This may sound alittle crazy but I have tried this when having the same Jerky problem with some code generated by Aspire on 2.5D carves. I changed the CV feed rate in settings to 40, also turned on Plasma mode in the general config. Turn off CV dist at angles. This made my 2.5D carves run much smoother. Also check that your read ahead is set at about 200.

Just my experiences so far. Plasma mode uses an algorithym to keep constant velocity so as not to stop and burn holes. At least that is what I would suspect the reason. By using it though it will round sharp corners. Now you can also leave the CV at angles on and this will help with the corner rounding. I applied this while milling Steel on a mill that would stall the steppers due to the mass/enertia problem of the stops and starts. The problems went away.

Just my .02cents worth.

Mike

This may sound alittle crazy but I have tried this when having the same Jerky problem with some code generated by Aspire on 2.5D carves. I changed the CV feed rate in settings to 40, also turned on Plasma mode in the general config. Turn off CV dist at angles. This made my 2.5D carves run much smoother. Also check that your read ahead is set at about 200.

Just my experiences so far. Plasma mode uses an algorithym to keep constant velocity so as not to stop and burn holes. At least that is what I would suspect the reason. By using it though it will round sharp corners. Now you can also leave the CV at angles on and this will help with the corner rounding. I applied this while milling Steel on a mill that would stall the steppers due to the mass/enertia problem of the stops and starts. The problems went away.

Just my .02cents worth.

Mike

One more thing. When milling metals this way and doing 2.5D carves. The Zaxis will plunge at a higher rate than what the plunge rate is in the Gcode. To overcome this and not break mills. Set your maximum Z axis rate to the fastest plunge rate you would use for that specific material. Set the accel rate to 10% of that value.

So if I know that I can only plunge into steel at say 2 IPM  with a particular end mill, I will also set the accel rate to 0.2. This only appears to apply when doing metal work in my experience. In my wood working it does not seem to be a problem.

Mike

hi mike

i was going to try your suggestions when i accidentally found the solution; i turned off the tangential control and got perfectly smooth high speed motion. however, i had to drag the knife instead to get it to face to the direction of cutting by disconnecting the A axis motor (this turns the knife) and positioning the knife behind the axis about which it rotates. this works fine provided  i have radius corners to go around.

i will give your suggestions a try though since ideally i need tangential mode on.

thanks for your help, and to everyone else who has replied.