Eradicate backlash I have two Prusa printers both are plagued by backlash. One has the machined timing gears and the other uses timing gears i printed myself. On Y axis i can not get below .008" (.2mm) backlash on the machine with machined timing gears. The belts are drum tight, its only 1 year old so i cant imagine the belts are worn out already. What is the best solution to eliminate backlash on these printers? What have some of you came up with for your own printers? Is there a better alternative to the timing gear and belt? I thought of making a tensioner pulley but how would that be any different than just making the belts as tight as possible? Ive fought this to the brink of madness, im stumped. https://reprap.org/forum/read.php?1,197409,197409#msg-197409 Fri, 09 Oct 2026 22:47:18 -0400 Phorum 5.2.23 https://reprap.org/forum/read.php?1,197409,198621#msg-198621 Re: Eradicate backlash https://reprap.org/forum/read.php?1,197409,198621#msg-198621 specifically generally caused by loose fit (or deformation) between two or more drive components, and it's unlikely you'll ever remove 100%, although you can get close. (personally, I don't usually consider friction based problems to be "backlash" and deal within them as different degrees of freedom from coupling issues)

Using machined metal gears, high precision on mounting, properly tensioned belts, using belts with steel wire strengtheners, replacing general purpose threaded rod and general purpose nuts with precision lead screw, etc will help immensely though.]]> xiando General Wed, 10 Apr 2013 11:41:52 -0400 https://reprap.org/forum/read.php?1,197409,198517#msg-198517 Re: Eradicate backlash https://reprap.org/forum/read.php?1,197409,198517#msg-198517
When moving in one direction, the belt is tensioned, so when stopping and changing the direction, you first have to reduce this tension... then, with friction and/or sticking (as in stick-n-slip) you'll need some force to start the mover again -- so this releasing+retensioning is the amount of 'play-free backlash' ... could be some hundred microns, what's visible as flats/'quadratures' when printing small circles ...]]> VDX General Tue, 09 Apr 2013 09:34:51 -0400 https://reprap.org/forum/read.php?1,197409,198514#msg-198514 Re: Eradicate backlash https://reprap.org/forum/read.php?1,197409,198514#msg-198514 nophead General Tue, 09 Apr 2013 09:19:21 -0400 https://reprap.org/forum/read.php?1,197409,198491#msg-198491 Re: Eradicate backlash https://reprap.org/forum/read.php?1,197409,198491#msg-198491
When you stop and change direction, most driving systems will show this symptoms - you can avoid (or reduce) it with high rigidity, pretensioning of ballbushings or adding ultrasonic oscillation to counter the stick-n-slip ...]]> VDX General Tue, 09 Apr 2013 07:32:49 -0400 https://reprap.org/forum/read.php?1,197409,198473#msg-198473 Re: Eradicate backlash https://reprap.org/forum/read.php?1,197409,198473#msg-198473
Quote
alj_rprp
even with 0 effective play can have backslash

:)]]> Traumflug General Tue, 09 Apr 2013 06:32:16 -0400 https://reprap.org/forum/read.php?1,197409,198372#msg-198372 Re: Eradicate backlash https://reprap.org/forum/read.php?1,197409,198372#msg-198372
Stepper torque is proportional to displacement, so if static friction is non zero it can come to rest with a displacement that gives enough torque to match it.]]> nophead General Mon, 08 Apr 2013 20:46:33 -0400 https://reprap.org/forum/read.php?1,197409,198335#msg-198335 Re: Eradicate backlash https://reprap.org/forum/read.php?1,197409,198335#msg-198335

also has the original issue in this topic been resolved yet?]]> jamesdanielv General Mon, 08 Apr 2013 06:11:16 -0400 https://reprap.org/forum/read.php?1,197409,198311#msg-198311 Re: Eradicate backlash https://reprap.org/forum/read.php?1,197409,198311#msg-198311 -------------------------------------------------------
> Backlash Wiki
>
> Wikipedia is wrong on this one.

Yes, but not for the reason you state.

> The stiffness of a zero backlash system is a
> different topic. For example, ball bearings are
> much weaker than bushings, because they have a
> point contact, only. With load, the balls sink
> into the rods surface and on high loads you can
> get to a point where the sink-in of ball bearings
> is bigger than the backlash of a bushing. That's
> why non-hobbyist milling machines usually have
> bushings instead of bearings.

