Stepper motor loses steps when hot bed shuts down

Hi Guys,

Me and my daughter we have a problem with our Prusa I3 Printer. We have problem with stepper motors, and hot bed.
Stepper motor loses steps when hot bed shuts down. Steppers moves around one mm exactly in moment when hot bed heating stops.
Motors do not react badly when hot bed switch on again It happens only when hot bed stops to heating.

Our configuration:
RAMPS 1.4
Stepper motors 1.2 A NEMA 17
Power supply ATX 12V 203W
Maybe someone know what can be wrong and can help.

Do you heat the bed directly from Ramps or do you use a relais between?
If a relais is used, the back EMV from switching off could cause errors.

-Olaf

Hi Olaf,

I'm heating the bed directly from Ramps.I build three Printers already and one CNC based on Ramps never seen such problem before.

Edited 1 time(s). Last edit at 11/05/2015 01:35AM by Tomu.

Tomu,

A couple ideas you might consider.

You may still be getting some inductive issues from switching the load.
A simple diode may do the trick, across the terminals going to the heated bed, at the Ramps.
Make sure the polarity is right!
See here.

Also, make sure the wires from your heated bed and stepper motors are not running parallel to any other wiring, or close to it.

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My printer: Raptosaur - Large Format Delta - [www.paulwanamaker.wordpress.com]
Can you answer questions about Calibration, Printing issues, Mechanics? Write it up and improve the Wiki!

Hi Guys, So we know where is the problem - In Power supply - we are using 203W power unit. After change of everything Ramps, Motors, Hot Bet - checking again all the connectors, stepsticks I come to conclusion that only one thing that left is Power unit ( it was at Friday 13 ). I change it and is ok. Now we are using ATX from my old first printer and it works fine. Thanks a lot for all ideas. I will try with 1N4001 any way to see what I get. I will let you know any way - someone can have similar problem in the future.

Tomu,
Please check out this thread, it could be helpful.

Thanks Paul, I never seen such solution, maybe becouse I never had such problems before - I will definitly wire it that way, even if that will take one day. I have time only on weekends but it seems to be good solution additionaly looks not bad