic field generating coil, the change characteristics of the magnetic flux of tie 1 <-,
FIG. 3 is a diagram showing voltage value characteristics detected by a detection coil. 10... Mold clamping device, 12... Injection device, 14...
Identification board, 16... Movable board, 20... Tie bar, 22
...Fixed mold, 24...+1J moving mold, 26...
Cavity, 28.30... Coil for magnetic field generation, 32
Detection coil, 34 Comparator, 36 Attenuation value setter, 38 Sequencer, 40 Alternating current energizer.

Claims (1)

[Claims] In a demagnetization control method for a magnetic field injection molding machine, in which a magnetic resin molded product molded by the magnetic field injection molding machine is demagnetized before being taken out from a mold, after the energization for magnetization is stopped, the tie bar When the absolute value of the detected voltage value detected by the detection coil installed in 1. A demagnetization control method for a magnetic field injection molding machine, comprising: energizing for a predetermined period of time, and then repeating the same operation a predetermined number of times or for a predetermined period of time.