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Teaching myself electrode surfacing


Sigurd
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I am a moldmaker who has been assigned self-teaching of electrode surfacing. I do have prior 2D and 2.5D mill experience. I've been reading various threads about lying about the cutter diameter, lying about the Z touchoff at the machine, etc. I'm having trouble wrapping my head around it all. The file 'electrode test' is an electrode I'm working on. I am programming with -.005" stock to leave on all surfaces. The manual sinkers only orbit circular and I don't think we've ever used spherical on the CNC sinker.

1. The top surface is ground and I don't want/need to cut it. If I touch my tools off on the top surface and then lie about the length at the control, I'll get what I'm after, right?

2. How do I go about picking out the corner between the flat and the angle? Pencil toolpath or rest strategy with a flat-bottom sharp-corner endmill?

3. How do I pick out the corner at the bottom? This is a vertical wall and I could 2D contour it, but I need to learn surfacing.

 

In the file 'electrode B', why is the Horizontal Area path not cutting the lower flats?

I appreciate any help as I learn and teach this to myself. Thanks.

electrode test.mcam

electrode B.mcam

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14 minutes ago, Sigurd said:

I am a moldmaker who has been assigned self-teaching of electrode surfacing. I do have prior 2D and 2.5D mill experience. I've been reading various threads about lying about the cutter diameter, lying about the Z touchoff at the machine, etc. I'm having trouble wrapping my head around it all. The file 'electrode test' is an electrode I'm working on. I am programming with -.005" stock to leave on all surfaces. The manual sinkers only orbit circular and I don't think we've ever used spherical on the CNC sinker.

1. The top surface is ground and I don't want/need to cut it. If I touch my tools off on the top surface and then lie about the length at the control, I'll get what I'm after, right?

2. How do I go about picking out the corner between the flat and the angle? Pencil toolpath or rest strategy with a flat-bottom sharp-corner endmill?

3. How do I pick out the corner at the bottom? This is a vertical wall and I could 2D contour it, but I need to learn surfacing.

 

In the file 'electrode B', why is the Horizontal Area path not cutting the lower flats?

I appreciate any help as I learn and teach this to myself. Thanks.

electrode test.mcam

electrode B.mcam

No reason to surface vertical or horizontal walls. Only surface the tapers on the test file. Same thing for the B file.

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I'm a mold maker as well, and I often machine electrodes, and run the EDM.  And yes, it can get tricky sometimes. 

Like Ron said, no need to surface vertical walls.

Ill usually scale the model to give me the outside dimensions that I need, and for the inside of the electrode I use stock to leave with a negative value, and sometimes I do have to lie about the size of the tool.  Its not that difficult once you wrap your head around it

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3 hours ago, Sigurd said:

Point taken: no needless surfacing. It would be nice to scale the model and just cut everything to zero. I don't want to scale in Z though. How do you accomplish that, AMCNitro?

You don't have to worry about it, just cut it the way you did, minus the surfacing in the walls.

The problem with scaling the model is the are features that you might want to scale the opposite way.  If you have a cube and you scale it you're ok, but if that cube has a pocket in it, and that feature needs to be burned as well, by scaling it your blowing your dimensions.  So you have to make the outside smaller and the inside bigger.  I usually don't have to time to model it that way, so I just scale it down and I use stock to leave on the pocket, to make it bigger.

Just takes a bit to wrap your head around it, once you've done a few you're going to get it.

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16 hours ago, Sigurd said:

Another way to do it is use flowline with a -.005 stock to leave, and flat endmill.  Its a bit more work, as you have to create surfaces and extend them.

Something that I see a lot is programmers forgetting that flat endmills can also be used for surfacing, and many times its the better option.  For roughing surfaces I use flat endmills exclusively.   

electrode test (2).mcam

Check this electrode out.  It was machine on Haas Mini Mill, no high speed spindle, nothing fancy.

V9_electrode.mcam

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54 minutes ago, AMCNitro said:

Something that I see a lot is programmers forgetting that flat endmills can also be used for surfacing, and many times its the better option.  For roughing surfaces I use flat endmills exclusively.   

100 % Ive used flat endmills with stock to leave all the time, it's great for roughing and even sometimes finishing if you don't have a ballnose of a certain size handy!!!

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1 hour ago, [email protected] said:

100 % Ive used flat endmills with stock to leave all the time, it's great for roughing and even sometimes finishing if you don't have a ballnose of a certain size handy!!!

Or if you have sharp edges, or really small radiuses in hard to reach areas.  Ive had people look at me like 🤨 when I suggest a flat EM.

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So what about cutter wear. Graphite wears like mad!  We use diamond tip cutters for our electrodes and find that ball nose has less wear. When you use a sharp E/M that sharp corner can disappear and give problems with tolerances? I would be interested in hearing how other get around this. A lot of our stuff has + -  .0002 and or shutoffs?

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4 hours ago, danatoem said:

So what about cutter wear. Graphite wears like mad!  We use diamond tip cutters for our electrodes and find that ball nose has less wear. When you use a sharp E/M that sharp corner can disappear and give problems with tolerances? I would be interested in hearing how other get around this. A lot of our stuff has + -  .0002 and or shutoffs?

I only use tellurium copper for our electrodes, I have used graphite in the past though, and it does wear a bit more.  But if you lose the sharp corners, you're leaving material behind, you're not taking any extra out.  On top of that you can always use a rougher and a finisher.  And if it doesn't work for you, then it doesn't, you don't have to use our suggestions, do what works best for you.👍

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