Interesting belt drive concept

Just ran across this in a CNC forum.
ServoBelt
This apparently combines the traditional belt drive's acceleration and speed with improved positioning stiffness and accuracy. On the negative side, this requires putting the motor in the moving mass, so this probably isn't a good idea for dedicated FDM machines. But it might be a good option for hybrid fabrication machines (machines capable of both FDM and subtractive methods).

Also requires a belt rack for the belt to engage in, but it is pretty cool. I'm not sure exactly what the advantage to this is over just a regular rack & pinion though...not much, except you can tension the belt to reduce backlash.

Here's the full thread for it on CNCZone:
[www.cnczone.com]

I have had that style drive system on my cnc machines for like 5 yrs..nothing new lots of people out there doing that..he will probably have a problem actually getting the patent as so many people are using that set up all ready..I stopped using it as it is always a p.i.t.a to properly tension the belts.As going under one idler then over the pulley to go under another idler and having them smashed between the rail makes it near impossible to get the belt tight between the idlers and pulley.. So it allowed for alot of backlash..They are probably tensioning the belt before putting the assembly on the rail ..That's what i had to do with mine but still didn't give the best results most of the time..

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tm america
I have had that style drive system on my cnc machines for like 5 yrs..nothing new lots of people out there doing that..he will probably have a problem actually getting the patent as so many people are using that set up all ready.

I'm going to guess you didn't notice the original thread and video were posted 6 1/2 years ago. It might have been a known concept even then, but saying you were doing it 5 years ago doesn't support the idea wouldn't be able to be patented 6 years ago.

... the idea is much older than 6 years - it's an 'inverted' belt-drive with only half the length than a normal one, but you have to move the motor with the wires, while it's fixed in the common types.

I've used a different setup with two adjacent belts, stretched with different forces (to change the tooth spacing between them) and only connected under the moving head to get a 'dislocated nano-positioner' - if I'll move the head along the two belts over one meter, the loose end of the 'active' belt will displace only the difference in tooth spacing ... this was normally set to 1:100000 - so 10mm head moving will result in 0.1mm positioning of the nano-positioner fixed to the end of the belt

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Viktor
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@VDX,

This sounds neat.
Can you provide a pic or something to help me better understand the concept.

... no pics - but if you are aware of the flex-spline in a harmonic drive, this is a similar concept, where the 'tooth-displacement' ist made by the difference in the inner and outer teeth counts. With the flex spline the two adjacent positions are 'in contact' ... and while rotating the inner gear, the outer ring is diplaced exactly the teeth difference between inner and outer numbers per revolution.

*** EDIT ***
Look here on the picture (or follow the links) - [de.wikipedia.org]

The image shows a flex-spline with only outer teeth, but the principle of 'diplacing' for different teeht counts between the outer ring gear and the flex spline is the same ... and this is possible with a linear setup, as with my two differently stretched tooth belts ...

Edited 1 time(s). Last edit at 12/05/2014 02:44AM by VDX.

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Viktor
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Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

@VDX,

Tks,
So I'm thinking that in the case of the servo belt, if I apply tension to the stationary belt opposite to the tension being applied to the belt winding around the drive pulley I could reduce backlash?

... yes, this should eliminate eventual backlash ...

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Viktor
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Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

Ok after reading thru the whole cnc zone thread i see this is similar but different than what i was running..Mainly he has a belt attached to the rail that the other belt is meshed into.. so this would eliminate needing to tension the sides between the idlers and the ends..And i see he is moving the stepper motor up and down to adjust the belt .So this can help with the ability to properly tension the belt .. The main questions or possible issues i see are....First how much heat or wear is made from having the two rubber surfaces hitting eachother ?second the type of belt he is using has clearance in the teeth to the pulley so even with all of that under heavy loads you would still have some backlash?Sure it would be better than most But might be better served with a different belt profile?

Edited 1 time(s). Last edit at 12/10/2014 06:32PM by tm america.