August Tip: Don't cut corners! Foci on your radii.

Whenever possible, a part to be injection molded should be designed with generously radiused corners to enhance its quality and moldability.

As illustrated in Figure 1, corners designed without radii can cause stress concentrations. These in turn may reduce the ability of the part to withstand load and/or cause warping in its geometry. Figure 2 illustrates how sharp corners might adversely affect the flow of resin during molding, potentially causing incomplete fill. They also tend to cause the part to stick to the mold during ejection, which can cause a variety of problems. And in Figure 3 we show how the judicious use of fillets can also help to improve mold life by helping to minimize corner stresses at the bottom of tall, thin cores in the mold (at the entrance to deep thin holes in the plastic part). These fillets also help to enhance the ability of the mold to fill and further reduce internal part stresses.

See the Protomold Design Guide for more details.

Special thanks to Mr. Luther Lieh for this "Design Tip" suggestion. A package of Protomold goodies is on its way as a small token of our appreciation.

Importance of 3D modeling Not at all - I don't even need it. Somewhat - I can live without it. Very - I almost always use it. Totally - I'm dependent upon it.

Let us know what you think. We'll include the results in next month's Rapid Injection Molding Design Tips. Suggestions for future survey questions related to the field of Rapid Injection Molding are welcome - just email them to us at marketing@protomold.com.