JPH02218517A - Electric discharge machining method and its device - Google Patents

Abstract

PURPOSE:To shorten processing time regardless of operator's skill by setting up an optimum processing condition only by the step of manually inputting data on electrodes, the material of a work piece, the maximum processing area at the time of roughing, and the surface roughness of final finish which are designated by manufacturing drawings. CONSTITUTION:When information on electrodes to be used by an operator, the material of a work piece, the maximum processing area of roughing and the surface roughness of final finish are inputted by an input section 12, the number of stages in multi- rocking processing, and the surface roughness of processing at each stage are operated by an operating section 11 based on the aforesaid information. Based on the result of the operation, an electrical condition and the amount of rocking which are required to obtain the roughness of processing at each stage, are operated at the operating section 11 respectively so as to be stored in a memory section 14. Then, the electrical condition and the amount of rocking for each processing stage (surface roughness of processing) are read out in order from the memory section 14 at the time of processing so as to be outputted to a process power section 16 and a machine actuating section 17 via a machine drive section 15 so that processing at each stage is performed by a machine main body 10.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method and an apparatus for performing electrical discharge machining by automatically setting machining conditions for multi-stage oscillation machining in die-carving electrical discharge machining.

[Conventional technology]

In die-sinking electrical discharge machining, the oscillating machining method, which performs machining while moving the electrode and workpiece relative to each other, provides high machining accuracy and is effective in improving machining efficiency. , is adopted in almost all numerical control 1 (NC) die engraving electric discharge machines. Among these oscillating machining methods, a multi-stage oscillating machining method in which machining is performed by changing machining conditions in multiple stages from rough machining to finishing machining is a particularly important machining method.

Typical machining conditions that must be determined when performing this multi-stage oscillation machining are machined surface roughness R1 electrical conditions (1, T
) (I is the peak current, T is the pulse width) and the amount of oscillation is 8. Table 1 below shows a series of machining conditions from rough machining to finishing machining.

Table 1 In Table 1, Ros (Io + To ) and ε0 are the machined surface roughness, electrical conditions, and swing amount during rough machining, and R ns (I n + Tn ) and εn
are the machined surface roughness, electrical conditions, and amount of oscillation in the final finishing process.

As a characteristic of electric discharge machining, under machining conditions that reduce the machined surface roughness to 1/2, the machining speed is approximately 175 (-machining time is approximately 5 times).
On the other hand, under machining conditions that reduce the machined surface roughness to a value less than 1/2, the machining speed becomes greater than 115. Therefore, in order to shorten the machining time, a method is adopted in which machining conditions are changed in multiple stages and machining is performed sequentially, from a rough machined surface to a finished surface.

Figures 3 (&) and (b) are diagrams showing an example of a typical machining state in 凇 carving υ electric discharge machining, where the electrode 1 and workpiece 2 are Indicates relative position status. In FIG. 3, (a) is an example in which the side surfaces are sequentially finished after the through hole is machined, and (b) is an example in which the side surfaces are sequentially finished by machining with eaves. Figure 3 (a
), (b), the hatched portion 3 of the workpiece 2 is.

This is the machining allowance for multi-stage machining.

[Problem to be solved by the invention]

In such multi-stage machining, the machining time is greatly influenced by the number of stages n and the value of the machined surface roughness R of each stage l among the machining conditions shown in Table 1 above.

Conventionally, the values of the number of stages n and the machined surface roughness R of each stage 1 were determined by an expert's intuition), or were determined by performing many test machining, or the number of stages n and the machined surface roughness R of multi-stage machining. Since there are an infinite number of combinations of values, it is extremely difficult to find the optimal conditions, resulting in a problem that the processing time becomes longer.

SUMMARY OF THE INVENTION An object of the present invention is to provide an electric discharge machining method and apparatus that can shorten machining time regardless of the operator's skill level in multi-stage oscillating electric discharge machining.

