@mrehorstdmd yes I knew its gonna happen but didn't thick it would be bad for the belt.

For BLDC motor I'm still figuring how much steeps per revolution I could get out of it.
If you'll watch this Youtube video link text
It looks there are issues when traveling at low speed with resonance frequency but he claimed that it could be solved in firmware update. This is all new to me so I'm learning as I go.

@Blv I'm impressed with your documentation, Great Job.

@mrehorstdmd odrive supports the step/dir interface. I'm not sure if I will have enough torque at low speeds so this will be like an experiment for me. I know the odrive creator had good results using odrive to control his Pick and Place Machine link text.

The reason for leaning toward BLDC motors is to decrease the tool change time during the printing as this printer will have a tool changer similar to E3Ds approach.

After Several revision, I think I'm happy with this design.
Thanks for the help at @mrehorstdmd and @Surgikill

@Surgikill I am stacking the belts to avoid the twisting. Fabtotum style dose look simpler. My goal is to make the XY belt path in such a way that the brackets for the pulley can be easily machined. As this will be a all metal machine, trying to avoid plastic as much as possible.

@mrehorstdmd hope you don't mind me using your photo as reference.
So do the position of the idlers P1/P2/P3/P4 have effect on the precision of the XY Motion?

For the BLDC motor I will be using odrive to drive the two motors.
Think ill be going with D5065 270kv Motor and a CUI AMT102 "8196 CPR capacitive encoder", haven't decide on the motor type 100%.

Thanks guys for the info and the links

This is what I came up with, any comments appreciated.

Here is an ISO View.

There are several different design on the belt path and keeping it tension, could you guys shear your experience.

Thanks,
Oleg

@dc42 Yes they aren't cheap. I have been think about DRO for quit time similar to this.
https://www.igagingstore.com/6-Absolute-Digital-Readout-DRO-Stainless-Steel-Su-p/205470.htm

I know the DROs aren't fast enough to keep up with the motion but it could be used a reference to pull the positions when requested, like during boot up. What do you think?

To my best knowledge absolute encoder will know its position after power cycle, I think its due to absolute encoders are providing a unique position values.

The place that I work they have a machine that has absolute encoders in its servo motor. It does not require homing sequence at startups.

Well on average the printers usual do not get close to 300mm/s, so on CoreXY using a .9 deg I wont see much improvement vs a 1.8deg motor, since by design CoreXY is geared down. Just making sure I understood it correctly.

I have a delta but at speeds 100mm/s quality is not good and seeing Rail Core II print results at 100mm/s got me inspired to build a CoreXY for my second printer.