Please sell me on the Duet3 closed loop boards?

TLAS

So honest question - can someone sell me on the value of the Duet3 closed loop controllers (over 6HC)?

I’m at a point where I could consider it, but I have same bad experiences with a previous step/direction design a few years back - namely the drivers I used had screw connections that seemed to always keep failing and my stepper motors didn’t have the nice position sensors so I’d keep missing steps.

What would a good setup look like with the Duet 3 closed loop drivers that would mitigate these issues? I saw a teaser photo of a possible Duet 3 closed-loop servo motor design - any details how this will make reliability better from a connection standpoint?

o_lampe

@TLAS
IMHO the CL-steppers we discuss frequently don't have sufficient count of pulses (CPR=1000). Some users changed their gear ratio, but that's not always possible.
The other killer-argument against CL is: we have no control over missed steps.
How will they be added and when?
Will the printer pause, if too many missed steps pile up?

CL-Servos seems to be the next step forward, but I guess with the more powerful servos we won't see missed steps at all. They need CL for their own control loop.

jay_s_uk

@o_lampe duet3d showed off a 16000 pulse encoder board so i would assume theres something similar in their all in one motor. maybe @T3P3Tony can comment further. I'm hoping the 16000 encoder board gets released for purchase

o_lampe

@jay_s_uk They had to come up with their own solution, which tells me that the available products are not up to the task.
The price tag will be accordingly, which is normal for new, low sales products.
Because of that, the scissor between hobbyist's machines and commercial machines will grow wider.
ATM I feel, I can build a machine as good as the commercial ones (but with a small budget), but the split starts to show already.

dc42

@TLAS from our perspective the main driver for closed loop steppers on 3D printers is OEM customers building very large printers. When a print takes many days to complete and uses many tens of kg of material, a print failure after several days becomes very expensive. Therefore even though missed steps/layer shifts caused by unexpected resistance to movement should be very rare, on these larger machines it's worth using closed loop motors to counter that increased movement resistance if possible, and if not possible then to pause the print so that an operator can intervene and maybe save the print.

That's why we've focussed our closed-loop efforts so far on large printers. Our EXP1HCL board can drive motors up to 6.3A peak @ 48V so it can be used with motor sizes up to Nema 34. Our prototype closed loop motors with embedded controller are Nema 23. But we're planning to bring this technology to Nema 17 motors too.

TLAS

@dc42
Glad to hear - what is the connector setup for the motors? I’m particularly interested in a robust connector solution as that is where my previous failures have been.

Any plans for the motors to be compatible with the main boards or expansion boards?

dc42

@TLAS on the prototype Nema 23 motors with integrated closed loop control we use M8 circular connectors. The Nema 17 version will use lower cost connectors such as JST.

Like the EXP1HCL board, they can be connected to any of the Duet 3 main boards via the CAN-FD bus.

TLAS

@dc42
So if I understand this correctly, it only needs a CAN connection and power? That’s pretty slick.

dc42

@TLAS said in Please sell me on the Duet3 closed loop boards?:

@dc42
So if I understand this correctly, it only needs a CAN connection and power? That’s pretty slick.

Correct. We have built a reduced version of the EXP1HCL with an improved brake control circuit into the motor.

TLAS

@dc42
Sounds like a great product! Any target on availability?

dc42

@TLAS we're not making any commitments at present, but I would hope sometime in Q2 2023.