The Importance of Draft and Radii in Effective Injection Molding Design

Why is Draft Important in Injection Molding Design?

Applying draft and radii to a part is vital to a properly designed injection-molded part. In Injection Molding Design, draft helps a part release from a mold with less drag on the part's surface since the material shrinks onto the mold core. Limited draft in Injection Molding Design requires an excessive amount of pressure on the ejection system that may damage parts and possibly the mold.

Draft helps a part release from a mold. Various degrees of draft are illustrated here.

What is the General Rule for Draft Angles in Injection Molding Design?

A good rule of thumb in Injection Molding Design is to apply 1 degree of draft per 1 inch of cavity depth, but that still may not be sufficient depending on the material selected and the mold's capabilities. LaFlesche uses CNC milling to manufacture most of the features in the mold. The result of our manufacturing process drives a unique wall thickness and draft angle based on the end mill that we are using for each feature in Injection Molding Design.

How Does Design for Manufacturability (DFM) Analysis Help in Injection Molding Design?

This is where our Design for Manufacturability (DFM) analysis becomes particularly helpful in Injection Molding Design, as our software looks at each part feature separately and compares it to our toolset. The design analysis highlights the part geometry where increased draft and thickness may be required, ensuring optimal Injection Molding Design.

Why are Radii Important in Injection Molding Design?

Radii, on the other hand, isn't a necessity for Injection Molding Design but should be applied to your part for a few reasons—eliminating sharp corners on your part will improve material flow as well as part integrity. In Injection Molding Design, the resin filling the mold cavity flows better around soft corners much like the flow of a river. Rivers don't have 90-degree corners as the water flow creates inside and outside corners, so it moves easily towards its final destination. Similarly, plastic resin wants to take a path of least resistance to minimize the amount of stress on the material and mold in Injection Molding Design.

Sharp corners have high-stress concentration and plastic flow is hindered. Rounded corners have reduced-stress concentrations and plastic flow is enhanced.

What are the Benefits of Radii in Injection Molding Design?

Radii, like draft, also aid in part ejection as rounded corners reduce the chance that the part will stick in the mold causing it to warp or even break. This benefit is crucial in Injection Molding Design.

Conclusion

Applying proper draft and radii to a part is crucial for successful Injection Molding Design. Draft angles facilitate easy part release from the mold and reduce the risk of damage, while radii improve material flow and enhance part integrity.

Our team at LaFlesche are standing by to help with all your injection mold design needs.