Solved Z Axis out of Tune ... or Something?

My z-axis is acting up a lot. It had been very jittery on moves and the motors were clearly not operating smoothly.

From doing some poking around between here, other forums, and Tom's Guide videos I took a guess at it being the stepper driver. Well me poking around down there did not help any as it is the same or worse now. I've tried countless different settings on the driver board to get it to run smooth and just can't seem to come up with anything. I'm starting to think I might need a new driver board or worse. The X and Y move fine though.

So I've surmised that the reference voltage can be set on the board to anywhere from 0 to 1.7 volts and this seems to occur over a range of about 270 degrees of rotation of the potentiometer. Does anyone know the voltage the Z axis should be set for and what sort of accuracy would be needed? My best guesses were .68 and 1.36. Neither of those seemed to work. I have also tried dynamically tuning at this point with and without the carriage. By sending the motor a command to move and turning the potentiometer at the same time and I can't seem to land on a spot that generates smooth movement. Only variations of jitters, stalls, and jerks.

My rate of movement (speed, acceleration, and jerk) on the Z are all stock out of the box.

Should I try swapping an X or Y motor into the Z stepper position on the board to see if it is the motor? And also try the opposite, connect a Z-axis motor to an X or Y stepper?

For now I'm going to go take care of the foot of snow outside.

 

Just out of curiosity have you lubricated your Z rods? That can help with any sticking or stalling that occurs.

 

Now that I am all shoveled out I swapped the X and You with the Z to isolate the driver from the motor. It is totally the driver.

Should I have Robo send me a new driver or just order a new one from someone else. If so is it worth anything to get the TI DRV8825 over the A4988?

 

Both I'd say.
That's a good question on the TI DRV8825 maybe @Ziggy would have a better insight on that.

 

Well I've ordered some replacements and asked Robo for some as well. Now I wait...

When they arrive the procedure would be to turn the potentiometer down such that the reference voltage is zero and slowly increase until the motor runs smooth?

 

So my bundle of replacement parts arrived and I am amazed out how easy it was to get the new stepper driver in and running.

Any recommendations for a heat sink adhesive alternative? Crazy glue?

 

Super Glue might work.

Better to use something more suited: http://www.arcticsilver.com/arctic_silver_thermal_adhesive.htm

 

I agree, I would not use superglue since it's not very thermally conductive. That's kinda the whole point of the heatsink.

I recently re-did my video card, and the temperature under full load went from 90C to 42C. Diamond loaded heatsink compound and a water jacket as opposed to air and crappy cheap thermal paste.

 

More of a case of not wanting to wait for better. I decided on loctite.

Besides I have four more spares...

 

Seriously good luck, but I wouldn't do it. I design PCBs for a living, and have seen what happens with undercooled power semiconductors.

Google on an article called "Low Voltage the incompetent ignition source". I've seen this happen on a board that I was holding in my hand. The brick power supply was in "hiccup" mode, supposedly protecting the system. Flames several inches high, and a totally destroyed PCB. I didn't design that one, but I did design its replacement.