JPS58120427A - Electrical discharge machining device - Google Patents

Abstract

PURPOSE:To highly effectively apply rocking processing by performing electrical discharge machining while providing a relative rocking motion between an electrode and a workpiece, and changing said processing from a rough to a finishing conditon when the amplitude of said rocking motion reaches to a set value. CONSTITUTION:A relative rocking motion is provided between an electrode 1 and a workpiece 2 to perform electrical discharge processing. The radius (r) of the rocking motion is controlled such that it is small in the first place and becomes larger with the progress of the processing. The rocking motion is performed by driving a table 3 in the X, Y directions with an NC control device 6. The processing condition is set in a rough processing condition in the beginning, and when the rocking radius (r) reaches the value set by a setting circuit 8, a signal is issued from a switching circuit 15 to change the time interval of a pulse generating circuit 13, permitting the processing condition to be changed to a finish processing condition. When the rocking radius reaches the final value, the processing is stopped. In this way, the processing efficiency of the rocking processing is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electric discharge machining apparatus that performs machining by applying relatively close feed to a machining electrode and a workpiece.

For example, it is known that a hole having a shape similar to the electrode shape is machined by electric discharge machining by making a relative oscillating motion between the workpiece and the workpiece in a plane perpendicular to the feeding direction of the electrode. When performing this relative oscillation motion, for example, when making a revolution movement with a predetermined radius, if the revolution radius is large, the machining speed cannot follow the revolution radius, and arcing and short circuits occur, making stable machining impossible. Therefore, the revolution radius can be gradually increased by a small value of about 1 μ to enlarge it to the desired predetermined radius, or the machining gap signal, for example, voltage can be detected and the machining can be gradually expanded while being controlled by servo control. A method is adopted. Then, when the radius of rotation reaches a predetermined radius, the radius of revolution stops increasing. However, during this oscillating machining, pulses with constant machining conditions are applied to the machining gap between the electrode and the workpiece, and if machining is performed under rough machining conditions, the machining speed is high, but the machined surface roughness, machining accuracy is poor, and the finish is poor. The disadvantage of machining conditions is that the machining speed is slow. The present invention has been proposed in view of these points, and involves driving the relative motion given between the electrode and the workpiece by NC control, and when the relative motion distance reaches the final set distance. The machining electrodes are switched in at least two stages so that a machining pulse that starts under rough machining conditions becomes a predetermined machining condition.

The present invention will now be described with reference to an embodiment shown in ten drawings.

Reference numeral 1 denotes an electrode having a machined shape, and 2 a workpiece in which a hole is formed in advance, into which the electrode 1 is inserted as shown, and is caused to perform relative orbital movement with a predetermined radius. 3 is the workpiece 2
The processing table is fixed, the 4°5u X-axis and Y-axis drive system is controlled by the NC11JII system w6. 7 is a pulse generation circuit that supplies output pulses to the NC control device;
8 is a preset device for setting the final radius of relative revolution, 9 is a discrimination circuit that discriminates the voltage signal of the machining gap and supplies a discrimination signal, 10 is an on/off switch element that generates a machining pulse, and 11 is a DC A power supply, 12 is a high frequency pulse generation circuit, 13 is a low frequency pulse generation circuit, and a pulse obtained by combining both output pulses by an AND gate 14 is applied to the switch element 10 to turn it on and off. 1
Reference numeral 5 is a control circuit which detects a signal corresponding to a change in the revolution radius output from the NCIIJIII device 6 and switches the output pulse width, body stop width, or both of the output pulse width of the pulse generation circuit 13.

As a result, the processing pulse applied to the gap between the electrode 1 and the workpiece 2 is low because the high frequency pulse train generated by the generation circuit 12 and the low frequency pulse generated by the pulse generation circuit 13 are AND-coupled at the AND gate 14. The high-frequency pulse train continues for a time corresponding to the pulse of the frequency pulse, and the high-frequency pulse train is interrupted for the time corresponding to the pause of the low-frequency pulse.A control pulse is applied to the switch 10 and turns on and off the DC power supply 11, corresponding to the control pulse. Electric discharge machining is performed by applying a repetitive number of machining pulses to the machining gap. The electrode 1 and the workpiece 2IIl undergo relative orbital movement due to NCIIJIII. As shown in FIG. 2, the orbital movement is such that the point p of the electrode 1 is the rotation center 0. The electrode 1 is caused to rotate with a radius of 100 mm, and repeats the movement of the point p approaching the workpiece 2, so that the entire circumference of the electrode approaches each part of the workpiece 2, and electrical discharge machining is performed. A machined hole with an enlarged shape similar to the shape is formed in the workpiece 2.The revolution radius r gradually expands until it reaches the final setting value of the relative approach operation.The final setting value is preset by the device 8. N
It is stored in the memory of G device 6.

