Belt drive on a router

[JAZZCNC]

Belts offer numerous advantages for driving ballscrews, the stretch is almost invariably negligible there since the belts are very short. However if you're using belts to replace ballscrews (i.e. the subject of this thread), then the stretch will be a factor - otherwise belt driven machines would be good for machining more than just soft materials.

Oh here we go.!!! . . . My machines is nearly 1500mm wide so thats over 3000mm long belt and stretch hasn't affected it yet.! This belt has been on machine probably coming up 2yrs, the first which I damaged had been on over 2yrs and hadn't stretched in that time.!

It's all relative to the machine and work load and I know, Again thru experience, that this size machine doing the kind of work John intends then it will be a very very long time before belt stretch even remotely comes into the frame.!! . . . Yes they clearly will stretch over time that's a given but ball-screws wear-out and I know a good quality belt will last just nearly has long has any Chinese ball-screw.!!

[Jonathan]

We're talking about different things. I'm not talking about the belts stretching over time (since as you say that just doesn't affect us). I'm saying when you apply a force to a belt it will stretch then spring back when you remove the force. So I agreed that when driving a ballscrew with a belt there's no problem. However I thought John S was asking about using the belt instead of a ballscrew? I.e. long open belts on either side of the gantry to push it along...

[JAZZCNC]

We're talking about different things. I'm not talking about the belts stretching over time (since as you say that just doesn't affect us). I'm saying when you apply a force to a belt it will stretch then spring back when you remove the force. So I agreed that when driving a ballscrew with a belt there's no problem. However I thought John S was asking about using the belt instead of a ballscrew? I.e. long open belts on either side of the gantry to push it along...

Ermm Ok but still the same applies in John's application belts will be fine.

[boldford]

I'm unsure where I saw it but one idea is to have the belt that wraps round the gantry mounted stepper motor meshed with another length of open belt firmly fixed to the machine bed. The only length of belt "unsupported" is that short length which is picked up to wrap round two idlers and the toothed pulley on the stepper motor IYSWIM.

You could also try the alternative of roller chain.

[John S]

I.e. long open belts on either side of the gantry to push it along...

I was thinking more about pulling it, tried pushing a bit of string years ago and not a good experiment

[boldford]

I was thinking more about pulling it, tried pushing a bit of string years ago and not a good experiment

Bit like putting a sausage up an entry.
Have you looked at http://www.mycncuk.com/forums/linear...elt-drive.html