Designing Living Hinges That Fold Flat and Last
A living hinge may be one of the simplest-looking features in plastic part design. It contains: Just a thin section of plastic connecting two rigid bodies. Yet despite its simplicity, the living hinge is one of the most frequently misdesigned features in injection molding. Many hinge failures occur long before the product reaches the customer. […]
Crush Ribs: Solving Tolerance Problems Without Tight Tolerances
One of the most common challenges in plastic product design is creating a reliable press fit. Consider a typical assembly: At first glance, the solution appears straightforward: Design the mating dimensions with a tight tolerance and create an interference fit. In practice, however, injection molding does not always favor this approach. Shrinkage variation, molding tolerances, […]
Sharp Corners Create Problems: Why Radii Matter in Injection Molded Parts
One of the most common comments during a DFM review is: “Can we add a radius here?” To many product designers, corner radii appear to be minor details. After all, a sharp corner seems simpler to design and often looks cleaner in CAD. However, sharp corners rarely benefit injection molded parts. In fact, they frequently […]
Design Parts That Are Easy to Change After the Mold Is Built
Every product team expects design changes during development. That is the purpose of prototyping. Engineers evaluate: And then make improvements. The problem is that not all design changes are equal. Some modifications can be completed by machining existing mold steel. Others require replacing inserts, rebuilding mold components, or manufacturing an entirely new tool. From a […]
Uniform Wall Thickness: The Single Most Important Rule in Injection Molded Part Design
When discussing injection molded part design, engineers often focus on: All of these factors influence the final product. However, if there is one design principle that has a greater impact on molding success than almost any other, it is this: Maintain uniform wall thickness. In practice, many molding defects—including sink marks, warpage, voids, dimensional variation, […]
Choosing the Right Surface Finish for Injection Molded Parts
When discussing injection molded parts, surface finish is often treated as a cosmetic decision. Questions usually focus on appearance: While appearance is important, surface finish affects far more than aesthetics. The selected finish can influence: In many projects, the surface finish decision is made late in development. By that stage, it may already be affecting […]
Designing Molded Text: Small Features, Big Manufacturing Consequences
Almost every plastic product contains molded text. Examples include: From a CAD perspective, adding text is simple. From a molding perspective, text becomes another geometric feature that must: Many text-related defects are not caused by the text itself. They are caused by text being designed without considering how molds are manufactured and how plastic behaves […]
Not Every Undercut Needs a Slide
Undercuts are often viewed as one of the most expensive features in injection molded parts. And for good reason. A relatively small undercut can trigger the need for: In many cases, the tooling required to release the undercut costs significantly more than the feature itself. However, not every undercut requires a moving mold component. Some […]
When a Plastic Part Needs Metal: Designing for Insert Molding
Plastic parts are remarkably capable. Modern engineering resins can withstand significant loads, resist chemicals, survive harsh environments, and replace metal in many applications. Yet even the best plastic materials have limitations. Threads wear out. Bearing surfaces degrade. Fastener locations strip. Repeated assembly causes damage. When these failures occur, the solution is not always a stronger […]
Designing for Overmolding: Bonding Matters More Than Geometry
Overmolding is often presented as a way to combine two materials into a single component. That description is technically correct, but it overlooks the real engineering challenge. The difficult part is rarely molding the second material. The difficult part is ensuring that the second material remains attached throughout the life of the product. In many […]