Preloaded or Spring tensioned nuts and other systems that reduce play like 2 gears angulary slided, even with 0 effective play can have backslash. This is caused by the hysterysis caused by the different point of application of forces when moving in reverse. This is typically a magnitude of order smaller, but still important to take in account with precise movements.

In fact, to eliminate play, you need some preload, and the more preload the more hysterysis (hertz pressure theory).

Backslash is compensation of (internal+external) plays plus hysteris. While the former can be mechanically eliminated (within limits), the latter can only be compensated in software.]]> alj_rprp General Mon, 08 Apr 2013 04:26:10 -0400 https://reprap.org/forum/read.php?1,197409,198303#msg-198303 Re: Eradicate backlash https://reprap.org/forum/read.php?1,197409,198303#msg-198303
Quote
Dirty Steve
Backlash Wiki

Wikipedia is wrong on this one.

Quote
Dirty Steve
A zero-backlash mechanical system would not be movable.

Nicely they describe a zero backlash system in the same article: [en.wikipedia.org]

With a double gear tensioned against each other, both sides of the teeth are in contact at the same time. And it's movable.

Quote
nophead
LM8UU bearings have preload

This is another example of having zero backlash. "Backlash", like in "the maximum distance through which one part of something can be moved without moving a connected part" (citation from the Wikipedia article).

The stiffness of a zero backlash system is a different topic. For example, ball bearings are much weaker than bushings, because they have a point contact, only. With load, the balls sink into the rods surface and on high loads you can get to a point where the sink-in of ball bearings is bigger than the backlash of a bushing. That's why non-hobbyist milling machines usually have bushings instead of bearings.]]> Traumflug General Mon, 08 Apr 2013 03:58:03 -0400 https://reprap.org/forum/read.php?1,197409,197981#msg-197981 Re: Eradicate backlash https://reprap.org/forum/read.php?1,197409,197981#msg-197981
One of my machines has the LM8UU self aligning bearings on ground and polished rods with the metal machined belt gears and the other has bronze bushings on non ground steel shafts with printed belt gears. I used to get perfect prints from both machines, then i had to keep hacking away and here i am.]]> GITRDUN General Sat, 06 Apr 2013 21:02:43 -0400 https://reprap.org/forum/read.php?1,197409,197944#msg-197944 Re: Eradicate backlash https://reprap.org/forum/read.php?1,197409,197944#msg-197944
This gives me a warm fuzzy.....:)

Have had several arguments about this, and usually you can't convince people of something they didn't find on Google.

I'm a French model.....]]> Dirty Steve General Sat, 06 Apr 2013 16:47:54 -0400 https://reprap.org/forum/read.php?1,197409,197828#msg-197828 Re: Eradicate backlash https://reprap.org/forum/read.php?1,197409,197828#msg-197828
Bearing slop isn't backlash but it gives similar looking results. LM8UU bearings have preload so should not have any slop as long as you use at least 2. They seem to have angular slop, which is why you need two. You do need precision rods to get the correct preload though and they eventually wear out and lose it. Bushings on the other hand always have some slop as they need some clearance or they would seize. The rolling balls in LM bearings avoid this problem.]]> nophead General Sat, 06 Apr 2013 07:46:40 -0400 https://reprap.org/forum/read.php?1,197409,197670#msg-197670 Re: Eradicate backlash https://reprap.org/forum/read.php?1,197409,197670#msg-197670
Also i noticed my X carriages have only about .001" ~ .0015" (.038mm) backlash. Id like to know why that is.]]> GITRDUN General Fri, 05 Apr 2013 14:07:07 -0400 https://reprap.org/forum/read.php?1,197409,197641#msg-197641 Re: Eradicate backlash https://reprap.org/forum/read.php?1,197409,197641#msg-197641 cobrageek General Fri, 05 Apr 2013 12:12:02 -0400 https://reprap.org/forum/read.php?1,197409,197639#msg-197639 Re: Eradicate backlash https://reprap.org/forum/read.php?1,197409,197639#msg-197639 -------------------------------------------------------
> @Traumflug
>
> Backlash Wiki
>
> backlash can be minimized, but not eliminated
> mechanically. A zero-backlash mechanical system
> would not be movable.

