JP2892028B2 - Electric discharge machine - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric discharge machining apparatus which automatically sets machining conditions for multi-stage swing machining in die sinking electric discharge machining.

[Conventional technology]

Oscillating machining, in which machining is performed while moving the electrode and the workpiece relative to each other in die-sinking EDM, has high machining accuracy and has the effect of improving machining efficiency. Control (NC) die-sinking EDM is used in this machine. Among such oscillating working methods, a multi-stage oscillating working method in which processing from roughing to finishing is performed in multiple stages with changing processing conditions is a particularly important working method.

Typical machining conditions that must be determined when performing this multi-stage rocking machining are machining surface roughness R, electrical conditions (I,
T) (I is the peak current, T is the pulse width) and the swing amount ε. Table 1 shows a series of machining conditions from rough machining to finish machining.

In Table 1, R ₀ , (I ₀ , T ₀ ) and ε ₀ are the surface roughness of roughing, the electrical conditions and the swing amount, and R _n ,
(I _n , T _n ) and ε _n are the machined surface roughness, electrical conditions, and swing amount of the final finish working.

As a characteristic of the electric discharge machining, the machining speed is about 1/5 (= the machining time is about 5 times) under the machining condition of halving the machining surface roughness. On the other hand, under the processing conditions in which the processed surface roughness is set to a value smaller than 1/2, the processing speed is larger than 1/5. Therefore, in order to shorten the processing time, a method is employed in which the processing is sequentially performed while changing the processing conditions in multiple stages from the rough processing surface roughness to obtaining the finished surface.

FIGS. 3 (a) and 3 (b) are views showing an example of a typical machining state in die-sinking electric discharge machining, and the relative positions of the electrode 1 and the workpiece 2 when the rough machining is finished and the finishing machining is started. The state is shown. FIG. 3A shows an example in which the side surface is sequentially finished after the through hole is processed, and FIG. 3B shows an example in which the side surface is sequentially finished by bottoming. 3 (a) and 3 (b), the hatched portion 3 of the workpiece 2 is a machining allowance for machining by multi-stage machining.

[Problems to be solved by the invention]

In such multi-stage machining, the machining time is greatly affected by the number of stages n and the value of the machining surface roughness R of each stage i in the machining conditions shown in Table 1 above. Conventionally, the number of stages n
And the value of the machined surface roughness R of each step i were determined by a skilled person by intuition or by performing a lot of test machining, but the combination of the number of steps n of the multistage machining and the value of the machined surface roughness R Is infinite, so finding the optimal conditions is extremely difficult.
After all, there was a problem that the processing time was long.

SUMMARY OF THE INVENTION An object of the present invention is to provide an electric discharge machine capable of reducing machining time in multi-stage swing electric discharge machining regardless of the skill level of an operator.

[Means for solving the problem]

An object of the present invention is to provide an electric discharge machine which performs electric discharge machining using a multi-stage swing machining method, in which a ratio of an allowable machining current per unit area determined in advance by an electrode to be used and a material of a workpiece to a maximum machining area. And a rough surface roughness is determined using a constant for converting the ratio into a processed surface roughness, and one of a final finished processed surface roughness and the determined rough processed surface roughness is an equivalent ratio of a predetermined equivalent ratio. The number of machining steps is determined with the first term of the series and the other term as the last term, the machining surface roughness at each machining step is determined, and the electrical conditions and swing amount for obtaining the surface roughness of each machining step from the obtained results. And calculating means for executing the machining of each machining stage in accordance with the obtained electric conditions and the amount of swing.

[Action]

When the operator inputs information about the electrode to be used and the material of the workpiece, the maximum machining area of the rough workpiece, and the final finished surface roughness, based on the input information, the number of stages and the number of each stage in the multi-stage swing machining are determined. Is calculated. Based on the calculation result, the electrical conditions and the amount of swing for obtaining the processing surface roughness of each of the stages are calculated, and the machining of each of the stages is performed according to the electrical conditions and the amount of swing obtained by the calculation. In other words, the operator only needs to input information on the materials of the electrodes and the workpiece to be used as described above, the maximum machining area during rough machining, and the roughness of the final finished machining surface. The processing of each stage is performed according to the conditions and the swing amount, so that the processing time can be shortened regardless of the skill level of the operator.

〔Example〕

 Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of the electric discharge machine according to the present invention. In FIG. 1, reference numeral 11 denotes an arithmetic unit comprising a CPU and the like, 12 an input unit comprising a tape reader, a keyboard and the like, 13 a display unit comprising a CRT display and the like, 1
Reference numeral 4 denotes a memory unit, and reference numeral 15 denotes a mechanical drive unit including X, Y, and Z-axis drive motors, and these constitute a CNC device. in this case,
The calculation unit 11 uses the electrode and the material of the workpiece to be used, the maximum machining area at the time of rough machining and the final finished machining surface roughness as input information, and based on these input information, the number of steps and the number of steps in the multi-stage swing machining. The surface roughness at each step is calculated, and the electric condition and the amount of oscillation for obtaining the surface roughness of each stage are calculated based on the operation result, and the electric condition and the amount of oscillation obtained by this operation are calculated according to the electric condition and the amount of oscillation. It also functions as arithmetic means for executing the processing of each stage.

Reference numeral 16 denotes a processing power unit including a processing power supply circuit and the like, 17 denotes a machine operation unit including a relay, a limit switch, and the like, 18 denotes a machine main body including a table, a quill, and the like, and 19 denotes a processing liquid supply device.

