Was wondering why most people dont use lead screws for the Z axis.

Was wondering why most people dont use lead screws for the Z axis. Is this mainly a cost thing or is there other reasons

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I’ve built a few Mendel/Prusa types from all thread, which is both cheap and abundant at most home centers.
And while its not precision worm drive, its pretty darned good for being so Inexpensive.
For the actual “Z” axis drive screws, I do go with metric sizes 8mm being a favorite. But in the U.S. these sometimes
Have to be special ordered. But they are still less expensive than any milled/machine part of the same size.
So save your bux, for the “Buck Rogers” stuff like micro-controllers and hot ends.

Ya I have a mendal as well and have used the allthread and it worked great for me. I’m just wondering why everyone uses the allthread and if there is any real benifit to get a lead screw instead

Yes, I think it’s mostly a cost thing, but I also think lead screws are usually much bigger than what is necessary for our printers. I would like to swap my 3/8-12 ACME rods for metric lead screws, but apparently there’s nothing smaller than M12 which is insanely big.

You can get 6,8 and 10 mm in Europe. The lead screw’s are not that expensive it’s the nut that the expensive bit.

I haven’t looked to see if they go small enough but i knew they cost alot

I use stepper motors and gear with track, rack and pinion milling capable… Puts the power into it ISO tweaking a puny screw drive… Just my preferred path… its based on ez router 4x4 table. That’s feet…I understand the 3d print head isn’t milling but you get precision from gear stepper and track.

Alex, was that a joke? Lead screws are not made of lead. In this context lead is a synonym of “guide”, leading. English is an imprecise language. :wink:

Openbuilds sell inexpensive lead screws now and delrin nuts. Wish they had done it earlier. I paid much more for my Misumi leads. But I will admit the Misumi ones are top grade.

Thanks for the info, @Eclsnowman , unfortunately they’re out of stock on the 8mm trapezoidal lead screws.

I just noticed they have 8mm travel per revolution. I’m not sure it’s suited to Z axis on a RepRap printer… It’s more for fast travel.

To get good results, you need a metric pitch, and trapezoidal (the metric version of ACME) screws have always been much harder to find, especially in the smaller sizes we need). I’d say that the TR88 size that’s now becoming more common is right on the edge of being too big, and is better when paired with a .9-degree stepper. The less common TR52 thread is a better match, but I haven’t been able to find a supplier for that, either integrated into a standard NEMA17 stepper (Robotdigg has them on a NEMA14) or in acceptable lengths (for most other applications, it’s probably too flimsy at the lengths we need) to be coupled to a shaft the way we do with cheap threaded rod.

The openbuilds leadscrew nut really needs to have some sort of anti backlash on it.

What about ball screws? Do they provide any benefit? Better, worse?

@Michael_Spano_Jr_Ama ballscrews are good for x&y, but z is a no-no, they have such low friction that they will back run under gravity if not braked in some way.

Ah

I use Igus 8mm x 1.5 pitch trapezoidal lead screws with DryLin nuts and they work great but there are many sources of error with the alignment/spacing of lead screws, nuts, couplers, etc. that I could’ve chased down first before I would’ve noticed much of a benefit from the more precise lead screws.

you can also find good leadscrews on ebay. Just search for gizmocnc.

@James_Zatopa Those are all ACME screws with a 2.54mm pitch. If you lose these screws, your steps/mm value will be a non-terminating decimal, which means you WILL have rounding errors in your layer heights, which cause banding in prints. This looks like Z wobble, but no amount of calibration can get rid of it. DO NOT use those screws.

Yes there is a rounding error if you print at tenths of a mm. I have not had any problems on my MM 1.5 running acme screw. Check out the http://calculator.josefprusa.cz/ and plug in info for a standard thread rod. Using 1/4"-16 you can see that if you set your step height to .2937 or .3016 you will not have an error. If I print @ .3 I get an error of .53mm over 10cm, an error but a small one. I guess I should have pointed that out.