a roller screws advantage is having the efficiency of a multi-start optimal lead-screw but with much higher reduction.
A lead-screw with an optimal pitch and a high helix angle (EG: multi-start lead-screw with helix angles in the 30°-45° range) will have just as high an efficiency as a good roller screw (EG:80-90%). The downside is much lower reduction ratio of turns/distance.
We might be talking past each other since I interpreted “a planetary roller screw also must have as much sliding as a lead-screw” to mean an equivalent lead-screw with the same pitch.
If you paid attention to the animation, you should see that, while it has rolling movement, a planetary roller screw also must have as much sliding as a leadscrew, since threads rolling around without sliding don’t produce net movement. Rather, the improved efficiency comes from a reduced coefficient of friction, which is caused by the rolling movement putting oil between the threads, producing hydrodynamic lubrication. This requires very smooth surfaces, and machining to those fine tolerances makes planetary roller screws relatively expensive.
Just to clarify, my above suggestion that roller screws and optimal low reduction lead-screws are the equivalent (lubrication concerns aside) is correct or incorrect?
Are you saying a roller screw with high reduction gets its efficiency from better lubrication only and would otherwise be equivalent to a lead screw with the same effective pitch/turn? If that’s the case I’d disagree. And this was my reason for raising that point initially.
Are you saying a roller screw with high reduction gets its efficiency from better lubrication only and would otherwise be equivalent to a lead screw with the same effective pitch/turn? If that’s the case I’d disagree.
Yes. OK, we disagree about that. Glad we could get to the point.
Perhaps we don’t disagree at all.
a roller screws advantage is having the efficiency of a multi-start optimal lead-screw but with much higher reduction.
A lead-screw with an optimal pitch and a high helix angle (EG: multi-start lead-screw with helix angles in the 30°-45° range) will have just as high an efficiency as a good roller screw (EG:80-90%). The downside is much lower reduction ratio of turns/distance.
We might be talking past each other since I interpreted “a planetary roller screw also must have as much sliding as a lead-screw” to mean an equivalent lead-screw with the same pitch.
No. Did you read my post?
Just to clarify, my above suggestion that roller screws and optimal low reduction lead-screws are the equivalent (lubrication concerns aside) is correct or incorrect?
Are you saying a roller screw with high reduction gets its efficiency from better lubrication only and would otherwise be equivalent to a lead screw with the same effective pitch/turn? If that’s the case I’d disagree. And this was my reason for raising that point initially.
Yes. OK, we disagree about that. Glad we could get to the point.