JPH01199792A - High frequency cutting method and its device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a method for cutting materials that can be heated by high frequency dielectrics, such as acrylic resin and nylon, and a cutting method thereof.
Concerning cutting positions useful for cutting.

[Prior Art] For example, an injection molded body is cut from the gate part f! When cutting, use a conventional cutter, rotary saw blade, etc. It is cutting in a reduced manner. However, mechanical cutting has the problem of inferior quality of the cut surface, such as cracking and whitening. In order to solve such problems, the applicant of the present application has disclosed Japanese Patent Laid-Open No. 61-8
No. 6198 discloses a cutting method and a cutting device for cutting 1 part of goo in a heated and softened state. It is convenient to heat and soften the gate portion by dielectric heating using high frequency power.

[Problem to be solved by the inventionffl] By the way, in high-frequency dielectric heating, the surface side in contact with the power supply side electrode connected to the high-frequency power source is heated significantly, and the surface side in contact with the ground side electrode is hardly heated, and the heated surface side is heated largely. It has become clear that objects have a 4 degree slope. This temperature gradient becomes larger as the thickness of the object to be cut becomes thicker and the voltage becomes higher. However, as this temperature gradient increases, the residual stress of the cut object increases.
Solvent cracks may occur during post-processes such as painting.

Furthermore, if the voltage is high, sparks may occur due to dielectric breakdown.

Therefore, the present inventor proposed a cutting device in which an insulating underlay made of an insulating material with low dielectric loss is interposed between the object to be cut and the electrode in Utility Application No. 189335/1982 and Japanese Patent Application No. 100963/1982. ing. According to such a cutting device, since the temperature gradient can be reduced, residual stress can be reduced, and sparks due to dielectric breakdown can be prevented.

However, in such a cutting device, the distance between the electrodes increases by the thickness of the insulating underlay. The amount of heat generated (T) in high-frequency electric heating increases in proportion to the square of the electric field strength (E). Further, there is a relationship of E=V/L (V: voltage between electrodes, L: distance between electrodes).

For example, assuming V is constant, if L doubles, T becomes 1/4
It becomes. Therefore, unless V is increased by an amount corresponding to the increase in L, a predetermined lower value cannot be obtained.

That is, in order to maintain a constant amount of heat generation, it is necessary to increase the voltage between the electrodes in proportion to the distance between the electrodes, which is increased by the insulating underlay, and a large amount of electric power is required. Furthermore, if the object to be cut is thick, a high voltage is required to heat the surface that comes into contact with the insulating underlay, and the heating time is also long. For these reasons, it cannot be said to be preferable from the viewpoint of energy saving. Furthermore, the device becomes large, causing problems in terms of space and cost.

The present invention was made in view of these circumstances, and
The present invention provides a high frequency cutting method and a high frequency cutting device that can prevent the occurrence of temperature gradients and residual stress without using an insulating underlay.

[Means for Solving the Problems] The high-frequency cutting method of the present invention includes a step of disposing a workpiece to be cut between a first electrode connected to a high-frequency power source and a second Ti electrode set to earth potential, and dielectrically heating the workpiece. 1 heating process, a 2nd heating process in which the first electrode is brought to earth potential and a frequency power source is connected to the second electrode to dielectrically heat the object to be cut; A cutting step of cutting a heated object to be cut is performed.

The greatest feature of the present invention is that the first heating step and the second heating T culm are performed.

In the first heating step, the first electrode is a power supply side electrode,
The second electrode is a ground side electrode. As a result, the object to be cut is heated preferentially from the surface side in contact with the first electrode, resulting in a temperature gradient that is higher on the first electrode side and lower on the second electrode side. Then, in the next second heating step, the first heating culm is
The pole is used as a ground side electrode, and the second electrode is used as a power supply side electrode.

As a result, the object to be cut is heated preferentially from the surface side in contact with the second electrode, and the surface side in contact with the first electrode is hardly heated. Therefore, by performing the first heating step and the second heating step, the temperature gradient of the object to be cut is averaged, and the entire object can be kept at a substantially uniform temperature.

The first heating step and the second heating step may be repeated several times alternately, or may be performed in -degree increments. Furthermore, the time allocation and high frequency power for both steps are appropriately determined depending on the shape of the object to be cut.

The cutting step is a step of cutting the object heated in the first heating step and the second heating step while maintaining a high temperature state. The cutting may be performed after the first heating step and the second heating step, or may be performed while the first heating step and the second heating step are being performed. In the latter case, the time required for cutting can be further shortened.

Among the devices capable of carrying out the above-described cutting method of the present invention, the high-frequency cutting device of the second invention, which is the most preferred embodiment, is as follows:
A cutter electrode whose tip is a cutting edge, a plate electrode facing the cutter electrode, a drive device that drives the cutter electrode and the plate electrode toward or away from each other, and a high frequency It is characterized by comprising a high frequency power source that applies a voltage, and a switching H1t that selectively and alternately switches the connection of the high frequency power source to the cutter electrode and the plate electrode to the power supply side and the ground side of the high frequency power source. .

