JPH04201125A - Electric discharge machine - Google Patents

Abstract

PURPOSE:To accurately and automatically secure a processing tank to an arbitrary position by providing a work height detecting means to detect the height of a work placed on a table, and a processing tank positioning means to position the upper end of the processing tank to a position further higher by a given distance than the height of the work by means of a drive means. CONSTITUTION:The height of a work W, i.e., the upper end position of the work W, is detected by a work detecting means 11. When detecting data is inputted to a processing tank positioning means, a vertical drive means 28 is controlled as previously inputted proper distance data from the upper end of the work W to the upper end of a processing tank 20 is compared with position data in a vertical direction of the processing tank 20 grasped by a numerical control device, and through vertical movement of the processing tank 20, the processing tank is positioned in a command position.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a machining tank that includes a child actor.

[Prior Art] In die-sinking electric discharge machining, an electric discharge is generated between a machining electrode and a workpiece in an oil-based machining fluid, and the workpiece is machined using the heat generated by the electric discharge. If the discharge point is close to the surface of the machining fluid, the machining fluid will become locally high in temperature due to the heat of the discharge, potentially causing a fire. Therefore, machining liquid is filled in a machining tank and machining is performed while soaking the electrodes and workpieces. However, in order to prevent fires, the level of the machining fluid must be deeper than the upper surface of the workpiece by a predetermined length or more, for example, 50 mm or more. Therefore, the distance between the machining liquid level and the workpiece surface is adjusted by moving the machining tank up and down, but if the machining tank is moved up and down while it is filled with machining fluid, the U-shaped machining tank and table The hollow tube-shaped seal provided between the base and the fixed base would be damaged.Therefore, before filling the machining tank with machining fluid, the virtual liquid level of the machining tank was determined, and the virtual liquid level was determined. The machining type is positioned by moving up and down so that the surface is at least a predetermined height above the top surface of the workpiece, and then the machining tank is filled with machining liquid so that the liquid level is positioned above the virtual liquid level. There is. In addition, when replacing the workpiece, after draining the machining fluid in the machining tank, position the machining tank as described above, and then fill the machining tank with machining fluid and adjust the liquid level to the above-mentioned virtual liquid level. I'm trying to position it at the top.

[Problems to be Solved by the Invention] Conventionally, positioning of a processing tank is performed using a vertical movement device, and this vertical movement device is operated manually or automatically. However, in the case of manual operation, the distance between the virtual liquid level and the workpiece surface is adjusted according to the operator's visual estimate in step 1, but the distance between the liquid level and the workpiece surface when filled with machining liquid does not meet the specified distance. Sometimes there isn't. In this case, after loosening the seal and draining the machining fluid in the machining tank, it is necessary to raise the machining tank again and make readjustments, which is troublesome and increases setup time.

Therefore, the two-machining time becomes longer by the readjustment time, and the operating rate of the electric discharge machine decreases.

In addition, when using automatic processing, the stop position of the processing tank is determined by limit switches or dog position adjustment, so the surface position may change depending on the thickness of the workpiece placed on the table. Since the machining tank is always fixed at the same position, the distance between the workpiece surface and the machining fluid level cannot be adjusted appropriately.

In view of the above circumstances, it is an object of the present invention to enable automatic and accurate positioning of a processing tank at any position.

[Means for Solving the Problems] The present invention includes a machining tank which surrounds a table and is movable up and down with respect to the table, and a drive means for moving the machining tank up and down by numerical control. The height of the workpiece placed on the table is detected in an electric discharge machine that performs electric discharge machining by immersing the workpiece placed on the table in machining fluid and moving it relative to a machining electrode attached to the spindle. and a machining tank positioning means for positioning the upper end of the machining tank at a position higher than the height of the work by a predetermined distance by the driving means. It is a machine.

[Function] When the height of the workpiece, that is, the top end position of the workpiece is detected by the workpiece height detection means and the data is input into the machining tank positioning means, an appropriate distance from the top of the workpiece input in advance to the top end of the processing tank is determined. The vertical drive means is controlled while comparing the data with the vertical position data of the machining tank grasped by the vertical movement numerical control device, and the machining tank is moved in the vertical direction and positioned at the commanded position.

