JPH03221323A - Working method for fine hole in electric discharging machine - Google Patents

Abstract

PURPOSE:To correctly work the hole depth in a fine hole working even for various working conditions, by setting the depth of a fine hole subjected to electric discharging on the way of the electric discharging, measuring the consumption factor of the electrode used so far and fixing the electrode feeding quantity thereafter based on this measured consumption factor. CONSTITUTION:The coordinate value (a) of a Z axis at the stoppage point in working is found, a work W and an electrode E are electrified and this electrode E is lifted. Then, the electrode E and work W are horizontally moved at the time of the stoppage of the electrification, lifted in the Z axial direction until no electrification after the electrification and horizontally moved after no electrification. The movement of the electrode E is stopped after its move ment in the specific horizontal distance d1 by repeating the above processes, this electrode E is descended vertically and the electrode E is stopped after the electrification. The coordinate value of the Z axis of this time is taken as (b). The working hole depth Cn is found from the difference (a - b) of these coordinates values, the working hole depth Cn is subtracted from the working feed quantity Z so far and an electrode consumption quantity Sn is found.

Description

[Detailed description of the invention] [Industrial Application Field J The present invention relates to a fine-machining method in an electric discharge machine.

[Prior Art] When machining a small hole with an electrical discharge machine, a pipe electrode is used, but this pipe electrode is worn out as a result of electrical discharge. Therefore, conventionally, when drilling small holes with an electric discharge machine,
Before starting the electrical discharge machining, predict the wear rate of the electrode,
Based on this predicted electrode wear rate, the electrode feed amount is determined and electrical discharge machining is started.

[Problem 8 to be solved by the invention] In the conventional method described above, the electrode feed amount is determined based on the electrode wear rate predicted before machining, so if the electrode wear rate is not accurate, the electrode There is a problem in that the feed rate is not appropriate and therefore the hole depth cannot be machined accurately.

This problem is caused by the difficulty in accurately determining the amount of electrode wear depending on machining conditions such as the electrode material, workpiece material, peak value of machining current, and on-time and off-time of the machining current pulse. do.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for machining a small hole in an electrical discharge machine, which allows accurate hole depth machining under various machining conditions.

[Means for Solving the Problems] The present invention measures the depth of the discharge machined small hole during discharge pressurization, measures the extinction u+ of the electrode used up to that point,
The machining depth is controlled by determining the electrode feed amount from then on based on the consumption rate added by 114.

[Function 1] The present invention measures the depth of the discharge machined small hole during electrical discharge machining, measures the wear rate of the electrode used up to that point,
The machining depth is controlled by determining the electrode feed amount from then on based on this measured wear rate.
Even under various machining conditions, the hole depth in small hole machining can be accurately machined.

[Example] FIG. 1 is a flowchart showing an example of the present invention.

First, electrode consumption rate α, depth measurement position indication parameter β,
Set the number of depth detection N, the upper limit tolerance value γ of the hole depth for the target value of the machined hole depth, the lower limit tolerance value (Sl), and the target value AO of the first machined hole depth. (S2). Then, the processing ordinal number n is set to 1 (S3),
The machining feed amount Zl for the first machining is set (S4).

Note that the electrode consumption rate α is the actual electrode consumption rate at the current machining ordinal number n, and αn = ((electrode consumption amount S)/(set machining feed amount Zn) x 100), but the initial electrode consumption rate α set in advance according to the material of the workpiece, the diameter of the electrode used, etc.

Further, the depth measurement position instruction parameter β=((depth to be left unprocessed the next time)/(all depths to be processed from now on)X100).

The number of times Nt of depth measurements is the number of times the depth of a hole is measured until the machining of one small hole is completed, and the divided number of times Nt of machining (total number of machining) is N+1.

Then, machining is started according to the set machining feed amount Zn in the nth machining (S5), and when the set machining feed rate Z at that time becomes equal to the current machining feed H2 (S
6), machining S7), machining hole depth C at that time
n (S8), and determine whether the machining hole depth Cn at this time is within the upper limit tolerance value γ and the lower limit tolerance value (which range is determined by the target value AO of the machining hole depth). (S9.5ii).

At this time, if the machining hole depth C0 - target mAO is larger than the upper limit allowable value γ, an error is determined because the machining hole is too deep, and the machining is terminated.

On the other hand, if the machining hole depth Cn - target value AO is less than the upper limit tolerance value γ, and if the target value AO - machining hole depth C0 is less than the lower limit tolerance value (if the machining hole depth Cn is less than the upper limit tolerance value), then the machining hole depth cn is within the set tolerance range. The electrode is returned to the machining stop position in order to repeat the machining until the machining stops (S12).

