Steps/MM for 1.2 deg stepper

Trying to figure steps/mm for config file on C3D mini which will be controlling 2 NEMA23 feedback steppers via Leadshine HS507 controllers. To complicate things the steppers are geared 1:3 BUT one is 20/60 and the other 24/72 so despite my planning I will have different steps/mm. Using 3mm pitch belts.
My real issue is that the online calculators only work with 1.8, 0,9 and 7.5* steppers and mine are 1.2*. So looking for a formula hopefully that does the pulley math for me. Any tips appreciated as I’d like to get maximum performance out of this.

I think I’m missing something there. While that all looks simple (1.2° steppers are 300 steps/rev), I don’t know what motion you are controlling, so I could easily give you a wrong answer. What kind of a machine are you making?

Do you know dimensional analysis? If not, it’s long words for a simple concept… :smiley: Clough42 has a good segment on dimensional analysis in his electronic lead screw series:

sorry running a geared belt drive laser. So my issue is figuring the effective diameter of say a pulley of 20 teeth with 3mm pitch. I also know my stepper driver does 1/20 steps so 300step/rev means 6000 microsteps/rev.

A timing pulley is just pitch * teeth, the “effective diameter” from a smooth pulley doesn’t apply. 3mm pitch * 20 teeth == 60mm per revolution of that pulley.

Great, so then 6000 step/60mm is 100step/mm then I triple that because of the 1:3 gearing. So ultimately it is 300 step/mm. Lower than I hoped but twice my stock K40. Another unknown for me is the driver can support up to 104K steps which seems absurd as thats around 60000 microstep/mm. I assume that even with feedback there is a minimum step resolution for the motor, but I can find no information beyond the 1000 line feedback encoder means 0.36 deg resolution. Despite this being an extremely popular combo seems like we are on our own when it comes to figuring out capabilties. I’m using a Leadshine 573HBM20-100 servo with a HBS507 controller on 36v.

Strangely enough, the video you posted was very helpful…not for my problem but because I have a lathe too and want to do the same mods.

Well, that is indeed why I found it in the first place. :grin:

Thought I’d report back…at this point I’m stumped. My math says the step/mm should be 250 but in the real world the number is 166.666. Maybe someone can point out my mistake- setup is C3D Mini on Smoothieware, 1.2 deg stepper with 20 micro steps so 6000 steps/rev. Output for motion is a 24 tooth HTD belt pulley with 3mm pitch. That pulley is geared 1:3 from the stepper, so it turns 1/3x24x3mm or 24mm per rev. 6000/24=250. Working backwards, the 166.666 setting would imply 13.333 micro step per step which is probably impossible to get. FWIW, my stepper controller is the Leadshine HSB507 running Leadshine 573HBM120 which are NEMA 23 feedback steppers. Once I find my ethernet to Serial adapter I will interogate the controller to verify setting but I bet its set at the default of 20 microsteps

Microsteps / fullstep normally go in powers of two, so 2, 4, 8, 16 etc…
The spec for your motor says Microstep range: 200~51200ppr@, ‘ppr’ is per/revolution, so you actually have max microstepping of 512

It’s done by dividing each step in half, then half again, etc… so is a power of two series

There are a bunch of controllers that have the powers of two but also 10 and 20 micro steps. My TB6600 controllers are like that.

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Thankyou @mcdanlj ; Every day, in every way, I grow a little Wiser.
(Well I; acquire information, not necessarily the same thing…)