Running NEMA 23 motors

I am hoping to build a larg(ish) Delta printer and have been advised (by RobotDigg who make the frame corners) to consider NEMA 23 (76mm)

These are rates at 6.7V 2.8A - am I right in thinking this is too much for the Allegro drivers on the Duet 0.8.5?

Thanks in advance

Yes 2.8A is too high for the Duet. However, you can also get Nema 23 motors with 1.5A or 2A rated current, which would be a better match. You will need 24V or 30V power.

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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 that - looks like I have some more reading to do, I have the specs of the recommended motors so I can match the torque settings with a higher voltage motor.

Is the Duet tolerant of 30V for the stepper drivers?

Have a look at the reprap wiki page 'Choosing stepper for a delta' [reprap.org]

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Pierre

- Safety [reprap.org]
- Embedded help system for Duet and RepRap Firmware [forums.reprap.org]
- Enclosed delta printers Lily [rouzeau.net] and Lily Big [rouzeau.net]
- OpenScad delta printer simulator [github.com]
- 3D printing on my site [www.rouzeau.net]

Quote
motley
Thanks for that - looks like I have some more reading to do, I have the specs of the recommended motors so I can match the torque settings with a higher voltage motor.

Is the Duet tolerant of 30V for the stepper drivers?

The absolute maximum input voltage to the Duet is 35V. I suggest 32V as a maximum planned voltage.

How large will your delta be? A larger machine doesn't necessarily need larger motors, because the effector of a large printer need weigh no more than the effector of a smaller printer. The belts will weigh more, but you can easily work out the additional torque you need to achieve the desired acceleration, given the additional mass of longer belts.

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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].

Pierre - thanks for the link, I will have a read through that

David - the one I have seen on RobotDigg is 1500mm tall with base edge of 700 mm.

The plan is for clay extrusion of various sorts with a need for two types of material (the second for support until initial firing)

The extra height is what is needed and with the double extruder I'm not sure of the weight of the effector at the moment.

Part of the research will be in the method of getting the material extruded smoothly with good repeatability - just the beginning at the moment.

I take your point about the effector not necessarily being any bigger and I may just start with something more standard in the motor department while we get the rest together, fairly easy to change motors later.

Thanks for the input :-)

Chris

A clay printer need less speed than a filament printer, so you may accept a stepper with higher inductance, hence lower current, especially if you run high voltage.
With steppers Nema17 at 6.5 kg.cm and 1.5A like this one [www.robotdigg.com]

You may run an effector of around 1kg with 16 teeth pulleys, if you go not too fast? You may play with arm length to limit overspeed at large diameter.

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Pierre

- Safety [reprap.org]
- Embedded help system for Duet and RepRap Firmware [forums.reprap.org]
- Enclosed delta printers Lily [rouzeau.net] and Lily Big [rouzeau.net]
- OpenScad delta printer simulator [github.com]
- 3D printing on my site [www.rouzeau.net]

I have just started commissioning my 1600mm tall 600 diameter bed Delta with 0.9 degree NEMA23 motors.
Currently running at 24v and 1.5A set current with these 23HM22-2804S, [www.omc-stepperonline.com]

Pierre,

Thanks again for the info - absolutely right about the slower speed, we will need to experiment with the amount of material the lower layers can support without sag.

Also may have to have fans to encourage faster drying (at least initially). Much will also depand on the mix of the material - thankfully that's not my bit !

As I said early stages but very exited about the project and very receptive to ideas :-)

I'm planning to stick with the Duet - there is a new version in the pipeline I believe...

Chris

Phil,

Thanks for the link - I would be interested to hear how you get on - are you posting the progress somewhere?

Chris

Quote
motley
Phil,

Thanks for the link - I would be interested to hear how you get on - are you posting the progress somewhere?

