Over burns on electrodes

[lowboy]

I was woundering when machining an electrode using surface toolpaths,if you input a negative number in stock to leave, will this account for an accurate and uniform distance over all the selected surface?(over burn)

Does it offset the surface evenly or do you need to do this your self by using the offset surface command?

Thanks

[Matt Berube at Ferron Mold]

quote:

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will this account for an accurate and uniform distance over all the selected surface?

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Absolutely.

 

Negative stock is the most accurate way to make electrodes as long as you're burning them with a "spherical" orbit. The only thing you have to remember is that if there are flat areas on the trode you need to machine those to negative depths as well.

 

We used to lie to Mastercam about the ball end mill diameters and use 2-d orbit but on tricky shut-offs we always had trouble.

[edmBosto]

Negative stock is faster to get the job done and the electrode depths do need to be checked as compensating can have its drawbacks. But it is quicker.

The other way is to just offset the wireframe on another level and offset surfaces manually (time consuming) or create a new surface. Solid shelling is pretty good and then saving the offset shell. Smart electrode (Pro-E add on)works but there is a learning transistion period.

[Mjölnir]

For sphericaly orbited burns, yes, using negative stock is usually the best method for making the electrodes.

 

For continuous orbiting (where Z is held (more or less) constant and the orbit pattern is an XY spiral), a combination of negative stock for the primary spark gap, and cheating the tool diameter for the orbit amount is typicaly the best and easiest method.

 

Square / vector orbiting may require some additional thought depending on the shape. I don't do it often, but in most instances the electrode needs to be re-modeled with orbit included by *translating* (NOT offseting) the sides in, then cut with just primary spark gap (typicaly .0005 to .003").

 

If you're working for a dinosaur shop that doesn't have EDM machines with orbiting capabilites, you're reduced to making roughing, semi-finishing, and finsihing electrodes, and they need to be made with negative stock.

[lowboy]

Thanks for the reply's!!

[TR Mfg.]

We always lied about the cutter diameter. A .125 ball would be programmed as a .121. Always worked for us.

[betts]

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If you're working for a dinosaur shop that doesn't have EDM machines with orbiting capabilites

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HEY- I resemble that remark! However I have built electrodes for several different brands of CNC sinkers with different controls, and I would concur with the advice above, but remember there are always exceptions, especially in mold building. No need to confuse lowboy with anything else now, just my .02

[mcpgmr]

I use negative stock as well when I have to and it's as accurate as cutting to nominal size.I did alot of electrode/electrode holder design for CNC die sinkers a few years back for gas turbine componants. I built the over burn into the design of the electrode and the operator made the adjustments with the orbiting function right at the machine.