The most distinctive feature of Mizui 2's invention is its switching device.

This switching device has a function of switching the connection state of the high frequency power source to the cutter electrode and the plate electrode. That is, for example, the cutter electrode is the first electrode and the plate electrode is the second electrode.
When using electrodes, the cutter electrode is used as the power supply side and the plate electrode is used as the ground side when performing the first heating step. In the second heating step, the cutter electrode is on the ground side and the plate electrode is on the power supply side. This switching lff1 can be constructed from a known circuit such as a relay circuit.

[Operations and Effects of the Invention] In the high-frequency cutting method of the present invention, in the first heating step, the first electrode is used as the power supply side electrode, and the second electrode is used as the ground side electrode. As a result, the object to be cut is heated preferentially from the surface side in contact with the first electrode, resulting in a temperature gradient that is higher on the first electrode side and lower on the second electrode side.

Then, in the next second heating step, contrary to the first heating step,
The first electrode is a grounding electrode, and the second electrode is a power supplying electrode. As a result, the object to be cut is heated preferentially from the surface side in contact with the second electrode, and the surface side in contact with the first electrode is hardly heated.

Therefore, by performing the first heating step and the second heating step, the temperature gradient of the object to be cut is averaged, and the entire object can be kept at a substantially uniform temperature. By cutting the workpiece with a small temperature gradient in a softened state at a high temperature, almost no residual stress is generated in the workpiece, and problems such as cracking and whitening of the cut surface can be prevented. Can be done.

Therefore, according to the cutting method of the present invention, since no insulating underlay is used, the distance between the electrodes is reduced. Furthermore, since the object to be cut is heated alternately from both sides, even if the object is thick, it can be heated at low voltage and in a short time. These effects can significantly reduce power consumption.

In the high-frequency cutting device of the present invention, the object to be cut is first placed between the cutter electrode and the plate-shaped electrode, and the cutter electrode and the plate-shaped electrode are driven by the drive device so as to approach each other. At the same time, a high frequency voltage is applied between the cutter electrode and the plate electrode (first heating step). As a result, the object to be cut is dielectrically heated, but the surface side of the cutter electrode and the plate-shaped electrode that is in contact with the power supply side electrode is heated preferentially, and the surface side that is in contact with the ground side electrode is hardly heated. A gradient occurs. At this time, if the cutter electrode is a power supply side electrode, cutting can be started with the cutter electrode at the same time as heating.

Next, the connection of each electrode is reversed by a switching device and a high frequency voltage is applied (second heating of one culm). That is, the electrode that was on the power supply side is made to be the ground side, and the M pole that was on the ground side is made to be the power supply side. As a result, the surface side of the object to be cut that is opposite to that in the first heating step is heated preferentially, and the temperature gradient tends to be opposite to that in the first heating step. However, since the object to be cut maintains the temperature gradient heated in the first heating step, the temperature gradient overlaps with the temperature gradient in the second heating step, resulting in a nearly uniform temperature distribution. When the high frequency power source is cut off in this state, the cutter electrode is brought closer to the plate electrode by the driving device, and the object to be cut is cut. Note that since the high frequency power source is rfI'Jj&, even if the cutter electrode and the plate electrode come close to each other at a distance that would cause dielectric breakdown, there will be no problem of sparks occurring. By being held in this state, the object to be cut is cooled, and the surface shape of the cutter electrode is transferred to the cut surface. Therefore, if the surface of the cutter electrode is made smooth, the cut surface will also be smooth, improving the aesthetic appearance.

Therefore, according to the cutting device of the present invention, the manufacturing method of the present invention can be easily implemented using a switching device.

Furthermore, since no insulating underlay is required and the output of the high-frequency power source only needs to be small, the structure of the device is simplified, which is advantageous in terms of space and cost.

[Example] This will be explained in detail below using examples.

FIG. 1 shows a schematic configuration diagram of a high frequency cutting device according to an embodiment of the present invention. This cutting device includes a cutter electrode 1 whose tip is a cutting blade, a plate-shaped electrode 2 fixed to a base 20, and a drive device that drives the cutter electrode 1 in a direction toward and away from the plate-shaped electrode 2. 3, a high frequency power supply 4, and a switching device 5.

The drive device 3 includes a cylinder 30 driven by hydraulic pressure, and a mounting plate 32 is held at the tip of a piston rod 31 of the cylinder 30. An aluminum holder 34 is fixed to the mounting plate 32 via an insulating sheet 33 made of an insulator such as 4-fluoroethylene resin with low dielectric loss. The cutter electrode 1 is detachably held in a holder 34 by a screw 35.

Note that the holder 34 and the cutter electrode 1 are electrically connected.

The plate-shaped electrode 2 is fixed to the surface of the base 20 via an insulating sheet 21 that is the same as the insulating sheet 33 described above. A receiver jig 22 is held on the surface of the plate-shaped electrode 2, and a molded body 6 is attached to the receiver jig 22, and a runner f! A6
0 is held on the surface of the plate electrode 2. At this time, the gate portion 61 is configured to be located at a position facing the cutting edge of the cutter electrode 1.

