# Timeline for Roller Screw drive - axial movement instead of friction

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Sep 9 '13 at 21:13 answer timeline score: 3
Sep 9 '13 at 16:43 comment I had a long talk with a colleague today, he says, that the full force Fp is affecting the bearing. But we weren't sure, whether the screw is self-inhibiting or not, but that would make a huge difference right? Actually a document which shows me the complete force and torque balance of screw would already help me a lot. And if this document would also explain the differences between self-inhibited to uninhibited - perfect! Already thank you to everybody participating!
Sep 9 '13 at 8:13 comment The force is actually not ground related, but for my posted simplified example it is. The roller screw's height is fixed related to rotor and chassis by the bearing, but the whole system can oscillate up and down. And I need to know if the whole system is oscillating (obviously it is) caused by the force Fp and how.
Sep 9 '13 at 2:40 comment Also Newton's third law applies. So the answer to your question is basically that in a properly designed screw system there will be forces acting on your chassis at the bearing. The servo motor shaft shouldn't see any forces along your Fp direction it's all taken by the bearing.
Sep 9 '13 at 2:31 comment When you use the right kind of bearings and mount them properly (e.g. see here: hiwin.com/pdf/bs/ballscrews.pdf ) your screw isn't going to move much when you apply a force. The load is taken by the bearing (and thus obviously also transmitted through your chassis)... (+ what Tim said about backdriving/friction and if it's a servo it will also fight any backdriving)...
Sep 8 '13 at 20:12 comment Is Fₚ (the process force that is shown as lifting the mass) also ground-relative? Is the roller screw's height fixed, relative to the frame and motor, but can vary relative to ground as the frame moves up or down?
Sep 8 '13 at 16:18 comment okay I added a sketch (I was logged out, don't be confused) - I hope my question is clearer now.
S Sep 8 '13 at 16:16 history CommunityBot