gear speed ratio accuracy

[wangp1283]

If I had a gear train with speed ratio of 300: 1

if an input speed into it is 0.3 m/s. Then the output speed should
theoretically be 1 mm/s.

Although in a gear pair each member has a whole number of teeth,
which fixes the transmission ratio in terms of integral number of
turns, the instantaneous ratio is likely to flutuate a bit. Of
course this depends on the accuracy of the teeth finish.

For example, if the teeth profile was very roughly done, then during
a portion of a teeth engaging another teeth, the speed ratio may not
stay constant.

My question: is it possible to have an accuracy of 98%-99% at all
times. so that the output speed at any instant does not deviate more
than 1 or 2% away from the theoretical value of 1mm/s.

Another way of wording it is: Are there any actuators (servo)
capable of a slow speed of 1mm/s with very good instantaneous speed
accuracy, so that at any instant, the real life speed is no more than (0.02)*(1mm/s) off the theoretical speed of 1mm/s.

Thanks.

 

[GregLocock]

If you drive your output via a spring mass isloation system then there s no reason why you should not attain that level of accuracy, even with rough gears.

I suggest you do a literature search on gte, gear transmission error, to find out whether that is necessary, my gut feeling is that a hypoid gear set is better than 99% already.

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[Warpspeed]

Backlash between teeth may be as big a problem as gear finish. Your best bet might be to use a split spring loaded gear in the final stage of reduction.

 

[patprimmer]

Not my area, but I would have thought that a very fine pitch, hypoid type gears assembled with a little pre-load should be very accurate.

Further improvement might be gained by bedding in with a very fine abrasive and some extra pre-load, then washing clean and readjusting to slight pre-load.

Regards

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[sreid]

Exlar has a good reputation in the precision electric cylinder business. The speed accuracy should be pretty good.

http://www.exlar.com/