max speed acme with rotating bronze nut

[smoker]

Hi, does anybody know what the speed limits would be with an acme rotating ballnut setup? I assume due to the friction this would not be too high? 400 IPM? 800 IPM?

David

[Oldmanandhistoy]

Originally Posted by smoker Hi, does anybody know what the speed limits would be with an acme rotating ballnut setup? I assume due to the friction this would not be too high? 400 IPM? 800 IPM? David

Hi,

I would think the max speed would be what ever speed was high enough to generate so much heat coursed by friction that it melted the nut or shaft (which ever came first).

Seriously your question is almost the same as “how long is a piece of string” as it depends on so many factors that I am unqualified to comment on.

To have a chance on a reasonable answer you need to add data; like size of screw, length of nut and lubricant used for example. Unless there is a simple answer to your question that in my ignorance I did not know your question can not be answered accurately. Maybe some one can give you figures generated from their experience of such a system (you may get lucky).

Having said all that it would be interesting to know and I think Nook have a calculator on their website that may answer your question but it will also require you to add more data before it can give you an answer.

Good luck,

John

[Oldmanandhistoy]

http://www.nookind.com/acme/AcmeCalculators.cfm


END FIXITY D

John

[ger21]

According to the chart John linked to, looks like you shouldn't have any problems getting 10,000 ipm, provided you choose the right diameter screw for the length you want.

Multi start screws are much more efficient than single start. A 10 start 1 inch acme screw is 69% efficient, vs 20% efficient for a single start screw the same size.

As John said, there are many, many factors involved that would determine your top speed. Choose the right screw, and the screw won't be one of those factors.

[Zumba]

Originally Posted by smoker Hi, does anybody know what the speed limits would be with an acme rotating ballnut setup?

Acme ballnut? Sounds like a new invention.

Those critical speed charts don't apply to a rotating nut and fixed scew, since obviously, a fixed screw can't whip.

Assuming you have a rigid linear rail setup, your screw should only be carrying an axial load. In that case, the max IPM will be dependent on the weight of the load (the G-force from acceleration) and friction. The latter will be your barrier.

Acme was never designed for speed. The friction simply causes too many problems. A loose nut will reduce friction but increase backlash. Pick one or the other... you can't have both.

If you want both, get ballscrews.

[ger21]

Originally Posted by Zumba Those critical speed charts don't apply to a rotating nut and fixed scew, since obviously, a fixed screw can't whip.

Nook lists critical speeds for fixed screws with rotating nuts in their charts.

[smoker]

thx! will have a look at nook site
I wa splanning on a 1 inch srew with 5 tpi....