[Zeppelin1007]

Hey guys...im ready to pull my hair out over this one. Since may I've been building an FLA-100 CNC router. I ended up scoring a HobbyCNC Pro board off of ebay, pre-assembled. 305Oz-in Kelling motors. 36V supply, 15A..switching supply. Using south bridge heatsinks and a giant delta fan for cooling. Chips hardly even get warm.

Everything worked fantastic! Setup in Mach3 was pretty easy. Got everything working, did some test cuts...life was grand from about june..til..now.

So...I tried to cut something about 3 days ago, and man, was it losing steps! Only in the X direction, but not too many, just enough to notice. Ok. Stop the machine. Check EVERYTHING mechanical...everything seems fine. Ok. Run again...missed steps getting worse...

confusion.

Replace paralell cable. Same results. Unhook X axis so the motor freely turns without any resistance. You can feel it. Set pulses to 5. Same. Play with motor tuning..Originally if i ramped up the Accel/Vel, the problem went away, but now, its at all times.

At one point when i cold started the machine, it got about 3 passes in before it started missing steps..actually i shouldn't even say missing steps, if i place my hand on the motor/leadscrew, you can feel it slow down, then go the opposite direction for a step, then back to the original direction and slow down...Y and Z work fine..

OK. So more troubleshooting. Check the board. Resolder...EVERYTHING...even swap the driver chips around...there goes my friday night. Same results. Hell i threw another computer in there! Nadda!

i should mention, I've only mainly been trying the same few programs, which are bass clefs i was cutting out of a 2x4..actually just occurred to me, i wonder if my code is causing the problems...coming from SolidCAM..but its only in the X direction...uses a lot of G1 and G2 commands...

I would ask the guys at hobbyCNC but i read they won't deal with second owners?

Im just confused. NOTHINGS changed! Everything has been in place since May. Nothing looks burned on the board. its just the X direction and mainly during deceleration.

Im only cutting around 25-30ipm, I'm using one of those cheapo harbor freight HSS end mills, and an adjustable dimmer on my router..which make nice chips...but like i said, even if i change the federate, its there no matter what, just in one axis..which is leading me to believe its the HobbyCNC board..

Is there any specific part that might cause this? why over time? My only guess is a value drifted?

Thanks in advance guys...

[ger21]

Is the screw lubricated?
What type of screws are they?
What acceleration setting are you using?

[Zeppelin1007]

Screws are only lubricated the little that they came so my bad
Theyre the leadscrews from Nathans stash, 5 start 10tpi i think?

Im running full step mode at 400steps per inch
Accel i started low around 4, brought it up to about 15, same results

Its something electrical id guess since the motor does it with nothing on it! Curious if there was a specific part or section on the board that might cause this if faulty...like i said the problem gradually began and now has escalated

[ger21]

Try running it at 1/8 or 1/16 microstepping.

[Zeppelin1007]

Well, its not the board. If i move the motor to another axis the problem follows the motor.

Upon disconnecting i noticed some small brown spots on the stepper where i added wire to meet the driver board. So i cut and resoldered....problem persists...little bit smoother though..

So im going to chop it off and start with new wire...wonder if the stepper is screwed?

[Zeppelin1007]

Alright. Mistakes were made, it tore everything out today, and it DOESN"t follow the motor. It is pin fact the x axis on the board. Ive switched motors and it only occurs on that axis.

I tried micro stepping, at 1/2, 1/4, and 1/8th..the problem persists, though seems smoother..its still there..actually took a little while to show up. If i hold the motor in my hand you can visually see the shaft chatter here and there.

So what i'd love to know/figure out is, what on this board has drifted/died that bad over time? It actually does it now during acceleration, but only at slower ones..mainly cutting arcs.

Ive swapped the driver chips, the current delay resistors, and now I'm just going to start swapping what i can on the x axis part of the board i guess, unless someone has another idea? I would guess this is chattering during a more high current movement?

Thanks guys

[ger21]

It could be a resonance issue.

Try running the X axis motor with the Y axis from the drive. If it still does it, then my guess would be resonance. If you have dual shaft motors, adding a damper can make a huge difference.

