Why do we have belts?
I was looking at a DIY for a CNC machine this weekend and noticed it was using "screw rods" (sorry, don't know the proper name) for all 3 axis rather than just the Z like we do.
Wouldn't using those rods on all 3 axis have all kinds of benefits (less play/ghosting, less maintenance (e.g. not having to stay on top of the adjustments), better rigidity, etc..)? Are there downsides that I don't see/understand?
Are there any mods that have replaced the belts? If so, what are the actual results?
Re: Why do we have belts?
This being April Fool's Day, I'm required to respond with: "To keep our pants up."
That said, I think the straightness of rods has historically been a real problem. A lot of newer inexpensive printers are using extruded rails, apparently with good success.
and miscellaneous other tech projects
He is intelligent, but not experienced. His pattern indicates two dimensional thinking. -- Spock in Star Trek: The Wrath of Khan
Re: Why do we have belts?
Are there downsides that I don't see/understand?
* Slower movement
* More wear and tear
* Less precision
* More expensive
Often linked posts:
Going small with MMU2
Real Multi Material
My prints on Instagram
Re: Why do we have belts?
This being April Fool's Day, I'm required to respond with: "To keep our pants up."
Nicely done 
That said, I think the straightness of rods has historically been a real problem.
Why would that be an issue with X/Y, but OK for Z?
Are there downsides that I don't see/understand?
* Slower movement
* More wear and tear
* Less precision
* More expensive
(Note: Not arguing, trying to understand/learn)
Wouldn't the slower movement and precision issues just be a factor of the motor's capabilities and thread pitch? Obviously more powerful/accurate motors would add to the cost equation.
More wear & tear seems backwards to me. Without the belt to stretch and degrade I would expect there to be less wear/maintenance for the axis. Does the existing Z wear more than X/Y? Watching mine since Dec it appears that I need to take it down to clean and tighten the X/Y, but Z seems solid (though it won't surprise me if some bolts need tightening).
I guess costs of upgrading after the fact would quickly rise if you are talking about new motors to retain the current performance, but would it be as significant if Prusa shipped with those parts instead of the belt system?
Re: Why do we have belts?
Wouldn't the slower movement and precision issues just be a factor of the motor's capabilities and thread pitch? Obviously more powerful/accurate motors would add to the cost equation.
Correct. You would most likely need gears with all the disadvantages.
More wear & tear seems backwards to me. Without the belt to stretch and degrade I would expect there to be less wear/maintenance for the axis. Does the existing Z wear more than X/Y? Watching mine since Dec it appears that I need to take it down to clean and tighten the X/Y, but Z seems solid (though it won't surprise me if some bolts need tightening).
Let the motor hold the Z and then move the carriage up/down. After 1.5 years printing there was no need to replace the belt but the Z-nut had around 1mm play. It's not that pronounced on the print because you have a weight pushing it down. But on the X/Y-axes it would be horrible visible.
Try to picture it this way. There are no bearings between the rod and the nut. But you have great forces working back and force by accelerating and decelerating all the time.
I guess costs of upgrading after the fact would quickly rise if you are talking about new motors to retain the current performance, but would it be as significant if Prusa shipped with those parts instead of the belt system?
At the end every penny counts. People are claiming to pay a "Rolls Royce " price for their MK3 already. I think the reason why PR is so successful is because they are hitting the sweet spot between copy-cat Chinese printers and the boxed "ready-to-go" printers. Raising the price means to compete with other printers.
Often linked posts:
Going small with MMU2
Real Multi Material
My prints on Instagram
Re: Why do we have belts?
I think this is it. The Mk3 was designed roughly 2 years ago and is based on the technology and pricing available then. New developments might have Prusa thinking differently for their next FFF printer, if there is another.
[...] At the end every penny counts. People are claiming to pay a "Rolls Royce " price for their MK3 already. I think the reason why PR is so successful is because they are hitting the sweet spot between copy-cat Chinese printers and the boxed "ready-to-go" printers. Raising the price means to compete with other printers.
and miscellaneous other tech projects
He is intelligent, but not experienced. His pattern indicates two dimensional thinking. -- Spock in Star Trek: The Wrath of Khan
Re: Why do we have belts?
At the end every penny counts. People are claiming to pay a "Rolls Royce " price for their MK3 already. I think the reason why PR is so successful is because they are hitting the sweet spot between copy-cat Chinese printers and the boxed "ready-to-go" printers. Raising the price means to compete with other printers.
Definitely a good point. I've had people with Ultimakers be impressed with what my MK3 has produced, but you can get it pretty cheap as the kit (even assembled it's much cheaper than the "big boys").
And I'm honestly not complaining as this has been a great first printer. Just saw something different and wondered. Thanks for the insights.
Re: Why do we have belts?
There are mechanisms that are better at positional accuracy than the current Prusa design. But the metrology lab needed to keep it calibrated would pay to refill Prusa's print farm with new printers; monthly.
Re: Why do we have belts?
Linear rails could be an improvement but nobody wants to pay for them 😉
Re: Why do we have belts?
Linear rails could be an improvement but nobody wants to pay for them 😉
agreed
Re: Why do we have belts?
Linear rails could be an improvement but nobody wants to pay for them 😉
Thanks for naming the system for me.
😮 Yeah there would definitely need to be some significant improvements to justify the prices I'm seeing. Ouch.