Build Problems - Z axis motor only goes in one direction

Hello,

i am badly in need of some advise, first time builder, almost there, i work as a mech and would say i am fairly good with the build. not really any issues until now.

when hooked up to the pc and working through the commisioning stage the z axis motor only winds down, lowering the z axis.

G1 Z5 F200 and then G1 Z0 F200 moves the assembly down 5mm each time.

any help would be great, have triple checked the wiring and cant figure it out

Edit: also dont seem to be able to get the x homing sensor to work, it reads fine, and shows a good range, but when attempting the homing command g28 x0 it hits on the frame and the motor goes nut so i very promptly shut down. just working through the trouble shoot guide now and not having any luck.

what sort of distance should there be between the sensor and the little knub

Edited 2 time(s). Last edit at 02/07/2015 11:28AM by paulwootton7.

the x axis homing sensor works fine now, just the z motor keeps lowering towards the bed

Here are some things to try. WARNING: never connect/disconnect stepper looms with the power on! It blows the drivers.

1. If you have a multimeter, disconnect the Z stepper loom from the Duet and check the resistance between each pair of wires on the Duet connector, in case either one stepper motor phase or one of the wires has a bad connection.

2. Lift the X arm up so that it is not resting on the Z nut, and support it there. Then see whether the Z motor turns both ways.

3. With the X arm still supported, swap the Z motor loom with one of the other motor looms (e.g. the extruder motor loom) at the Duet end. Then test again and see whether the fault moves to that motor (indicating a probable fault on the Duet), or stays put (indicating a fault in the Z motor or Z loom).

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

thanks for the help, i dont have a multimeter i'm afraid, plan to get one asap though.

i switched the x axis and z axis plugs so the pc thought they swapped, and the z axis worked fine and the x axis moved in the same direction each time. they swapped the cables completely so the correct port was being used just a different cable and i had the same problem.

guess that means its the board? could a long pin short and cause this issue? i checked them several times so dont think its that

thanks for any help!

Yes, it sounds to me that the Duet board is faulty. Ask RepRapPro for a replacement. If you examine the stepper driver chip just above the Z motor connector, you may find it has a solder bridge between a couple of pins - although there are several other possible faults that could cause this symptom.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].