Rebond offers a service called plastic injection molding to produce high-performance plastic parts in wide variety of shapes and sizes. If you are going to design your parts for the plastic injection molding process, following are 5 common pitfalls you should avoid.
Uneven wall thicknesses
Varying Wall Sections are common in part designs and can cause unintended part properties when molding. Plastics have a hard time flowing and transitioning between uneven wall thicknesses. Thick wall sections create differential shrinkage which may lead to part deflection. Try to keep the walls at least thicker at the gate area and thinner at the end-of-fill. Shoot for .080-120” wall thickness and utilize ribs and gusset features in your part design.
Unnecessary undercuts
We often take Undercuts for granted, but undercuts will add cost to the mold. An undercut in the mold will need to be released before the part ejects or it will tear the feature out. There are many ways to release the undercuts with thru-coring design, slides, cores or lifters in the mold action. Simple rule for tooling: Minimize undercuts=Save money.
The wrong materials selection
Material Selection is another common mistake. Choosing right material for your parts is of great importance. Client need take the end product application, material property, and target price into consideration.
Not embracing radii
Corner Radius is often overlooked in the part design. Corner radii strengthens that area and makes it more robust in the long term. Radii reduces stress concentrations and fractures in the plastic part. It also makes the part look aesthetically pleasing and lowers any risk of injury when handling.
Not adding draft
Draft is needed in the mold to release the plastic part from the mold. Plastic generally shrinks towards the center of the part. Without draft, the part will stick in the mold and will not eject correctly. Design in 1° per side if possible, but any draft will be helpful to release the part.
