What kind of finish will a edm produce?

[drivefast]

I have the choice of producing an engraved logo via edm or cnc mill. The prices for both are competitive. I have had several small badges made from 6061 with the mill so I know what to expect from it. However, I have never seen a graphite edm working so I don't know what the part will look like. The logo is .040 deep into 6061. I like the fact an edm can create sharp corners where as the mill is limited to the diameter of the endmill. So, my question is will the edm produce a finish comparable to milling. Will the surface be uniform. We are planning on powdercoating the part, will that matter.

 

[CorBlimeyLimey]

EDM will produce a slightly rough surface finish. It can vary from say 600 to 300 grit sanding paper depending on the power used during the process.

http://images.google.ca/imgres?imgu...images?q=edm+finish&gbv=2&hl=en&safe=off&sa=G

If you plan to powder coat the part, you will lose much of the surface detail and round out the corners to boot.

 

[Heckler]

What type of EDM? Wire or graphite electrodes (Plunger type)?

So, my question is will the edm produce a finish comparable to milling

No, the EDM process has no lay like a mechanical cut surface.

Heckler
Sr. Mechanical Engineer
o
_`\(,_
(_)/ (_)

This post contains no political overtones or undertones for that matter and in no way represents the poster's political agenda.

 

[SincoTC]

Solid sink EDM can give a very wide range of surface finish, ranging from something like quite coarse emery paper (100-200 grit), through fine bead blast to a mirror finish. Many factors influence this and include cutting speed, roughing/finishing, the quality of the carbon used for the electrode and whether another finishing electrode is used, the sophistication of the control electronics and its programming and the component material itself. CBL's link looks very good and goes into this well.

You should ask for a sample from the company that quoted you and see what they are offering for that price. You know what you can easily achieve by CNC engraving, but it can be very time consuming and if you need large numbers, it can soon dull tools and wind up giving you a lot of fiddly de-burring to do. The great joy of EDM for this type of thing is small corners a uniform finish and no burrs!

Trevor Clarke. (R & D) Scientific Instruments.Somerset. UK

SW2007x64 SP3.0 Pentium P4 3.6Ghz, 4Gb Ram ATI FireGL V7100 Driver: 8.323.0.0
SW2007x32 SP4.0 Pentium P4 3.6Ghz, 2Gb Ram NVIDIA Quadro FX 500 Driver: 6.14.10.7756

 

[KENAT]

What finish do you really need? Specify this on the drawing and then ask the EDM place if they can meet it.

If they can't but come close consider if you can relax the requirement.

While process capability is a very important thing to consider, you usually need to start out by defining what you think you need.



KENAT, probably the least qualified checker you'll ever meet...

 

[tripleZ]

What will the part look like off of EDM?

Pretty much whatever you put into the electrode, with the possibility of a pit or two if the flushing isn't optimal. The fact that this is 0.040 deep though can pose an issue. While EDM can give you sharp corners, it's only as good as what you put on the electrode. So if you have to ball mill the form on the electrode, your results might be comparable.

Will EDM produce a finish comparable to milling?

Yes. With a CNC machine that features tight orbiting control, you can get an excellent finish. A lot of it though is a function of how much time you want to spend burning the part. You can run multiple low amp burns and get a smooth finish surpasses a mill...but not in the time a mill will do it. While EDM might get you a better finish, the process will take longer and you'll have the added time of machining multiple electrodes.

Will the surface be uniform? Yes.
Can you get powdercoating to stick to it? Not sure. I would assume that the recast layer would hold powder just like a standard surface. But the depth of the detail would likely lead to some distortion or pooling.

 

[tbuelna]

If your part is highly stressed, I would stay away from EDM. The EDM process, whether wire cut or sinker, leaves a remelt slag on the cut (eroded) surface that must be removed.