Segments/s on Duet3 mini with polar kinematics

dc42

@cncmodeller the rated current of that motor is 4.0A according to the Amazon listing, so 1.49A is very low. If you have good fan cooling of the Duet then you can try increasing the motor current, up to the maximum supported 2.0A. But in truth the Duet 3 Mini is a bit under-powered for driving Nema 23 motors.

CNCModeller

@dc42 said in Segments/s on Duet3 mini with polar kinematics:

@cncmodeller the rated current of that motor is 4.0A according to the Amazon listing, so 1.49A is very low. If you have good fan cooling of the Duet then you can try increasing the motor current, up to the maximum supported 2.0A. But in truth the Duet 3 Mini it a bit under-powered for driving Nema 23 motors.

@dc42 thanks for pointing that out, to be honest this was a stepping stone to introducing the UStepperS to go closed loop on the bed, albeit the UStepperS only has a rated current of 2.5A, but then my Ethernet is 2.4A anyway. I'll probably just go that way rather than using my D2 Ethernet board as that earmarked for my Wanhao D4S conversion so I can add a couple of extra extruders for ditto printing small part production runs.

Will the rumoured new Duet closed loop motor control expansion board support higher currents? I think last time I heard anything you mentioned you needed to change out the processor.

As an aside, do my acceleration ad jerk settings look reasonable, I have no idea what good ballpark figures would look like.

Many thanks for your help.

Barry M

Phaedrux

M566 X450.00 Y450.00 Z60.00 E120.00          ; set maximum instantaneous speed changes (mm/min)
M203 X6000.00 Y6000.00 Z360.00 E2400.00      ; set maximum speeds (mm/min)
M201 X250.00 Y250.00 Z20.00 E500.00          ; set accelerations (mm/s^2)
M906 X800 Y1499 Z800 E800 I30                ; set motor currents (mA) and motor idle factor in per cent

They seem conservative to me, but I don't have any experience with Polar printers. Nothing stopping you from going even lower.

Maybe this macro set will help make it easier to experiment.

https://forum.duet3d.com/post/56174

CNCModeller

@phaedrux said in Segments/s on Duet3 mini with polar kinematics:

M566 X450.00 Y450.00 Z60.00 E120.00          ; set maximum instantaneous speed changes (mm/min)
M203 X6000.00 Y6000.00 Z360.00 E2400.00      ; set maximum speeds (mm/min)
M201 X250.00 Y250.00 Z20.00 E500.00          ; set accelerations (mm/s^2)
M906 X800 Y1499 Z800 E800 I30                ; set motor currents (mA) and motor idle factor in per cent
They seem conservative to me, but I don't have any experience with Polar printers. Nothing stopping you from going even lower.

Maybe this macro set will help make it easier to experiment.

https://forum.duet3d.com/post/56174

Thanks for the links to the macros @Phaedrux , I'll have a look when I get a decent chunk of free time at the weekend.

dc42

@cncmodeller said in Segments/s on Duet3 mini with polar kinematics:

Will the rumoured new Duet closed loop motor control expansion board support higher currents? I think last time I heard anything you mentioned you needed to change out the processor.

Yes, it should support up to 6.3A peak when moving, 4.5A in standstill (same as Duet 3 MB6HC).

CNCModeller

@dc42 said in Segments/s on Duet3 mini with polar kinematics:

Yes, it should support up to 6.3A peak when moving, 4.5A in standstill (same as Duet 3 MB6HC).

@dc42 that's great, sounds like I'm definitely heading in that direction when they become available

Is there any information available about the general specifications of the closed loop add-on board? I assume it'll communicate over CAN interface and include relevant axis specific IO like end stops?

Many thanks again.
Barry M

dc42

@cncmodeller the new design has CAN interface, 2 medium current outputs switchable together between VIN and an independent power input, two I/O ports, one thermistor input, one quadrature encoder input, and one SPI connector for other types of encoder. So you will be able to use the IO ports to connect endstops. Maximum nominal input voltage will be 48V. The independent power input is to allow for using 24V or 12V brakes, fans etc. when VIN is 48V.

