Re: Reduction Ratios for Steppers

As long as you keep away from the prime numbers in any part of the
assembly you can easily get the number to round off pretty easily.

in reality it does not make that big of a difference. Turbo-CNC for
one software package runs out to over 8 decimal places so if you have
a odd number it doesn't round before then. and that means when you
send a signal to go to 1.5000000000000 inches and it goes to
1.5000003 inches or some such, the error in intended location will be
way less than the error in your machine.

second, you program in G-code and never see the math going on in the
software and are totally removed from it. the software does not care
if you are direct connect or go thru 100 gears to get there or if
your movement is 0.00001 inches per step or 0.000018345982 inches per
step.

there is the possibility or a rounding error when you stop and start
a hundred times on a part.

so the answer is it critical ? NO.
is it desired, ? yes. I hate seeing 1.499999997 when I expect 1.50000

in either case, my machine has a postioning accuracy of better than
0.005" so even the 4th digit is not important to me, it just looks
funny.

Dave

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "cinelogic" <cnc@v...> wrote:
> Hi, ("Joe Newbie" here!)
> I'm designing the timing belt reduction that will work the rack &
> pinions for my first XYZ table. I know this question has probably
> been kicked to death here, but, not even knowing the right search
> terms, I'll ask it again:
>
> In designing the drive reduction ratios, how important is it to
> achieve a "round" number like [.001" of travel per 1.8 degree motor
> step] ?
>
> If the system I settle on comes out to, say, .00125" per step, is it
> going to cause me all kinds of setup problems?
>
> And,
>
> Do all [three] axis need to have the exact same drive ratio?
>
> Thanks,
> --SC