Torque Calculation for Screw Ball: TL Preload Nut

AI Thread Summary
Fa refers to the force due to acceleration, calculated using F = ma. Ball nuts can be either low friction for less precision or internally preloaded for high precision applications. Low friction ball nuts are suitable for applications tolerating location errors of 0.005", while preloaded nuts are used for precision tasks with tolerances of +/-0.0001". The discussion also touches on the inertial forces during machining, indicating that both acceleration and deceleration can be analyzed using the same formula, with deceleration represented as negative acceleration. Understanding these concepts is crucial for selecting the appropriate ball screw and nut configuration for specific applications.
Justin71
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Hi

I don't understand what Fa mean ? This the weight or no ? And i don't understand too why in the torque TL, we have an additional part with the preload, the internal friction coeff of preload nut ... What is it ? Thanks.
 

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It appears that Fa is force due to acceleration (F = ma).

Ball nuts are available with internal clearance for low friction, or internal preload for precision motion. Low friction ball nuts are used with low precision (lower cost) ball screws in applications that tolerate location errors of 0.005" or so. Internally preloaded ball nuts are used with precision ground ball screws (higher cost) in applications where higher precision is needed. Typical applications are machine tools where the motion is controlled to +/-0.0001".

Study some ball screw catalogs. You will find specifications for location error, backlash, allowable speed, and allowable acceleration.
 
Ok thank's a lot for your answer ! I had an other question for the acceleration (inertial force).
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If we machine like drilling, we have an acceleration, then a deceleration during machining. We can decompose their inertial forces with (Fi(acceleration)=m.a and Fi(deceleration)=-m.a ? Or it's an other thing ? Thank's.
 

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