I’m experiencing a strange issue with my PCNC 440 (PathPilot).
Machine powers on normally, no errors.
Axes home fine.
When I try to move the X axis at max feedrate (135 IPM), the axis tries to move but immediately stops, almost as if it were hitting a limit switch or soft limit.
At a lower feedrate (ex: 80 IPM), the X axis moves normally and smoothly.
No alarms or error messages appear.
I shut down and restarted the machine, and after reboot everything worked normally again, including X axis at 135 IPM.
Has anyone experienced something similar?
Thanks!
EDIT:
continued machining after this, and at the end of the program I lost X axis position.
I heard a strange noise on the X axis, and immediately after that my chamfering tool cut in the middle of the part, clearly indicating that the machine lost its X home / position reference.
It sounds like the physical motion is binding intermittently. The first thing would be making sure the oil lubricator is working and giving sufficient oil to the ways. If the machine has been heavily used, the ways could be worn in some areas more than others when doing rapids. I had this problem with a different CNC mill where the center area had worn and adjusting the gibs would cause it to bind when it moved to the outer edges. You might try following this to see if it helps. Lost Motion Testing and Gib/ACB Adjustment - PCNC 440 | Tormach Knowledge Base. It won’t necessarily fix the binding, but it may help show how well the gibs are working.
Worst case, you might just slow down the maximum speed to limit the risk of it binding during fast motions.
Like Duane, I would suspect a binding issue. The steppers don’t have a ton of torque and moving at max speed is asking for a lot of accelleration, and therefore torque. A small amount of binding when the motor is already trying to deliver as much as it can could definitely lead to lost steps.
I would probably check the gibs and the AC bearings to make sure everything is moving smoothly, along with verifying that your oiler is working properly and all surfaces are properly lubricated. With the stepper removed, you should be able to turn the lead screw just by grabbing the coupler. It will have some resistance, but it should turn smoothly. Any roughness or stiff spots would be an indication of a problem.
Check the belt and coupler under the X axis stepper cover. May be slipping. Feel the ways for an oil film. If the gib adjusting screws aren’t tight against each other, the gib can wedge in snug or worse.
The jog speed slider applies only to jogging with keyboard or pendant and does not affect G0 rapid moves. Rapid moves can be slowed down by max velocity override (bottom left of the screen), but that was set to 100% in the video.
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