| Gallery, Projects and General > Project Logs |
| Titivating a Wire EDM Machine |
| (1/35) > >> |
| awemawson:
Sorry about this chaps but I'm starting another re-build thread that might go on for the odd page or two :ddb: I bought this machine on a whim back in October 2011. It was basically working but was in dire need of some TLC. No preventative maintenance had been done in years, various panels and covers were missing, and although working, the Fanuc 6 CNC control was hard to use due to most of it's indicator bulbs being blown, and several key buttons either missing or broken. |
| awemawson:
So what is a "Wire EDM Machine" :scratch: Well the EDM stands for Electro Discharge Machining - otherwise known as spark erosion. In this machines case, the work piece is attacked with a thin brass wire (0.25 mm diameter) and the electronics creates a controlled discharge between them. A gap is maintained across which the discharge occurs explosively dislodging minute bits of the work piece and also the wire. For this reason the wire is 'use once only' and runs off a feed spool, via several cunning mechanisms, and ends up on a take up spool ready to go to the scrap man. The gap between the work piece and the wire is 'flushed' with de-ionised water to clear the removed material, maintain electrical isolation and very importantly, cool the wire. Mean while the CNC controller moves the work piece by servo action in X & Y taking all sorts of parameters into consideration to keep accuracy of the part. A second set of servos can move the wire in 'U & V' tilting the wire up to 20 degrees to make three dimensional cuts. So in concept you can imagine it as a band saw that uses an extremely thin blade, and can cut tool steel up to 200 mm thick |
| awemawson:
So the wire starts life nice and fresh and new on the feed spool, which is gently biased in reverse to stop it 'running on'. It then passes through a set of tensioning rollers and brakes, and a 'wire break sensor' eventually being presented to the lower wire guide, which is a diamond with a hole in it. As the wire is electrically 'live' all the parts have to be insulated from the body of the machine. |
| awemawson:
Near the lower guide there is (or rather SHOULD be - more on this later) a sliding contact that energises the wire. This is a fat disk of Tungsten Carbide over which the wire passes. This contact is duplicated near the upper wire guide so that current is fed into the wire both from below and above the work piece. Both wire guides have co-axial water feeds, the flow of which is manually controlled to form a thin 'string' of water surrounding the wire |
| awemawson:
So having passed through the work piece and also through the upper guide, the wire goes through another set of tensioning rollers and on to the take up spool |
| Navigation |
| Message Index |
| Next page |