Question about stepper motors and drivers

Hi,

All of my stepper motors are rated 1.7A (but different voltage levels).

I use LV8729 drivers,( these), and according to the web site above they are able to output 1.5A (but more advisable to use at 1.3A).

Would that mean it is not possible to use these drivers with these motors? The machine works somehow and I don't have missing steps problem. I can even observe that the motors can get very hot to touch if I turn the pot on the drivers to high current levels. Isn't this illogical? If I am not able to provide enough current, how can the motor get hot?

Do you have a proper stepper driver option (silent running of course) if you use 1.7A motors? Seems like the silent options (TMC2100 and LV8729) cannot provide this much current (TMC 2100 is limited at 1A).

I am confused right now, because I have a setup that works but I also have some Z axis inconsistencies (the layers are not perfectly aligned and it doesn't seem to be a mechanical problem as I use linear rails on X and Z axis, combined with lead-screw shafted mototrs). I was wondering if this problem with currents is the reason for that.

It's normal to run stepper motors at somewhat less than their rated current.1.3A should be enough for 1.7A motors in most 3D printing applications. I use 1.68A motors in one of my printers and I rarely run them above 1.0A.

If you really do want to run them at 1.7A then you'll need a controller board with the drivers soldered on so that they can be properly cooled. The TMC2660 drivers on the Duet WiFi and Duet Ethernet provide up to x256 microstepping, which makes printers using them very quiet apart from any fans. The current Duet firmware limits them to 2.0A but this is about to be increased to 2.4A, with higher to come later.

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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 dc42.

I used a voltmeter to measure the vref and the maximum that can be supplied is 5.5 volts (even though the web site tells they can go to 7.5 volts) so they can only provide 1.1A. Is it also enough?

And for the Z axis, where there are 2 1.7A motors, is this still enough current? (considering RAMPS of course).

When you tell that the current Duet limits TMC2660s and that is about to be increased, are you talking about a firmware update or hardware update? What is the maximum current that can be physically provided by TMC 2660s?

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drmaestro
I used a voltmeter to measure the vref and the maximum that can be supplied is 5.5 volts (even though the web site tells they can go to 7.5 volts) so they can only provide 1.1A. Is it also enough?

It all depends on your printer, what the steps/mm is, what acceleration you are trying to achieve, and how much mass the motors have to move. The printer on which I run my 1.68A motors at 1.0A is a delta printer so there is not much mass to move.

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drmaestro
And for the Z axis, where there are 2 1.7A motors, is this still enough current? (considering RAMPS of course).

You would almost certainly be better off connecting your Z motors in series instead of in parallel.

Quote
drmaestro
When you tell that the current Duet limits TMC2660s and that is about to be increased, are you talking about a firmware update or hardware update? What is the maximum current that can be physically provided by TMC 2660s?

It's a firmware update. The TMC2660s can in theory handle more than 3A peak current with sufficient cooling, but for that you need to implement standstill current reduction in firmware, which we haven't done yet.

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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].

Quote
dc42


You would almost certainly be better off connecting your Z motors in series instead of in parallel.

Can this be achieved in RAMPS? In its original form, you have 2x4 header pins in front of the Z stepper. If you directly use those two, does that mean you are connecting the motors in parallel? If so, how can you modify it to be in series? Do you have to solder the corresponding motor wires together and use only one of the 4 header connector?

Can you connect Z motors in series in Duet?

Update: I ordered Duet Wifi. Let's see if things get better on it

Edited 1 time(s). Last edit at 04/02/2017 11:18AM by drmaestro.

Yes the two Z motor connectors on RAMPS are wired in parallel. To connect the stepper motors in series, you use just one of the Z motor connectors. If you google "connect stepper motors in series" you will find wiring diagrams.

The two Z motor connectors on the Duet WiFi and Duet Ethernet are wired in series already. If you have only one Z stepper motor, you fit 2 jumpers in the unused Z motor connector.

Edited 1 time(s). Last edit at 04/02/2017 11:20AM by dc42.

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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].