``Embodiment'' An embodiment of the present invention will be described with reference to the accompanying drawings, where the same reference numerals have the same names and functions.

The column 2 of the electrical discharge machining device 611 equipped with the numerical control device NC has a base 3 serving as a base, a front wall 4, a side wall (not shown), and a back frame 5.

A saddle 61 and a ram 62 are placed above the back frame 5 so as to be movable in both X and Y axes directions perpendicular to each other in a horizontal plane. A spindle head 7 is fixed to the entire surface of the ram 62, and a spindle 9 is attached to the spindle head 7 so as to be movable up and down.

This main shaft 9 is provided with a tVil mounting plate 8. This one-electrode number plate 8 is separated from the table 10 on which the workpiece W is placed by a predetermined distance, for example, 620 mm. A contact sensing ball (contact element) 11 used for measuring the position of the workpiece is attached to the plate 8 for this t-scraping. The table 1o is fixed to the upper end of the base 3, and a workpiece W is appropriately fixed to the upper part by a mounting jig. A seal groove 13 is formed at the upper end of the base 3, and a hollow tube-shaped seal 14 is accommodated within the seal groove 13. A machining liquid tank 15 is formed by a front wall 4 and side walls that are provided in the front area and left and right side areas of the base 3 and surround the base 3, and this machining liquid tank 15 is a machining liquid that is formed in the back frame 5. It communicates with tank 16.

The machining liquid tank 15 is formed in a U-shape when viewed from above. A processing tank is provided as a movable tank 20 that can move up and down so as to surround the four sides of the table 10 at the top of the base 3. An appropriate number of overflow holes 21 are provided in the upper part of this movable tank 20, and excess machining fluid is discharged through a recovery channel 2.
The machining liquid is formed so as to flow out to the machining liquid tank 15 through the pipe 2. A rack 25 is fixed to the side surface of the movable tank 20, and a guide rail 26 is attached to a suitable position on the back. The edge 25 meshes with a pinion 27 driven by a motor 28. The amount of rotation of the pinion 27 is input to the numerical controller NC via an encoder 29 which is a position detector of the movable tank 20. Note that a gas spring 3 for weight balance is attached to the bracket 30 of the movable tank 20.
1 are provided in a pair on the left and right.

Next, the operation of this embodiment will be explained.

Release the air from the seal 14 to release the seal, and remove the processing tank 20.
After all the machining fluid inside is discharged, the motor 28 is driven to lower the upper edge of the machining tank 20 to the position indicated by the solid line (the zero point of the machining tank in FIG. 2), and the workpiece W is taken out. Then, the new workpiece W is appropriately fixed on the table 10 with a mounting jig, and the shaft 9 is lowered to bring the contact ball 11 into contact with the upper surface of the workpiece W. The position of the upper surface of the workpiece W is stored in the numerical controller NC by the contact alarm signal at this time, and the thickness t of the workpiece W is automatically calculated from the following equation 1 based on this value.

1=1. -12-1. Equation 1 In Equation 1, tl is the distance from the surface of the table 10 to the lower surface of the electrode mounting plate 8 when the main shaft 9 rises to the reference position, and is constant in design, for example, 620 mm. t2 is the distance from the tip of the contact ball 11 to the lower surface of the electrode mounting plate 8, and is also constant. t, is touch sensing taste 1
1 to the surface of the workpiece W.

Next, based on the thickness t of the workpiece W determined by Formula 1, the position of the virtual liquid level of the machining fluid, that is, the position of the upper edge of the machining tank, is calculated from the following Formula 2.

t4-t5+t+t6... Equation 2 In Equation 2, t is the distance between the upper edge of the processing tank and the table 1o when the processing tank 20 is lowered to the lower limit, and t6 is the distance above the processing tank from the top surface of the workpiece W. The distance to the edge is usually calculated as 90+a+a~10L)+++m.

In this way, the set value yl t of the upper edge of the processing tank
4 is calculated, this set position is stored in the numerical control device NC as the command value 1 for the machining tank. Then, when the numerical control device NC outputs an output to the motor 28, the motor 28 rotates and rotates the pinion 27, so that the rack 25 rises and the machining tank also rises. As the binion 27 rotates, the encoder 29 outputs a processing tank position signal pulse to the numerical controller NC. The numerical control device NC counts the position signal pulses input from the encoder 29, compares them with the command value 1 of the machining tank, and then controls the motor 28. When the machining tank reaches the command position, the motor 28 is stopped, and the Figure 2,
The processing tank 20 is fixed at a set position as shown by the chain line in FIG.

