· Select the screw diameter and lead based on the calculated results:
Using the calculated Ca_req and the determined Ph, consult the supplier’s catalog.
Find a screw nominal diameter series that satisfies Ca > Ca_req (e.g., Φ12, Φ16, Φ20, Φ25, etc.).
Confirm that this diameter and lead combination meets the critical speed Nc > n * 1.2 (safety factor) and DN value requirements.
· Select the accuracy grade:
Select based on positioning accuracy and repeatability requirements.
Common grades (e.g., HIWIN, THK): C0, C1, C2, C3, C5, C7, C10. The smaller the number, the higher the accuracy and the higher the price.
The catalog provides the cumulative error within 300mm of travel for each grade.
·Select Nut Type and Preload Level:
Nut Type: Standard single nut, double nut (for ultra-high rigidity and zero backlash), flange nut, compact nut, etc. Select based on space and performance requirements.
Preload Level (to eliminate backlash): P0 (no preload, with backlash), P1, P2, P3 (increasing preload levels).
Higher preload reduces backlash and increases rigidity, but also increases frictional torque, temperature rise, and life.
Select P1 or P2 for general precision applications. For ultra-high precision and high rigidity, select P3 or a double nut. For applications insensitive to backlash (e.g., manual adjustment), select P0.