One of the keys to creating small plastic parts that are free of cosmetic blemishes is consistent wall thickness. When wall thickness is not relatively uniform throughout a part, the plastic cools at different rates, and problems can occur. Thin wall sections in the middle of a part can be especially problematic, as they lead to improper filling and issues like sink and warp. But, by following a few guidelines, you can ensure that your parts are both visually appealing and functionally sound.
Key Considerations for Plastic Part Wall Thickness
Here are some things to keep in mind as you design and produce your small plastic parts:
- Know your material. Each type of plastic has recommended thickness ranges. Be sure you know what those are and that all the walls in your part fall within the range for the type of material you’ll be using.
- Adjacent walls are especially important. When it comes to designing your part, no wall should have a thickness that is less than 40 to 60 percent of the walls adjacent to it.
- Avoid certain part geometries. Things like sharp internal corners and long unsupported spans make maintaining uniform thickness difficult, and they pose other problems as well.
- Follow the guidelines on draft angles. Generally speaking, one degree of draft per one inch of cavity depth is what you should design for. And that draft angle should be maintained throughout the part.
- Use properly designed bosses. Bosses are typically cylindrical structures that can serve many functions, including providing support. They should follow the same 40 to 60 percent rule regarding the walls or structures around them.
- Use radius curves. Sharp corners on the exterior of a part are not a problem, but internally, the design should make use of radius curves.
- Use ribs as needed. Rather than increasing the thickness of a wall, if extra support is needed in an area, consider using ribs. They add strength without affecting the consistency of wall thickness throughout a part.
- Pay close attention to transitions. Places within a part where wall thickness changes are particularly susceptible to problems. Your design should focus on smoothing those transition points.
Let’s Talk Tricks of the Trade
Finding a combination of design and material that will produce uniform wall thickness and deliver picture-perfect parts can be a challenge. Having over two decades of experience in small plastic part injection molding, we’ve collaborated on some very clever tweaks in part parameters that have helped our customers achieve their desired outcomes over the years. And, we’re happy to share our insights.
Let’s talk about your next project. Contact us and stop by our facility. Longmont is just north of Denver and a great place to sit down for a cup of coffee.