December Tip - Consistent wall thickness can be a core issue

We've previously recommended that you maintain a consistent wall thickness throughout your part. One of the more useful techniques to do this is known as "coring out," which involves cutting away blocks of material that don't contribute substantially to the strength or function of the part. Of course we always try to hit it the first time, but if the second rev needs strengthening, the mold can be modified relatively easily by removing metal. In this way you can add plastic to the weak areas, leaving the rest of the part with consistent wall thickness. The illustration to the left is an example of a simple part that was originally turned out of bar stock. When it came time to manufacture the part using injection molding, the designer cored out all the thick sections to a consistent wall thickness. Another example can be found on the Protomold sample part. It contains an example of the shrinkage problems that can occur with thick features and illustrates how coring out the feature can resolve the problem. The table* shows wall thicknesses Protomold recommends according to resin. Please note that thin walls only work on small parts and thicker walls are required where the resin has a long way to flow (Protomold makes parts with dimensions of about 0.25" to 15" or more).

As always, you can visit the Protomold Design Guide for helpful Rapid Injection Molding design information.

December Designer Survey : Which is your favorite Internet search engine? There are numerous search engines available for designers looking for information on technical and/or business topics. Which one do you rely on the most to help you find what you are looking for? If you don't see your favorite listed here and you'd like to enter it as a "write-in candidate," please e-mail it to us at marketing@protomold.com along with any ideas you may have for future survey questions.

What is your favorite Internet search engine? About.com Altavista.com AOL.com Ask.com Business.com Excite.com Findwhat.com Google.com Hotbot.com MSN.com Netscape.com   ODP.com Yahoo.com Other

November Designer Survey Results:

One year ago we asked the questions "Which 3D CAD software do you currently use?" and "Which 3D CAD software would you prefer to use?". As seen in the October 2003 Design Tip, the results indicated a potential future shift from Pro/E to SolidWorks.

We asked the first question again in our November survey and about twice as many people responded this time. A comparison of the results between 2003 and 2004 are shown in the pie charts.

Overall the results didn't change very much, but as illustrated in the bar graph it appears that SolidWorks may actually have lost a little ground to Pro/E over the past 12 months. We'll take another look down the road.