Need mechanical help with ball screws for DIY CNC

[tas99]

I’m in the process of designing a small DIY CNC light duty engraver and I need some help with the best method of securing the ball screw shafts. I know there are blocks that can be used at each end of the screw but I’m interested in securing with a bearing in the frame. Is it simply a matter of machining the end of the screw and pressing a bearing into the frame or is there more to it than that? Is a bearing needed on both ends of the screw or is the motor secured to the shaft through a coupling adequate?

Any other suggestions or ideas would be greatly appreciated.

[packrat]

The bearing on the motor end is the most important. The motor bearings won't take the linear force that the screw produces. You need a way to take the linear/thrust force.

[RICHARD ZASTROW]

Timken (Fafnir) makes a sealed ball screw support bearing. The bearing is the typical 60 deg. contact angle A/C bearing. Split inner races produce heavy preload when the ball screw lock-nut is tightened. The outer race has a larger than normal O.D. that has mounting holes in it. This allows direct mounting.

Dick Z

[tas99]

Thanks for the replies.

The info on linear force should have been obvious to me but I just missed it. Thanks.

As for the Timken bearings, they sound like what I need but I couldn't find the bearing that was suggested on their site. Could you provide a part number or a link to that bearing type? I'd sure appreciate it.

Thanks again.

[RomanLini]

You said "a small light-duty engraver", which should not need anything too much in the way of thrust bearings for the ball screws.

Because it's a light duty application I will disagree with Packrat and say that the stepper motor bearings may be sufficient. NMEA size23 steppers are usually rated for 6kg axial load which is probably more than any linear force you will get from light-duty engraving. Unless you have a massive heavy moving gantry or something, but I did not get that impression from your first post.

[RICHARD ZASTROW]

Timken (Fafnir) flanged sealed ball screw support bearings
12mm = MMF512BS55PP DM ~ 60mm = MMF560BS145PP DM

As RomanLini suggests, this may be overkill for a light duty engraver. I do not know what you may have suspended on that ball screw.