Titivating a Wire EDM Machine

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awemawson:
A bits and pieces day today.

First I cleaned up and etch primered the 'drawing arm' that allows a replica of the part in the CNC memory to be drawn in pencil. Was going to 'satin black' it but my 'spare' can proved to be a dud :bang: More on order.

Then I replaced the 'tray' that surrounds the work area, using ordinary sanitary caulking to seal it.

Then I made a replacement cover sleeve for the work arm - the original had corroded and looks as though rats have been nibbling it

awemawson:
I don't like sheet metal work at the best of times, and stainless steel is the pits ! My guillotine doesn't like cutting it, and it's quite difficult to get sharp bends in the folder, despite this only being 1 mm and supposedly annealed. Turned out ok in the end.

Then I set to making the longer holder for the wire pulley - this was needed not only as the original was corroded, but also as the pulley needed shifting to the right a bit to give adequate 'wrap' of the wire around the tungsten carbide contact. It should just have been a matter of cutting the 10 x 30 mm stainless 'flat stock' to size, and drilling and tapping a few holes. However the stock was so 'un-square' I ended up milling it on all sides to square it up.

The position of the pulley is rather arbitary based on the 'that looks about right' school of design - time will tell if it is !

Now I'm puzzling how the wire is supposed to be routed when the arm has the sliding seal that attaches the 'curtains' fitting round it. Time to search the web for picture :scratch: :coffee:

awemawson:
So at last the slab of white Delrin arrived and I could make up the mounting for the tungsten carbide contact. What lovely stuff delrin is to machine - such a contrast to the stainless steel I've been working on !

Having roughly cut the slab to size on the band saw, and milled to final size I needed to spot through the existing machinable ceramic insulator to pick up the mounting hole centres. Then it was just a case of drilling and countersinking to finish that item.

Next on the list was the stubby axle that mounts the contact. Turned down from an old stainless pump shaft, axially tapped at one end 5 mm to mount it and 4 mm to take the screw that both holds it on and also takes the electrical connection. This was followed by a couple a thick washers to complete the assembly.

awemawson:
In that last picture I've stretched a length of the edm wire round the pulley to show the way the new contact just rubs the wire.

So now I need to re-mount the arm temporarily so that I can take some measurements for the sliding seal arrangement.

awemawson:
Having re-installed the arm, complete with the stainless steel cover that I made, it was immediately obvious that the cover wasn't long enough to make a seal for the full travel of the machine. I just slavishly copied what was there when I got it. Bad move as it's apparent now that this machine has been at some stage re-worked using bits from slightly different ones. Ah well - just bend up another one :bang:

The black paint arrived today, so the drawing arm got another coat of paint

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