View Full Version : Can anyone help me?
09-27-2010, 05:40 PM
I have a small hobby cnc which has been acting up and giving me fits! The best way I can describe it is to say it seems as though the machine is getting hung up or stuck in both the X and Y axis. Occasionally, while moving to the next position, the head will stop moving (either in the X or Y or both), while the DRO on the screen is still moving, and brains think it is still moving, so when the Z finally comes down, it is way in the wrong place, and thus ruins the work piece. That being said, however, I have spent hours insuring that it is in fact NOT getting "hung up" or "stuck" on anything. Iíve cleaned and inspected all bearings, disconnected the lead screws from the lead screw nuts - everything is clean of debris and nicely lubed. I have replaced the motors and $100 later still have the same problem. We have tried testing our power supply and to the best of our knowledge, that too is OK. We changed the power cord to one which has a ground, but that didn't help either. I have ordered a new driver board, but am reluctant to start changing that b/c according to the instructions, there is a fair amount of recalibration that is going to be required and that's a little over my head.
Does anyone have any other ideas as to what could be causing this, or know of an easy way to calibrate a new driver board? Is it easier than it sounds?
09-27-2010, 05:49 PM
Do the motors make noise while the table is not moving and the DRO is changing?
09-27-2010, 07:13 PM
Can you tell us a little more about the mill, controller, motor drives, etc.? My first guess is that your motors are stalling but it would help to have some more info on your setup.
09-27-2010, 09:20 PM
Yes - the motors make noise while the DRO continues on with the program. They sound like they are laboring, and when the machine is "stuck" I can grab hold of the lead screws and turn them by hand. I also suspected the motors, but even after replacing them I sill have the same problem.
The mill is just a small little hobbycnc. I bought it off from ebay, it is not name brand. I'm sure it is probably made in China.... It has Hybrid Stepper Motors from Kelinginc.net. Part #'s KL23H276-30-8B & KL23H276-30-8A. Specs for the motors are available at http://www.kelinginc.net/NEMA23Motor.html
The replacement driver board that I purchased is from here: http://www.hobbycnc.com/
I have pictures and even a video. Is there a way to attach pics or videos to this forum?
09-28-2010, 01:06 AM
Best guess is the acceleration is set to high. Try backing it off in Mach. If it tries to go to fast too quickly the motors will loose step and just sit there and whine. Also you can try lowering the max speed.
How many volts are you running the motors at?
09-28-2010, 08:15 AM
Make sure the couplers from the motors to the screws aren't slipping.Check the set screws. Just a thought.
09-28-2010, 08:13 PM
Check your gibs. Make sure all slides are not too loose otherwise they can wedge (jam).
09-29-2010, 07:37 AM
What are my "gibs"?:o
09-29-2010, 08:38 PM
In manual, w/o the power to the drive motors, try moving the axis' using the table dials, knobs, or whatever you have to move the axis. If the movement is very easy than the "gibs" probably need adjusting. Each axis should have a slight drag & no side to side movement (opposite the travel direction).
Each axis should have a piece of tapered metal in between the moveable axis & the non-moveable part of the machine. The tapered piece of metal should have a screw that when turned will either push or pull the tapered metal in or out. If your axis is loose you push the tapered piece in to tighten that axis up a little. This gets down to a "feel" kind of process till the "gib" is adjusted properly. It's not rocket science just patience & once you teach yourself the "feel" you'll be able to do it when needed since these moveable slides & gibs wear. Make small adjustments at first till you feel the axis start to bind than back off a little on the screw. Good luck.
10-19-2010, 04:30 PM
I understand you have no mechanical blockages and are using Mach control.
Have a read through this page at CNCZone, might give you some ideas.
Steppers stalling (http://www.cnczone.com/forums/mach_mill/78202-admitting_defeat_stepper_stalling-3.html)
10-20-2010, 09:14 AM
Thank You - that did give me some new ideas. Hope to try some out soon.