Z Axis Steppers sometimes switching directions

I had a prusa v2 for about a year until i decided to tear it down a make a i3. Since my rebuild, the z motors occasional turn in opposite directions. I at first thought that the motors where plunged in in opposite directions but the problem only occurs occasional. I have them plugged into the same pololu driver on the RAMPS 1.4 board. I have done plenty of Google searches on the topic and have found nothing. Any advice?
Thanks, Tom

Well, of course both motors connect to the same plug which leaves me thinking that either, one of the motors (or the motor wiring between motor and Ramps) has a problem or maybe the pololu voltage needs tweaking?

---

_______________________________________
Waitaki 3D Printer

Sort of a random guess - are both motors the same manufacturer / model? Since they are run in parallel they pretty much need to be same / same.

I beleive this is an issue with cross talk between your wires at the z axis 4-pin connector. It was happening to me and I could see that, because of having wired both z motors to the same 4pin connector, my crimping job was not the cleanest. The crimp pin doesn't fit around the double wire insulation. (don't think that's even expected for when you have 2 wires into the same pin). I turned off the printer, disconnected the z axis connector from the Ramps, used a little box cutter to lift the tabs of the connector to release the pins. then I put a little strip of Kapton tape around the end of each pin where the crimped connector meets the wire insulation. This provides better issolation between the pins. I put it back together and the issue was gone.

Hi,

I'm getting a similar issue, but I don't have both motors plugged to the same 4-pin. Instead, I have a RAMPS 1.4 board that has the two 4 pin connections on the board (but share the same stepper driver). I've had this issue since the beginning, but temporarily fixed it by swapping a stepper motor. Now it's back with a vengeance.

It seems like the original fix is to make sure that the part where the connector and the wires meet are properly insulated - is this correct? Should I wrap the part where the connectors and the wires meet in electrical tape so that there is a barrier between the two z-motor connections?

Thanks,
Luke

Have you tried powering the Z axis while waggling the connectors on the Ramps board?

---

_______________________________________
Waitaki 3D Printer

I was having trouble dialing in my Z axis on a new printer I am working on, so I disconnected the couplers and raised the entire carriage so I could observe the motors under no load at all. I could see that every third or fourth time I'd try to move them, they would move in the opposite direction. I popped in a new driver board and they started working fine. I assume I must have zapped the driver while I was trying to make adjustments; they are pretty finicky.

I was using the cheapo stepper driver(white) that came with my Makerfarm kit, but after frying one, I got a Pololu(green) and put it on the extruder. Swapping out the cheapo on the z with the Pololu, and upping my power supply to a 500W (34A on 12V) from a 250W (18A on 12V) seems to have fixed the issue (fingers crossed).

Moral of the story, best to get the good quality stepper driver on the z-axis since it needs to push out the most current.