Ball Mill Step Over Calculator

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twforeman
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Ball Mill Step Over Calculator

Post by twforeman » Mon Apr 04, 2016 4:03 pm

If you are doing 3D surfacing with a ball mill you know about step over and the scallops it leaves. There is a diminishing return on reducing the step over value - making it smaller increases machining time without really improving the finish.

Here is a good blog post discussing the "sweet spot" for step over.

tl;dr: the sweet spot is around 1/10 of the cutter diameter, also if you can use a larger cutter it will reduce the scallop height.

Here is an online step over calculator that will show you how much scallop your settings will leave.

On most of my work I use a 1/4" ball mill and .020" step over. According to the calculator and the blog post that's a little finer than the "sweet spot". Next time I generate a tool path I'll use .025" and see if I can tell the difference.
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xfredericox
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Re: Ball Mill Step Over Calculator

Post by xfredericox » Mon Apr 04, 2016 6:32 pm

from experience, I use 5%. 10% leaves visible ridges. Probably the sweetspot is somewhere in between those 2, but I always take 5% just to be sure.

I'd rather have the machine work 30mins overtime than having to sand 10. :D
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WillAdams
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Re: Ball Mill Step Over Calculator

Post by WillAdams » Mon Apr 04, 2016 7:00 pm

FWIW, the CNC Cookbook article was in the Glossary entry for stepover.

I've added the on-line calculator link, and added both to the ball endmill shape section of the endmill page.
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twforeman
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Re: Ball Mill Step Over Calculator

Post by twforeman » Mon Apr 04, 2016 7:40 pm

Thanks Will!
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