Does anyone have any ideas on how to align this belt carriage? Perhaps a jig of some kind?

Hello all,

I’ve run into frequent issues with the x-axis belt on these machines, particularly the larger ones, and wanted to see if any of y’all have any wisdom you can share on aligning the belt carriage so the belts do not have uneven tension on them, which causes them to be pulled onto their bearings on the end and ultimately destroys the belt.

Do any of y’all have any thoughts on how I can ensure the carriage is perfectly aligned? I was thinking a box jig with channels cut for the rails/belts may work, but am unsure. Eyeballing it has had mixed results so far.

Really can’t see enough of it to tell… I have a different belt system on mine…

Many of these have really low cost pulleys on the ends… either have to accept the best adjustment or modify them to your liking…

There are a lot of these out there and I wonder what issues you are having to diagnose it as uneven belt tension. These belts are timing belts and seem to last a long time…

Do you see odd output or?


I apologize, I can take more pictures tomorroe at work!

The belts get pulled onto their bearings on the end and the bearing grinds away the rubber of the belt. Then the wires get exposed and caught up in the bearings and materials get ruined, costing quite a bit of time and money.

We think its because the carriage in the picture I posted has some vertical wiggle room and being pulled upward or downward compared to the bearings on either end causes uneven tension.

Definitely sounds like it’s an issue… Never seen a factory machine, so that…

When it bids like that it affects the speed…

I have a low cost bracket that came on my machine…

When I get moving I’ll take a photo and post it for you… Assume it’s the end without the motor?


I believe you have a belt tracking issue, not a frame alignment issue.

A belt will walk across the face of a pulley (bearing?) or roller because the tension on the sides of the belt are different. A crown roller (larger in the middle) is one solution. The other is the ability to tilt the mounting that fastens the belt. By this, I mean the belt tensioner is not movable on one side, and slotted on the other side. You can get a better understanding by Googling “conveyor belt tracking”.

Just so you know, you will be very lucky if you get it right on the first try. And to get it right, start with a new belt.

I would think a factory built machine wouldn’t have this issue…


Yeah, like diode lasers should have solid mechanical construction and a good configuration right out of the box. I’d cry a single tear every time somebody unboxes a lemon of a tabletop laser, but I’m running out of juice …

If there is anything loose in there, fix that before doing anything else, because all the other adjustments depend on stable mechanical parts.

The Gates World of Timing Belts book (download & rename without the .txt) @jkwilborn linked to has a checklist of tracking gotchas in Section 9.7. From the picture, getting the belt lined up with the pulleys would be the first step, because the anchor points on the laser head look badly offset.

Timing belts don’t use crowned pulleys, so the idler pulley may need an angular alignment adjustment (after the belt gets lined up) to equalize the tension on both sides.

They recommend Moah! Tension! as a cure for tracking problems, but none of their tension measurement techniques seem feasible without the specialized instrumentation none of us have.

I get the distinct impression all of the adjustments must be done while checking the results, so a fixture to align the pulleys won’t be sufficient.

Yes, the issues arise at the end without the motor! Thank you for your help.

Will do, thank you!

How did I miss this? I cannot find it (the link, I got the file)…

I confess: it was faster to dig it out of my browser history than figure out which keywords would unearth it here. :grin:

Hahaha! Fair enuff. The path of least resistance.