Wire EDM Aluminum?
I have never wired aluminum...until today. Having huge problems with an edge start (non submerged machine Mitsubishi 90C) The wire breaks instantly as soon as it contacts the work piece. Right now I'm about at wits end, I have been playing around with it pretty much all day and while I got one part started (after it started it cut fine), this next part seems like its even worse (same thing as the first, just another one), and I can't get the wire to stop breaking. I have tried all different flushing settings, and even machined a little piece of material with a slot in it and clamped it to the work to contain the fluid, cranked the wire speed all the way up, dropped the voltage change over (for different work piece thickness) as low as it goes (64 volts), power as low as it will go, tried coated wire, plain brass wire, (all .012) and nothing seems to make a difference. Material is Alcoa 6061, 1" plate (Made in USA) Got a good ground, nothing mechanical I see that would be breaking the wire.
Is there some special procedure you have to use for Aluminum? I have no epacks for Al. so in the dark. I'm kind of leaning towards it being something with the machine, if you hand jog the wire in .0001" increments, it cuts, but since I don't have any experience with Al. trying to find out if there could be something I'm missing to make sure I eliminate all the simple things it could be. Thank you so much for any input!
Did you do anything to the surface of the Al? Aluminum develops an oxide layer that can make it tough to start on; use a little emery cloth on the area where you're starting to get past that skin. As you've already seen, it cuts fine once it's in!
I've personally never had trouble starting on an edge. The only time I have trouble is in a hole that's been hole-popped (almost impossible to start the cut unless I run a drill through it or scratch up the sides with a tiny file or something like that).
You might try increasing the dwell/off time... I usually run that considerably higher than on steel.
I think Dan's advice is great though -- try sanding the edge.
If the aluminum is clear anodized, it will be non-conductive for your wire start
A standard startup E-pack should be fine; I believe 590-593 for that machine.
The advice given about the oxide layer is 100% true. Very important to prep grounding surfaces and the start edge before WEDM, especially if the material is an older piece of stock that was laying on the stock rack.
Only trouble I've had was with an exotic (to me anyway) aluminum-lithium alloy. Literally from NASA. Would start, cut a little then break the wire. Gave up had the dogbones cut on a CNC mill. (dogbones=tensile test specimens)
Didn't know much about EDM parameters at the time, but I don't recall being the only brain there cracking the nut.
Haven't cut aluminum for some time, but recall having no troubles with 6061. Machine is a Brother HS-300
How tall is the workpiece?
Do you have any secondary flush?
Thanks a million for the ideas!The edge was milled the same the day before EDMing. Still sanded it and made no difference. I turned up the off time as far as it will go, and also stabilzer "B" as far as it would go. The fantastic news is I got it to cut that way...barely, its not a bit happy going through it. I was mistaken on it cutting good after it started, that on another part of the work piece that's another piece of 6061. It flys through that with no problem...night and day difference!
Maybe its like in Keiths case there is something messed up with the metallurgy piece of stock? Its printed right on it Alcoa USA 6061. I'm at a loss!
The good news is I only have one more cut to do in it, and like I said I can cut it without the wire breaking endlessly now that the electrical conditions are jacked way up.
Jay Cee, Its 1". What is secondary flushing? I got the lower and up flow meters, that's pretty much all to control flushing. Control has it to set for weak for regular flushing, but that doesn't seem to work. Usually I just vary the flow and pressure with the flow meters and it works great.
What type of raw material is this block of 6061 Aluminum? Is this from a solid billet or is this a cast material? If it is a cast, you might have some issues with porosity in the material that is making for a bad day, and there isnít much more you can do beyond what you have already tried! If it is a cast material, you might try using a coated wire (like Topas or MegaCut-D), which won't help with the speed, but it should help cut down on the wire breaks.
All the comments given so far are helpful hints. What I do when cutting alum. is use standard steel/stainless settings the reduce the power about 30%, increase the off time to about 80% just to get started. Good flushing is a must as alum. has a low melt temp and has larger eroded particles. When beginning my edm career I can remember cutting alum and when I got to the end of the cut the kerf was totally filled with eroded material! You will also have to increase your offset to maintain size and set your conductivity to not use your resin bottle during cutting as alum. particles in the resin will kill it very quickly. If you have a long run, get the conductivity of the water as low as you can before you begin cutting and then set the conductivity high so that the deionizing circuit is not operating.