When building a CNC router or upgrading a 3D printer, the first question is usually: "Is NEMA 17 enough, or do I need NEMA 23?" Most beginners look at the Holding Torque and stop there. This is a mistake. A NEMA 23 motor isn't just "stronger"—it is physically different in ways that affect your speed, your driver choice, and your machine's ability to avoid missed steps. If you choose a NEMA 17 for a heavy gantry, it is far more likely to overheat or lose steps under cutting load. If you choose NEMA 23 for a fast 3D printer, it might actually run slower than the smaller motor. This guide explains the engineering limits of each frame size. Table of Contents 1. Physical Difference (The Frame Size) 2. Torque & Speed (The Inductance Trap) 3. Driver Compatibility 4. Selection Summary Advertisement 1. Physical Difference (The Frame Size) "NEMA" is just a standard for ...
Figure 1: The Critical Stress curve. Note how the J.B. Johnson parabola is tangent to the Euler curve at C c , creating a perfectly smooth transition between failure modes. The Danger of the Wrong Formula In Column Design (Part 4) , we introduced the Euler formula. However, Euler's equation assumes the column fails purely by elastic instability (buckling). If you try to apply Euler's formula to a Short Column (where the slenderness ratio KL/r is less than the transition value C c ), the results are dangerous. The formula will predict a critical load much higher than the column can actually support. In reality, the material will yield (crush) long before it buckles theoretically. Advertisement Search for Structural Analysis Books The J.B. Johnson Formula To accurately predict failure in short or intermediate columns, we use the J.B. Johnson parabolic formula. Recall: The Column Constant (C c ) Before...