Controller constant velocity setting?

[jcwoodworking]

Does anyone know if there is a constant velocity setting in the controller for my ar8 pro+? When cutting ovals, the xy movement is very jerky, I know it's probably something in the g code. I use aspire and converted my vectors to curves to eliminate many of the nodes, but that didn't really help. Any ideas?

[grg]

Have you tried to just program a simple circle (or an oval from a cleanly drawn oval) and programmed from that? What software are you using to generate the g-code? There may be some additional options in there.

[jcwoodworking]

I am using vectric aspire. What I did was draw an oval then extrude a moulding profile on it to make a picture frame around a 3d carving. I'm using a 3d finishing toolpath. I've made ovals and circle using profile toolpaths and never had a problem with them.

[Deleted]

For ovals, the toolpath is made up of line segments so that is what you're seeing. You can eliminate line segments altogether for arcs and circles as in version 9.5 Vectric finally got around to adding Helical toolpath generation. Unfortunately, they only added the ability to a few Shop Sabre machines so I've added it to various other manufacturer's machines including Axiom. What you're asking for is the right thing though, there is a mode to reduce error that requires the machine to go to each specified point in the G-code (G61 exact mode) and another that eliminated the stop and start at each vertex as long as you get close to it, within the specified error limit, while you go by it (G64 constant velocity mode).

gnipsel.com/linuxcnc/reference/index.html

[jcwoodworking]

Thanks for the info fean. Now the question is is there anyway to turn it on on the controller? I don't know if it's even possible. The thought has crossed my to convert the machine to a wincnc controller, but I don't know if I want to go down that rabbit hole just yet.

[Deleted]

Nov 15, 2018 9:00:06 GMT -5 jcwoodworking said:

Thanks for the info fean. Now the question is is there anyway to turn it on on the controller? I don't know if it's even possible. The thought has crossed my to convert the machine to a wincnc controller, but I don't know if I want to go down that rabbit hole just yet.   

The controller is not suppose to ignore or change G-code commands, it can ignore ones that aren't implemented, thus a "flavor" that deviates from the specification for each machine. In itself, that is a problem and it would be better if everyone held to the standard instead of doing their own thing. You change it in the source which is the post processor or edit the G-code file (plain text so any editor will work). Typically the G61/64 will only be in the file once at the top so you should be able to find it with Ctrl-F and replace it.