[Zeppelin1007]

Ok.

Hooked up the Y axis to the X axis on the board. Problem persists. Run the X axis on the Y axis of the board, problem gone.

But, now, i can't even cut/draw a circle..its even worse jitter wise. This is with or without a load on the steppers, i.e. just sitting in the palm of my hand.

Its something with this damn hobbyCNC board. I really wish second hand owners could access the yahoo group. interesting point, if i check the 5V ref, its actually 8.3V. When i first set everything up, it was 5V. or 5.3 or something close.

My guess? that 8.3v is overloading/overheating logic somewhere. I need to find a schematic (HAH good luck) or just sit here and trace the thing and see if that makes sense. However, my current settings for the axis are just fine.

[Zeppelin1007]

ok. With NO MOTORS i get 5.01V on the 5VRef. WITH motors i get like 8.3V. Um. Is this normal?

im hitting my wits end with this damn board. Im taking it with me to work tomorrow and changing all the other components on my lunch break. Beyond that...it might be time to suck it up and buy a real driver. Ive had this machine since may, and its been sitting for weeks now because of this problem. Heck i swapped the X and the Z motors and pins, and i can do 2D cuts...as long as i don't have to do TOO much Z axis movement, cause it just stalls and stutters...

Wonder if anyone on the hobbyCNC yahoo group had similar issues. I'll never know.

[Zeppelin1007]

Cathy ive been wondering this myself. If its true, why is it only affecting one axis? Also, can i run this board without a load on all axis? Or will i blow something up?

[Zeppelin1007]

FINALLY SOME USEFUL RESULTS

Alright guys. i believe maybe this is that resonance that was mentioned before.

So instead of running the board without 2 motors, i simply put the other 2 axis in sleep mode, by removing the jumpers that set the micro stepping.

I noticed my X axis instead of hissing, now lets out a high pitch noise, similar to a CRT TV. Moves fine Still studders/loses steps.

Tried putting weight, heck my own hand against the shaft..same results..

AH! but if i place the entire motor on a flat table, and press on it, not a single missed step throughout the program. But if I'm not pressing on it, just lightly holding it, it starts its fits. Its worse if i pick it up.

So whats this cause? why would it gradually appear then ramp up? like i said I've swapped motors around...i added one motor at a time and the hiss/pitch lowered...ive swapped driver chips, even reflowed this whole board at work thursday on the expensive Weller Sucker/Solder station. Swapped some resistors, checked the caps, though nothing at all has drifted..im so stumped

Resistance on the shaft itself doesn't affect it, but pressing on the motor body does? yet I've swapped motors?

and changing velocity/accel doesn't seem to affect the number/amount of missed steps. And all axis are set the same and the other 2 run flawlessly.

Also i was poking around with my continuity tester on grounds...my case is grounded to my computer just fine through parallel port. As is my power supply. The "-" on the board checks out, the motor grounds check out, but only briefly until the caps discharge...My board IS however sitting on a block of wood. Could i be missing a ground somehow?

Also when the machine, or i should say motor by itself was first fired up, it didn't seem to miss anything...made one little jitter near the end of the program, a simple circle, but past that initial warmup, it got uglier.

Any suggestions? at least i found a direct effect on the symptom here..but why? whats causing it? why now? why not months ago? And how can i solve it?

[Zeppelin1007]

I just thought id update this...

I disconnected the motors from the machine..did extensive tinkering.

If i run between 20-40ipm, the problem persists on all 3 axis. So. I simply run higher. And thats been grand until tonight...i think

Im battling between CV mode and exact stop. Router bits dont like exact stop but endmills seem to deal with it just fine. Guess its a board issue?

[ger21]

If i run between 20-40ipm, the problem persists on all 3 axis. So. I simply run higher. And thats been grand until tonight...i think

I'd try some dampers, if you have dual shaft motors. The quickest way to see if they'll help, is to drill a 1/4" hole (or 15/64") in a hockey puck and push it on the shaft. If it's resonance, it should immediately run much better.