@WillAdams Typically there is a “minimum” bend radius for belts, since a tighter bend is worse for belt fatigue. So are you saying that the SO3 has a smaller bend radius with its size pulleys than the manufacturer’s spec, or the other way around?
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The SO3 with its very high pulley engagement has a very tight bend radius (wrapped almost fully around the pulley — fortunately, the idlers are larger in diameter).
There was a bit of discussion at:
I’m not involved in product testing or specification, just do off-site support a bit and kibitz on the forums some — when I installed them on my SO3 the installation was much easier than a typical belt install, and the belt tension seemed much more even with much less fussing, which is the reason why I presume they were changed to.
Any specification is written to an average performance expectation — the use of a Shapeoko or Nomad seems to be intermittent/occasional, so belt replacement shouldn’t be too onerous an expense. Folks running the machines in light production can just factor in the cost of on-going replacement, and if it doesn’t make economic sense, switch back to fiberglass (or try Kevlar) — the original belts work fine when correctly tensioned, it’s just trickier, esp. the first time.
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Yes, as @WillAdams says, the bend radius is awfully tight. As I said, I’ve got both, after I run out of steel, I’ll likely replace from there with Kevlar.
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Because of hardware, software, and/or other inadequacies?
I think the steel belts suffer from over tensioning easier as well. Also being able to visually see a failure before the belt just snaps is better imo.
My first set gave 8 months of hard use and and I change mine out after 6 months or so, always thought belts were a consumable lol.
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I think you’re right @Vince.Fab - over tensioning is easier, but I’ve also found they stretch far less over time as well. The fiberglass belts seem to get progressively more loose, then suddenly more so. The steel ones seem to hold tension pretty well right up until they fail. I’ve also measured that when installing the steel and kevlar belts that they stretch much less during install. My steel belts were calibrating in at 80.022 steps/mm (microstepping 2x more than stock) for steel, and 80.066 for the kevlar. I was nearly 82 steps/mm on fiberglass. You use your machine far more heavily than I do mine!
Although I agree that steel isn’t probably the best choice, it was worth the experiment. I’ll use my last length of steel, and switch back to kevlar.
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I’m running fiberglass reinforced belts on my machine, for 3+ years. I did have an issue with my X axis breaking but it was caused by the stepper pulley coming a little loose and then getting stuck to where the belt had been rubbing on the carriage until it was weak enough to just break. Aside from that haven’t had to replace them at all. Fingers crossed!
sure but vince is a bit closer to https://www.youtube.com/watch?v=1nyuby7oA6w than most other folks
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