[Means to solve the problem]

The above purpose is to use the electrode and workpiece material used, the maximum machining area during rough machining, and the final finished surface roughness as input information in electrical discharge machining using the multi-stage oscillating machining method. Based on this calculation, the number of stages in multi-stage oscillating machining and the roughness at each stage are calculated, and the electrical conditions and the amount of oscillation to obtain the surface roughness of each stage are calculated from the results of this calculation, and the number of stages obtained by this calculation is calculated. υ is achieved by performing the processing at each stage according to the electrical conditions and amount of oscillation.

[For production]

When the operator inputs information about the electrode to be used, the material of the workpiece, the maximum machining area of the rough workpiece, and the final finished surface roughness, the number of stages and each stage in multistage oscillating machining is determined based on this input information. The machined surface roughness at is calculated. Based on the calculation results, the electrical conditions and swing amount for obtaining the machined surface roughness of each step are calculated, and the processing of each step is performed according to the electrical conditions and swing amount obtained by this calculation.

In other words, by simply inputting information about the electrode and workpiece material to be used, the maximum machining area during rough machining, and the final finished surface roughness as described above, the operator can select the optimal electrical Since the machining at each stage is performed according to the conditions and the amount of oscillation, the machining time can be shortened regardless of the skill level of the operator.

[Example]

Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the electrical discharge machining method according to the present invention. In this Figure 1, 11 is the CPU
12 is an input section consisting of a tape reader, square board, etc., 13 is a display section consisting of a CRT display, etc., 14 is a memory section, and 15 is a mechanical drive consisting of X, Y, Z axis drive motors, etc. In some parts, these constitute a CNC device.

In this case, the calculation unit 11 uses as input information the electrode to be used and the material of the workpiece, the maximum machining area during rough machining, and the final finish machining surface roughness, and based on these input information, performs processing in multi-stage oscillating machining. Calculate the number of stages and the surface roughness at each stage, calculate the electrical conditions and swing amount to obtain the surface roughness of each stage based on the calculation results, and according to the electrical conditions and swing amount obtained by this calculation. It also functions as a calculation means for executing the processing at each stage.

16 is a machining power part consisting of a machining power supply circuit, etc.; 17 is a machine operation part turtle consisting of a relay, a switch, etc.; 18
1 is a machine body consisting of a table, tiles, etc., and 19 is a processing fluid supply device.

Next, using the flowchart of FIG. 2, the method of the present invention,
An example of the device function will be explained.

First, the operator inputs the electrode to be used, the material of the workpiece, the maximum machining area 81 for rough machining, and the machined surface roughness Rf for final finishing machining from the input unit 12 (Stera input 21). The input information is generally values written on the manufacturing drawings, and the operator can easily input this information while looking at the manufacturing drawings.

Next, from the materials of the electrode and the workpiece, and the maximum machining area S for rough machining, the rough machining surface roughness Rrt- is calculated using the following formula (1) (step 22).

Rr-ni-8/J ・・・・・ ・・・・・・・
(1) Here, J is a constant determined by the electrode used and the material of the workpiece, and sb is the allowable machining current that can be passed through the unit area. Further, K is a constant for converting the machining current obtained from S/J into machined surface roughness.

Next, using the input final finish machining surface roughness Rf and the rough machining surface roughness R obtained by the above formula (1),
The number of stages n from rough machining to final finishing machining is calculated by the calculation unit 11 as follows (step 23). In other words, the inventors have determined the optimal machining conditions that will minimize the machining time in multi-stage machining. Nine results analyzed using the drawing method,
It has become clear that the machined surface roughness R can be reduced approximately in a geometric progression, and the reduction rate φ can be determined by the general equation shown in Figure 3 (IL) and (b). In the processing of 1111
．． It turned out that 6-0, 8 was appropriate.

Based on this, the number of steps from rough machining to finish machining, n, can be determined by the following formula (2).

Log(Rf/Rr) n=...
・・・・・・・・・・・・・・・・・・(2) Logφ However, Rf is the machined surface roughness of finishing process, and Rr is.

The machined surface roughness of rough machining, Φ, is the machined surface roughness reduction rate of 6°.

