Rough edges

Computer Numerical Control

Rough edges

Postby loyd » Thu Nov 28, 2019 9:39 am

I'm having difficulty on rough edges with the CNC. There a lots of options on cutting but I'm not too sure which ones to use. I'm guessing that I'm letting the default tool Feed Rate is at least part of the problem.
There are options in setting up the toolpath. You can for instance select the number of passes and set the last cut to whatever you want, but by that time the damage may already be done. You can set the tool Feed rate which defaults to 100 inch/min [that may be the clue but what feed rate to use isn't obvious]. And then there's the option to use a 'Separate Last Pass which you can check, but the options for that pass are grayed out. You can specify tool path direction to Climb or Standard. I've been using Climb but I'm not sure that's the right thing to do either. Any advice?
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Re: Rough edges

Postby southpaw57 » Thu Nov 28, 2019 4:19 pm

Climb is good. Can you specify how much to leave for a finish pass? if so, you might leave a little more. Can you change the feed rate before the finish pass? if so, I would cut it in half. Let me know how it turns out. :geek:
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Re: Rough edges

Postby loyd » Thu Nov 28, 2019 5:32 pm

I'll try that out. It would probably be two tool paths but I can do that pretty easy.
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Re: Rough edges

Postby rgulley » Tue Dec 03, 2019 7:23 pm

The best (and simplest) method I've found to set feed rate and rpm is by sound. I vary the feed rate and rpm of my spindle while it is cutting. It doesn't take long to find a sweet spot. The bit shouldn't be screaming. That doesn't necessarily mean slower. Sometimes faster rpm of feed rate does the trick. It all has to do with chip load. More top brand manufacturers are supplying recommended rpm/feed rate with their bits and I've seen formulas for calculating. But the "sounds right" works for me. *Disclaimer - bits need to be sharp. Dull bits scream, burn, chatter, and leave a rough surface.
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Re: Rough edges

Postby loyd » Tue Dec 03, 2019 8:23 pm

Thanks for the advice.
Have you noticed a difference with climb versus standard cut direction?
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