Re: Rack and pinion

I look after 4 large laser cutting machines made by Bystronic in
Switzerland. These are state of the art machines at present and these
use rack and pinion on X and Y but still use a ball screw on Z.
They use rack and pinion because they cannot get the speeds needed on
long screws.
They use Swiss precision rack and pinion that's preloaded so there is
NO backlash. They guarantee an accuracy of 0.01mm in linear and
circular moves.
Both axis have twin pancake DC servo motors with a coupling shaft
between both motors to stop any crabbing.
Because the laser cutting process is non contact cutting speeds are
fantastic.
I was there today replacing a new head mount after a collision. They
were cutting flap valves for big compressors from 1mm thick spring
steel, about 4" diameter, quite complex shape but I noticed on the
controller that the cutting speed was 30 metres per minute, about
1200 in / min.
Rapids are a lot faster than this but the controller doesn't list the
rapid speeds.
They still have one of the older Quantum machines on ball screws and
the best this can do is about 9 metres per minute or about 350 in/min
because of the nearly 4 metre long screw.

John S.

--- In CAD_CAM_EDM_DRO@yahoogroups.com, JanRwl@A... wrote:
> In a message dated 12/4/2003 10:03:05 AM Central Standard Time,
> dexlabboy@l... writes:
> I am also worried about a screw wobbleing at higher speeds.
> Definitely a potential problem! A way around this would be to FIX
the screw,
> and rotate the nut. This would take some creative engineering and
machining,
> but it might be worth it. Don't take MY word, as I never did that--
-the only
> long run with a screw I did, I used 1.5" dia. ball-screw with
double
> ("fixed") angular-contact BB's at both ends. $$$!!! and time!
>
>
> [Non-text portions of this message have been removed]