Then, it is determined whether the next machining is the final machining. In other words, if the total number of machining operations up to that point Nt is less than or equal to (current machining ordinal number n+1), (S l 3), β=
O and S 14), machining feed amount Z in the next machining n+1. , 1, first, α. Calculate (
S15). On the other hand, if the total number of machining operations up to that point N
Find and set n-1 (S16). Then, the current machining ordinal number n is incremented by 1 (517), and machining is started (S5).

As mentioned above, in the middle of electrical discharge machining, the depth of the small hole machined by electrical discharge is measured, and the feed rate of the electrode used up to that point is determined each time the measurement is performed. The hole depth can be accurately machined in large-scale machining.

By the way, in S4, when setting the machining feed amount Z1, the machining feed amount Zl is determined by the following formula (2).

Z+=Ao(1+(α/100))(1-(β/100
))・・・・Formula 2 In addition, in 516, when setting the machining feed amount 2° and 1 in the next machining, Zn-+ is determined by the following equation 2.

Zo, +=Ao-111:n(1+(an/100)8
1-(β/100))...■Formula, where the electrode wear rate α is. is the value obtained by dividing the electrode wear amount Sn by the machining feed amount Zn and multiplying that value by 100. Note that the electrode consumption amount S1 is the electrode consumption amount in the n-th machining, and is obtained by subtracting the measured n-th machining hole depth C0 from the set machining feed amount Zn. therefore,
Cn can be determined using the following equation (2).

Cn = (ZnCn) /ZnX100・
= ■ Formula The following method is used to determine the machined hole depth Cn.

As shown in Fig. 2 (1), a certain machining is performed, the coordinate value a of the Z-axis at the stopping point of the machining is determined, the workpiece W and the electrode E are energized, and the electrode E is pulled up and energized. When the electrode E and the work W are depleted, move the electrode E and the workpiece W horizontally, and when energized, pull them up in the Z-axis direction until they are no longer energized, and when they are no longer energized, move them horizontally. This state is shown in Figure 2 (2).
This is shown below.

These steps are repeated, and when the electrode E is moved by a predetermined horizontal pressure #dl, the movement of the electrode E is stopped, the electrode E is lowered vertically, and when the electrode E is energized, the electrode E is stopped. The coordinate value of the Z axis at this time is b
shall be. When the coordinate values a and b are determined in this way, the machined hole depth Cn can be found using the following formula: machined hole depth Cn=a-b.

Thereafter, the electrode E is raised by a predetermined height and returned to the original coordinate value a of the processing center.

In addition, when measuring the depth of a machined hole, there are other methods:
Find the Z-axis coordinate value a at the machining stop point, raise the electrode E by a height higher than the depth of the machined small hole H, then move horizontally by a length dl, and then move the electrode Et-Z-axis direction. The Z-axis coordinate value when lowered and energized is b, and Cn=
The machined hole depth Cn may be determined by calculating a-b.

After the machining hole depth Cn is determined as described above, this machining hole depth Cn is subtracted from the machining feed amount Z up to that point, and this subtracted value becomes the electrode consumption amount Sn. That is, 5n=ZnCn.

In order to obtain the electrode consumption amount Sn, another method may be adopted.As this other method, the electrode E is brought into contact with the upper end of the small hole H (energized), and the coordinate value of the Z axis at this time is is e, and after that, when the electrode is raised in the Z-axis direction from the processing stop point and the tip of the electrode E is brought into contact with the upper end of the small hole H (
If the coordinate value of the Z-axis at the time of conduction is f, then
e−f becomes the electrode consumption amount Sn.

[Effects of the Invention] According to the present invention, the hole depth in small hole machining can be accurately machined under various machining conditions, and if the target value of the hole depth is set, the electrode feed can be controlled. Even without setting the amount, the hole is machined to a depth according to the target value, resulting in the effect of improving the operability of small hole drilling.

[Brief explanation of drawings]

FIG. 1 is a flowchart showing one embodiment of the present invention. FIGS. 2(1) and 2(2) are explanatory diagrams of the hole depth measuring operation in the above embodiment. FIG. 3 is an explanatory diagram of the depth measurement position designation parameter β in the above embodiment. α...Setting electrode wear rate, β...Depth measurement position specification parameter, N...
...Setting number of depth measurements, Nt...Total number of machining, AO...Target value of machined hole depth. γ...lower limit value of hole depth for target value AO, (...
Upper limit value of hole depth for target value AO, n... Machining ordinal number, Zn... Set machining feed amount for n-th machining, Z.
...Current machining feed amount, Cn...Actual machined hole depth in n-th machining, Sn...Actual electrode consumption amount in n-th machining, ...N-th addition Actual electrode wear rate.

Claims (1)

[Claims] During electrical discharge machining, we measure the depth of the small electrical discharge machined hole.
A fine electric discharge machine characterized in that the machining depth is controlled by measuring the wear rate of the electrode used up to that point and determining the electrode feed amount from then on based on the measured wear rate. Hole drilling method.