Depending on the machining gap discrimination signal from the circuit 9, the gap is expanded continuously or stepwise to the final set value. The orbital motion is based on multiple basic patterns of orbits of relative approaching motion.
It is written in the memory of the control device 6, and by selecting it with a switch (not shown) and inputting the selected pattern, the approaching movement of the specified pattern can be performed.
Relative orbital motion can be performed by specifying the orbital motion shown in FIG. 2, where r>G. The specified orbital movement pattern and the final orbital radius set by the preset device 8 are processed logically and logically by the cup in the NG control device 6, the locus data is memorized, and electrical discharge machining is started. The oscillation circuit 7 operates, inputs pulses to the program counter of the NC control device 6, outputs distribution signals to the X and Y axis control circuits, controls the drive devices 4 and 5, and moves the table 3 in the direction opposite to the electrode 1. The robot is controlled to move in the vertical X-Y plane and given relative orbital motion.Due to the machining progress of the workpiece 2, the electrode 1 and the workpiece 2 are
As the gap between them widens, detection signals such as voltage increase accordingly, a discrimination output is input from the discrimination circuit 9, and the revolution radius gradually expands in accordance with this signal, and stops when it expands to a set value. The revolution continues with the revolution radius stopped, and when the final finishing gap is reached, the revolution is stopped by the output of the discrimination circuit 9 and the machining is completed. During machining due to this orbital movement, the signal associated with the change in orbital radius is NCIIJIII
It is used sequentially starting with I@16.

However, in the figure, a signal is outputted and added to the control circuit 15 only when the revolution radius reaches the preset radius in w8. At this time, the control circuit 15 switches the pulse generating circuit 13 to control switching of the pulse width and stop width. At the start of machining, the pulse generation circuit 13 sets the pulse during the pulse to be large or the pulse during the pause to be small, and the rough machining conditions are set such that the duration of the pulse train generated by the pulse generation circuit 12 is lengthened or the interruption time is shortened. The electric discharge machining continues under these rough machining conditions, but when the revolution radius finally reaches the set value, the preset finishing machining with a shorter pulse train duration or longer interruption time is applied. The processing is then switched to and the processing is completed under these finishing processing conditions. Therefore, it is possible to first perform high-speed machining using rough machining and strip welding, and then finally complete the machining with good surface roughness and accuracy under finishing machining conditions, greatly improving machining efficiency. can. Of course, the machining conditions are not limited to two-stage switching.
Three or more stages of machining conditions are preset in the pulse generation circuit 13 and the III control circuit 15, and the control circuit 15 is activated by signals sequentially output from the NC61l'm device 16 to switch the machining conditions of the pulse generation circuit 13. can be made to do so. Further, the machining conditions can be changed by changing the pulse output from the pulse generation circuit 12, or by controlling the voltage of the power source 11, the number of parallel switch elements 10, or the circuit resistance to control the peak value of the discharge pulse, so that the peak value of the discharge pulse is large. It is possible to switch from rough machining conditions to finishing machining conditions with a small wave height value.

Although the above has been explained using one embodiment, if the oscillation state of the pulse generating circuit 7 is controlled by the state of the machining gap, that is, the voltage signal, etc., the revolution movement will be controlled by the state of the machining gap, and when the gap narrows, When the speed decreases and spreads, the speed increases (or vice versa can be controlled,
The revolution movement can be performed by servo depending on the state of the machining gap, allowing stable machining. Further, the machining may be performed while expanding the radius of revolution in steps according to manually set steps using a step amount and a rotational speed that have been previously experimented with respect to the machining conditions.

The oscillation pattern by the NG control device is not limited to orbital movement,
When moving the X-Y plane in the X-axis and Y-axis directions, when moving the X-Y plane in an arbitrary radial shape, when dividing the X-Y plane into four quadrants and moving each pattern in combination in each quadrant, etc. Other known pulses or power sources can be used as the power source for applying machining pulses to the machining gap.

The electrodes can be of a general shape in cross section, with a general shape in the tip, or in the form of a simple rod, wire, or pipe, and can be processed by cutting, cutting, wire cutting, etc. Machining can be done as desired, and all processes can be performed efficiently and with high precision.

[Brief explanation of the drawing]

FIG. 1 is a circuit configuration diagram of one embodiment of the device of the present invention, and FIG. 2 is a sectional view illustrating the relative approach operation. 1. Electrode 2. Workpiece 4, 5 Drive device 6, NC1,
III! l device 8. Approach distance setting device 10°11.
12.13.14. Power supply for processing 15. Processing Condition Switching Device Patent Applicant: Inoue Japax Co., Ltd. Procedural Amendment (Method) 1. :I) f'l no (1982 Patent Application No. 1,231 2, Name of Invention Electrical Discharge Machining Apparatus 3 Amended by: April 27, 1982)

Claims (1)

[Claims] A processing power source that supplies processing pulses between the electrode and the workpiece, an NC control device that provides a relative approach movement between the electrode and the workpiece, a device that sets a final approach distance to the NC control device, and and a switching device for the machining power source, which switches the machining pulse that started under rough machining conditions to at least two stages so that predetermined finishing machining conditions are reached when the final approach distance set by the device is reached. Device.