The method of plastic injection molding can produce perfect products for your needs quickly and cost-effectively. Still, as with any manufacturing process, there are certain “gotchas” that can cause less than ideal results. The five design guidelines should follow to help ensure that your production runs deliver an outstanding finished product.
It’s All in the Design Details:
Determine the ideal wall thickness. In designing parts, thinner walls need less raw material and can be produced faster thanks to more rapid cooling. However, a thicker wall is, of course, stronger. It’s important that you think carefully about product requirements as you design apart and find the right balance of production time and cost versus the strength of the finished product.
Maintain consistent wall thickness.In order to be mechanically sound, plastic parts must have walls that are even in thickness. This characteristic helps prevent warping and variable shrinkage and ensures that molds will fill properly. Wall thickness differences of more than 10% can lead to processing challenges and quality issues.
Choose the proper gate location.The situation of a gate injunctions how a mold is filled. Ideally, the material should enter through a gate positioned at the thickest part of the cavity and then make its way into more narrow areas. Gate location is particularly important if minor variations in wall thickness can’t be avoided.
Design corners with a generous radius.As plastic transfers into a mold it must direct corners. The more rounded the turns, the more simply the material will flow through them and continue to other areas. By comparison, sharp corners tend to cool and harden with irregular shrinkage that produces stress points and can result in sink marks.
Use the appropriate draft angle. The best draft angle, in terms of cost and manufacturability, is the greatest angle that will not negatively affect your satisfaction with the product. As for the minimum angle, the resin supplier is in the best position to make that judgment. Normally speaking, between 2° and 5° per side is preferable, although 1° per side is sufficient in selected cases. Level a small draft angle is preferable to none.