Zaribo Y axis lead screw conversion by slink6

Last crawled date: 3 years ago

This is a mount for a nema 17 motor mounting to a 3030 extrusion. This orients the motor so that you can replace the belt driven Y axis with a lead screw.
Links below for the lead screw, Tnut, and Tnut holder. Your particular application may vary with the difference in height between the 3030 extrusion and your Y axis bed plate. I needed to add two washers as spacers to maintain alignment of the lead screw from the motor to the idler bearing.
I found the easiest way to acheive proper alignment between the Tnut holder, motor, and idler bearing was:
-First mount the Tnut and holder to the Ycarrage plate
-install the motor / motor mount and idler bearing onto the 3030 extrusion. Install the mounting hardware but do not tighten down full into the 3030 channel nuts at this time. They should move freely along the extrusion with minimal effort.
-insert the lead screw through the idler bearing, and into the Tnut. Continue screwing the lead screw until you can insert it until the coupling, attaching it to the motor.
at this point it will be obvious if you need to adjust the heights (raise the motor mount and the idler bearing, and or lower the Tnut holder by adding a spacer between the plate and the holder. I printed a small spacer block to lower the holder, and used washers to raise the motor mount and the idler bearing)
-assuming at this point the 3 parts (motor mount, Tnut holder, and idler bearing) are in vertical alignment with one another we now have to achieve horizontal alignment. Misalignment will be obvious as the Tnut will bind on the lead screw if alignment is too far off, and feel more resistant when slightly off.
-position the motor mount and idler bearing so that the lead screw appears as straight as possible. manually rotate the lead screw to move the bed to the rear. The motor mount should be loose enough that the tension of a misaligned lead screw will move it to a more aligned position as you get closer to the motor mount with the Tnut holder. If you need to, manually slide the motor mount along until there is the least amount of resistance possible when you manually turn the screw. Move the bed to it's most forward position and do the same with the Idler bearing, trying to achieve the least amount of resistance when you turn the screw.
-Move the bed back to the rear most position, continue to correct the position of the motor mount if needed and tighten the motor mount down to the extrusion.
-Now again manually turn the screw to move the bed to the most forward position, adjusting the idler bearing's position if required. Once you find the lowest resistance position, tighten down the idler bearing.
-Now that both the motor mount and the idler bearing are tightened down, manually rotate the screw through the entire possible travel distance the bed can make, all the way back and all the way forward. The resistance felt as you turn the screw should be minimal, and constant and not varied at this point.
if you are confident in your motor and idler position but still feel increased resistance towards the fully forward and fully rearward positions, the likely issue is that your vertical alignment is off. Binding will be most obvious at the extreme positions, nearest the motor and the idler. Re assess the height difference between your motor, idler, and Tnut. Adjust the number of washers you are using to raise the motor and idler or lower the Tnut holder by using a thicker spacer if needed.
-when you have achieved proper alignment in both vertical and horizontal you will not notice an increase in resistance when you turn the screw at the maximum forward and rearward positions.
-You will need to mount your Yaxis end stop switch to the motor mount (see my picture) The position will depend on the height of your Y carriage plate. I positioned mine after printing when I could fit the switch to the plate properly. Drill 2 small holes and screw into the plastic.
I use lithium grease on the lead screw to aid in smooth operation, but many do not. This seems to be up to you.
-Use the prusa calculator to determine your new steps / mm value to input to your firmware's Yaxis steps/mm value.
(if you use a 2mm pitch, 14mm lead lead screw like I did the value you will use is 228.57)
a word on motor / shaft couples
you have really only two options when it comes to coupling your leadscrew to the motor, either a rigid or flexible coupler.
The flexible option is the better choice in my opinion, as it will allow for some slight misalignment between the motor and the lead screw. There is an important exception however:
If you are using a large bed / heavy Y carriage plate like I do, you will want to use a rigid coupling. The inertia of the larger bed/carriage plate will cause a flexable coupling to expand slightly (like a spring) when the motor changes direction rapidly. This may not be an issue with a lighter bed/carriage plate combination.
Links
X axis screw idler
"Oil-Embedded Mounted Sleeve Bearings"https://www.mcmaster.com/#catalog/124/1255/=1d9xeu8
Lead screwhttps://www.aliexpress.com/item/304-stainless-steel-T8-screw-length-500mm-lead-1mm-2mm-3mm-4mm-8mm-10mm-12mm-14mm/32695471104.html?spm=a2g0s.9042311.0.0.73bb4c4dYYWtUt
Tnut the Tnut must match in pitch and lead values to the lead screw you intend to usehttps://www.aliexpress.com/item/T8-eliminate-clearance-nut-anti-backlash-nut-trapezoidal-screw-nut-pictch-2mm-lead-8mm-1pcs/32732745669.html?spm=a2g0s.9042311.0.0.73bb4c4dYYWtUt
Tnut blockhttps://www.aliexpress.com/item/T8-Trapezoidal-Lead-Screw-Nut-Housing-Bracket-For-3D-Printer-Parts-Reprap-CNC-Free-Shipping/32846308484.html?spm=a2g0s.9042311.0.0.73bb4c4dYYWtUt
Rigid couplinghttps://www.amazon.com/gp/product/B01M8QXY8N/ref=oh_aui_detailpage_o02_s00?ie=UTF8&psc=1
Flexible couplinghttps://www.amazon.com/gp/product/B01HBPHSII/ref=oh_aui_detailpage_o03_s00?ie=UTF8&psc=1

Prusa Calculatorhttps://www.prusaprinters.org/calculator/