Chains instead of belts on Rostock.

[lordbinky]

Has anyone investigated the use of roller chains or ladder chains instead of the belts on a Rostock? From what I can tell so far, the increased accuracy and consistency could be well worth the additional cost of the chain over a belt.

[cambo3d]

Ive seen some diy cnc machines that use chains, so i know its possible.

So question here is whether you want to devote the time and effort to finding correct parts in order to get it to work with the rostock parts.

if you get it working successfully, that would eliminate the wear/adjustment issues on the belt version and would be another option for others.

[lordbinky]

The parts should be straightforward and standard, pick a chain that fits in the run for the belt, 3 gear fittings, and likely 9 somethings to replace the roller bearings. I would think that will be less annoying than adjusting the software settings. I think the worst part is finding a supplier of decent chain for a reasonable price.

[lordbinky]

So I researched this and some other options a little since I don't have much else to do while I wait. It seems initial reprap designs using chains went to belts in part to minimize backlash.

Once I get running I will get back to this as soon as it's my limiting factor of whatever goal I have then.

[ApacheXMD]

What about a spectra fishing line conversion?

Graber has these spools to fit onto Kossel machines:
http://3d.grabercars.com/?product=filam ... for-kossel

We'd just need to figure out a grooved bearing cover for the idler pulleys so the spectra will roll nicely on them

[JohnStack]

What about a spectra fishing line conversion?

Graber has these spools to fit onto Kossel machines:
http://3d.grabercars.com/?product=filam ... for-kossel

We'd just need to figure out a grooved bearing cover for the idler pulleys so the spectra will roll nicely on them

So how would these be used? Two Steppers per axis running in the opposite direction or a single with ends wound in opposite directions?

[lordbinky]

I suppose you would get enough friction with 30 windings to run fishing filament similar to how the belts are setup on the rostock, although that's dubious because spectra is quite slick. Spectra doesn't have much stretch to it unlike normal monofilament fishing lines so that doesn't make it implausible either. Wear resistance is the other thing I'm completely unsure of.

As for spools, all other things being equal, their diameter will determine your steps per mm so you want to keep in mind whether you want to trade off possible accuracy with smaller diameters or greater speeds with larger diameter spool.

[ApacheXMD]

Just a list of stuff I've found regarding repraps and fishing line:

Steve Graber (the guy selling those spools) built a delta using fishing line:
https://groups.google.com/forum/#!topic ... 7iiwp2TyDI

Other deltas using fishing line:
http://richrap.blogspot.com/2013/04/ros ... build.html
http://www.youtube.com/watch?v=7qNsSOrZ9Oc

Johann (creator of the original Rostock) originally designed the Kossel with fishing line in mind, though I think it's using belts now:
https://groups.google.com/forum/#!topic ... PyHiZkdNcs
http://reprap.org/wiki/Kossel

And of course the amazingly small Tantillus reprap printer used spectra fishing line with great success:
http://www.tantillus.org/Home.html
http://reprap.org/wiki/Tantillus

The tantillus wiki says it uses only 5 wraps around a pulley to achieve enough friction to drive each axis, so 30 should be more than enough.

[Polygonhell]

My blog also has an entry on line drives.
The design of tantilus means it can't slip, the line goes through the rod and is wrapped on either side.
The issue with this configuration is that as the line winds it walks on the pulley, assuming you have enough space this isn't necessarily an issue. However, as the run of line gets longer, you run into issues where the line walking results in significant change in tension.
Doesn't mean you can't use it, just that the solution like most is imperfect.
Belts are generally a better more accurate solution, just more expensive.

[ApacheXMD]

My blog also has an entry on line drives.
The design of tantilus means it can't slip, the line goes through the rod and is wrapped on either side.
The issue with this configuration is that as the line winds it walks on the pulley, assuming you have enough space this isn't necessarily an issue. However, as the run of line gets longer, you run into issues where the line walking results in significant change in tension.
Doesn't mean you can't use it, just that the solution like most is imperfect.
Belts are generally a better more accurate solution, just more expensive.

That makes sense. But when you're looking at 60+ dollars for a belt change on the Rostock Max, the spectra starts looking pretty good.

[RichW]

I don't think chains are a good idea on the Rostock, or any printer for that matter. If something malfunctions with the belts, they will skip before causing serious damage. A chain drive might transmit enough force to result in injury to the machine or it's operator if not carefully designed. If I had to choose between a 2 mm rubber belt or a steel chain to get a finger caught, I'd choose the belt, --but maybe that's just me.

[foshon]

Rich I may be wrong, but I believe he is talking about polylink chain. It's fairly common, but would require changing the pulleys, the idlers, and one would have to design their own mounting system.

[RichW]

Oh, a plastic chain, --- Never mind.