Ramps motor jerking

Hi all,
I recently purchased a china RAMPS board. After inserting the A4988 drivers the motors keep jerking whenever I try to move it. It moves abit( not to the set distance) but mostly jerks. I have tried changing the voltage on the driver and following the wiring guide on the wiki. I aslo tried all wiring combinations but nothing seems to work.

... seems you try to move it faster than possible, so it stalls - try to reduce the max. speed ...

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Viktor
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Did you install Micro stepping jumpers?

Quote
VDX
... seems you try to move it faster than possible, so it stalls - try to reduce the max. speed ...

I have been using similiar values to my old set from an outdated version of marlin which worked fine.

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Dust
Did you install Micro stepping jumpers?

Idk if I need to use any jumpers from the board. I looked at the wiring diagram and it didnt seem to use any additional jumpers. I aslo have no clue if microstepping has to be set in firmware

So under each a4988 is a 3x2 jumper header. All three need to be populated in order to get 1/16 microstepping. With none present you are on full steps. Unless you have a ramps from a dodgy batch where these jumpers have been connected by traces on the pcb and are redundant and locked to 1/16. (oddly the manufacturer included the jumper headers and fancy coloured jumpers on the board I had with this fault so it can't be intentional).

Make sure you identify the two pairs in each set of 4 motor cables, the colours of the wires are not reliable. Check the 4 motor cables resistance to determine the pairs. One pair go to pins 1&2 on the ramps motor connector and the other obviously to pins 3&4, which pair occupy each side of the connector determines motor direction. But firmware can reverse it also.

The motor current is best set using a voltmeter placed very carefully onto the trim pot measuring dc volts with the ground to the negative of the psu. Aim for 0.4v for starters that should make most reprap typical nema 17s turn reasonably well. Fine tune them later but that's usually a safe setting to know your not hopelessly under powering then or cooking them.

Edited 1 time(s). Last edit at 06/15/2016 10:16AM by DjDemonD.

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Simon Khoury

Co-founder of [www.precisionpiezo.co.uk] Accurate, repeatable, versatile Z-Probes
Published:Inventions

Quote
DjDemonD
So under each a4988 is a 3x2 jumper header. All three need to be populated in order to get 1/16 microstepping. With none present you are on full steps. Unless you have a ramps from a dodgy batch where these jumpers have been connected by traces on the pcb and are redundant and locked to 1/16. (oddly the manufacturer included the jumper headers and fancy coloured jumpers on the board I had with this fault so it can't be intentional).

Make sure you identify the two pairs in each set of 4 motor cables, the colours of the wires are not reliable. Check the 4 motor cables resistance to determine the pairs. One pair go to pins 1&2 on the ramps motor connector and the other obviously to pins 3&4, which pair occupy each side of the connector determines motor direction. But firmware can reverse it also.

The motor current is best set using a voltmeter placed very carefully onto the trim pot measuring dc volts with the ground to the negative of the psu. Aim for 0.4v for starters that should make most reprap typical nema 17s turn reasonably well. Fine tune them later but that's usually a safe setting to know your not hopelessly under powering then or cooking them.

Thanks that solved it. My y and z axis are still broken though. My z axis can only move in one direction.

This is almost certainly firmware now. You need to ensure your motor direction, homing direction and endstops are all set correctly.

Edited 1 time(s). Last edit at 06/19/2016 03:25AM by DjDemonD.

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Simon Khoury

Co-founder of [www.precisionpiezo.co.uk] Accurate, repeatable, versatile Z-Probes
Published:Inventions

I got only jerking too when I build my printer. I have heavy build plate in my i3, I put acceleration down. Marlin's 3000mm/s^2 is quite high. I started with 100 and ended up with 700. Motor moves and never misses a step. Z had same kind of problem, but It got something like 50 for acceleration and 50 mm/s max speed. I'm not interested to optimize that and losing step single side only is terrible.

It is nice to watch when I crank something like 175mm/s print speed and Y moves so much slower than X.