Toothed Idlers :S love'em or hate'em Any opinion on toothed idlers? I have been thinking about giving these a shot GT2 Idlers https://reprap.org/forum/read.php?1,184159,184159#msg-184159 Sun, 07 Jun 2026 22:47:22 -0400 Phorum 5.2.23 https://reprap.org/forum/read.php?1,184159,447421#msg-447421 Re: Toothed Idlers :S love'em or hate'em https://reprap.org/forum/read.php?1,184159,447421#msg-447421
Ohm is right. In situations where you want your belt to do 20 years instead of 15 under heavy loads it's probably important, but for our purposes there's not really a point.]]> SamS General Wed, 24 Dec 2014 23:29:40 -0500 https://reprap.org/forum/read.php?1,184159,447269#msg-447269 Re: Toothed Idlers :S love'em or hate'em https://reprap.org/forum/read.php?1,184159,447269#msg-447269
They both use different solutions for the idler.

My MendelMax even uses very small bearings for an idler on the X-axis and I see not wear at all. We can of course keep on talking about hypotheses, and it can be fun at times, but real scale tests don't really show much difference between the two solutions.

The only thing I can say is that it probably will make a difference on huge CNC routers that make use of very heavy tools and work all day and night in factories. I think it is safe to say that on most* 3D printers it doesn't matter what you use.

One thing is for certain, if you use the wrong spaced tooth idler (for example T2.5 idler with a GT2 belt) you will surely have worse prints and shorter belt life than if you use a belt on a bearing. And since I don't like the printed toothed idlers, I would suggest using a bearing.]]> Ohmarinus General Wed, 24 Dec 2014 07:34:51 -0500 https://reprap.org/forum/read.php?1,184159,447250#msg-447250 Re: Toothed Idlers :S love'em or hate'em https://reprap.org/forum/read.php?1,184159,447250#msg-447250
Quote
Rectangled
So basically, it is like what you said the pulleys themselves have to be spaced at the exact distance (belt teeth pitch x how many teeth between pulleys) to mesh perfectly with belt.

I see no reason why this whould be neccessary. We talk about idlers, not pulleys. Idlers rotate freely and, if there are two, independent of each other. If distance doesn't match perfectly, one of the idlers whould simply rotate a bit and everything is fine.

Quote
Rectangled
[attachment 45728 CompressionTheory-01.jpg]

Yes, this compression certainly happens. In bad cases it's also a problem, e.g. T5 belts with weak, pure silicone teeth. The idea of GT2 belts is to reduce this compression and also to make the difference between tooth on the edge vs. tooth not yet on the edge small enough to not cause visible artefacts on the printed parts.

A printed toothed idler might be not precise enough to show the advantage of a toothed idler, but I'm pretty sure toothed idlers have some precision gain when machined well.]]> Traumflug General Wed, 24 Dec 2014 06:35:48 -0500 https://reprap.org/forum/read.php?1,184159,447178#msg-447178 Re: Toothed Idlers :S love'em or hate'em https://reprap.org/forum/read.php?1,184159,447178#msg-447178
However, I thought about it and I could imagine that maybe if the pulleys where at a slightly off distance from each other that the belt segment in between the pulleys is forced to become slack (say when reversing) due to its teeth. Almost as if there where too many teeth on the belt to fit between each pulley, I illustrated it:

[attachment 45727 CompressionTheory_Artboard2.jpg]
Please, do not take these diagrams serious as they have not been proven.

So basically, it is like what you said the pulleys themselves have to be spaced at the exact distance (belt teeth pitch x how many teeth between pulleys) to mesh perfectly with belt. I am actually starting to see how this could suck. Could it be not fixed by allowing one of the pulleys to have some adjust-ability in where you put them?

Also, to illustrated what I mentioned earlier about if the teeth would compress when running the belt over smooth idlers, over time:

[attachment 45728 CompressionTheory-01.jpg]
Please, do not take these diagrams serious as they have not been proven.

I am trying to weight the pros/cons of each but this might be an imaginary fear of my'n? I see lots of people doing the smooth idler as less has to be considered about pulley placement.

Thoughts?

-B]]> Rectangled General Wed, 24 Dec 2014 01:47:33 -0500 https://reprap.org/forum/read.php?1,184159,447136#msg-447136 Re: Toothed Idlers :S love'em or hate'em https://reprap.org/forum/read.php?1,184159,447136#msg-447136
xclusive is right, no industrial machine would just use a bearing but that's because in most applications the belts undergo much much more wear. I really don't think it's done because of positioning.

The only reason I can think of would be to decrease wear on the teeth, but the the teeth going over the idler won't ever be used anyway.

Good thought rectangled, but you have to keep in mind that the pulleys are usually made up of three parts with the aluminum crimped or press fir or brazed together...it's pretty tough to machine those little pulleys. I had a few with a 3/16" bore and our machinist couldn't even open them up to 1/4" without coming apart and breaking.

Sidenote: Did you grab those off of Mcmaster? I love how they have STL's of almost everything.]]> SamS General Tue, 23 Dec 2014 18:47:08 -0500 https://reprap.org/forum/read.php?1,184159,447060#msg-447060 Re: Toothed Idlers :S love'em or hate'em https://reprap.org/forum/read.php?1,184159,447060#msg-447060
I am running into the same area of thinking; to use toothed idlers or not. I think it is a good idea; not for timing obviously but because I feel it would just add better control, guidance, and syncing all around.

