I’ve had my machine for over 6 months and have not had a belt break.
Take a picture look down into the Xcarriage showing the X stepper pulley and belt.
Do the idler wheels turn freely?
It looks like its riding the outer edge of the idler and the stepper pulley. I’d expect it to be more centered on both.
I’ll take a picture of mine when I get home to show you what I mean.
Can you please send the broken belt back to Inventables for testing and we can send you some new belts?
So, funny story, I went to check my pulleys and 2 of 3 were slightly out of alignment. I guess when I upgraded my steppers, I did a poor job aligning the pulleys on the new steppers. Correcting it was actually simple, leave the belt tensioned, loosen the set screws and slowly push the pulley outward. Tighten the screws back down and then slowly move the axis back/right and then front/left. Then check the belt location on the pulley. You should see aluminum on both sides of the belt on the pulley.
Here’s out of alignment:
And how I corrected them enough to prevent edge loading (and unless it’s just camera angle, I may adjust one of the Y pulleys again):
I broke a few belts on my machine because the pulleys werent aligned properly. I visually checked them 1000 times and they looked good but the belt would ride against the flange on one of the pulleys. Adjusted them so the belt didnt touch the flange and its been fine ever since
Edit: Mine looked just like justins pictures above!
Thanks Zach , I received the belt today
Thanks for all the comuinty who write in this issue
I think there are two things causing break the belt
The aliment and the tension
Tomorrow I will change the belt and do these things
i am currently building my machine and i came across this post prior to starting and i knew to pay close attention to the position of where the belts are hitting the pulleys.
seems that the belt is riding against the stepper pulleys AND the drive pulley.
i removed the X motor to see if maybe some debris or something wasn’t seated properly. clean as a whistle…
so i decided to look for set screws. and there are none on the nema 23 motors?
i’m afraid to continue hahaha because i am a perfectionist and i’d rather not run the risk of breaking a belt during a job.
any suggestions?
Thanks,
Mac
The stepper motor pulleys on the newer (current) kits are pressed on - no set screws.
i see that haha so the question stands what should i do?
Are your belt clips straight? They can end up twisted when tightening down, which pulls the belt to one side or the other.
i noticed that also when tightening and they are parallel to the gantry rail. i wedged a flat head to the one side to keep them from moving while i was tightening the belt clips
On my 100th plus carve and broke a belt 
Not too happy about it. Haven’t changed anything or adjusted anything. Been running into more and more issues with my X-Carve. Looking for a different CNC honestly. I will be posting mine for sell if my luck or this machines shortcomings continue.
That looks more like it is probably due to the condition of the machine. I would look into dust collection. The V-Wheels are supposed to be riding on clean V-Rails and when there is a large enough chunk of something on the rails the machine might experience binding. The stepper motor, on the other hand, just keeps on chugging; it will cause the pulley to shed that belt very quickly.
{:0)
Brandon Parker
Judging by the photos of your machine, I wouldn’t be blaming the X-Carve !