Every linear motion design starts with the same choice: How do you convert rotary motor motion into linear travel? The two most common answers are the Lead Screw (simple, cheap, friction-based) and the Ball Screw (complex, expensive, rolling-based). Making the wrong choice here is costly. Use a lead screw where you need precision, and you get backlash. Use a ball screw in a vertical lift without a brake, and your load crashes to the floor. In this guide, we compare them side-by-side. Table of Contents 1. The Physics: Sliding vs. Rolling 2. Efficiency & The "Back-Driving" Danger 3. Accuracy and Backlash 4. Selection Table Advertisement 1. The Physics: Sliding vs. Rolling The fundamental difference is friction. Lead Screws rely on Sliding Friction . The nut (often bronze or plastic) slides directly against the steel screw threads. This generates heat and wear. Ball Screws re...
Figure 1: The Column Constant (C c ) marks the boundary between Inelastic Buckling (where material yielding dominates) and Elastic Buckling (pure instability). The Great Divide: Long vs. Short Columns In Part 2 , we learned how to calculate the Slenderness Ratio (Le/r) . This ratio tells us the geometry of the column. However, geometry isn't enough. We also need to account for the material properties. A steel column behaves differently than an aluminum one. To decide whether to use the Euler Formula (for elastic instability) or the J.B. Johnson Formula (for inelastic buckling), we must calculate a transition value known as the Column Constant (C c ) . Advertisement Search for Mechanics of Materials Books Calculating the Column Constant (Cc) The Column Constant represents the specific slenderness ratio where the critical stress equals half of the material's yield strength. It is the borderline between ...