Post processor problems regarding constant velocity/exact stop



I am setting up my third masso controller but my first on a router. The other two were plasma.

On some but not all of the toolpaths I am posting from fusion 360, the machine will run its path in a jerky motion. Starting and stopping at every successive motion. It will run a straight line fine but when it comes to a transition between that and a curve it stops then starts the curve. Then runs the curve fine. This causes a bad oscillation in the gantry of the machine. I previously did a lot of mach3 builds and in mach3 the parameter that would remedy this was called constant velocity/exact stop. Adjusting the parameters under constant velocity/exact stop would remove this error. I can not find any way to manipulate this with Masso. I am trying the masso post as well as other posts. The masso post does it the worst. I can get a mach3 post to work better but it still stops running with constant velocity at some points in the path causing a nasty oscillation in my machine. Its worse on full 3 axis movements than running flat curves.

If anyone can help that would be great. Would hate to have to remove the masso and go back to mach3 just because of a bad post processor.


MASSO Support
Staff member
Hi @sculptyourbrain

Do you have a sample of the Gcode that is giving you problems that we can have a look at?

Masso runs exact stop and not constant velocity. The problem with constant velocity is you are basically saying "can you cut me something that looks a bit like this?" Constant velocity makes up its own toolpaths to smooth things out by cutting corners. If you want to do that you are better off doing it in CAD / CAM than letting the controller try and do it on the fly.

One thing I learnt recently is the curves are not arcs and are made of tiny little lines that will cause the issues you describe. The solution is to convert them to arcs and things will smooth right out and your Gcode file will shrink considerably. The processor in your PC is a lot more powerful and can easily convert the drawing accurately to arcs for smooth cutting

You may also find that changing your axis acceleration and making it longer will smooth things out as it won't have the same abrupt start stop.

Hope this helps