When the materials listed in a catalog are not familiar to the engineer, that catalog should have material property tables included. These are also readily available online nowadays, with a simple word search. These material property tables are especially useful when sourcing such materials as thermoset rubbers, urethanes, thermoplastics and especially the emerging thermoplastic elastomers for end products such as washers, bumpers, gel sheets, anti-vibration pads and others. If the information included in the catalog is not sufficient, a quick call to the supplier’s customer service department is possible. Sometimes, such calls will require application engineering assistance and it is always advisable to take this additional step, if there are any questions about a material’s suitability for use in the application under design.
As more exotic metal and composite materials come into use, this service is increasingly necessary, but will benefit the designer in many ways. With cost issues always a factor, as well, making such calls can often lead to alternatives the engineer might not be considering during the design phase.
 The most comprehensive component catalogs will generally include material hardness conversion tables, such as this one, as well as material variety/application and surface treatment option/performance charts. The hardness chart here details and compares the various scales used in industry today, namely, Rockwell C, Vickers, Brinell, Shore) |
A good supplier will generally provide as much information as needed for the engineer to reach a functional, cost-effective and deliverable solution to the design challenge in materials. Occasionally, material availability will not affect the pricing on a component, but it might affect the delivery and therefore should be investigated prior to determining a final specification. An engineer who calls a supplier with a predetermined material might want to conduct a quick review of the specifications to be certain of that material’s viability in application. For example, there is a commonly held notion in many engineering departments that stainless steel does not rust. This is, of course, untrue.
Stainless does indeed rust, but at a much slower rate than carbon steel, which begins to corrode literally as it is produced at the mill. How much slower the stainless rusts depends on its material grade (303, 304, 440 etc.) and such information should be readily available from the component supplier.
Surface treatments are many today. All have their function and a price point to consider, when designing. Two major factors to assess in choosing the proper surface treatment are corrosion resistance and cosmetic improvement. For example, black oxide is chosen to slow down the corrosion process when the part is in storage. It is not particularly durable and will usually wear off in use. It is also utilized to give a consistent appearance to the final structure by providing a uniform coloration.
Nickel plating assists in corrosion resistance and is more durable than black oxide. However, it will also wear over time in use. It is very effective in improving cosmetic appearance on a part, as well. Hard chrome plating will increase the surface hardness of the part and improve its corrosion resistance. Clear, black and the newer color anodizing are often used for aluminum parts as a primarily cosmetic improvement, while zinc galvanizing is used quite effectively for corrosion resistance.
Be sure to read the final installment of PD&D’s three-part series focusing on proper component selection en route to optimum machine performance.
Click here to read part one in the series. 
Mr. Chris Blaszczyk and Mr. Mike Melone of Misumi contributed to this article. They may be contacted for further information at 1-800-681-7475.