1HCL compatibility question

ironhydroxide

@T3P3Tony With the current motor/mount I have ~1.5mm clearance from the back of the motor to the nearest obstruction, With a modified mount I can get that to ~5mm. I'm 99% certain that is too close, especially when the magnet for the current board is 4mm thick. (shaft not recessed).
I am looking at options for shorter motors, but I'm already at a 19mm motor, so options are scarce.

With some redesign of parts (and added machining I'm hoping to avoid) I can probably get 7mm max clearance with the current motor. Again, not very much room.

Edit. Found a motor that's only 12mm long that "should" work for this (of course have to test). This would give me 9-12mm clearance at the back of the motor (9mm with my current motor mount, up to 12mm with modified motor mount.)

T3P3Tony

@ironhydroxide you may be able to get versions of the motor with a recessed shaft to (say) 3.5mm which might just allow you to fit a magnetic encoder board with a different header from our standard on into the gap. Then mount a board on one of the motor sides rather than on the back for the closed loop control. Let me know once you have explored the options for creating clearance on the back.

ironhydroxide

@T3P3Tony said in 1HCL compatibility question:

Then mount a board on one of the motor sides rather than on the back for the closed loop control

Good call on the recessed shaft, I'll look into them.

I also found some diametrically opposed magnets on McMaster that are only 1.6mm tall (up to 12.7mm diameter) so that could help with clearance as well.

Sadly the back of the motor is the most feasible location without a complete redesign/machining of the rotation system.
the max swing radius is 30mm, giving me at most 60mm(really only ~50 usable). as the motors are ~42mm that leaves ~8mm for mounting, electronics, wiring, etc.

I think I'll pick up one of those 12mm long motors, and a larger diameter but shorter magnet, and do a static test, see what clearance the encoder chip can deal with, with larger diameter but thinner magnets. That will at least get me an idea of remaining space (and if that motor can drive the feed system)

dc42

@wayneosdias I took a look at your schematic. The TMC5160 needs external mosfets to drive the stepper motors. For small motors the TMC2240 would be better, if you don't mind the max VIN voltage being about 36V.

T3P3Tony

@ironhydroxide check the max temperature the motor will get to and look at the specs of the magnets. We use high temperature magnets for mounting on the motor shaft (which is not needed in many cases but could help if running hot). A slightly wider diameter magnet will work slightly better for the same flux density, up to about 10mm see this figure from the AMS application note:

We chose a 6mm magnet because that fits even in recessed shaft NEMA 17 motors

ironhydroxide

@T3P3Tony Good call, I didn't think about heat. The current motors never get above 40c, a thinner might get hotter due to the same energy in a smaller package (or less efficient), will have to test.
Magnets are all rated to 54c and 80c depending on diameter so I think/hope I'll be fine there.

for the widest use case, the 6mm makes perfect sense.
I'm just on the far end of the curve, so I get(have) to look at all options, and if a 10mm magnet is more accurate that can't hurt if it also gives more space to work with.

T3P3Tony

@ironhydroxide its more that a 10mm magnet that is thinner and has a lower flux density may match the thicker 6mm magnet in performance.

ironhydroxide

@T3P3Tony OH, thanks for explaining that. Magnets are magic to me.

wayneosdias

@dc42 yes thanks re 2240.
Re motor/magnets. I have purchased every flavor of the MKS 42Servo B C D and some diff/similar control boards from btt. They all kinda initially work but would become unstable at some point, overshoot/correct and or lose their 'mind' requiring an in situ recalibration. These were just the control boards mounted to the back of old nema17 motors with magnets glued to the shaft.

I then tried a motor/control board combo of MKS servo D and it has worked very well in terms of long term stability. When I installed the motor, I noticed the drive side of the shaft. It appears to be an 8mm shaft turned down to 5mm. Taking the control board off looking at the non drive of the shaft and it appears to be milled with the magnet recessed into it. Or maybe the magnet is banded to the shaft? What ever may be the case, the fb/encoding of this controller/motor combo has been rocks solid.

Just food for thought

T3P3Tony

@wayneosdias yes a pocket on the back of the motor shaft is ideal.