View Full Version : EDM machines.
30-10-2014, 01:59 PM
EDM's anyone running one of these machines. I became interested when researching how to make injection molds.
From what I can see there are two types ram/sinker and wire.
Both machines work by bruning/eroding away metal particle by particle. A wire edm wire cut through 12 inches of steel with amazing accuracy and a sinker will sink a copper elctrode shaped in any way into a sold block of hardened steel.
It looks like slow process but the results are amazing.
30-10-2014, 09:16 PM
I run and program both types in work, and as you say they are amazing, exspensive to run but quite easily make the money back as they specialist machines!
Can be slow but then again very quick, cutting carbide profiles in minutes, and thin sheet at 20mm a minute, not bad for a 0.3mm bit of brass wire!
30-10-2014, 09:51 PM
I made one of them, great fun. Started with some huge Russian paper capacitors and built it as a state machine using a PALCE22V10 gate array and 555 timers.
Charge the capacitors
Dump the charge across the spark gap
Look see what is left on the capacitors...
Fully charged = didn't spark, move down one step
Dead flat = shorted out move up one step
Residual = did spark, stay where you are
The every few seconds lift clear so the electrolyte can wash the soot away.
I made two mistakes...
Trying to pump paraffin electrolyte using a peristaltic pump, who'd have thought that paraffin would degrade just about every kind of silicone tubing to the point where it splits.
Should have used a high voltage initiator spark followed by a timed burst of 40 Volts, my erosion voltage was too high, a bit hard on the copper electrodes.
30-10-2014, 10:39 PM
I was looking at a youtube video recently showing one of the moving tensioned wire machines. Very impressive performance although it appeared to eat its way through enormous amounts of electrode wire.
30-10-2014, 10:42 PM
We have a large roller about 25kgs of brass wire, about 8inch dia spools, one roll is about 60-80hrs running, but after its been used its chopped up and then sold to redeem some of the cost.
Building one is on my roundtuit list.
http://homebuiltedmmachines.com/index.php?page=home has books and PCBs for R/C (Resistor/Capacitor) and Pulse sinker machines. There is also a Yahoo group for discussing the machines at https://groups.yahoo.com/neo/groups/EDMHomeBuilders/info
I have the original RC book somewhere
Or if you're interested in wire, https://groups.yahoo.com/neo/groups/plasmaboog/info although I'm not sure on the current state of available plans.
Actually, just checked and it's this book I've got - https://secure.villagepress.com/store/items/detail/item/797
Still only covers a basic RC build though.
31-10-2014, 08:24 AM
I made mine to despike a 6 pounder ships cannon. After days of burning the note suddenly changed and started coming out of the muzzle. I dashed round the front and peered down the pipe at a fog of paraffin vapour with a crackling spark just bursting through at the bottom. Not so much a bang as a womp when it reached it's flash point, made me leap backwards :beer:
31-10-2014, 10:33 PM
A wire EDM machine would be a nice project - there's a couple of DIY ones on youtube.
There's one in the workshop for electrical engineering at uni (and more in mech. eng). They mainly use it for cutting electrical steel laminations for research into electrical machines. I took a few photos a while ago, to get some ideas:
It does use up the wire quickly and as expected the feedrate is very low - a few mm/min and much less round sharp corners seems typical. Linear motors too...
31-10-2014, 11:03 PM
They really don't want you to reuse that wire, do they?
31-10-2014, 11:11 PM
I just remembered about Mr Mawsons rebuild thread of his wire EDM over on madmodder - http://madmodder.net/index.php/topic,10085.0.html
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