By Terry Wohlers
An edited version was published in Rapid Prototyping Journal, Vol. 7, No. 3, 2001, MCB University Press. Copyright 2001 by Terry T. Wohlers
who are familiar with www.efunda.com (efunda is short for engineering
fundamentals) may consider it to be one of the best kept secrets in the
industry. If you are an
engineer, you will find this site an absolute gold mine.
It includes an impressive number of engineering facts,
descriptions, tables, formulas, conversions, and other helpful references.
What’s more, it’s free and it doesn’t even require you to
register prior to using it.
The site is organized into categories and subcategories, as shown in the following table. The subcategories (in small print) are links that take you to another page.
If you click on Polymers, for example, the site displays the following information.
The items in small print are links to additional pages. If you click on Epoxy, the page explains that epoxy has been mass-produced since 1946 and it gives a description of the material’s applications and general properties, along with many trade names. It also lists 12 specific grades of epoxy, such as ”epoxy, aluminum filled, casting resins and compounds.” If you click on it or one of the other 11 grades, it displays tables showing the mechanical properties (tensile strength, hardness, etc.), thermal properties (coefficient of thermal expansion, deflection temperature, etc.), physical and electrical properties (specific gravity, water absorption), and process properties (melting temperature, linear mold shrinkage). Furthermore, it provides detailed contact information on the suppliers of epoxy resin.
The depth of the site is extraordinary. You can drill down deep into most other areas and find similar detail. Few sites, even those that require a fee, provide such depth and breath on technical subjects.
As shown in the first table above, the site includes information on rapid prototyping. The information is not entirely up-to-date (e.g., Sanders Prototype has not been changed to Solidscape), but it offers some helpful illustrations that show many RP processes. It even attempts to compare some processes with others, a sign that someone knowledgeable assisted with the collection and presentation of the information. In other words, it wasn’t simply extracted from company brochures and websites.
Visitors of the site will find the information on engineering fundamentals engineering the most useful. The site includes a search engine that works well and a discussion forum on topics ranging from battery chargers and CNC machines to unified screw threads and vibration dampeners.
The website says the following: Almost all engineers would agree that most of the knowledge needed for our daily jobs is college level material. Yet we often find ourselves looking for information that we vaguely remember or just simply forgot. The sought information could be as simple as a beam-bending formula, or as specific as the thermal conductivity of Aluminum Alloy 6061. Our reference books are not always available when we need them. When we do have our books, we can lose precious time searching for obscure information. We have felt the need for a convenient Internet resource where common engineering questions could be answered quickly and efficiently. Since no such resource currently exists, we have resolved to build one.
Indeed they have. It’s one of the best websites out there for practical, useable information for the engineer. The people behind www.efunda.com should be congratulated for making this rich collection of information available on the web.