Stratasys Dimension Rebuild.

KalTol1994

I'm working on an old decommissioned Stratasys Dimension, I've gutted the entire thing. The Power supply is rated for 24V @ 21A. My main concern being the NEMA 23's current consumption compared to the driver output of the Duet board. Is there some sort of amplifier I can use to increase the power I can use without burning up the duet board?
I've yet to buy one but as soon as I find out I can safely use these motors at or near full power it's a safe bet I will. I've been getting a lot of information from the good people posting on the thread I created on another forum ( http://forums.reprap.org/read.php?1,703331,704783#msg-704783 ) but the people here would know more about the Duet board and its limitations obviously.

More info on the NEMA 23's;
POWERMAX II
Model: M21NRFA-LNN-NS-04
2.8A bipolar series ( fairly certain it has a 6A peak)
Made by: Pacific Scientific

The person who informed me of the Duet board said the following about the current draw;
"A Duet WiFi should be able to drive those motors adequately. We're limiting the current in firmware to 2A peak per phase at present, but that's 71% of the rated motor current and it's quite common to run 3D printer stepper motors down to 50% of rated current. We plan to increase the current limit to around 2.4A in future firmware. The driver chips themselves are rated at 2.8A if you take the correct precautions in firmware.
The phase inductance of those motors is only 2.8mH according to the datasheet, so 24V should be sufficient voltage to the drivers."

But my Z-axis will probably need full power while turning the three ball screws via a single belt. I mostly say this because of the bushings I made for it are a tad bit of a tight fit I do need to ream out the center hole that holds the ball screw just a hair. But even afterwards I feel with the weight of the bed and everything I'll need more power than what can be produced straight from the Duet board.

Thanks in advance!

P.S. I've been reading up on the board but please tell me everything you wish you had known about yours.

T3P3Tony

Hey Kal, looking at the reprap forum post DC42 has replied. DC42 is David, one of the Duet hardware designers and the firmware developer so the advice you have is from the best source!

If your Z axis needs higher power then you can use an highter power external stepper driver for that axis, connected to the expansion header.

KalTol1994

How can I get more info on the external steppers drivers? I saw one on the options when you go to buy a board but I haven't seen any info on it.

T3P3Tony

We don't supply external drivers, however there are a number of options available (I have not used any of them though):

http://www.massmind.org/techref/ecomprice.asp?p=416074
https://www.alibaba.com/product-detail/DM542-digital-micro-stepper-motor-driver_1587581201.html?spm=a2700.7724857.0.0.4x2IzN

Note I am not recommending either of these as definitely working, just showing examples. You would connect an external driver to the expansion header (say the third extruder channel) and then remap the Z axis to that channel using gcode (http://reprap.org/wiki/G-code#M569:_Set_axis_direction_and_enable_values). If the driver requires 5V logic to control it then you would need a small level shifting board in between the Duet and the driver (as the Duet logic is 3.3V).

On the other hand you may find that with 2A your Z axis moves fine with and you don't need an external driver. Also the Z axis does not normally need to move very fast as its raising only a little bit per layer so you can drop the acceleration or potentially use gearing to reduce the stepper motor torque required.

dc42

I agree with Tony, I think that your Z motor will probably work just fine at 2A once you sort out the bushings.

KalTol1994

The bushings are the bulk of my concern the X and Y axis are geared down so they shouldn't have trouble. Could anyone tell me if the on-board drivers have thermal and/or overcurrent protection? Thank you all for your help this is going to make my project a breeze!

dc42

Yes the on board drivers have thermal protection, and the current is limited to 2A in firmware at present.

KalTol1994

In the future I would like to modify the firmware to act as both a laser burner and 3D printer while only swapping the printer head. Has this already been reduced to a simple fix or will I have to brush up on my coding skills?

chrishamm

@KalTol1994:

In the future I would like to modify the firmware to act as both a laser burner and 3D printer while only swapping the printer head. Has this already been reduced to a simple fix or will I have to brush up on my coding skills?

About a year ago another user installed a Duet in his laser cutter, see https://reprappro.com/2015/06/16/reprap-duet-electronics-running-a-laser-cutter-guest-blog/ and http://forums.reprap.org/read.php?133,521301. This didn't require any firmware modificiations and I guess you should be able to achieve what you've been planning by doing the following steps:

1. Add an extra tool with an unused E drive (haven't checked yet if M571 requires one to be configured, but I'd assume so)
2. Run M571 in the tool change macros of your new tools. That way you could enable and disable this particular feature for a specific tool.
3. Use G10 to set the offset of your laser