Top Ten Design Tips

Design for Manufacturability, or DFM is a time-tested tool to help designers minimize costs and time to market. Complex designs cost you money. Sometimes complexity is necessary, but unnecessarily complex designs cost you unnecessary amounts of money. We at Guttenberg Industries aim to help you use DFM in order to keep your designs as simple as possible while keeping costs to a minimum. Here are some simple DFM tips to help you maximize your profits. For even more information please contact us for a free, no pressure conversation.

Tip #1: Understanding Draft

Draft is an angle incorporated into the wall of a mold, thus the shape of the plastic part, so that the opening of the cavity is wider than its base. For those unfamiliar with draft, you might notice that plastic drinking cups are always wider at the mouth of the cup than at the bottom. This shape is a demonstration of draft. It is smaller at the base than at the mouth so that the cup will come out of the mold. Draft is essential for injection molding.

In very basic terms, an injection mold involves a cavity – or female half, and a core – or male half. During the injection molding process molten plastic is injected into the mold and fills in the gap between the cavity and core. As the plastic cools it solidifies and takes this shape. As the plastic cools it also shrinks, and in so doing effectively grips onto the core. Without draft, this gripping action caused by the plastic shrinking onto the core can become nearly impossible to overcome without damaging or destroying the shape of the plastic part. But with sufficient draft, the part is able to break free of the core with much less distortion and after a very short distance of travel.

From a molder’s perspective, the more draft the better. Yet from a designer’s perspective, draft often requires a change in shape from the original design concept. So as a designer, it is in your own best interest to keep the concept of draft in mind as your design takes shape. If you are experienced with designing parts in plastic, it can be helpful to anticipate where the two halves of the mold will separate, known as parting line, and shape the part to allow for draft in both directions away from parting line. If you are not experienced in designing for plastics, we can help you anticipate draft during the early stages of design in order to avoid costly or frustrating design changes in later stages.