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<Noxz>
hrm, cant find my bookmarks on 180-step/rev steppers.. anyone with a known source?
<Noxz>
I finally figured out (via simulations) the gear ratio for that rotary stage (with a resolution of 6 arc minutes per rev of th e crank, a 180 deg stepper, not microstepping, would give a res of 2 arc seconds/step)
<Noxz>
which I like better than 1.8 arc seonds/step w/ a 200-step/rev stepper
<mrdata|>
why
<Noxz>
because of a rounder number
<Noxz>
I guess if you take microstepping into account then it doesnt matter?
<mrdata|>
it's only rounder in arbitrary units
<mrdata|>
arc seconds are pretty arbitrary
<Noxz>
yeah, I guess it all sorta that.. actually, I recall this discussion last time, didnt I just give up looking?
<mrdata|>
idk
<Noxz>
having a tough time finding any source, so meh
<Noxz>
I guess I could go w/ 400 step (0.9 deg) over the 200 if I really want to get a little better
<mrdata|>
if you want 2 arc sec per step, then if you have a 200 step/rev motor you want a gearing ratio of 3240:1
<Noxz>
I already figured out my gear ratio.. one rev of the "crank" results in 6 arc minutes
<Noxz>
so I want to step that
<Noxz>
the gear ratio was a differential rotary stage that I designed (and finally simulated yesterday)
<mrdata|>
6 arc minutes per step is 3600 steps per rev; where does the 1.8 or 2 arc sec come in?
<mrdata|>
ok, i see. you get 6 arc min per rev of your crank
<Noxz>
Yes
<Noxz>
which was where most of my "design" efforts were located
<Noxz>
now I just want to schtick a motor on that crank because no way in hell would I do it by hand :P
<mrdata|>
do you like unipolar or bipolar
<Noxz>
I believe my first setup with steppers (I have barely used t hem) wsa bipolar ebcause I needed the added amperage/torque
<Noxz>
for this, I doubt I need as much torque
<mrdata|>
how many volts
<Noxz>
just rotating a disc of steel a little bit (the purpose is to make indexing plates/rings)
<Noxz>
I think the Smoothieboard can do 24v safely?
<Noxz>
I ran 12v on it before, but the big NEMA34's I have started to get a little hot
<Noxz>
and the drivers
<mrdata|>
steppers run the most current when holding unless you dont need powered hold
<Noxz>
I might.. I need to index an dhold position as a notch is cut
<Noxz>
but the actual weight/force neede dto hold wont be much, especially with the gearing
<mrdata|>
how much holding torque do you need
<Noxz>
havent actually calculated that yet
<mrdata|>
in millinewton meters
<mrdata|>
or oz/in
<Noxz>
all I got thus far is the correct gearing
<mrdata|>
the motors i can find from digikey with numbers of steps per rev divisible by 3 are 480 steps per revmaybe
<Noxz>
hrm, that may work.. I've also been told to just microstep (which the smoothie can do) .. any inaccuracies past a point is going to be within the cutting machine/wahtever itself
<Noxz>
I think I should compute how heavy the "Standard" workpiece is (plus all the other gears/whatnot) and figure out what is needed to keep it stationary/hold
<Noxz>
I really dont want to shrug and just buy something without fully understanding the forces involved