A new Z-axis nut - metal on metal w/ built in anti-backlash

discussion of design changes / improvements / suggestions
samc99us
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Re: A new Z-axis nut - metal on metal w/ built in anti-backl

Post by samc99us » Fri Mar 07, 2014 5:20 pm

ACME anti-backlash nuts already exist a@ dumpstercnc.com. Just need to make a mounting bracket.
Modified Shapeoko 2: 1500mm fully supported y-axis, 1000 mm 4060 x-axis, ACME Belt Drive Z-axis, Dewalt DNP611, full aluminum t-slot table, 4x NEMA23 180 oz/in stepper motors driven by a G540

WillAdams
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Re: A new Z-axis nut - metal on metal w/ built in anti-backl

Post by WillAdams » Fri Mar 07, 2014 5:21 pm

Unfortunately, I can't find a source of even the 8mm cross dowel nuts --- I don't think these exist in an Acme version.

jhilt67 did come up w/ a version for Acme which looked pretty straight-forward to manufacture though: http://www.shapeoko.com/forum/viewtopic.php?f=11&t=751 --- list of other options here: http://www.shapeoko.com/wiki/index.php/ ... the_forums
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Threefer
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Re: A new Z-axis nut - metal on metal w/ built in anti-backl

Post by Threefer » Tue Jul 08, 2014 6:47 pm

Link to a post I just made about this anti-backlash nut design.
http://www.shapeoko.com/forum/viewtopic ... 325#p28325
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Shapeoko# 3456, Makita RT0701c. Stock size for now but have 13"x13" travel by trimming down belt clamps and lip on smooth idler. Dovetailed wooden track clamping setup. Dust shoe in works.

Improbable Construct
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Re: A new Z-axis nut - metal on metal w/ built in anti-backl

Post by Improbable Construct » Tue Jul 08, 2014 7:26 pm

Is anyone actually having backlash problems with their ACME nuts?

I have looked at a few different designs (and tried a couple) but really feel they are unnecessary.
I have been running the same Delrin nut on a few different machines for quite a while and it still has no measurable backlash.
If you are having depth issues a better place to look is in the Z to X axis transition. There is often a fair amount of twist there.
An anti-backlash nut on a shapeoko is like 6 piston Wilwood brakes on a golf cart.

Also:
If you are running steel nuts on steel screws you need to have some sort of lubrication or the steel on steel will cause friction and heat and quickly wear out the softer of the two. Oil and grease are good choices for lubrication but are bad for CNC routers because they tend to capture dust and other grit that also causes premature wear.

Anti-backlash nuts also increase the amount of friction on the screw, requiring more torque which often means less speed, to turn it.
Shapeoko #Classified some of the bolts may be original parts.
Shapeoko 1 # ???? Stainless plates, still in the box.
Shapeoko 2 # 3926 not stock
Shapeoko 3 # 0003
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Threefer
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Re: A new Z-axis nut - metal on metal w/ built in anti-backl

Post by Threefer » Tue Jul 08, 2014 10:17 pm

I was really just doing it for fun, experimentation, and practice in designing for 3D printed parts to print on my new Printrbot Simple. I recently bought some filament on Amazon and ended up buying a pack of the cross dowel nuts to play with. I did notice that when removing the delrin nut there wasn't much slack at all so this mod may be unnecessary, but I could see increasing wear in the delrin possibly becoming a problem if you mill alot of contoured parts where the Z moves up and down constantly. The anti-backlash nut in that situation may be a better solution, but it may be necessary to get a bigger stepper because of the increased resistance. I'll eventually do some testing when I get bored with my new 3D printer.
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Shapeoko# 3456, Makita RT0701c. Stock size for now but have 13"x13" travel by trimming down belt clamps and lip on smooth idler. Dovetailed wooden track clamping setup. Dust shoe in works.

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