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SoliForum - 3D Printing Community → Hacks & Mods → Mounting a New Anti Backlash Nut
getting the torque back
Full step torque is constant wrt micro stepping. By extension, increased micro stepping resolution does not change the holding torque at multiples of the original micro stepping resolution.
1/32 = some fraction of 1/16 holding torque
2/32 = same as 1/16 holding torque
3/32 = some duration of 1/16 holding torque
4/32 = same as 1/16 holding torque
etc...
Ball screws are more efficient that lead screws as they have less friction. The lower friction coefficient, means they can be driven faster without wear and tear, and impose a smaller load on the motor (require less torque).
Agreed. Note that MC's leadscrew came with a stepper motor permanently attached to it too - that was one of the attractions, and probably brings the price up a bit...
No doubt it would be beautiful, but I would think that for the SD z-axis a ballscrew is way overkill. They're indispensable if you need to apply a bit of force with the axis (e.g. cutting machines) and still want no backlash, but the backlash nut will be more than capable in this case. As long as the motor can handle it, a bit of friction won't be a killer here either - esp. as the z-axis can be pretty slow and it doesn't matter too much.
The trapezoidal thread may be made more accurately than the usual M3/M5 threaded rods that are used commonly as a z-axis upgrade - I can see this being pretty slick! Looking forward to seeing some smooth prints. 
adrian wrote:getting the torque back
Full step torque is constant wrt micro stepping. By extension, increased micro stepping resolution does not change the holding torque at multiples of the original micro stepping resolution.
1/32 = some fraction of 1/16 holding torque
2/32 = same as 1/16 holding torque
3/32 = some duration of 1/16 holding torque
4/32 = same as 1/16 holding torqueetc...
was in reference to torque of movement at 1/4 vs 1/16 vs 1/32 etc, where there is a degradation of the torque applied relative to the torque that can be applied as a full step..... not that its different within bands of steps within the same steps
anyway - wrt to the whole steps things in the specific instance - I never looked at the specs and just took molecular concepts word for it being 8*2 
so my apologies for the bum steer there but at least that got sorted out
pirvan wrote:Ball screws are more efficient that lead screws as they have less friction. The lower friction coefficient, means they can be driven faster without wear and tear, and impose a smaller load on the motor (require less torque).
Agreed. Note that MC's leadscrew came with a stepper motor permanently attached to it too - that was one of the attractions, and probably brings the price up a bit...
No doubt it would be beautiful, but I would think that for the SD z-axis a ballscrew is way overkill. They're indispensable if you need to apply a bit of force with the axis (e.g. cutting machines) and still want no backlash, but the backlash nut will be more than capable in this case. As long as the motor can handle it, a bit of friction won't be a killer here either - esp. as the z-axis can be pretty slow and it doesn't matter too much.
The trapezoidal thread may be made more accurately than the usual M3/M5 threaded rods that are used commonly as a z-axis upgrade - I can see this being pretty slick! Looking forward to seeing some smooth prints.
It's still an issue of cost.
I agree that buying a ballscrew from one of the major hardware places like McMaster Carr would cost a small fortune, but there are a lot of cheaper alternatives.
There are many Chinese vendors on eBay selling them for cheap. I bought a SFU1204 x 350mm screw for like $40 shipped, then got a 8mm x 5mm flex adapter for another $5-6.
My conversion to a ball screw cost less than $50.00 in parts, and installation on the aluminum bed takes about 15 minutes.
http://www.soliforum.com/post/42550/#p42550
it was 75 including shipping it was 36 for the nema 17 leadscrew combo and 10 for the anti backlash nut to 46 total 28 shipping basically i paid more for shipping.
and apart from me screwing it up and now its loud but still works
You guys should know that ordering from Derek from Robotdigg he usually quotes fedex. You can always ask him to price HKpost and get the shipping cheap.
prints are noticeably smoother. the bed is pretty sturdy too. im workin on getting some pics up.
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