After reading your example, I see that I mis spoke in my last post. Mach doesn't always accelerate at the set rate. It will not, however, ever exceed it. Which answers your question I think.

OK, then I think I will be pretty safe for the time being. I'm quite familiar with calculations for pick 'n place robots but CNC is so much different with the constant interpolation. If necessary I can reduce the gear ratio to slow down the top speed as this is a hobby machine, not needing full scale production speeds. Thanks Gerry and Rich too.

PS. Obviously there was a typo in my previous post, should of course have read dx/dt and dy/dt.