Backlash is just a fact of life. But software can compensate effectively if used right. Its not as much of a problem when making rectilinear moves but when you go to make a circle it will show up like an ugly sore. Ive been adjusting backlash comp settings on CNC machines for 15 years. Which is why i dont understand why my Sprinter software doesnt have anything to compensate for it.]]> GITRDUN General Fri, 05 Apr 2013 11:58:07 -0400 https://reprap.org/forum/read.php?1,197409,197633#msg-197633 Re: Eradicate backlash https://reprap.org/forum/read.php?1,197409,197633#msg-197633
Backlash Wiki

backlash can be minimized, but not eliminated mechanically. A zero-backlash mechanical system would not be movable.]]> Dirty Steve General Fri, 05 Apr 2013 10:56:30 -0400 https://reprap.org/forum/read.php?1,197409,197609#msg-197609 Re: Eradicate backlash https://reprap.org/forum/read.php?1,197409,197609#msg-197609
Gary H. Lucas]]> garyhlucas General Fri, 05 Apr 2013 08:50:56 -0400 https://reprap.org/forum/read.php?1,197409,197605#msg-197605 Re: Eradicate backlash https://reprap.org/forum/read.php?1,197409,197605#msg-197605 GITRDUN Wrote:
-------------------------------------------------------
> I think i have narrowed it down to the Y axis
> carriage. It is twisting side to side just a hair
> when reversing direction just enough to cause the
> backlash.

This is the kind of problem I was expecting you to find.]]> garyhlucas General Fri, 05 Apr 2013 08:45:37 -0400 https://reprap.org/forum/read.php?1,197409,197574#msg-197574 Re: Eradicate backlash https://reprap.org/forum/read.php?1,197409,197574#msg-197574
Quote

It is impossible to mechanically remove backlash 100% in a reversing mechanical system

It is possible. In fact, it's a requirement, because removing it by software at non-zero speeds is impossible.

I guess you have a reason to write this. What makes you think zero-backlash is impossible?]]> Traumflug General Fri, 05 Apr 2013 06:52:05 -0400 https://reprap.org/forum/read.php?1,197409,197503#msg-197503 Re: Eradicate backlash https://reprap.org/forum/read.php?1,197409,197503#msg-197503 www.thingiverse.com]

it is parametric, so it is adjustable in size]]> jamesdanielv General Thu, 04 Apr 2013 23:10:05 -0400 https://reprap.org/forum/read.php?1,197409,197500#msg-197500 Re: Eradicate backlash https://reprap.org/forum/read.php?1,197409,197500#msg-197500 GITRDUN General Thu, 04 Apr 2013 22:57:53 -0400 https://reprap.org/forum/read.php?1,197409,197468#msg-197468 Re: Eradicate backlash https://reprap.org/forum/read.php?1,197409,197468#msg-197468 Dirty Steve General Thu, 04 Apr 2013 18:37:31 -0400 https://reprap.org/forum/read.php?1,197409,197416#msg-197416 Re: Eradicate backlash https://reprap.org/forum/read.php?1,197409,197416#msg-197416
Hope this helps,
Gary H. Lucas]]> garyhlucas General Thu, 04 Apr 2013 15:16:14 -0400 https://reprap.org/forum/read.php?1,197409,197415#msg-197415 Re: Eradicate backlash https://reprap.org/forum/read.php?1,197409,197415#msg-197415 akhlut General Thu, 04 Apr 2013 15:14:32 -0400 https://reprap.org/forum/read.php?1,197409,197409#msg-197409 Eradicate backlash https://reprap.org/forum/read.php?1,197409,197409#msg-197409
What is the best solution to eliminate backlash on these printers? What have some of you came up with for your own printers? Is there a better alternative to the timing gear and belt?

I thought of making a tensioner pulley but how would that be any different than just making the belts as tight as possible? Ive fought this to the brink of madness, im stumped.]]> GITRDUN General Thu, 04 Apr 2013 14:51:04 -0400