Unanswered Upgrade z axis to acme screw lead screws?

I am very impressed with my R1 so far. However, my only complaint, and its not limited to this machine, but almost all lower cost printers, is the standard threaded rod for the z axis. standard threaded rod is not built for precision movement.

I have built several CNC routers, which are basically just larger versions of a 3d printer. When using a lead screw, i always used an acme rod, as it has no play, much less friction, and is more precise.

Has anyone looked into swapping in acme screws for the z axis? There may be a variation on the steps per inch, but this can be corrected in the firmware, correct?

 

I don't think there's anything really intrinsically wrong with the standard coarse thread screws.

I did upgrade to lead screws though. I'm fairly confident that all my issues stemmed from the helical couplers and not the screws themselves.

 

what did you do to resolve the issues with the couplers?

 

I believe Mike installed steppers where the screw is the motor shaft.

 

I got a set of helicals from robo, one of them was bad. I bought 2 of my own. Seems to have mostly resolved it.


@donhuevo was the one who installed linear stepper motors: http://www.omc-stepperonline.com/th...per-motor-48mm-body-300mm-t635-x-2-p-225.html

 

as anyone looked into a more rigid coupler? I never liked the helical on my cnc router.

 

You'd probably need to machine one as I've never come across a 8mm to 5mm rigid coupler (for a decent price)

 

what do you consider a decent price? I guess a machine shop could mill me up a set.

 

less than $10 per coupler.

I'd suggest buying a 5mm rigid coupling or smaller and bored to 5mm.

Then drill one side to 8mm, or tapped for M8/5/16" depending on your threaded rod size.

You probably wouldn't need a machine shop for that.

Also having trouble finding a 5mm solid, this was the closest I found: http://www.mcmaster.com/#2424k9/=w4zi8v

 

I had one bad HC and really bent threaded rods, robo sent me new ones, only one HC was good in that pair, both threaded rods were fine and took care of my ribbing issues, I also did the ball bearing in the HC, following Ziggy's guide. The current HC do not fit even the new R1 without some gunk or tape on them, I did 3 even wraps of aluminum foil with some thread lock let it sit over night in the HC then super glue it after its tightened down.
If we could find decent HC's then problem solved for most.

 

What about these?
http://www.ebay.com/itm/Set-of-2-Sh...710?pt=LH_DefaultDomain_0&hash=item27f9cda606
or
http://www.ebay.com/itm/5mm-x-8mm-5...155?pt=LH_DefaultDomain_0&hash=item27f8809623

And are their any down side of using solid coupler?

 

Major potential downside is torque stall. Especially if you use coarse threads. Because they're not pure trapezoidal shapes when the nut moves around it it kinda spins in a sinusoidal pattern. The helical couplers account for this.

If you use a lead screw they'd be good because that movement is more flat. Though it may require more torque and more precise calibration.

Thanks for finding those. I'm gonna look around for some 5mm to 5mm as well

 

Here you go.
http://www.ebay.com/itm/5mm-x-5mm-R...741?pt=LH_DefaultDomain_0&hash=item27f8808cb5

And might something like this be the best of both worlds?

http://www.ebay.com/itm/BF-5mm-X-8m...681?pt=LH_DefaultDomain_0&hash=item2a3a06b5a9

 

Yeah spider couplings are almost always better.

I found some 5x5 helicals I wanna try first. I'm not really getting ribbing right now but i can get a few more mm of travel if I flip my rods around. http://store.makerstoolworks.com/motion/single-start-lead-screw-and-nut-single/

 

Personally I'd skip Acme thread lead screws and go ahead and upgrade to actual ball screws and ball nuts. They are extremely precise, and from my hunting around not expensive at all for 8mm diameter ball screws.

 

If you find 300mm+ ball screws and nuts for less than $20/side please share

 

Here is one source: http://www.zappautomation.co.uk/mec...ews/miniature-ballscrews-6-12mm-diameter.html

 

£33 for 300mm, not including a nut.

Too rich for my blood.