Refurbing an old BigRep v1.2

waruta

Hi All,

I've been searching the web high and low and it doesn't seem like anyone has done this yet but I recently had the chance to acquire a BigRep minus the entire control panel, boards etc. It's pretty much just the stepper motors/frame.

The upside is that it is in near-perfect condition with less than 20 hours on the machine. I've been looking through the wiring diagrams/schematics but now with no control panel, stepper drivers or boards I think I will try the following:

Try to buy the original stepper drivers from BigRep here in Singapore (highly unlikely)
Find an alternative stepper driver
Buy the Duet 3 6HC to control everything else.

The good thing is that I'm trying to convert this BigRep into a concrete printer so I don't need any thermocouples/sensors on the "hotend" side and don't need a heated bed either. Just need the XYZ steppers to work and a way to control the concrete nozzle which seems like can be easily done through the 6HC.

My question is - is the 6HC a good choice and does anyone have any suggestions on stepper drivers?

Regards,

Wouter

dc42

@waruta the 6HC does not support external stepper drivers. What stepper motors does the BigRep have? Perhaps the 6HC can drive them directly.

waruta

@dc42 Many thanks for the reply.

I had forgotten to take pics of the other steppers but the largest one is the Z-axis one (https://en.nanotec.com/products/571-st8918m4508-a#technical-specifications)

Will take pics of the other two tomorrow but they are considerably smaller NanoTec units as well.

Seems like the NEMA 34 just slides under the 4.55A RMS that the board can push out

dc42

@waruta it's usual to run stepper motors at between 60% and 85% of their rated current to avoid them getting very hot. So the MB6HC can drive those motors. The current MB6HC is limited to 32V VIN, so if the BigRep was using a 48V supply then the maximum speed may be reduced a little. You can estimate the maximum speed before the motor torque starts to reduce using the calculator at https://www.reprapfirmware.org/emf.html.

waruta

@dc42 I'll be able to take pics tomorrow of the steppers but I do remember the label of the NEMA 34 stating that its 4.95V and 4.56A - seems kind of low for voltage but it is just the Z-axis stepper so its not running all the time

dc42

@waruta that voltage sounds correct, it's quoted when the motor is at standstill and passing the rated current. The issue here is that are high speeds the drivers needs to be powered from a much higher voltage, to counter the inductive back emf of the motors.

The Z axis speed is unlikely to matter, but on a large printer it's helpful to be able to achieve high travel speeds on X and Y.

waruta

@dc42 Found some pics of the X and Y axis steppers - looks like they are both NEMA 24 sized (https://en.nanotec.com/products/560-st6018l3008-b)