Machine Slow on Curves

[Neale]

In your original post, I think you said that it was fine when you cut a circle, but not a curve made of arcs of different radius. My experience with LinuxCNC cutting circles is that even with a circle made from four quarter-circle arcs (which is what Vectric VCarve seems to generate), the arcs themselves cut at full speed but LinuxCNC slows as it goes from one arc to the next, even though it's still a smooth curve. I want to follow up the ideas already given about G64 and so on, but it may well be that even if you have a series of arcs, it's not going to make much difference as you still get slowing going from arc to arc. However, you did say that your curve was a series of arcs of different radius so it's possible that Cambam can't actually do much optimisation into constant-radius arcs which is why it settles for a series of straight lines and lets the machine controller do any optimisation.

[swisscheese]

In your original post, I think you said that it was fine when you cut a circle, but not a curve made of arcs of different radius. My experience with LinuxCNC cutting circles is that even with a circle made from four quarter-circle arcs (which is what Vectric VCarve seems to generate), the arcs themselves cut at full speed but LinuxCNC slows as it goes from one arc to the next, even though it's still a smooth curve. I want to follow up the ideas already given about G64 and so on, but it may well be that even if you have a series of arcs, it's not going to make much difference as you still get slowing going from arc to arc. However, you did say that your curve was a series of arcs of different radius so it's possible that Cambam can't actually do much optimisation into constant-radius arcs which is why it settles for a series of straight lines and lets the machine controller do any optimisation.

Just want this to be clear. When i have a curve made up of lots of different radius circles added together I dont have problem. The problem arises when I try and cut a curve that is made up of lots of small straight lines.
If you're having problems with the machine running slow, like you are with the circle made of four different arcs i suggest you play around with G64 G61, P and Q parameters like has been suggested in this thread and you should be able to get it to work.