Upgrading CNC to Duet 3, keep or replace existing motor drivers?
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Hi All,
I am planning on upgrading a CNC router table to use a Duet 3, but I'm looking for some advice on whether to use the existing motor drivers or go with the built-in drivers on the Duet 3 6HC.
The router currently runs on LinuxCNC through a parallel port, and has one Gecko G201 motor driver and two drivers that look like they are either rebranded or imitation Gecko G201s. These are connected to a 40V supply. The X and Y axes both use Nema 34 5A motors and the Z axis is a Nema 23 (I didn't check the current rating on that one). I'm looking to make the upgrade as simple as possible, but I'd also like to get the most possible performance out of the machine, and so if the built-in drivers on the Duet 3 would provide me with that then I would rather use those. As far as I can tell the main advantage of the existing drivers is that they could run higher voltages (up to 80V), but since they aren't it seems to me that they would just be adding unnecessary complication in this scenario.
BTW the machine does currently run, and I have made some parts with it. The main reasons I'd like to switch to the duet are that I believe that the current setup is limiting my speed and I am also much more familiar with configuring the Duet firmware as I run them on both of my 3D printers and I have always been happy with the quality and features.
Thanks in advance for any input!
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@gershb0mb you have one of two routes to go down.
- Buy a 6XD and use the existing external drivers. Wiring would be simpler as you'd just be modifying the wiring between the existing drivers and the mainboard to suit the 6XD. You also wouldn't have to change any settings on the existing drivers
- Buy a 6HC and replace the existing drivers and use the onboard ones. Cons going against you here is you may need some fairly significant cooling to run the built in drivers at ~5A. You also couldn't go higher than 48v in the future if you chose to.
I would probably go 6XD and stick with the existing drivers.
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@jay_s_uk Thanks for your input, yes those are the two options I am deciding between.
@jay_s_uk said in Upgrading CNC to Duet 3, keep or replace existing motor drivers?:
Cons going against you here is you may need some fairly significant cooling to run the built in drivers at ~5A.
I completely forgot to ask about cooling in my initial post so I am glad you mentioned this; the existing drivers are attached to a pretty substantial heatsink and if the Duet would also need extra cooling it would definitely make the replacement a bigger project.
It sounds like the 6XD is the way to go then if there are no big advantages to the drivers that the 6HC uses over the existing ones.
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@gershb0mb I suppose the only thing that could be a downside with the 6XD is that the Comms time with the drivers will be slightly longer than using internal ones so it could limit the maximum speed. How fast are you able to move the machine now?
Owns various duet boards and is the main wiki maintainer for the Teamgloomy LPC/STM32 port of RRF. Assume I'm running whatever the latest beta/stable build is
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@gershb0mb There's quite a few nice additions that using the onboard drivers of a 6HC will give you, such as stall detection and sensorless homing, stealthChop/spreadCycle (though you will want to use spreadCycle), probably a higher step rate, higher microstepping and interpolation than your external drivers, and tight integration of stepper drivers with controller for fault detection and other fine tuning.
Cooling is basically a fan blowing over the board, and you're going to have a fair amount of space in your control box with the old external stepper drivers removed! You can run the 6HC (v1.02 and later) on the existing 40V PSU.
Ian
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@jay_s_uk Currently the max speed is ~150ipm.
@droftarts Of all of those the tighter integration was the main advantage I was thinking of. I'm far from an expert on stepper motor controllers, so would you be able to elaborate on the practical benefits of e.g. spreadCycle or any of the other additions that you mentioned?
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@gershb0mb said in Upgrading CNC to Duet 3, keep or replace existing motor drivers?:
Currently the max speed is ~150ipm.
whats that in motor RPM?
what steps/revolution do the existing drivers use?
Whats a realistic target speed for travel moves? -
@T3P3Tony I would think that I could get at least double that speed for travel moves; as I understand it that is currently limited by the LinuxCNC controller and not by the motor drivers. I will have to check the current settings and the motor gearing though to be able to answer your other questions.
