VFD Programming Questions

[Jim Becker]

The speeds and feeds in the tooling manufacturer's chart many not be ideal for your particular machine, especially if it's a smaller, non-industrial tool. It takes time, but you'll figure out what speeds/feeds for a given tool work best on your machine with what material. Nature of the beast...

[Michael Burnside]

My buddies Haas has a 50hp spindle and it only hits 10000 rpm. I assumed cutting aluminum at extreme speeds would require higher rpm. But no, theres no assumptions in cnc work. Take known quantities and adjust slightly with trial and (skip the error). I buy amana bits and use there catalog in vectrics to set speeds and feeds. I dont do enough work with the cnc to know better or worry about the cost of the amana bits.

Only problem with that approach is the feeds and speeds in the Vectric libraries for Bits&Bits, Amana and Whiteside are wrong 90% of the time. And to say they're conservative is actually not exactly a correct statement. Yea the feed may be conservative, but the speeds are usually way too high. I imported a new compression bit from the Whiteside library into my own, to save some time, and I forgot to update their speed. My chip load was 0.001 in hard maple LOL. It was feeding slow but got so hot the bit snapped. I actually burned up two bits before I realized my mistake and adjusted the g-code to feed faster but spin at 6k RPM less. Bit didn't break that time or since.

There are some machine variables that come into play too, but chip load (the purpose of feed and speed) are still relevant to any machine. Once you know how to calculate F&S yourself, you'll have a lot more confidence in the overall process. I recommend people search online for target chip loads of a given material, adjust to -30% and test. If you don't have an industrial machine, reduce your depth of cut and see how the machine behaves.