5 Tips for Quality Plastic Part Design
You’ll save time and money with plastic parts designed to be cost efficient and as easily moldable as possible. And remember, after you start building the mold or worse, once your parts are in the production phase, problems are much more expensive to fix.
Here are 5 tips to keep in mind for better plastic part design:
1) Think about adding draft angles to make sure your parts can be easily removed from the mold. Parts with longer or deeper side wall surface areas may need larger draft angles. Textured surfaces will also require larger draft angles because the parts are more likely to stick.
2) Don’t forget that even with draft added, you need to have some way to get the parts out of the mold. To help keep the cost down on your mold, try to leave areas for ejector pins whenever possible. Some designs may require ejector blades or a stripper plate, but remember that these will add additional cost. Try to include the desired pin locations clearly in your drawings and keep in mind that you will have a visible indentation in these places.
3) Try to maintain a uniform wall thickness throughout your part. This helps prevent voids, warpage, and molded-in stresses. It also facilitates proper melt flow. To avoid sink marks, try to keep ribs or internal wall features around 2/3′s the thickness of the main wall. Also, be sure to design the part with the thinnest wall possible. The thinner the wall, the faster the cooling rate and the less your parts will cost you.
4) One way you can achieve a consistent wall thickness is by rounding all the edges. It’s good to avoid sharp corners (insufficient radius) as you design your plastic part because this will help you minimize stress concentrations and other defects.
5) Plastic part designers must also pay attention to gate location and type. Some of the choices you have include a direct sprue gating into the part, tab, fan and tunnel gates (just to name a few). Gate type and location are important because they help determine how the plastic flows through the part. Remember that the gate will leave a visible mark or a small vestige that may not look right in some areas or could interfere with the intended function of the part.
If you have any questions on plastic part design, please call me at 315.841.4101 or email at rbateman@chplastics.com.
I look forward to speaking with you about any design issues you might have. You can check out our pre-quote engineering checklist to get an idea of what we look at during the design/engineering phase.
Until next time,
Rollin
