First off remember that my experience is with fast moving gantry type extractors.
In any event the belts can wear significantly in areas of high acceleration causing position errors. I suppose any belt will do this but the design or mate up of the pulley and lugs seem to impact AT belts more. Now remember we are talking large gantries with high acceleration and saddles with more mass than the average router.
The interesting thing is that this localized wear is not as noticeable on smaller HTD derived belt systems. Here I’m talking pick and place, buffers, and the like. Of course the acceleration profiles can very widely and at times the drive is overmatched for the load.
On another note we have a few Fanuc/Cincinnati electric mold machines using very large Fanuc motors driving leadscrews and extruders. These use HTD type belts that are in some cases very wide. I’m actually surprised at the lifetimes on these belts. The axis strokes are relatively short and obviously on these sorts of machines the motion is back and forth constantly.
It might not even be a problem. There are all sorts of factors when it comes to belt wear as you know. It could be an issue with the design or the high acceleration. Note we have engineers that love to “speed things up” so that is a factor. What I find interesting is the high wear at points of acceleration but almost nothing in the other sections. This might indicate fewer problems with “random motion” machines like routers.My first machine used T and has given very good service. I have moved to AT as they are twice as stiff per width but they have not been used enough yet to comment. Comments appreciated.
Unless one can find the parts prebuilt it can be expensive. If a person has the ability to DIY the drives that can save money too. Perhaps the best bet is to look for used plastics machinery as parts donors. Even going the used equipment route has its pitfalls.As you say the peripherals of a belt drive do add up in cost. I do not like U drives as they reverse bend the belt and shorten their life and the idlers and mounts have to be made then this is $$$.
Little things like idlers do impact belt life. Having an idle of reasonably large diameter can make a big difference.
This is what I’ve found belt drives designed for positioning service can position reliably. Usually if there is a problem something else has happened. What is always the question is the belt drive good enough for the intended usage, usually that is a question of stiffnessSo I use a single run system, but this doubles the belt length so belt stiffness is important. To combat this I intend to run a stepper at each end of a simple belt system. Some people think this is a bad idea others don't know. The cost of the stepper is the same as the cost of the idler, mount etc.
I agree with your bullet list... especially about preload. If it's correct then the system once settled in is very stable. Cheers Peter S
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Note:
Used or old machinery can have its negatives. Special gear boxes that are no longer produced have caused us issues at work. This is where making sure the hardware on used equipment supports standard mounting interfaces is important. I recently had to source new gear boxes, come up with an adapter plate, and a custom pulley simply due to a custom gearbox no longer being produced. So while retrofiti g old plastics machinery has its positive it also has some negatives.