If the number of stages n calculated by the above formula (2) is not an integer, round it to an integer (Step 24), and convert the number of stages to N.
shall be.

Next, the corrected machined surface roughness reduction rate l that satisfies the genus number N is determined using the following equation (3) (step 25).

φ' = (B 1 / Hr) 1 /N...
・・・・・・・・・・・・・・・・・・・・・(3) Next,
The machined surface roughness Rt (t=x~N) of each stage is increased using the following equation (4) (step 26).

Ri ``” / ' Rr ・Song”=Song (4
)RomaroRr+RN ”” Rf, a series of 〃
Lo-work side.

The roughness (RI IRl +Rs...RN) is expressed by the above formula (3)
It is determined by

Next, each stage lo electrical conditions (It, Ti) and swing/amount #1
(Step 27). Here, ■ is the peak current of the pulse current, and T is the pulse current.

Electrical conditions for machined surface roughness RIK of each stage l (process 1, Ti
) and the amount of oscillation ttFi, the same operators as before.

Find the optimal value using the method. The electrical conditions (11, Ti
), the relationship between the swing amount #1 and the previously calculated machined surface roughness R1 is shown in Table 2 below.

Table 2 As shown in Table 2, the electrical and electrical conditions (I
i, Ti) and the amount of oscillation #lt are sequentially determined and stored in the memory unit 14 as a look-up table. Then, during machining, the electrical conditions for machining stage 1 (machined surface roughness R1)
Ii, Ti, and the amount of swing 11 are sequentially read from the memory section 14 and applied to the machining power section 16 and the machine operation section 17 via the mechanical drive section 15 to execute machining in the machine body 11 (step 28).

In the above embodiment, each stage 1 from rough machining to finishing machining is
Electrical conditions (It, Ti
) and the amount of oscillation 61 are stored in the memory section 14 as a look-up table, and during machining, this is read out sequentially according to the machining stage l to execute the machining, but the present invention is not limited to this. do not have. For example, the relationship between the machined surface roughness R1, the electrical conditions (Is, Tt), and the swing amount 61 shown in Table 2 above may be expressed as a mathematical expression, and the calculation may be performed using the expression.

〔Effect of the invention〕

According to the present invention, in multi-stage oscillating electric discharge machining, data about electrode and workpiece materials, maximum machining area during rough machining, and final machined surface roughness, which are usually described in manufacturing drawings, can be manually input. Since the optimal machining conditions can be set simply by manual effort, the machining time can be shortened regardless of the skill level of the operator.

[Brief explanation of the drawing]

Fig. w41 is a block diagram showing an embodiment of the device of the present invention, Fig. 2 is a rounded flowchart explaining the method and device of the present invention, and Fig. 3 shows an example of a typical machining state in die-sinking electric discharge machining. It is a diagram. 1... Electrode, 2... Workpiece, 3... Machining allowance, 12... Input section % 13... Display section, 11.
...Arithmetic section, 14...Memory section, 15...Machine drive section, 16...Machining power part, 17...Machine operation section, 18...Machine main body, 19...Machining fluid Feeding device. Figure i, Figure 3

Claims (1)

[Claims] 1. In the electric discharge machining method using multi-stage oscillation machining, the electrode used and the material of the workpiece, the maximum machining area during rough machining, and the name of the final machined surface roughness are input information. The number of stages in multi-stage oscillating machining and the surface roughness at each stage are calculated based on the input information of An electrical discharge machining method characterized in that machining of each stage is performed according to electrical conditions and an amount of oscillation obtained by calculation. 2. In an electrical discharge machining device that performs electrical discharge machining using the multi-stage oscillating machining method, the input information is the electrode used, the material of the workpiece, the maximum machining area during rough machining, and the final finished surface roughness. Based on the input information, calculate the number of stages in multi-stage oscillating machining and the surface roughness at each stage, and use the results of this calculation to calculate the electrical conditions and amount of oscillation to obtain the surface roughness at each stage. An electric discharge machining apparatus characterized by comprising a calculation means for executing the machining of each stage according to the electrical conditions and the amount of oscillation obtained by the above.