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View Full Version : How fast does a home-brew EDM machine cut ?



Dan_the_Chemist
06-10-2019, 01:57 PM
Yeah, I know that's a bit like asking "How long is a home made length of rope?". I am sure the answer varies a lot depending on the amount of power one can put into the electrode, the control circuit, etc. But there must be a ball park figure.

The reason I am asking is that I want to start making some very small radius parts using a CNC mill. The problem is that the radius is like 1/32'nd or smaller. Oh yeah, I want to make them in steel. I don't think I can do that with my current machine. So my thought is to rough them with a .250 cutter, and then used an EDM modified 3D printer to finish off the fine bits.

Technically I think it's a "solved problem". I've seen people mount knives, lasers, and what-not on 3D printers. I've found a few pages of people putting EDM on a 3D printer, but the only comment I've seen about speed is "Slow as F".

So, if I had to EDM a small square hole about .125 square with .025 radius corners through .125 steel using a "well made" home-brew EDM mounted on a 3D printer that moves the EDM electrode around, what sort of time are we talking about? Note, this is not using a graphite square electrode, but using a 16 gauge wire as the cutting bit...

Chris Evans
06-10-2019, 04:26 PM
EDM by it's very nature is slow. I spent 35 of my 50 years in toolmaking (mold and die) working "Spark Eroders" . You need a stable machine to generate a shape EDM machines can profile though. The job sounds ideal for a wire cut EDM machine.

Bented
06-10-2019, 09:33 PM
When you say "steel" do you mean hardened tool steel?

Wire EDM does not play well with mild steel, the harder the material the better it will finish.
Impurities in the material will cause problems as well so begin with the cleanest material that you can afford. Clean means a steel of known origin with few impurities, do not buy off the rack at home depot or from a scrap dealer, you never know what you are going to get that way.

Also you have not mentioned the most important question about making parts which is Number Of Parts required and tolerances desired. Unless the parts are not suitable to it this is a punch press job, you could punch 100's of such parts per minute with a punch and die

Rich Carlstedt
06-10-2019, 09:46 PM
I built Ben Flemings Home Brew EDM machine 15 years ago and it burns nicely
What I don't know is your 3D Printer reference. ?
I think I understand what you want to do, but having it done with a 3 D printer is a whole new game..maybe that why you are asking I presume?
And using copper is not the best for speed
I burned a 3/16 square hole through 1/8" thick Carbide in 20 minutes with Ben's unit.
I can tell you right off the bat that trying to put all your power into a small wire that has exposure to small areas is not a recipe for speed, let alone production Your control will be trying to give you the correct power at a particular point , but you are moving the electrode ?/
Now I have heard of a rotary electrode that used a wire to burn out taps by cutting through the flutes and not the core, but the power was determined by each step as the electrode moved .001" deep and continued until the contact points diminished and then it proceeded from there. I don't think 3 D printers do that..
For whats its worth , make a graphite electrode and plunge for speed.

Rich

darryl
06-10-2019, 11:25 PM
It's possible that the biggest player with EDM is how fast can you remove the heat that's being generated. The faster you want the job to go, the more power you have to use- and the more power you have to carry away with a pumped coolant (and probably the less precise the job you can do). Just a guess here, but I think the coolant could be a slurry of some kind of finely granulated conductive particles. It would 'fire up' as the current flowed, and would simultaneously erode by electrical discharge and from a burning or melting action. This method uses the powdered material as a consumable, and it's simply flushed away with the coolant. I know that edm can be a very precise method of machining, but something like including this method I'm talking about as part of the process could improve the speed greatly, and the results could easily be quite satisfactory.

Just an idea that came to me- I find edm interesting but know little about how the technology has developed.

reggie_obe
06-14-2019, 11:56 AM
Here IS: https://www.practicalmachinist.com/vb/machinery-for-sale-or-wanted/brother-hs-300-wire-edm-357083/
a wire EDM (unknown condition) Cheap. Might be within driving range to pick up.

PStechPaul
07-01-2019, 04:08 AM
Sadly, it was scrapped:
https://i.postimg.cc/KvvrHzFb/DSCF3661.jpg

I saw a post on HomeMadeTools.net about a DIY EDM machine, and it looked quite impressive, especially for making a planetary gear set:

http://www.homemadetools.net/forum/home-shop-made-wire-electrical-discharge-machine-73660?utm_source=newsletter&utm_medium=email&utm_campaign=06-28-19#post136550


https://www.youtube.com/watch?v=OuI3vj0prnw

To answer the question posed by the OP, the speed of this machine is 5 mm/min.