Please help me choose between Duet3 and Duet2.

Garfield

Kind of answered your own question really - I've no problem confirming the thoughts you've probably already had.

Your expansion plans and the fact that you're clearly into tinkering screams Duet 3 to me. This will run what you currently have and be significantly more 'expandable' in the future.

The only thing that stands out is your '30A Mosfet for the heated bed'. What do you know about the bed that is installed i.e. wattage. The most you can pull on the Duet 3 is 18A and I'd see that as a limit personally.

I'd avoid sensorless homing as the stall currents aren't predictable enough and are dependent upon the speed at which moving - you could get false stall signals during printing which is a pain in the butt ( I've been there ).

deckingman

@caviara You will doubtless get numerous opinions, but I'll add mine for what it's worth. I used to use Duet 2, now I have Duet 3. My two main reasons to change are that firstly, I needed more than 12 stepper motors and that is the maximum that Duet 2 allowed me to have. Secondly, I have 6 extruders mounted on a separate moving gantry which meant that including all the wires for the hot ended, with Duet 2, I had a cable chain with 40 plus conductors going to that gantry. When I changed to Duet 3, I was able to mount 2 expansion boards on that gantry and now I just have power and data instead of the 40 plus conductors so the wiring is a lot neater. If I was building another printer such as one that you have described, I would choose Duet2.

caviara

Thank you all for your answers!
I didn't expect such a quick response (one more reasons to stay here)

@Garfield said in Please help me choose between Duet3 and Duet2.:

The only thing that stands out is your '30A Mosfet for the heated bed'. What do you know about the bed that is installed i.e. wattage. The most you can pull on the Duet 3 is 18A and I'd see that as a limit personally.

I just wanted to say, that i have one module and will drive Heated Bed trough it - so the amperage limit of the output is not a problemhere

dc42

From what you have described, Duet 3 has two advantages:

More options for making the stepper drivers quieter, because Duet 3 support StealthChop;
Expansion to tool changer. Duet 3 has 6 stepper drivers on board, so one spare after your XY + dual Z + extruder. You can use that spare driver either to drive a small stepper motor for the tool change locking mechanism (as E3D does on their tool changer), or for a second extruder. If in future you want to additional add tools with direct drive, you will be able to use Tool Boards to drive them, which will simplify the wiring.

Danal

Opinion, free and worth every penny:

Everything I do from this point forward gets either an ESP32 (long story, and for a different forum) if it is small enough, or a Duet3. With Pi.

DaBit

@dc42: How would you classify 'quieter stepper drivers'? 'somewhat more silent' or 'a lot'?

When the printer was running LinuxCNC I used ST L6470 voltage mode drives connected to the Pi over SPI. These were extremely silent; the linear rails were the loudest components in the printer. The flipside of the coin: they are a total disaster to tune well and very prone to resonance. I managed to tune that out, though.

With Duet2 my printer suffers from quite a bit of midband resonance with the NEMA23 steppers on the CoreXY, current capability is so-so, and with 2 Z-motors, 2 extruders and the XY motors I basically lack 1 driver on the Duet2 Wifi; the 2 Z-motors in series is not an ideal situation. Easy to solve with an external stepper drive or Duex2 board, but still. I also have a Pi3 and the 7" Pi screen already mounted in the front panel since I used to run LinuxCNC on that Pi.

Sound like my printer is a good candidate for Duet3. I only hate it to throw out the 165 euros that the few months old Duet2 costed and spend another 260 euros on the Duet3. But if the stepper motors are really more silent I might.

deckingman

@DaBit If it helps, I have Duet3 and used to run Duet 2 on the same printer. The small extruder steppers are now completely silent to my ears whereas they were audible using Duet2. But I can't say that the larger Nema 17s that I use on the main axes are any quieter with Duet 2 compared to Duet3 and I've tried with and without stealthchop2. I do now have some Nema 23s as well but I never ran these on Duet2.

dc42

@DaBit said in Please help me choose between Duet3 and Duet2.:

@dc42: How would you classify 'quieter stepper drivers'? 'somewhat more silent' or 'a lot'?

Hard to say, because it depends so much on the motors. Some Duet 2 users find it difficult or impossible to reduce the standstill noise to a level that they consider acceptable. My Duet Wifi powered delta produces a slight hissing sound when idle. It's quite noisy during homing (I think it may be hitting some sort of resonance, but so quiet during printing that I sometimes have to look at it to be sure it is still running.

On Duet 3 you have the option of stealthChop. This uses the minimum current it can get away with. The snag is, if the nozzle hits a blob or curl-up, you may get missed steps because the driver doesn't respond instantly to the increased load. When I switched my Duet Maestro-powered Ormerod printer over to stealthChop, I started getting missed steps. I now have it set to stealthChop at very low speeds (so it is silent at standstill), switching over to spreadCycle at a very low speed.

The Prusa i3 Mk3 has two print modes: normal and silent. I suspect that the silent mode runs the drivers in stealthChop mode and uses low travel speeds, and the normal mode doesn't use stealthChop except at very low speeds. But this is only my guess.

DaBit

I am using 1.6Nm NEMA23 motors with 8mm shaft, 3.0A nominal winding current. A bit overpowered for a 3D printer, but I had a bunch of them on the shelf and they tolerate a fair bit more radial loading than a NEMA17 motor with 5mm shaft.

Standstill noise is not really an issue. I can hear the motors hissing at standstill, but especially with the door closed the volume is low. It is the midband resonance that happens at 25-40mm/s print speed I would like to get rid of. It does not build up enough to cause missed steps or hurt print quality, it just makes an awful sound.
Using x16 microstepping with interpolation, reducing the motor current to 1800mA and keeping belt tension on the low side reduced the noise somewhat, but it is still sounds like the printer is rattling to bits in the next few seconds.

After reading your and deckingman's posts I am not sure Duet3 is the answer. Printing and mounting a mechanical 'rattler' probably works better.

caviara

Thank you all for the answers and suggestions!
Yesterday evening one more Duet 3 have been ordered