Segments/s on Duet3 mini with polar kinematics

[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".