prusa i3 GT2 pulley size?

just wondering if anyone has come up with the optimal number of teeth for the pulleys.

I only use 20 tooth pulleys.

I would like to hear the opinions of others as to what may be better.

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Yvan

Singularity Machine

Define optimal?

16 and 20 teeth pulleys are common

the difference?

16 tooth gives you 10micron theoretical resolution and 20 tooth gives you 12.5micron (presuming 1.8 steppers and 1/16 micro stepping)
If you can spot 2.5 micron difference.. good for you. Most of us can't.

But as you can see the more teeth the lower the resolution... when does it become an issue? well that depends on what your resolution requirement are.

The fewer the teeth the more jitter you get on the belt. Teeth and belts do not match 100% and more teeth lets this average out better. Fewer teeth needs less torque from the motors - do you have small motors? Smaller gears will wear faster, they might only last two lifetimes.

As long as you *know* how many teeth you have, it's pretty much a non issue. The main issues with the belt drives are backlash and stretch. They contribute a lot more to a typical print than any of the gear issues.

I use the 20 tooth on the assumption that there is less "jitter" as uncle bob says, but I don't really know how much of this jitter is reduced with a 20 vs 16 tooth pulley.

My take is this style of machines is they are just a big pile of quivering jitter, so the less the better.

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Yvan

Singularity Machine

ecelent respones guys, I guess I could have been more clear as to what I mean with optimal, perhaps prefered would have been a better choice of words?

I have seen cheap 16 tooth pulleys
cheap belt and pulley combo's for 20 tooth
and then 30 and 40 tooth pulleys

al for about the same price, I was wondering if their was a reason to go for the larger ones.

from the sounds of it the 20 tooth one should be fine, and as a bonus it comes with the belts too.

feel free to weigh in and advise me to get the 30 - 40 tooth ones if it will make a difference, I'm hopig to print printer parts for others, so I know I will need to get soem level of quality out of my printer.


cheers guys

20 has the advantage that it's pretty much the standard with GT-2 belts. They are the "ones to get" at the moment.

Make sure that the inner diameter of the pulleys matches the diameter of your stepper motor shafts .... With NEMA 17's that's not a common problem. It can be an issue if you are using something larger.

Don't worry about the pulleys, if you use 20 tooth they are just fine in the big scheme of things. After that you will be chasing down other sources of play, like belt tension, caliberating and adjusting everything in the firmware etc.

The biggest steps up in quality I've seen on the half dozen or so machines I've built over the last two and a half years has been firmware upgrades, hot end upgrades(twice) and obvious mechanical slop like belt tension or shaky X and Y axis carriages.

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Yvan

Singularity Machine