CNCModeller

@dc42 Thanks for the information. Sounds like a really useful piece of kit. I'll keep an ear to the ground for further development progress.

CNCModeller

@dc42 said in Segments/s on Duet3 mini with polar kinematics:

@cncmodeller the new design has CAN interface, 2 medium current outputs switchable together between VIN and an independent power input, two I/O ports, one thermistor input, one quadrature encoder input, and one SPI connector for other types of encoder. So you will be able to use the IO ports to connect endstops. Maximum nominal input voltage will be 48V. The independent power input is to allow for using 24V or 12V brakes, fans etc. when VIN is 48V.

@dc42 Just thinking ahead, which SPI encoders are you planning to support?

I might get a couple in to help with designing encoder mounts etc.

Many thanks
Barry M

o_lampe

@cncmodeller said in Segments/s on Duet3 mini with polar kinematics:

@dc42 Thanks for the information. Sounds like a really useful piece of kit. I'll keep an ear to the ground for further development progress.

What would a closed loop bed-motor do for you?
It might be able to cope from skipped steps and a clever motion planner would be able to tell other motors to wait, but you'd see oozing filament in the meantime.
It would be OK for a CNC router, but a FDM printhead will have issues.

CNCModeller

@o_lampe said in Segments/s on Duet3 mini with polar kinematics:

@cncmodeller said in Segments/s on Duet3 mini with polar kinematics:

@dc42 Thanks for the information. Sounds like a really useful piece of kit. I'll keep an ear to the ground for further development progress.

What would a closed loop bed-motor do for you?
It might be able to cope from skipped steps and a clever motion planner would be able to tell other motors to wait, but you'd see oozing filament in the meantime.
It would be OK for a CNC router, but a FDM printhead will have issues.

Hi I @o_lampe,
Even when fully tuned and running at Max capacity I'm expecting my prints to take days possibly over a week to complete. Minor glitches in the print I can cope with but major layer shifts when I'm using up well over 2kg of filament is just too much of a planning and financial risk. The plan is to sell prints so failures will effect my income. I'm prototyping in PLA but the final prints will be carbon fibre reinforced filament = £££...

The bed is fairly heavy due to the required mechanical rigidity to print tall, so are the prints, and I want to print at the limit and closed loop is a safety net. To be honest it's as much as about piece of mind as anything else too.

I also have a CNC lathe, mill, & laser cutter that I'm going to convert to modern electronics over the next few years and should that be Duet this project is serving as a de-risking activity for that too.

In terms of dropped steps behaviour I'm sure if the planning could react then it could also do a retract to help with oozing. I'm guessing there will be a onlayershift.g file to customise behaviour if that were the case.

Anyway that's a download of where my head is at.

Cheers
Barry M

dc42

@cncmodeller said in Segments/s on Duet3 mini with polar kinematics:

@dc42 Just thinking ahead, which SPI encoders are you planning to support?

We have prototype encoders already using a magnetic encoder chip, designed to fit on the back of a motor.

CNCModeller

@dc42 cool. Sounds great

o_lampe

@CNCModeller
Just remembered the "minimum print speed" setting in Prusaslicer. If you'd have set that too high in your slicer, you see skipped steps long before it's unavoidable.

CNCModeller

@o_lampe I'm using S3D, I will however double check that all of the settings are consistent with the config.g settings.

o_lampe

@cncmodeller
My gutt feeling tells me, that a polar bed printer can't print close to the center of rotation. Because the bed motor would approach 'infinite' speed requests?
Am I right?

CNCModeller

@o_lampe yeah there is a singularity at the bed centre. However the kinematics have a maximum bed rotation speed setting that reduces print speed accordingly. All of my prints are open ended "tubes" by design so I only really need to get small enough that my other printers can do the "end caps".