How to obtain the best finish of wire cutting

2022-09-19
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Wire cutting: how do we get a good finish so that we don't have to develop new products from scratch

the finish of wire cutting is composed of two elements. One is the size of pits etched by a single discharge, and its RZ is usually 0.05 μ~ 1。 five μ Between, this is secondary to the cutting finish. The second is the convex and concave stripes caused by commutation, whose RZ is usually 1 μ~ fifty μ Between, up to 0. It is also possible to be more than 1mm, which is the most important factor in the finish of wire cutting. At the same time, it is accompanied by white stripes such as reversing black porous ceramsite, which has a strong visual impact

it is easy to control the size of pits caused by a single discharge, which only needs to reduce the energy of a single pulse. It is just that the energy of a single pulse is small to a certain extent, resulting in a relatively thick workpiece that cannot be cut, or even a non sparking state with only short circuit and no discharge, which is similar to the fine gauge in EDM, resulting in unstable machining with extremely low efficiency and poor chip removal ability. Moreover, the RZ caused by discharge pits is not within the same order of magnitude as that caused by commutation fringes, so it is most important to control the RZ accompanied by commutation fringes. The accuracy of guide wheels and bearings, the constancy of tension when going up and down, and other reasons cause the inconsistent motion tracks of the wire up and down. This mechanical factor is the main reason for the convexity and concavity of the reversing

the following measures will improve the finish to a certain extent:

1. Appropriately reduce the pulse width and peak current, that is, reduce the size of the etch pit

2. The guide wheel and bearing maintain good accuracy and stability of operation, reduce wire chattering and wire jumping, and keep the wire motion track to minimize the displacement of the first line

3. The tension in the working area will remain unchanged when the wire is up and down by holding an appropriate tension and adjusting the guide wheel and the power inlet block

4. The wire should not be too tight, and the water should not be too new. New water is certainly beneficial to the cutting efficiency, but the cutting finish is not the best with new water

5. Add a splint on the upper and lower sides of the workpiece that is too thin, so that the reversing stripes are buffered within the range of the splint

6. Stable and accurate XY movement, good follow-up fidelity and non blocking crawling are also extremely important

7. Keep stable and loose frequency conversion tracking

8. Re cutting or multiple cutting with appropriate allowance. When the cutting amount is very small, the stress coaxiality of ASTM G105 SAE recommend is tested according to article 7.2.7 of jjg556 (2) 011, and the standards such as ended practice (Falex dry sand/rubber wheel apparatus) are small, sweeping the cutting surface once will have a beneficial effect on dimensional accuracy and finish. Sweeping three times in a row will basically remove the reversing stripes, as long as the repeated positioning accuracy of the machine tool is high, The progressive processing with appropriate allowance will improve the smoothness of the cutting surface by one or two orders of magnitude. The effect is similar to that of slow wire walking, and it is not too time-consuming. This is one of the strengths of fast wire walking cutting machine

thicker workpieces can use short wires appropriately, and the feed rate of one reversing is less than half of the wire diameter, which also covers the reversing stripes. Of course, it's just a cover up. (end)

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