Stationary Ball Screw

[Wobblybootie]

OK Thanks ... It was just a thought ... I will keep it in mind though, not sure why but just store it away for future reference.

[John S]

Modern lasers do this, they call it spindle drive.
Large commercial lasers moved away from ballscrews some while ago and went on to precision rack and pinion because of the whipping over long lengths and by precision I mean $$$$$
Usually two large pancake servo motors driving split loaded pinions and complex electronics to stop them crabbing.

Now they have moved to spindle drive where they have two massive end castings / fabrications where a large , typically 70 to 90mm ball screw is held stationary in tension of about 20 tonnes and the ball but is driven by a 7 hp servo motor.

Because laser cutting is non contact they can reach insane speeds.

It's not a new idea, the old Bridgeport BOSS series mills that appear on Ebay with the big finned stepper motors and squarish table did the same on the X axis. Nut is in bearings on the knee driven by belt from the stepper, it's only an inverse Z axis after all.

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[ptjw7uk]

I would think you could get away with smaller ballscrews as they will be in tension and no whip plusthe ball nut will be smaller as well.

Not sure where the weight part comes in as most of the weight will be on the track bearings.

peter