Anyone know what the best/ideal dimensions (number of teeth, effective diameter, etc…) for a hobbled pulley/drive gear would be for 1.8 degree Nema 17 motor, 1/16 step? EDIT: this is for extruder
An 8 degree stepper? Did you mean 1.8 degree?
Ideal is relative to the torque of the motor, what voltage you’re running it at, and what you need your max speed and resolution to be.
It’s easier to just pick a standard size. Effective diameter is not important, number of teeth is.
Also Make sure your idler is chosen to keep the drive path parallel.
Also remember that you can only go so small on the pulley, too small and the surface area and radius of the belt will cause slipping.
I think the standard for gt2 is 16-20 teeth.
Is this for an extruder or a drivetrain? I assume extruder? There are different schools of thought. The “standard” is around 11mm measured diameter (tip of teeth) for ungeared NEMA 17 1.8 degree direct drive extruders, but smaller will output more torque at the expense of a smaller contact patch and thus possibly more stripping the filament.
1.8 degree? 0.9 degree? I’ve never heard of an 8-degree motor.
I don’t really think I’d consider there being an “ideal” - everything is a tradeoff.
There is an ideal range in terms of resolution and step rate, though since you’re using smoothie, I would probably suggest more steps per millimeter of filament than I normally would. I’ve seen a printer print significantly slower than the specified speed because it has too many steps per mm on the extruder and couldn’t maintain the step rate.
Oops… sorry. Yeah 1.8 degree and this is for extruder. Currently we’re using Reprap Discount’s drive gears. They bite really well, but we’re looking to make our own now.
This is also for 1.75mm filament.
I see that E3D uses 23 teeth for theirs. They changed it to 23 from 22 per the revisions on the drawing… I wonder why?
Basically trying to understand what the formula is for choosing a certain number of teeth and a certain effective diameter.
The diameter changes the effective torque and resolution. The teeth is experimentation on gripping ability. There isn’t an explicit formula for number of teeth, it depends on materials mostly.
There are also different schools of thought on tooth profile. I like extremely sharp teeth with relatively wide valleys between them (see the Deezmaker gears), but others insist that high tooth density is more important.
Like @ThantiK said its all a trade off. Gears with smaller diameters have a relatively smaller amount of surface area to but onto the filament. They however have more torque. If you increase the diameter there is more surface area available for the filament to go to but the torque is lessened.
It’s all relative to what your ideal print spreads are and then you can try to find a good gear size that compliments your setup.
Some use flint wheels, which barely have teeth. Some use really low profile. Do your own experimentation. Try different materials, pla, abs, nylon, pet. Best way to test is to get a good motor, put the filament on a simple weight gauge (one of those cheap ones that you use to weigh fish) or use weights. Run it until the filament slips, or the motor stalls.
Imho I think a 0.9 degree motor is better for direct drive. Need more resolution to keep the extrusion accurate.
@Shai_Schechter Airtrippers blog post is always good to revisit for some hands on info;
http://airtripper.com/1676/3d-printer-extruder-filament-drive-gear-review-benchmark/
@korpx Unfortunately, that was a very poorly-controlled experiment. Rather than recommending specific gears, the only conclusions he should have drawn were the blatantly obvious: that the brass gears he tested that didn’t really have teeth made for gripping filament didn’t grip filament as well as gears that were intended to grip filament, and that a smaller drive gear provides more pushing force for a given amount of motor torque.
@Shai_Schechter the change to 23 teeth is likely because 23 is a prime number. 22 is divisible, and as such, will wear uneven at an interval of any divisor.
@Chris_Burger That only matters if it’s running over the same thing over and over. Other than a little retraction, the same bit of filament should never go over the drive gear twice, so it doesn’t matter if the number of teeth is prime.
@Whosa_whatsis (sigh) I’ll admit to thinking I knew what was being discussed, I thought it was a gear driven extruder drive, so gear on gear. Good call man.