On 9/4/2014 9:07 AM, Viesturs Lācis wrote: > Hello! > > I have a strange situation: > Stepper motor of Z axis on a cnc router is losing it's position - > doing a series of numerous holes in material will end up with various > depths of holes. > > The strange part is: > 1) for each time, when machine is running, it will lose position only > in one direction; if holes are getting deeper, then they only get > deeper, not the other way; > 2) the direction of "drift" will change randomly as machine is > restarted and only then; simply running another g-code file will not > change the direction of "drift";
First thing I'd look at is your spindle speed and feed rate. If the bit is pulling itself into the work faster than the control is commanding, it can force the motor to 'run ahead' of the commanded steps. If the control is trying to push the bit in faster than it can cut, the effect is a 'push back' where the step signals go to the motor but it doesn't actually move. Combine either or both with a slight variance in density of the material and you'll get randomness. If tweaking the speed and feed doesn't completely cure it there are hardware solutions. Were this my machine I'd find a way to put a scale (magnetic type, crud and fluids don't mess them up and can be cut to length) or rotary encoder on so the control always knows where the axis is. Another possibility is more power. Put on a larger stepper with more torque so it can't be pulled ahead of or pushed behind the stream of step signals. Another cause of it might be variability of chip loading in the bit. What do you have for keeping the bit clear? For material that can't take liquids use an air nozzle and vacuum. --- This email is free from viruses and malware because avast! Antivirus protection is active. http://www.avast.com ------------------------------------------------------------------------------ Slashdot TV. Video for Nerds. Stuff that matters. http://tv.slashdot.org/ _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
