JPH07299665A - Mold engraving electric discharge machine - Google Patents

Abstract

PURPOSE:To improve machining precision by restraining the relative displacement of a main spindle Z axis direction and a table generated due to the temperature rise of the main spindle caused by machining heat during electric discharge machining. CONSTITUTION:A cooling circulation passage 14 and a thermocouple 17 are provided at an electrode fitting plate 7 at the lower end of a main spindle 6, and by delivering into the circulation passage 14 a machining liquid whose flow temperature management is carried out according to detection temperature by the thermocouple 17, intercepting the thermal conduction of machining heat to the main spindle 6, and keeping the main spindle 6 approximately in the vicinity of a room temperature, the thermal displacement of the main spindle Z axis direction in regard to a table 2 is restrained, and machining precision is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric discharge machine, and more particularly to a die-sinking electric discharge machine having a cooling mechanism for preventing relative displacement of an electrode and a workpiece due to heat generation during electric discharge machining.

[0002]

2. Description of the Related Art Conventionally, in a die-sinking electric discharge machine as shown in the schematic view of FIG. 1, a table 2 is fixed to a machine base 1 via a table lower base 3, and the machine base 1 can be moved in X and Y directions. A spindle head 5 movable in the Z direction is provided via a column 4, and a chuck 8 is attached to an electrode mounting plate 7 at the lower end of the spindle 6 of the spindle head 5,
The electrode 10 is attached via the holder 9. The electric discharge machining is performed in a state in which the workpiece W is immersed in the machining fluid 11, and the heat generated by machining is radiated by the machining fluid. However, since the lower part of the electrode is immersed in the working liquid, the heat dissipation effect is large, but since the parts above the upper part of the electrode are in the air, the heat dissipation effect is small and the temperature easily rises.

[0003]

In the die-sinking electric discharge machine described in the prior art, the temperature of the spindle 6 rises due to the machining heat generated by the electric discharge, and the relative displacement between the workpiece W and the electrode 10 causes It adversely affects the processing accuracy. FIG. 7 is an example of measurement data showing the temperature transition of the electrode mounting plate at the lower end of the spindle during electric discharge machining, and FIG. 8 is a corresponding measurement data showing the transition of the Z-axis displacement of the spindle based on Table 2. This is an example.

According to this measurement data, the Z-axis displacement amount reaches a maximum of 18 μm, and the Z-axis position constantly changes during the standard working time of 8 hours. For this reason, there is a problem that the processing depth becomes larger than the specified dimension, the processing accuracy deteriorates, and the processing time becomes longer as the depth increases. The present invention has been made in view of such problems of the conventional technique, and an object of the present invention is to suppress a temperature rise of a spindle due to machining heat generated by electric discharge, and deteriorate machining accuracy due to thermal displacement. The present invention aims to provide a die-sinking electric discharge machine with a cooling mechanism that is simple and easy to maintain.

[0005]

In order to achieve the above object, a die-sinking electric discharge machine according to the present invention is a die-sinking electric discharge machine which performs machining by electric discharge between an electrode and a workpiece.
The electrode mounting plate at the lower end of the main shaft is provided with a cooling circulation path, and means for supplying a cooling fluid to the circulation path is provided.

Further, means for detecting the temperature of the electrode mounting plate,
And means for adjusting the flow rate of the cooling fluid according to the detected temperature. In addition, the cooling fluid is a working fluid.

[0007]

According to a first aspect of the present invention, a cooling fluid is caused to flow through a cooling circulation path provided in an electrode mounting plate at the lower end of the spindle to shut off the machining heat transmitted from the electrodes to suppress an increase in the temperature of the spindle and to prevent the table and the spindle from being heated by the machining heat. Reduces relative thermal displacement and improves processing accuracy.

According to a second aspect of the present invention, a cooling fluid having a flow rate proportional to the temperature of the electrode mounting plate is flowed to maintain the spindle at a substantially constant temperature irrespective of the amount of processing heat generated which varies depending on the processing conditions and the like, thereby further improving the processing accuracy.

The third aspect of the present invention facilitates maintenance such as replenishment / replacement by using a working fluid which is easy to obtain a cooling fluid and is harmless to the machine such as corrosion.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. In the die-sinking electric discharge machine of FIG. 1, a table 2 is mounted on a machine stand 1 installed on the floor via a table lower stand 3.
Is fixed, and the workpiece W is placed on the table. A saddle 13 is placed on the machine base 1 so that the X axis can be moved and positioned, and a column 4 is placed on the saddle 13 so that the column 4 can be moved and positioned in the Y axis direction.

A spindle head 5 is mounted on the front end surface of the column 4 so that the spindle head 5 can be moved and positioned in the Z-axis direction.
Are installed vertically and downward. An electrode attachment plate 7 is attached to the lower end of the main shaft 6, and an electrode 10 is detachably attached to the electrode attachment plate 7 via a chuck 8 and a holder 9. Further, a machining tank 12 surrounding a part of the table 2 and the table lower table 3 is provided, so that the workpiece W is soaked in the machining fluid filled in the machining tank 12 so that the electric discharge machining is performed. Has become.

As shown in FIGS. 2 and 3, the electrode mounting plate 7 is provided with a circulation passage 14 therein. The machining fluid is fed into the circulation passage 14 through the intake port 15 and discharged through the discharge port 16. It is supposed to be done. Further, a thermocouple 17 is attached to the electrode mounting plate 7, and as shown in FIG.
Is output to the controller 18. The controller 18 supplies a current corresponding to the signal (detected temperature) of the thermocouple 17 to the solenoid of the electromagnetic flow control valve 19,
The working fluid cooling device 22 is a device for cooling the working fluid to keep it at a constant temperature, 21 is a pump, 23 is a filter, and 24 is a relief valve.

