[natev]

I'm using a k2cnc 2539 machine with Kmotion/KmotionCNC

I'm finding that when the machine is moving very slowly <15in/min the action seems normal, however when moving at a quicker pace the machine shakes due to very abrupt changes in direction. Is there a way to tell the machine to slow into a point, change direction and slowly pick up speed again?

I'm new to using CNC machines and this might be normal at those speeds, but it seems hard on the machine. I've seen posts about Constant Velocity in Mach3 but I'm not currently using that softeware.

I'll also note, that the cuts seem relatively fine but based on the problem amplifying I worry that going any faster will break a motor or shake the machine apart.

thanks
nate

[TomKerekes]

Hi natev,

I'm not familiar with that machine. Is that using servos?

Could you make a screen shot of the Trajectory planner settings under KMotionCNC | Tool Setup | Trajectory Planner?



The Break Angle setting should determine when the machine decides to come to a stop at a corner rather than slowing down to "round" the corner.

You may want to reduce the acceleration.

For more information see here.

Regards

[natev]

Yes, it's using servos. The axis that jerks is the Y which is perpendicular to the gantry. This is probably common in that the gantry only has X axis supports and there is no support on the Y. E.g. a ladder is more likely to tip forward or back rather than side to side. Anyway, here's a link to the machine and a tool setup shot. Desktop HD CNC Router | KG3925HD | K2CNC

Attachment 234624

[TomKerekes]

Hi natev,

I really liked your ladder analogy. I agree that seems to have significant mass high up with narrow support.

I don't see anything major wrong with your settings. The break angle of 10 degrees should cause a stop for most angles.

The 30in/s2 acceleration seems pretty aggressive for such a system. To accelerate to your mentioned speed of 15ipm would only take 8ms which is virtually instant for a system like that.

Have you tried reducing the acceleration settings? This will not effect your Rapid or Jogging acceleration which uses 3rd order motion specified in the KFLOP Acceleration and Jerk settings. Also with KMotionCNC you shouldn't have the issues with lower acceleration that you might have with other systems - like rounded corners.

Regards

[amowry]

I have the same machine, and I found the "factory" acceleration setting of 30 in/s^2 to be way too high, as Tom said. I set it to 5 for most work, and 2 for fine detail work like cutting mother of pearl inlays. This is probably conservative, but it works well for me.