[blau_schuh]

I got a bunch of ballscrews pretty cheap from an auction. They range from 15mm diameter to well over 2.5" in diameter.
The two I had in mind are brand new German STAR screws.

One screw is 84" long and has something like a 50mm diameter.
One screw is around 72" long roughly 50mm diameter. Would make a hell of an X axis (nuts)
TOTALLY overkill for a home cnc machine.

Can a run of the mill Keling servo motor (maybe the 1100oz) even turn these puppies?

I'd like to try and use 1, maybe toss the other on ebay

[Hommersimpson]

can you post some pictures ? And geared down why not ?

[Doug Laser]

it's a good bargain to buy from auction. and leave one for you ,the others toss to ebay or other B2B site.

[blau_schuh]

can you post some pictures ? And geared down why not ?

no pics yet, they are sitting at the shop.

[CaptainVee]

On another forum, a guy that seemed to know his stuff said that acceleration becomest difficult at the screw, not the weight of the gantry.

That means that the 50 mm ball screw would be totally useless for a home cnc.

I built my cnc to advice from another person that should know his stuff, the most important bit being to use high pitch ballscrews with high torgue motors. This seems in line with the other guy's advise.
High pitch means the motors operate at low revs, where torgue is highest.

I now have blistering acceleration.

[blau_schuh]

On another forum, a guy that seemed to know his stuff said that acceleration becomest difficult at the screw, not the weight of the gantry.

That means that the 50 mm ball screw would be totally useless for a home cnc.

I built my cnc to advice from another person that should know his stuff, the most important bit being to use high pitch ballscrews with high torgue motors. This seems in line with the other guy's advise.
High pitch means the motors operate at low revs, where torgue is highest.

I now have blistering acceleration.

Link to the other forum?

I'm at work right now do I don't have the link, However, last night I found a page where a guy was using a pretty beefy screw and was having success by just gearing it down a bit.

I'm currently getting an easy 120+ipm without trouble on my gantry with close to a 4' long close to 1" diameter gantry screw and a tiny 30 oz-in litton clifton servo motor.

[awerby]

At least you won't have much trouble with "whipping"...

Andrew Werby
ComputerSculpture.com — Home Page for Discount Hardware & Software

[blau_schuh]

At least you won't have much trouble with "whipping"...

Andrew Werby
ComputerSculpture.com — Home Page for Discount Hardware & Software

no kidding, ha.

I've wanted to try and get an AC servo motor up and running with a granite devices driver as an experiment. maybe this might be a good project to try. if i'm not mistaken, ac servos have a pretty flat torque curve through a large rpm band

[FPV_GTp]

Hi , ebay link isn't working my end when clicked on, Have you sold the ballscrews ? if not , What prices do you have on the 50mm ball screws ?

Cheers

[blau_schuh]

Hi , ebay link isn't working my end when clicked on, Have you sold the ballscrews ? if not , What prices do you have on the 50mm ball screws ?

Cheers

Hi, that wasn't a link to an actual auction, but rather a link put in by the ad software on the cnczone site.

haven't even thought of a price yet... I'm in the USA though, shipping would be expensive to Australia. Feel free to PM me about it. Im going to grab some pics tonight. got a couple of shorter ones too.

[harryn]

If you have it, the other interesting info about bal screws will be:
- Rotating nut or rotating screw
- Picture of the screw ends, so people know what mounts will be needed
- Screw lead pitch - how much the nut moves for each rotation
- Screw grade. A rolled C7 grade is entirely different than a ground C2 grade.

I would think that finer pitch screws would be better for metal machining, and coarser ones for routers, but there is some flexibility in that.

[blau_schuh]

If you have it, the other interesting info about bal screws will be:
- Rotating nut or rotating screw
- Picture of the screw ends, so people know what mounts will be needed
- Screw lead pitch - how much the nut moves for each rotation
- Screw grade. A rolled C7 grade is entirely different than a ground C2 grade.

I would think that finer pitch screws would be better for metal machining, and coarser ones for routers, but there is some flexibility in that.

Yo Harry,

The 3 screws (2 long 50mm diameter 1 short 40mm diameter) are all rotating screw, 10mm pitch. The STAR specs I've seen claim its a rolled C5 grade, I thought rolled maxed out at C7. I've got C3's on my current machine cause they were cheap.

The ends were factory machined to accept 30mm and 35mm bearings. I've got some cheapo angular contact bearings on order just so that I can get the ball rolling and build some bearing blocks.

At some point I'll get back to the shop and take pics.