Correctly setting trim pots on pololus???

[bloomingtonmike]

I need help Correctly setting trim pots on pololus. I have some crazy stuff happening to my prints.

I have stepping up to left (not a ramp but like a step is off). Other times it goes crazy and randomly places the zozzle somewhere for a layer.

I have played with the pololu trim pots. I cant seem to get it right randomly. If I turn up too much the ddrives click - I can feel it in the belts and couplers.

any advice - it is driving me nuts!!

[bdring]

The clicking is a sure sign of over heating.

I glue heatsinks on with Arctic Silver most of the time, but you rarely need the full power out of the steppers. Check your acceleration. Make sure you can rapid to high speeds then back down the acceleration by about 25%.

[SystemsGuy]

If they are "normal" pololus, you are not going to get more than an amp out of them without overheating. Check the voltage on your trim pot, and start at about .4 vdc

[cvoinescu]

The A4988 is designed to sink most of its heat through the PCB, and the green Pololus aren't really designed to spread that heat very well. The black ones are better. What helps a lot is airflow, especially under the driver boards. Get a fan to blow sideways. Or you can get the Panucatt Devices SureStepr, which is upside-down so you can put the heatsink on the opposite side of the driver IC, where it helps most.

[bloomingtonmike]

Mine are the black ones and I do have small heatsinks on them. I may try the fan as well.

[Medel]

yeah, heatsinks help a little on those guys, a fan blowing so that air goes under them seems to go a long way, too.

[cvoinescu]

With the black ones, with good airflow, you should be able to go 2 A. Please note that, due to a strange design decision, the current adjustment on Pololu drivers maxes out well before the end of the travel of the pot. Do not go over 0.8 V on Vref with Vmot applied, or they may explode and/or throw spectacular sparks and/or eject black smoke, thermal protection notwithstanding.

[bloomingtonmike]

I think I may have found the issue. I have an Ord bot that uses belts to move carriages on Makerslide. The belt is captured in a block on the back side of the X and Y carriages. Well the belt was SLIPPING through the block on the X carriage!! This is why I was seeing the issue only on the X axis. The Y belt I secured more because the black was crappy from teh get go. Well I just added two layers of gorilla tape to the bet and then that compresses in the block. BAM!! Started a owl on a lego print and it is working great.

Just want to say THANKYOU to you guys for teaching me about my pololus!!! I have MUCH better setup pololus now.

I may soon replace the nema17s with something better suited to the pololus!!

[bloomingtonmike]

Printed an owl.