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Idler pulley for GT2 belt with ComfortFit flange

by jltx Jan 20, 2018
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I replaced the Y axis idler pulley on my MK3 with this last night and got a really nice result on a calibration cube. It was slightly better than the "pre-test" cube that I printed, particularly around the shadowing on the Y axis. A follow-up test benchy was very interesting. You could still see shadowing on the curves around the bow, but shadowing was otherwise greatly reduced. I guess it's time to replace the idler pulley on the X axis.

One additional note - I sanded both sides of the washers and the outsides of the flanges with 1000 grit sandpaper to reduce friction. As I was assembling it I noted that the bearings weren't spinning as freely as I expected. After sanding they spun much more smoothly.

I was curious where you found the GT2 dimensions you used for this thing. I would like to remix this for a 16t idler and smaller bearing but it doesn't seem like there is a good source of data for these profiles anywhere.

You can send me the file for solidworks. Thanks

Hi, apart from standard 0.4mm nozzle I also have 0.2mm. I don't have 0.25mm. Which is better to print this with?

ps: will 0.1mm layer height do?

0.2. 0.1 layer will work, you just wont get as smooth of a flange.

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Question, why do you recommend it be printed in PLA and not PETG? I'm going through all your stuff right now trying to figure out what I need to buy (I only have PLA right now and I think I need a spool of ABS and PETG just don't know which one needs to be black)

PLA resolves detail better than petg typically. The flange and teeth may not resolve cleanly but you can try.

Ahh okay. Good to know. (Super new so I'm still trying to retain everything I read and all the little details) Thank you for the super fast reply.

Thank you for this, printed a 24T for my y-axis perfectly... but I want to print one for x-axis as well. I was under the impression that the x-axis idler is 20T, or am I wrong?

I can't really say since I don't know what printer you have. My printer didn't have toothed idlers at all. But it does now. :-)

Thanks for the prompt reply! Oops, my mistake... I have a MK3 and a MK2S.

For mk3 the X axis idler is exactly the same as the Y axis idler. Not sure that answers your question.

Hah, not so much. I'm fairly certain 20T is the stock size, I assumed you were replacing the pulleys on a MK3 as well considering most of your designs are for that printer. Any chance you could post a 20T pulley if you get a chance? Not sure how hard it is, worst case I can just fiddle around in Fusion until something usable comes out. Thanks again for the design, seems to work very well.

Sorry, I really don't understand. The stock idler is smooth, no teeth, unless Prusa changed things. Even so, it is passive and does not contribute to any gearing ratios. If you are worried about belt position (which is highly overblown), consider: the radius is 6mm. The belt rides on the teeth with the smooth idler. The 22T I have has an inner radius (where teeth engage) of ~6mm. If you assume some tooth compression on the smooth, half would be ~0.4mm, but it would rebound some on exit. The belt exit path is maybe different by 0.3mm, depending on tension. Do the trig on the 250+mm X span and see if you lose sleep. I have been running this for months with exquisite prints.

To answer your question, a 20T won't print cleanly (last I checked) due to thin walls etc. And following the above logic, might be smaller than you really want.

No they still ship smooth idlers. My apologies, but yeah that was my concern. The belt position. Thank you for taking the time to answer my question. I'll print up a 22T and put that on there, thanks again!

Just wanted to say thanks jltx, I installed your gear idler pulley this morning, and my MK3 has been printing all day, nice and quiet. =)

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I made a remix for F623 bearing https://www.thingiverse.com/thing:2781072

Prusa MK3 MK2S X axis pulley 24T

Sorry I got distracted in another project and didn't get back to you yet. I was worried that the bearing flange would weaken the gear flange connection but looks like you got it to work. Nice job!

will F623ZZ with flange fit? if not do I need to scale Z? the flange is 0.95mm, bearing total height 3.95mm, flange diameter 11.45mm
got this one https://www.aliexpress.com/item/10-pcs-lot-F623-ZZ-Flange-Bushing-Ball-Bearings-F623ZZ-3-10-4-mm-Free-Shipping/32560418002.html

Would be possible to make remix of it in one piece (w/o the split in the middle) for F623ZZ

Also, I don't have 0.25 nosel, just 0.2 and 0.3, which one will be better?

No, sorry, this design assumes std 623 dimensions. Trying to incorporate the flange violates assumptions in my design intent. It will get tricky fast due to overhangs, minimum extrusions, bearing alignment. Feel free to remix though. One piece won’t print well which is idea behind split.

0.2 would be better to capture the detail, but 0.3 might work too.

do you have files I can redesign in F360 or can you export?
will then remix it.

Nice design! I heard that it is sometimes not a good idea to have teeth on the idler, have you heard about this?

Yeah, I ordered the 'smooth' idlers when I built my i3 clone, and now I'm looking for ways to get toothed ones faster than ordering cheap imports.

Mainly because I see ribbing in my prints on the x and y axis, regardless of my acceleration settings (I've done everything to remove ringing, now it just looks like it's all belt tension).

This design has the epic bonus of the 'comfort flt flange' which should really help out my belt... my belt got chewed up a bit on one side when the x-end idler cracked and put the pulley out of square. ;-/

no, the opposite actually. For idlers on the tooth side of belt it is better, and smooth for back side of belt, often seen in CNC set ups.