Acme Vs. Threaded Rod

Hi, I'm building a repstrap soon and I found some cheap threaded rod at the hardware store that seems to have very little back lash when combined with the matching nut and seems to be quite straight. I was wondering if you guys thing it's worth it to start with that as my lead screws or should I invest in some good Acme threaded rods right off the bat. My goal is to have accuracy within a millimeter for my prints.

Threaded rod works fine on the Mendel and Darwin Z axis; resolution is about 0.003 mm/step on a direct threaded rod drive. Most people have trouble running the X and Y fast enough with threaded rod though, thus the belt drives.

Standard nuts are not precise enough to be used as a lead screw. I ended up with these, the spreading end cut off:



Made from brass, they pair nicely with a steel rod for a good bearing combination. Probably there are more examples of brass pieces with an extra-long thread.

And yes, threaded rods are precise, but not the fastest. With standard firmware, you don't have acceleration ramps and can expect about 600 turns/min for the usual steppers. Acceleration ramping will extend this to about double the speed. Multiply this with your thread's pitch to get speed numbers.

Typical Mendels run between 10 mm/s and 50 mm/s, according to some posts in this forum.

Keep in mind filament extruding machines require a lot of "mileage", a lot more than milling. For getting started or extra-precise requirements, rods should be fine, though.

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Generation 7 Electronics	Teacup Firmware	RepRap DIY

The M5 rod in WolfStrap seems to be enough to get these results:
[forums.reprap.org]
[reprap.org]

But you may want to try a toothed-belt WolfStrap
[reprap.org]

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-Sebastien, RepRap.org library gnome.

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Remember, you're all RepRap developers (once you've joined the super-secret developer mailing list), and the wiki, RepRap.org, [reprap.org] is for everyone and everything!

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SebastienBailard
The M5 rod in WolfStrap seems to be enough to get these results:

Small correction: For the two fast axes, Wolfgang had M10 rods, just for the higher pitch:

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Wiki page
Threaded rod 2x approximately 350mm M10; X-Y-axis (I started out with M5s, which I cannot recommend. The machine will move too slow)

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Generation 7 Electronics	Teacup Firmware	RepRap DIY