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ayahoo

No pulley simple drive system

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Hi All, again with some crazy idea, in my line of work, we are using a drive system that uses friction to move many shafts over large distance.

The idea is simple, taking the two 8mm shafts, wrapping few wraps of cable (in our systems it is steel cable) then going to the second shaft, wrapping few wraps of cable and then connecting them in the middle with a tensioner.

the only thing that is needed to adopt the system is just to find the correct material (steel cable wire plastic nylon what ever) to use.

then we get cheaper system with less parts & much more accuracy.

I'm attaching some photos :)

Screen

System with plastic cable arrange

 

Untitled 1

just few wraps around the shaft.

waiting to hear what you think.

 

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Great link! this is the same idea :) now it is hard to assemble because he is not using any parts to allow easy assembly, but if we use some printed parts like the plastic part that i showed, it will help with the wrapping & we need just a simple part to connect the ends :), I think I'll try it since the accuracy of the pulley is not high, and using this system will greatly improve the accuracy.

Nice to know somebody already tried it :)

 

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since the accuracy of the pulley is not high

[citation needed]

I've never seen a something that indicated MXL or GT2 pulley accuracy problems. Cable stretching however, can be a real problem. Which is why steel cable is most likely a bad idea.

 

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The problem is not with the belts, the problem lies in the pulleys:

http://umforum.ultimaker.com/index.php?/topic/1611-fixing-pulley-innacuracy/

As you can see there are many complains about it.

Hihi, that's not many complains, just a bunch of people that notice they are not 100% centric.

But only 1 post that might indicate that it causes actual changes in the print.

 

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Does it even matter if the steel cables expand / contract? With the right construction this shouldn't matter:

The cables are only used to move the axes, and the endstops provide the "where is my zero" information. If you have a simple construction to even out the cable warping (like some strong spring at the ends of the cable) then it shouldn't matter: The motor makes 10 turns, the cable transmits 10 turns. Doesn't matter if the cable gets longer or shorter with time, or does it?

 

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Cable stretch introduces backlash, and backlash contributes to a number of problems including fills not properly filling, and dimensions not correctly printing. Honestly, the best means of "simplifying" for the sake of accuracy that I've been able to uncover is SG's direct drive conversion. The other option you would have would be to modify the gear ratios of the pulleys, but that has consequences on speed. For what it provides, the UM is a highly accurate FDM printer. If you need more accuracy than what a well built and calibrate UM provides, you likely need to consider some sort of SLS or SLA printer.

 

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