Next, air is forced into the hollow tube-shaped seal 14 to expand it, sealing the space between the side of the base 3 and the movable tank 20 to form a leak-free machining fluid reservoir in the machining tank, and then When machining fluid is filled into the machining tank from the machining fluid tank 16 by a suction pump (not shown), the liquid level of the machining liquid coincides with the virtual liquid level S. Therefore, the distance between the upper surface of the workpiece W and the level of the machining fluid is maintained accurately as designed.

The embodiments of this invention are not limited to the above,
For example, when replacing an electrode, the machining tank may be lowered to a predetermined position where the electrode can be replaced, and then returned to its original position. Even at this time, the current position of the processing tank is controlled numerically. After that, the processing tank is lowered to a predetermined position where the electrode can be replaced while the position of the processing tank is detected by the encoder 29. After the electrode is replaced, the encoder 2
It is also possible to automatically return the machining tank to its original position by driving the motor 2S3 by the numerical control device NC before counting one position signal pulse.

In the above embodiment, the case where the processing tank is a U-shaped movable tank has been described, but the processing tank may be formed into a box shape with an open top surface as shown in FIG. 4. This processing tank 4
The bottom surface 41 of the base 42 is slidably fitted onto a columnar section 43 of a base 42, and a table 44 on which a workpiece W is placed is fixed to the upper end of the columnar section 43. When the motor 45 is driven by the numerical control device NC, the feed screw 47 screwed into the nut 46 rotates, and the machining tank 40 is moved from the position of the M line to the position of the solid line. At this time, similarly to the embodiment described above, the position detector 48 constantly detects the position of the processing tank 40, and outputs the position signal pulse to the numerical controller NC as control data.

This machining tank 40 differs from the previous embodiment in that it does not use a hollow tube-shaped seal, so the machining tank 40 can be moved up and down while it is filled with machining fluid. Therefore, after finishing machining the workpiece, the machining tank 40 filled with machining fluid is lowered to expose the workpiece W, and after replacing the workpiece W on the table 44 with the workpiece W in the pond, the machining tank 40 By raising the liquid level again to bring the liquid level to a predetermined position, the setup time can be shortened, and electrical discharge machining can be performed efficiently. In this embodiment, a contactor may be used as the workpiece height detection means, or a conventional method such as contact sensing by electrical connection between the workpiece and Ti whose dimensions are known may be used, and the processing tank positioning means may be a numerical control device. A separate microcomputer may also be used.

[Effects of the Invention] Since the present invention is configured as described above, when the position signal pulse of the position detector of the processing tank is input to the numerical control device,
The processing tank positioning means controls the vertical drive device while comparing the commanded position of the processing tank with the data. Therefore, the processing tank can be accurately and automatically fixed at any set position.

[Brief explanation of the drawing]

Figures 1 to 3 are diagrams showing an embodiment of the present invention, with Figure 1 being a schematic perspective view showing the driving means for the movable tank, and Figure 2 showing the method for measuring the thickness of the workpiece and the virtual liquid level. FIG. 3 is a partial cross-sectional schematic diagram showing the main body of the electrical discharge machine, and FIG. 4 is a vertical cross-sectional view showing an embodiment of the pond. 1... Electric discharge machine 3... Base 10... Table 20... Movable tank 25... Rack 27... Binion 28 ... Motor 29 ... Encoder NC ... Numerical control device

Claims (1)

[Claims] (1) It has a machining tank that surrounds a table and can move up and down with respect to the table, and a drive means that moves the machining tank up and down by numerical control, and the workpiece placed on the table is immersed in machining fluid. In an electric discharge machine that performs electric discharge machining of the workpiece by immersing it and moving it relative to a machining electrode attached to the main shaft,
a workpiece height detection means for detecting the height of the workpiece placed on the table; and a processing tank positioning means for positioning the upper end of the processing tank at a position higher than the height of the workpiece by a predetermined distance by the driving means. An electric discharge machine characterized by comprising: