Mechanical Design Handbook

Posts

Conveyor Motor Sizing Guide: Torque, Power, Inertia & Gearbox

Designing a conveyor system involves more than just bolting a motor to a frame. If you undersize the motor, it won't start under load due to breakaway torque . If you oversize it, you waste thousands on electricity and oversized VFDs. In this guide, we will walk through the engineering math required to size a conveyor motor and gearbox correctly, specifically focusing on the critical "Dynamic Tension" resulting from inertia. Table of Contents 1. The Physics: Effective Pull (Te) 2. Calculating Motor Power (Worked Example) 3. The Inertia Problem: VFD vs DOL 4. Gearbox Ratio Selection 5. Frequently Asked Questions Advertisement 1. The Physics: Effective Pull (Te) The first step in any sizing calculation is determining the Effective Pull ( T e ) . This is the sum of all forces resisting the motion of the belt. The Basic Formula: T e = F friction + F gravity + F material...

Laser Rust Removal: Engineering Guide & Tools

There is something inherently satisfying about watching a layer of heavy oxidation vanish instantly under a beam of light. But for engineering design managers and automation specialists, this isn't magic—it is Laser Ablation . In the field of industrial maintenance , non-contact surface cleaning is becoming the gold standard for restoring precision parts without altering the substrate tolerance. The Physics: Ablation Thresholds & Selectivity Laser cleaning operates on the principle of sublimation via selective absorption. The process relies on the fact that rust (iron oxide) has a much lower Ablation Threshold than the steel substrate. When the high-energy pulse hits the surface, the selective heating mechanism takes over: The Oxide Layer (High Absorption): The rust absorbs the laser energy, rapidly heating beyond its vaporization point and turning into plasma/dust. The Substrate (High Reflection): The underlying steel reflects the laser wavelength...

Servo vs. Stepper Motors: The Engineer's Guide

Figure 1: Visual comparison . Steppers (Left) are dense and simple. Servos (Right) are longer and include a visible feedback encoder housing on the rear. The Million Dollar Question: "Which Motor Do I Need?" If you are designing a CNC machine, a packaging robot, or a conveyor system, you face the same dilemma every time: Stepper or Servo? Make the wrong choice, and you face two disasters: The Stepper Trap: Your machine "loses steps" (positional error) without knowing it, scrapping parts. The Servo Trap: You spend $5,000 on a system that could have been done for $500, blowing your budget. This guide bridges the gap between mechanical requirements and electrical reality. Advertisement 1. The Stepper Motor: The "Digital Ratchet" Think of a Stepper Motor like a very strong, magnetic ratchet. It divides a full rotation into equal steps (typically 200 steps per revolution, or 1.8°). Pros...

Stop Breaking Taps: Cutting vs. Forming Threads

Figure 1: Conceptual illustration showing how cut threads sever the metal grain (Left), while Form threads displace it (Right). The Most Dangerous Operation in Machining Ask any machinist what keeps them up at night, and they will likely say: "Tapping a blind hole in expensive material." Tapping is often the final operation. You have already spent hours machining the part, holding tight tolerances, and facing high surface finishes. If the tap breaks inside the hole now, the entire part is scrap. Every shop has the same story: a tap snaps in a nearly finished part, EDM removal is unavailable, and a $300 billet becomes scrap. The real cost isn’t the tap—it’s the lost machine time, setup, and delivery delay. Figure 2: Visualization of the nightmare scenario. A broken tap in a blind hole is usually unrecoverable without expensive spark erosion (EDM). The difference between a successful thread and a broken tool usually comes dow...

Precision Alignment Guide: Dowel Pins, Diamond Pins & Fits

Figure 1: The golden rule of fixture design: One Round Pin + One Diamond Pin = Perfect Alignment without binding. The Unsung Heroes of Precision: Dowel Pins & Locators In the world of Precision Engineering , the difference between a high-quality product and a scrap part often comes down to microns. While bolts hold parts together, they are terrible at positioning them. This is where Dowel Pins and Locating Pins become essential components in industrial tooling. Advertisement What is a Dowel Pin? A Dowel Pin is a standardized hardware component. It is a solid cylindrical pin, typically defined by international standards such as ISO 8734 , DIN 6325 , or ASME B18.8.2 . They are precision-ground to extremely tight tolerances—often as tight as ±0.0001–0.0002 inches (±2.5–5 microns) depending on the grade—and are available in materials like: Hardened Steel: For high-wear applications in CNC fixtures. Stainless Steel: For corr...

Design Hoeken’s Linkage in Excel (with Free VBA Simulator)

Figure 1: Geometry of the Hoeken’s straight-line linkage and resulting coupler-point trajectory. The lower portion of the curve approximates straight-line motion over ~180° of crank rotation. The Hoeken’s Linkage is a mechanical engineer's favorite magic trick. It is a four-bar mechanism that converts simple rotational input into a near-perfect straight-line output. Unlike the Watt Linkage (which traces a figure-8), the Hoeken’s Linkage creates a "tear-drop" shape with a long, flat bottom (see Figure 1). This makes it the standard choice for walking robots and intermittent linear actuators. But how do you find the link lengths? If you guess, you get a wobble. This guide provides practical "Golden Ratios" and an Excel VBA tool to simulate the motion path. Advertisement 1. The Geometry: Practical Design Ratios To achieve a usable straight line, link lengths must follow specific proportions relative ...

Pneumatic Cylinder Sizing: Bore, Force & Air Consumption

Figure 1: The "Pull" force is always weaker than the "Push" force because the rod takes up space. If you walk through any factory, you will hear the hiss of wasted compressed air. This is usually the sound of oversized pneumatic cylinders dumping energy. Many engineers size cylinders by "eyeballing it"—picking a 50mm bore because it "looks strong enough." This leads to sluggish cycle times and massive energy bills. This guide covers the physics of Force vs. Pressure , the critical difference between Extend and Retract force , and the often-ignored cost of Air Consumption . Advertisement 1. The Physics: F = P × A Pneumatics is simple: Pressure (PSI or Bar) acts on a Surface Area (Square Inches or mm²) to create Force. Force = Pressure × Area Unit Conversion Cheat Sheet: Pressure: 1 Bar = 0.1 MPa ≈ 14.5 PSI Force: 1 Newton (N) ≈ 0.225 lbs_force Area: 1 mm² ≈ 0.00155 in² ...