Re: Alternative Stepper Motor mountings, etc.

Dave,

Thank you for letting me know I'm helping.

I don't recall any travel speeds being discussed, but if you are
trying to go very fast at all, consider my earlier posts recommending
spinning the NUT(S) and tensioning the screw at each end of the
machine.

It's also worth a look at the design decisions made by Dennis bohlke
at super-tech. His long travel leadscrew machine utilises some unique
approaches. First, he uses a screw with a large lead(pitch). This is
more efficient at tranferring power than the typical 10tpi acme. BUT,
it won't multiply the power as much, so... He uses bigger steppers.
But, these will take expensive drives, so... He uses high amps, low
volts,and unipolar type. Now low volts would "typically" "cost" top-
end speed, BUT... We're using a "fast" leadscrew remember?! Also,
this lower rotational speed allows smaller diameter screws to be used
without getting into their 'critical' speeds. A nice bit of
engineering, IMO. (But I don't like two motor axis drives with
steppers!!!)

The best way to minimise overall tolerance buildup is to move the
axis a large distance (in your case, something like 90 inches) and
then measure the distance ACTUALLY traveled. You know how many steps
were sent to move THIS far, so adjust it to move the distance you
WANTED it to move! This will spread the error over the distance
traveled. (this calibration can be done for shorter parts as well.
Doing this with poor quality leadscrews will help you to get the best
performance of which they are capable. Also, if you are making mating
parts, make them in the SAME 'part' of the machine travel. This way ,
any variations in the drive (leadscrews) will be duplicated in both
parts.

--- In CAD_CAM_EDM_DRO@y..., davemucha@j... wrote:
> Thanks, well writen.. I could see the angles as you were writing.
>
> opps, 200 Rev on 10 TPI is 0.0005" per inch I left out a '0'
>
> My tolerance for overall length and what I'm hoping for are
> different. I'm aiming to get 0.005" but my requirements are to be
> wihin about a 1/16" foot to foot, and 1/8" over the 8 foot part
> length.
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