Requirements:

• zero backlash/preloaded
• preferably rolled, no high precision is needed
• outside diameter between 20 and 30mm
• high lead, 50mm/rev or larger, if possible
• lead time no longer than five days

I've already searched skf, ina, thomson, nook, amazon and other places, plus did extensive googling. But maybe the most mechanically experienced among you know other suppliers, preferably in the U.S.

The closest I've come to what I want is INA's KGS 2550 (25mm od, 50mm lead, see page 9 of linked document), but the problem will be finding a supplier that can supply it immediately.

Another option is thomson's KGM-N-2050-RH-D-EE. But I personally don't like that brand too much, plus I doubt they'll be able to sell it to me in such short notice.

All suggestions will be thoroughly appreciated.

@MaxHeadRoom , @shortbus

 

When you can obtain them, I have purchased HiWin from Taiwan and been very happy with them, not sure if they make a rolled version, but imagine they do.
Another source to try is Misumi USA, They have quality CNC hardware.
Max.

 

That diameter with that lead seems to be a problem without going to a ground thread. The first place I look for motion control when imagining something is Anaheim Automation. There 25mm stuff is here, http://www.anaheimautomation.com/pr...m.php?sID=681&serID=268&pt=i&tID=1101&cID=525

Maybe there could be another solution to the problem if you can share more information, here or in PM.

 

That diameter with that lead seems to be a problem without going to a ground thread. The first place I look for motion control when imagining something is Anaheim Automation. There 25mm stuff is here, http://www.anaheimautomation.com/pr...m.php?sID=681&serID=268&pt=i&tID=1101&cID=525

Maybe there could be another solution to the problem if you can share more information, here or in PM.

Yeah, it's a problem alright... I've seen ball screws with extremely long leads used in CNC punching machines... but they seem to be custom made... and I'm already familiar with anaheim automation, although I hadn't considered them until you brought them up, thank you.

Right now I'm seriously analyzing a rack and pinion configuration instead. I've used it aplenty before, and it can be extremely accurate if the components are designed correctly. Many thanks.

 

I'm sure this isn't a new idea for you, so more of curious question than a suggestion. Why don't you use a more common pitch ballscrew and just gear up from the servo to the ballscrew with a toothed belt or gear?

 

R&P can be quite accurate, especially with helix gear and rack, also now 20° pressure angle is used.
Max.

 

I'm sure this isn't a new idea for you, so more of curious question than a suggestion. Why don't you use a more common pitch ballscrew and just gear up from the servo to the ballscrew with a toothed belt or gear?

I also considered that. But the calculated rpms for what I need, using a 25 mm pitch ball screw is about 5,400 (90 rps)! ... and on a 25mm diam, 800mm long ball screw it would most likely cause unacceptable vibrations

 

R&P can be quite accurate, especially with helix gear and rack, also now 20° pressure angle is used.
Max.

Funny you should say that. Most of the time I use 24 pitch @ 20° rack and pinion for my designs.

 

have you checked https://www.mcmaster.com/
does not seem to have exact size but they stock things and ... how desperate we are talking about?

 

@cmartinez Ever seen these devices, they are pretty neat, I have seen them used on CNC back gauges, zero backlash.!
http://www.uhing.com/en/rolling-ring-drive/
Max.

 

@cmartinez Ever seen these devices, they are pretty neat, I have seen them used on CNC back gauges, zero backlash.!
http://www.uhing.com/en/rolling-ring-drive/
Max.

Oh yeah, they're pretty cool. I've seen them used extensively on wire winding machines. But they're friction based, and therefore un-synched. So they're useful for applications different from the one I have in mind.

On the other hand, there's an ultra high precision rack and pinion mechanism out there in which the pinion uses rollers instead of teeth that might save the day, depending on the supplier's lead time.

I'll do a little search on that and come back here with an image and a link... see what you think.

 

Maybe Koyo has some. NSK seems to have a ton of distributors all over North America.

 

Again not knowing more about this inhibits things. I have some linear actuators and have seen others that used a timing belt and pulleys to move another item along a path. A motor driven pulley at one end, a spring loaded pulley at the other, with the belt attached to the moving object. Some of the early DIY CNC machines did this for the axis movements. As do some inkjet printers and plotters.