Plus, could it be possible to compress or tire out the teeth of the belt by having it roll over a perfectly round surface, like a bearing OD? I haven't actually gotten to do any tests yet, but I feel that if tension was added to the system the lobes or teeth could compress against the idler a little (multiplied by each pulley and you have a significant slop stack-up?)

I modeled a dual idler assembly that I think I might try and make by modifying some timing pulleys to accept small bearings.

[attachment 45718 IdlerAssembly.jpg]

Thoughts?

Thanks,

-B]]> Rectangled General Tue, 23 Dec 2014 15:19:46 -0500 https://reprap.org/forum/read.php?1,184159,184321#msg-184321 Re: Toothed Idlers :S love'em or hate'em https://reprap.org/forum/read.php?1,184159,184321#msg-184321 As for size, it's not important. What is important is that the belt remains in a straight line on the side where there carriage is connected, otherwise the movement becomes non linear if you get near the idler.]]> Srek General Wed, 13 Feb 2013 07:11:33 -0500 https://reprap.org/forum/read.php?1,184159,184257#msg-184257 Re: Toothed Idlers :S love'em or hate'em https://reprap.org/forum/read.php?1,184159,184257#msg-184257 -------------------------------------------------------
> Not everything works out in practice like it does
> in theory... I have a printer that uses T5 belts
> that outclasses most GT2 belt using printers. I
> bet toothed idlers have potential to be a good
> thing...


Again, looking at machine designs in industry.... Always always always a toothed idler for timing belts. And typically yes the idler is the same size as the pulley, though it shouldn't be that important. But the idler is only going to do you any good if it's machined accurately.

I'm happy with the flipped belt method for Reprap purposes. But for an industrial design I would use machined metal toothed idlers.]]> xclusive585 General Wed, 13 Feb 2013 03:03:32 -0500 https://reprap.org/forum/read.php?1,184159,184256#msg-184256 Re: Toothed Idlers :S love'em or hate'em https://reprap.org/forum/read.php?1,184159,184256#msg-184256 IanJohnson General Wed, 13 Feb 2013 02:52:40 -0500 https://reprap.org/forum/read.php?1,184159,184218#msg-184218 Re: Toothed Idlers :S love'em or hate'em https://reprap.org/forum/read.php?1,184159,184218#msg-184218 Idolcrasher General Tue, 12 Feb 2013 20:31:06 -0500 https://reprap.org/forum/read.php?1,184159,184213#msg-184213 Re: Toothed Idlers :S love'em or hate'em https://reprap.org/forum/read.php?1,184159,184213#msg-184213 Idolcrasher General Tue, 12 Feb 2013 20:24:04 -0500 https://reprap.org/forum/read.php?1,184159,184211#msg-184211 Re: Toothed Idlers :S love'em or hate'em https://reprap.org/forum/read.php?1,184159,184211#msg-184211 IanJohnson General Tue, 12 Feb 2013 20:20:11 -0500 https://reprap.org/forum/read.php?1,184159,184210#msg-184210 Re: Toothed Idlers :S love'em or hate'em https://reprap.org/forum/read.php?1,184159,184210#msg-184210 james glanville General Tue, 12 Feb 2013 19:37:37 -0500 https://reprap.org/forum/read.php?1,184159,184206#msg-184206 Re: Toothed Idlers :S love'em or hate'em https://reprap.org/forum/read.php?1,184159,184206#msg-184206
Did any of the old maker bots use toothed idlers?]]> Idolcrasher General Tue, 12 Feb 2013 18:57:16 -0500 https://reprap.org/forum/read.php?1,184159,184203#msg-184203 Re: Toothed Idlers :S love'em or hate'em https://reprap.org/forum/read.php?1,184159,184203#msg-184203 printed toothed idler Nudel?]]> xiando General Tue, 12 Feb 2013 18:33:35 -0500 https://reprap.org/forum/read.php?1,184159,184197#msg-184197 Re: Toothed Idlers :S love'em or hate'em https://reprap.org/forum/read.php?1,184159,184197#msg-184197 billyzelsnack General Tue, 12 Feb 2013 18:00:04 -0500 https://reprap.org/forum/read.php?1,184159,184177#msg-184177 Re: Toothed Idlers :S love'em or hate'em https://reprap.org/forum/read.php?1,184159,184177#msg-184177
Better to twist the belt like akhlut.]]> Nudel General Tue, 12 Feb 2013 16:53:53 -0500 https://reprap.org/forum/read.php?1,184159,184173#msg-184173 Re: Toothed Idlers :S love'em or hate'em https://reprap.org/forum/read.php?1,184159,184173#msg-184173 akhlut General Tue, 12 Feb 2013 16:29:31 -0500 https://reprap.org/forum/read.php?1,184159,184159#msg-184159 Toothed Idlers :S love'em or hate'em https://reprap.org/forum/read.php?1,184159,184159#msg-184159
I have been thinking about giving these a shot GT2 Idlers]]> Idolcrasher General Tue, 12 Feb 2013 16:02:40 -0500