Threaded rods vs pulleys for x and y axes

I'm currently designing my first 3D printer and whilst doing this I've noticed that threaded rods are always used for the z axis and pulleys are used for the x and y axes. Is there an advantage to using pulleys for the horizontal axes? I've heard that they're faster but more prone to jitter than threaded rods but couldn't the rods be sped up by using higher speed steppers?

Sorry if this has been discussed before - I couldn't find what I was looking for with a quick search

Andrew

Belts weigh less, are faster than a leadscrew, and eliminate the transfer of unwanted movement from a wobbly leadscrew, but there are workarounds for that.

For guides you also have the option of using V-slide, OpenRail, or makerslide rails.

[openbuildspartstore.com]
[makerslide.com]

Thanks A2. The belt does weigh less than a rod but the rod can take the place of a linear rail or other guide giving you the roughly the same weight for both methods. I hadn't considered that the rod might be wobbly but how likely is that if it's made well?

Andrew

Quote
Andycb
but the [[b]threaded[/b]] rod can take the place of a linear rail or other guide

Threaded rods are not used for guiding. That would be poor engineering, a bad practice, not recommended for precision applications, but fine for a toy. You might find a RepRap using a ground, harden recirculating ball screw as a linear guide, but it will still be considered a poor engineering practice.

Quote

I hadn't considered that the rod might be wobbly but how likely is that if it's made well?

I would think that every hardware store threaded rod ever made is not straight. You're comparing a threaded rod to a precision, harden, centerless ground linear rod.