Next, an example of an apparatus function according to the present invention will be described with reference to the flowchart of FIG.

First, the operator determines the material of the electrode and the workpiece to be used, the maximum machining area S in the rough machining, and the machining surface roughness R in the final finishing machining.
_f is input from the input unit 12 (step 21). These input information are generally values described in the production drawing, and the operator can easily input these information while looking at the production drawing.

Next, operations and material of the electrode and the workpiece, from the maximum machining area S in roughing, the surface finish R _r roughing the following formula (1) (step 22).

R _r = K · S / J (1) where J is a constant determined by the electrode used and the material of the workpiece, and is an allowable machining current that can flow per unit area. K is a constant for converting a machining current obtained from S / J into a machining surface roughness.

Then, using a surface finish R _r roughing obtained by surface finish R _f and the above formula of the final finishing input (1), final finish from O connexion roughing to the arithmetic unit 11 processing Number of steps n up to
Is calculated as follows (step 23). That is, as a result of analyzing the optimum machining conditions that minimize the machining time in the multi-stage machining using mathematical programming, the inventors have found that it is sufficient to reduce the machined surface roughness R approximately in a geometric progression. It has become. The rate of decrease Φ is shown in FIG.
It has been found that 0.6 to 0.8 is appropriate in general processing as shown in FIG.

Based on this, the number n of stages from rough machining to finish machining can be obtained by the following equation (2).

However, surface finish of R _f is finishing, R _r is the roughing surface finish, [Phi is surface finish reduction rate.

If the number n of steps obtained by the above equation (2) is not an integer, it is rounded to an integer (step 24), and the number of steps is set to N.

Next, the corrected surface roughness reduction rate Φ 'that satisfies the integer number of steps N is obtained by the following equation (3) (step 25).

Φ ′ = (R _f / R _r ) ^{1 / N} (3) Next, the processed surface roughness R _i (i = 1 to N) of each step is obtained by the following equation (4) (step 26).

R _i = Φ ′ ^-i R _r (4) If R ₀ = R _r and R _N = R _f , a series of machined surface roughness (R ₁ ,
R ₂ , R ₃ ... _RN ) are obtained by the above equation (3).

Next, the electric conditions (I _i , T _i ) and the swing amount ε _i of each stage i are obtained (step 27). Here, I is the peak current of the pulse current, and T is the pulse width.

The electrical conditions (I _i , T _i ) and the amount of swing ε _i for the processing surface roughness R _i of each stage i are determined by the same calculation method as in the prior art. Table 2 below shows the relationship between the obtained electrical conditions (I _i , T _i ), the swing amount ε _i, and the previously calculated machining surface roughness R _i .

As shown in Table 2, the electrical conditions for the surface finish R _i in each stage i to the final finishing roughing (I _i,
T _i ) and the swing amount ε _i are sequentially obtained and stored in the memory unit 14 as a lookup table. At the time of machining, the electrical conditions (I _i , T _i ) and the swing amount ε _i for the machining step i (machined surface roughness R _i ) are sequentially read from the memory unit 14, and the machining power unit 16 is transmitted via the machine drive unit 15. To the machine operation unit 17
The processing is executed in step 11 (step 28).

In the above embodiment, the electrical conditions (I _i , T _i ) and the swing amount ε _i for the machining surface roughness R _i at each stage i from the rough machining to the finishing machining are stored in the memory section 14 as a lookup table.
And at the time of processing, sequentially read out and execute the processing in accordance with the processing stage i, but the present invention is not limited to this. For example, the surface roughness shown in Table 2 above
The relationship between R _i , the electrical conditions (I _i , T _i ), and the swing amount ε _i may be expressed by a mathematical expression, and the relationship may be obtained by an operation using the expression.

〔The invention's effect〕

According to the present invention, in multi-stage oscillating electric discharge machining,
Optimum machining conditions can be set simply by manually inputting data on the materials of electrodes and workpieces, the maximum machining area during rough machining, and the final finished surface roughness stored in the production drawing. There is an effect that the processing time can be shortened regardless of the skill level of the operator.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the apparatus of the present invention, and FIG.
FIG. 3 is a flowchart for explaining the apparatus according to the present invention, and FIG. 3 is a view showing an example of a typical machining state in die-sinking electrical discharge machining. DESCRIPTION OF SYMBOLS 1 ... Electrode, 2 ... Workpiece, 3 ... Processing allowance, 12 ... Input part, 13
... Display unit, 11 ... Calculation unit, 14 ... Memory unit, 15 ... Machine drive unit, 16 ... Machine power unit, 17 ... Machine operation unit, 18 ... Machine body, 19 ... Machine fluid supply device.

Claims (1)

(57) [Claims] In an electric discharge machine for performing electric discharge machining using a multi-stage swing machining method, an allowable machining current and a maximum machining area per unit area, which are previously input and are determined by an electrode to be used and a material of a workpiece. Roughness surface roughness is determined by using a ratio and a constant that converts the ratio into a processing surface roughness, and one of a final finishing processing surface roughness and the determined rough processing surface roughness is determined in advance by an equal ratio or the like. The number of machining steps is determined with the first term of the series and the other term as the last term.
Obtained processing surface roughness in each of the processing steps obtained, the electrical conditions and the amount of swing for obtaining the surface roughness of each processing step from the obtained results, respectively, and according to the obtained electrical conditions and the amount of oscillation, An electric discharge machining apparatus comprising an arithmetic unit for executing machining at a machining stage.