Chris

Been rather slackly updating [forums.reprap.org] ...... need to do an update for the last few days but need to take some photo's

David, I feel 3V is a very thin margin, I will be afraid of voltage spikes due to return current generated by deccelerating stepper, especially if you use higher inductance steppers and/or high mobile mass. In addition, if using Nema23 you get mid-band resonances, that may also creates spikes. 0.9° stepper will also increase return current for a given inertia.
Nearing the max voltage may need high capacitors.

I have no usable scope, so I cannot check decceleration spikes but I found these links :

• [electronics.stackexchange.com] stepper-motor-causes-massive-spikes-in-power-supply-when-decelerating
• [forum.pololu.com] stepper-motor-deceleration-causing-large-voltage-spikes
• [www.phidgets.com] Using_Steppers_in_High-Energy_Applications

Also, Paul Wanamaker built a large machine and faced miscellaneous problems with large steppers. You may find posts from him on the forum.

Quote
dc42

The absolute maximum input voltage to the Duet is 35V. I suggest 32V as a maximum planned voltage.

How large will your delta be? A larger machine doesn't necessarily need larger motors, because the effector of a large printer need weigh no more than the effector of a smaller printer. The belts will weigh more, but you can easily work out the additional torque you need to achieve the desired acceleration, given the additional mass of longer belts.

Edited 1 time(s). Last edit at 05/16/2016 10:27AM by PRZ.

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Pierre

- Safety [reprap.org]
- Embedded help system for Duet and RepRap Firmware [forums.reprap.org]
- Enclosed delta printers Lily [rouzeau.net] and Lily Big [rouzeau.net]
- OpenScad delta printer simulator [github.com]
- 3D printing on my site [www.rouzeau.net]

This particular post of Paul Wanamaker seems of interest for Nema23 use :
[forums.reprap.org]

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Pierre

- Safety [reprap.org]
- Embedded help system for Duet and RepRap Firmware [forums.reprap.org]
- Enclosed delta printers Lily [rouzeau.net] and Lily Big [rouzeau.net]
- OpenScad delta printer simulator [github.com]
- 3D printing on my site [www.rouzeau.net]

Quote
PRZ
David, I feel 3V is a very thin margin, I will be afraid of voltage spikes due to return current generated by deccelerating stepper, especially if you use higher inductance steppers and/or high mobile mass. In addition, if using Nema23 you get mid-band resonances, that may also creates spikes. 0.9° stepper will also increase return current for a given inertia.
Nearing the max voltage may need high capacitors.

You may have a good point. A decelerating stepper motor feeds power back into the supply, which is likely to increase the supply voltage depending on the load on the supply (which may or may not include other stepper motors, extruder heaters, bed heaters, and fans) and the total amount of capacitance across the supply. I guess one of the worst cases will be on a delta when commanding the head down to the bed at full speed with high acceleration. I'll do some measurements when I have time.

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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].

David, if I well remember, your machine use low acceleration (2000) and have a relatively light effector. However, you use 0.9 stepper. This is not very demanding compared to some others machines.
My D-Box with similar steppers as yours is using acceleration 6000 (and was tested at 8000) with an effector weighting slightly above 200g. It works well, but I am only in 24V.

So, For tests, I think you may increase acceleration and may be add weight on your effector.
And that will be still much lighter than AussiPhil and Motley will have.

Also, most of us are using LED power supply. I think we can reasonnably assume they are not designed for hard power transient.

I have seen in one of the listed link that some people are using active dump circuits. Interesting, but complex.

Very big printers face same problems as CNC and that is more difficult to handle than simple printers.

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Pierre

- Safety [reprap.org]
- Embedded help system for Duet and RepRap Firmware [forums.reprap.org]
- Enclosed delta printers Lily [rouzeau.net] and Lily Big [rouzeau.net]
- OpenScad delta printer simulator [github.com]
- 3D printing on my site [www.rouzeau.net]

It occurs to me that on a printer with the heated bed driven from the same power rail as the stepper drivers, an effective way of dumping the excess energy would be to turn on the bed heater during hard deceleration.

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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].