As the high frequency power source 4, one with an oscillation frequency of 100 MH71 and an output of 2 KW is used, and the voltage applied between the cutter electrode 1 and the plate electrode 2 is 3000V.

The switching device 5 includes a relay circuit (
(Detailed circuit diagram is omitted), and contacts A and B are electrically connected to the holder 34 and the plate electrode *2, respectively. The output terminal 40 and the ground terminal 41 of the high frequency power source 4 are selectively electrically connected to either the holder 34 or the plate electrode 2 at contacts A and B, respectively. This switching device 5 is controlled by a control device (not shown) to control the cutter.

The movement distance of the electrode 1 and 115 are controlled.

A method of cutting the gate portion 61 of the molded body 6 using the cutting device configured as described above will be described below.

First, as shown in FIG. 1, the molded body 6 is mounted on the jig 22. Then, the drive device 3 drives the cutter electrode 1 in a direction approaching the plate-shaped electrode 2, and the cutter electrode 1 presses the gate portion 61.

(First heating step) At the same time, the high frequency power supply 4 is turned on, and in the switching device, the holder 34 and the output terminal 40 are electrically connected at the contact point A, and the plate-shaped electrode 2 and the ground terminal 41 are electrically connected at the contact point B. . As a result, the gate section 61
The surface in contact with electrode 1 is dielectrically heated with a high temperature gradient, and the surface in contact with plate electrode 2 has a low temperature gradient. Due to this heating, the portion of the gate portion 61 that is in contact with the cutter electrode 1 is preferentially softened, and the cutter electrode 1 begins to sink into the gate portion 61 due to the driving of the eat@11.

(Second heating step) After heating under the above conditions for a predetermined time, switching [11
5 is activated, the plate electrode 2 and the output terminal 40 are electrically connected at the contact A, and the holder 34 and the ground terminal 31 are electrically connected at the contact B. Thereby, the gate portion 61 is heated preferentially from the surface in contact with the plate-shaped electrode 2. Therefore, the gate part 61
The temperature distribution is almost uniform in the thickness direction, and the cutter electrode 1 is dug deeper.

(Cutting process) Then, the cutter electrode 1 has a thickness of 1/2 to 1/2 of the thickness of the gate part 61.
When it penetrates about 2/3, the high frequency power source 4 is turned off to prevent sparks due to dielectric breakdown. However, the temperature of the gate portion 61 is sufficiently high, and the cutter electrode 1 completely cuts the gate portion 61 by driving the drive device 3.

By holding the cutter electrode 1 in contact with the plate electrode 2 for a predetermined period of time (about several seconds), the cut surface is cooled and solidified, and the cutting process is completed.

(Processing Example) Cutting was performed using the above-mentioned apparatus and the above-mentioned method using molded bodies 6 made of acrylic resin and 6-nylon. Note that the thickness of the gate portion 61 is 3 mm, and the cutting length is 1 mm.
00mm1 cylinder 3017) The thrust is 50kQ, and the blade width of the cutter electrode 1 is 120mm. Then, heating and cutting were performed using the values shown in the table for the first heating step, second heating step, and cooling time.

The cut surface quality of the obtained product was visually judged, and the solvent cracking property was tested, and the results are shown in the table. The solvent cracking property was determined by immersing the cut product in a thin solution containing ester, alcohol, and benzene for 1 hour, then air-drying the product for 112 days to determine the presence or absence of cracks.

As shown in Table J, the products obtained in this processing example had excellent appearance and no residual stress was generated. Also, the heating time is 1.6
~2.5 seconds, which is 1/2 of the conventional general heating time ~
It was shortened to 2/3. Furthermore, the output of the high frequency power source was also able to be reduced by 172 to 27/3 compared to the conventional one.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram illustrating the configuration of a high wave cutter 1iIA'ei according to an embodiment of the present invention. 1... Cutter electrode 2... Plate electrode 3...
・Drive device 4...High frequency power supply 5...Switching device 6...Molded object 20...Base
21.33...Insulating sheet 22...The receiver is a jig
30...Cylinder 34...Holder
61...Gate section patent applicant Hiroshi Okawa, Toyota Motor Corporation agent, patent attorney

Claims (2)

[Claims] (1) A first heating step of dielectrically heating the object to be cut by placing it between a first electrode connected to a high-frequency power source and a second electrode set to ground potential; and setting the first electrode to ground potential. a second heating step of dielectrically heating the object to be cut by connecting the high frequency power source to the second electrode; and a cutting step of cutting the object heated in the first heating step and the second heating step. A high frequency cutting method characterized by performing the steps. (2) a cutter electrode whose tip is a cutting edge; a plate electrode facing the cutter electrode; a drive device that drives the cutter electrode and the plate electrode toward or away from each other; a high-frequency power source that applies a high-frequency voltage between the plate electrode and the cutter electrode and the plate electrode; and alternately switching the connection of the high frequency power source to the cutter electrode and the plate electrode to a power supply side and a grounding side of the high frequency power source. A high frequency cutting device comprising a switching device.