General manufacturing

Injection Molding Snap-Fit Connections Help Manufacturers Save Time and Money

2 min read

Updated: 05/30/2018

WHAT ARE Snap-Fit JOINTs?

Snap-fit designs, also called snap joints, are an effective way to replace fasteners/hardware in injection-molded plastic parts or products. For most applications, snap joint connections are the simplest and most cost-effective way to assemble two parts — making them ideal for high-volume production. The quick and easy connections help reduce the risk of improper assembly, which occurs more frequently in applications that require more components (fasteners) and tools.

Benefits of Snap-Fit Connections

Manufacturers are interested in injection molding snap-fit because it can save time and money, as well as being just as strong as fastened connections. Other primary benefits:

Can replace nuts, screws, washers, etc., with no other adhesives, solvents, or fastening processes needed
Can be designed right into the molding process, eliminating assembly steps and speeding up assembly and throughput
Reduces material needs, saves on material costs, and makes the product lighter weight

An added benefit is environmental — because snap-fitted products can be easy to take apart it’s easier to separate and recycle different materials.

How to Determine Snap-Fit Design

Which snap joints are best for your product depends on the intended use and the material/design strength that is required to keep it secure. Snap-fits can be engineered to be a permanent connection or allow frequent assembly and disassembly (like battery compartment covers in electronic products). Gas-tight and fluid-tight snap joint connections can even be made when snap-fits are engineered to work with seals and O-rings.

Even though snap-fits are relatively simple in design and how they operate, incorporating them into product design does add complexity to the molding process. This is because engineers have to consider the functional requirements of the connection and the product, assembly requirements, mechanical properties of the thermoplastic (strength, flexibility, recovery), and changes to the design of the mold (including part ejection). The design must ensure that the snap-fit has the proper “holding power” to keep the connection secure without bending too much, or breaking. These calculations become more complex, too, if the snap-fit application requires hundreds of openings and closings. Since most snap-fits require an undercut, a more complex mold is often needed.

Depending on the design and intended use of the product, snap-fit connections can increase tooling cost. However, once the snap-fits are designed and production is underway, the extra cost is usually quickly recovered by lower assembly costs, faster throughput, and less rework.

To learn how partnering with an experienced injection molder can help you overcome complex design and production challenges, read our Industrial and Critical-Use Injection Molding Part Histories.

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About the Author: Ken Glassen Ken Glassen is VP of Engineering at Kaysun Corporation. He earned a BSME-Mechanical Engineering from Marquette University, and a Masters of Science in Manufacturing Management from Kettering University. With nearly four decades of experience in plastics and plastics engineering, Ken brings deep, cross-disciplinary insight to complex injection-molding programs. His technical leadership and broad industry knowledge guide Kaysun design and engineering teams through every phase of plastic part design and process optimization. Central to Ken’s skillset is extensive experience with mold flow analysis, a capability he has developed throughout his career. His ability to model flow behavior, cooling efficiency, and potential defect zones enables Kaysun to proactively address challenges early in a program, ensuring accurate, data-driven decisions that lead to top-quality, reliable parts.