Toolpath logic: is this the norm?

So right now I’m cutting my first carve using the post processor from VCarve. This is a simple pocket cut - the Green Bay Packers “G” logo for some kid’s birthday in the 'hood.

It’s on its 3rd or 4th pass now for the big pocket and I’ve been watching it wondering: why the hell is it doing all of these extra movements to detail each pass?? It seems like it spends 3/4 of its time on each pass, clearing tiny bits that would just be cleared by the next pass (in depth) anyway.

This is the VCarve post processor for X-Carve, exported and run in UGS. Is this logic the norm, or am I just choosing the wrong options when I setup the toolpaths in VCarve? If the former, I have to find a better CAM solution!

My experience with the toolpaths from Vcarve has always been good. I have cut lots of pockets and it always does a spiral clearing path starting in the center then winding back to the center till done.

Are you doing the standard offset pocket path?

Yes, standard offset pocket. I reran it using an end mill instead of a ball nose and it did much better (I think the main difference was in the stepover value between those two runs) but I’m still curious about how the logic hasn’t been formed to eliminate these unnecessary moves.

I took some videos last night and as soon as I figure out how to upload them to the web, I’ll share them. I think they’ll make my point more clear.

Using a ballnose bit for a clearing operation is usually a bad choice. It forces you to either have a very small step over (which takes lots of time) or to spend lots of time cleaning up the ridges that the ball nose leaves on each pass.

The toolpath logic is looking at the depth of cut you have set and determines that it needs to clean up all the ridges before starting the next layer so it can keep the DOC as close to constant as possible.

I think you will find that the toolpath created in Vcarve is very efficient if you choose the correct tool.

What material, feedrate, DOC and size bit are you using?

Thanks @AllenMassey - I figured that out (the part about the stepover) pretty quickly last night. I understand that it wants to find ultimate consistency when it’s planning the toolpaths, but it spends so much time on the the tiny nibbles at the end of each pass - even with the a traditional, flat end mill - that I think logic and time savings should rule instead of perfection. The extra amounts it would have to clean up on the next pass down (in Z direction) would not come close to impacting performance. But, I digress.

I’m using 1/8" bits at 1/8" DOC. Works great with either bit at ~60 IPM in walnut at the 611’s lowest RPM. When I tried switching to a 2 x straight flute and bumping up to 100 IPM, I think the RPMs needed to be increased because it dragged the clamped-down material a little on the wasteboard when it was doing some of the longer cuts on the X axis. I do have GWiz and (I think) your spreadsheet, but I’m trying to keep myself in the “feel” stage for now so that I can learn from first-hand mistakes.

Thanks again - I’m giving up on this minor toolpathing complaint to move on to one that’s much more interesting! This whole process has been a blast.

It sounds like you have a good feel for the machine. My only suggestion would be to decrease the DOC to half the bit diameter and then increase the feedrate. In hardwood like walnut it seems that a smaller DOC will give better results.

We are all learning how best to use the 611 with the XC so please post back how it works out and what you find gives you the best result.

good tip re half the diameter…I know I’ve read that only about 17 times by now. I’m hoping to report back with a matrix of some findings for S&F, but that will take some more spindle hours.

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