Next, the operation of this embodiment will be described.
Most of the machining heat generated by the discharge is radiated by the machining liquid 11 in the machining tank 12, but some of the electrodes 10, the holder 9,
It reaches the electrode mounting plate 7 at the lower end of the spindle through the chuck 8.
The machining fluid kept at a constant temperature by the machining fluid cooling device 22 flows through the cooling circulation passage 14 in the electrode mounting plate 7 to block the heat conduction to the spindle 6. The machining fluid flowing through the circulation path 14 is controlled by the controller 18 and the electromagnetic flow rate adjusting valve 19 to a flow rate proportional to the temperature of the electrode mounting plate detected by the thermocouple 17. Therefore, when the amount of processing heat generated is large, the valve opens and the flow rate increases and the amount of heat absorption increases.When the amount of generated heat is small, the valve is throttled and the flow rate decreases and the amount of heat absorption decreases. Therefore, the temperature of the electrode mounting plate 7 is always kept constant regardless of different amounts of processing heat generated.

FIG. 5 is a graph showing the measured data of the temperature transition of the electrode mounting plate 7 when cooling is carried out at a flow rate proportional to the electrode mounting plate temperature as described above, and FIG. 6 is a table-based main spindle at this time. It is a graph figure of the measurement data of the change of the amount of Z-axis displacement of No. 6. Comparing this with the graph diagram (FIG. 7) of the temperature transition of the electrode mounting plate 7 when the cooling is not performed and the graph diagram (FIG. 8) of the displacement amount of the Z-axis of the main spindle based on the table as described in the conventional technique As is apparent, the temperature of the electrode mounting plate 7 which had risen to a maximum of 30 ° without cooling is stabilized at about room temperature, and the table-based Z-axis displacement amount of a maximum of 18 μm falls within a displacement width of about 5 μm.

Incidentally, even if the working fluid of a constant flow rate is circulated without controlling the flow rate of the working fluid for cooling in accordance with the temperature of the electrode mounting plate 7, the working temperature of the working fluid cooling device 22 can be controlled. If appropriate, the Z-axis displacement amount of the table-referenced spindle can be suppressed within a certain fluctuation range. Further, it is not always necessary to limit the cooling liquid to the working liquid, and any liquid having a relatively low viscosity which does not corrode the machine and is free from pollution can be used.

[0016]

Since the present invention is configured as described above, it has the following effects. According to a first aspect of the present invention, the cooling fluid is caused to flow in the circulation path of the electrode mounting plate at the lower end of the spindle to block the heat conduction of the machining heat to the spindle during electric discharge machining, thereby suppressing the temperature rise of the spindle. The relative displacement of the table and the spindle in the Z-axis direction due to heat is reduced, the machining accuracy is improved, and the machining time is shortened.

Since the flow rate of the cooling fluid is adjusted according to the temperature of the electrode mounting plate, the temperature of the electrode mounting plate becomes almost constant regardless of the change of the heat generation amount due to the processing conditions and the like, and the machining accuracy is improved. Further improve.

According to the third aspect, the cooling fluid is the working fluid.
It is easy to obtain, there is no risk of corroding the machine, and maintenance such as replenishment and replacement is easy.

[Brief description of drawings]

FIG. 1 is a view showing only a machining tank of a die-sinking electric discharge machine of the present embodiment in a cross section, which also serves as a description of a conventional technique.

FIG. 2 is a detailed view of a table and a portion around a spindle head, mainly showing a cooling liquid circulation path of an electrode mounting plate.

3 is a cross-sectional view taken along the line AA of FIG. 2 and is a view of the cooling liquid circulation path as viewed from directly above.

FIG. 4 is an explanatory diagram showing a cooling liquid control circuit.

FIG. 5 is a graph of measured data of temperature transition of a cooled electrode mounting plate during electric discharge machining.

FIG. 6 is a graph diagram of measured data of changes in the amount of displacement of the spindle Z-axis based on the table, corresponding to FIG. 5;

FIG. 7 is a graph of measured data of a temperature transition of an electrode mounting plate according to a conventional technique.

FIG. 8 is a graph diagram of measured data of transition of the displacement amount of the spindle Z-axis on the basis of the table corresponding to FIG. 7.

[Explanation of symbols]

1 machine 2 tables
5 Spindle head 6 Spindle 7 Electrode mounting plate
DESCRIPTION OF SYMBOLS 10 Electrode 14 Circulating circuit for cooling 15 Coolant inlet 16 Coolant outlet 17 Thermocouple
18 Controller 19 Electromagnetic Flow Control Valve 21 Pump
22 Coolant for machining fluid

Claims (3)

[Claims] 1. A die-sinking electric discharge machine for machining by electric discharge between an electrode and a work piece, wherein a cooling circulation passage is provided in an electrode mounting plate at the lower end of a spindle, and means for supplying a cooling fluid to the circulation passage is provided. A die-sinking electric discharge machine characterized by being provided. 2. The die-sinking electric discharge machine according to claim 1, further comprising means for detecting the temperature of the electrode mounting plate and means for adjusting the flow rate of the cooling fluid in accordance with the detected temperature. 3. The die-sinking electric discharge machine according to claim 1, wherein the cooling fluid is a machining fluid.