JPS5852777B2 - Electric discharge machining method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention mainly uses wire electrodes to cut plate materials.
This is an improvement to the electrical discharge machining method that performs processing such as cutting.

As shown in Fig. 1, the normal processing mode is to roll and sell the wire 1 while pulling it from one reel to the other, and to form a processing gap by placing the workpiece 2 opposite the wire being wound and moving. Pulse discharge is performed by supplying machining fluid such as water from the upper and lower nozzles 3 and 4 and repeatedly supplying machining pulses from the terminal 5. The workpiece 2 is cut into the moving shape of the wire 1. At this time, if the moving direction of the wire is 2, feeding in the X and Y directions perpendicular to this allows cutting and sampling of various shapes. Process.

In the figure, reference numerals 6 and 7 indicate guide rollers that support and guide both upper and lower ends of the portion of the wire 1 facing the workpiece 2.

In the above, when the machining fluid is jetted from the nozzles 3 and 4,
(Of course, the liquid may be jetted from only one nozzle.) Although the liquid is well distributed and supplied to the surface of the workpiece 2, the amount of liquid that flows to the center of the workpiece 2 is small; The effect of removing machining debris deteriorates, and electrical discharge machining is performed through the machining debris.Also, even though the electrode wire 1 is supported by the guide 6.7, the middle part between the two becomes the center of vibration when vibration occurs. As a result of these interactions, the inner central portion of the workpiece 2 is over-processed than the upper and lower surfaces as shown in the figure, the gap with the wire 1 widens, and the cut surface becomes bulged in the shape of a drum.

Normal plate thickness is 80-100mm thick or 1-20mm.
Although even thin objects can be machined, this deviation phenomenon increases as the thickness of the workpiece 2 becomes thicker, which has the disadvantage that processing accuracy decreases.

The present invention has been devised to eliminate this drawback.

That is, according to the results of various experimental studies, it has been found that the amount of expansion of the cutting groove changes greatly depending on the electrical conductivity of the machining fluid.

In other words, Figure 2 is a graph of the machining error in groove width due to bulges in the cutting groove when wire-cutting workpieces with plate thicknesses of 80 mm and 20 mm, based on the experimental results of the electric conduction velocity of the machining fluid (water). It is something.

Processing was done using 5KD-11 material with a copper electrode with a wire diameter of 0.2 tnm, a tension cuff of 00 to 750 y, and a discharge capacitor of 1 μF when the plate thickness was 801 LrIL and 0 when the plate thickness was 20 mm.
．． When the plate thickness was 80 mrn, the average machining current was changed to 5 μF, and the average machining current was approximately 3.6 to 6 A. When the plate thickness was 20 mm, the average machining current was approximately 1.5 to 4 A.

According to this, when processing a thick plate with a thickness of 80 mm,
If the conductive dust is low (10' U/crrL), the machining error will be as much as 0.12 mm on one side, but if the conductive dust is high <(5X10''
U/crn), the error is reduced to approximately 0.03 mm.

On the other hand, when processing a sheet material thinner than the front of a sheet with a thickness of 20, the error is about 0.0 when the conductive dust is low (10-5U/CrrL).
The one with 02mm diameter has high conductive dust (5X10'
U/crrL), the error increases to approximately 0.04 mm.

According to this, when processing a plate thickness of 80rILrIL, it is better to use a liquid with low conductive dust in a higher region (IXIO' to 5X
Using a liquid of 10-'U/crrL) to increase the machining speed will reduce machining errors, and when machining thin plates (20 mm), it will be easier for a large amount of machining fluid to flow into the inside of the workpiece, resulting in faster machining. Since debris is removed well, there are few blistering phenomena and the area with low conductive dust (IXIO-5 to IX1
High precision machining is possible using a liquid of 0'Q/crfL).

In addition, it can be seen that machining errors increase when processing a thin plate using a liquid with high conductive dust and high current.

Therefore, as mentioned above, when machining workpieces with a thin plate thickness of about 1 to 20 mm to a thick workpiece of about 80 to 100 mm, the electrical conductivity in the machining gap is 10-5 to 10"0/c.
When the thickness of the workpiece is thick, the conductivity of the fluid is in the high range, and when it is thin, the conductivity is in the low range. By controlling this, high-precision machining is possible, and the present invention has been proposed for this purpose as well.

In Fig. 1, water is normally used as the machining fluid supplied from nozzles 3 and 4, and tap water or the like is passed through an ion exchange resin.
In other words, it can be easily changed by changing the ion concentration, and cutting powder is mixed in the liquid that passes through the machining part when circulating the machining fluid, and the concentration can be changed by removing this cutting powder. Conductive dust can be easily controlled by controlling the liquid temperature, adding conductive liquid, metal powder, emulsion, etc.

In particular, liquid temperature control is easy to continuously control, and when the liquid is cooled, it is difficult to evaporate even if there is a small amount of liquid flowing into the processing area (
This has the effect of increasing crab speed, etc.

For example, in the above embodiment, by increasing the conductive dust in the machining fluid when processing a thick plate material, and conversely, by lowering the conductive dust when processing a thin plate material. Then, by setting it to 5x1o'U/crrL, and when processing a plate material with a thickness of 20mm, it is 5x1o'U/crrL.
By using a liquid of approximately 0-5 to 1 x 10-4 U/CrrL, it is possible to perform high-precision machining while minimizing errors due to blisters, etc.

[Brief explanation of the drawing]

FIG. 1 is an example diagram for explaining the present invention, and FIG. 2 is an explanatory diagram of processing characteristics.

Claims (1)

[Claims] 1 When processing workpieces with a thin plate thickness of about 1 to 20 mw to a thick workpiece of about 80 to 1001 m using a wire-shaped electrode, the electrical conductivity in the machining gap is 10-5 to 5 × 1.
In an electrical discharge machining method in which a machining fluid of approximately 0"U/crrL is supplied and a pulse discharge is performed for machining, when the thickness of the workpiece is thick, the electrical conductivity is in a high range in the range of the electrical conductivity. An electric discharge machining method characterized in that the electric conductivity of the supplied machining fluid is controlled to be changed to a low region when it is thin.