MD_Fastening and Joining Monthly_: Explosion-proof motor designs face compliance deadline

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October 18, 2010

October is halfway over and soon we'll be naming another monthly winner from World's Smartest Design Engineer. September's winner was Nick Bruin (aka: nbruin) from BAE Systems. His skills earned him a $250 Best Buy Gift Card. Will you be our October winner? If you're new to the game, give it a try. You'll be in the running when the next montly cycle starts Nov. 1.

In this month's issue we're looking further into the assembly process. Check out recent articles on:

Adhesives for explosionproof motors
Ways to model biodegradable implants
Part inspection in the age of 3D models

Don't forget to scroll down for new products and news from machinedesign.com. And let us know your thoughts on articles at machinedesign.com, on our discussion forums, or by email.

Jessica Shapiro.

Articles

Explosion-proof motor designs face compliance deadline

Electric-motor manufacturers seeking Underwriters Laboratories’ (UL) “explosionproof” certification face a Dec. 11, 2010 deadline that could change the way they design and build their products. On that date, UL will require that motors fully comply with the UL 674 standard before being labeled explosionproof.

Explosionproof means the motor will prevent an explosion or spark from within the motor from propagating into the surrounding atmosphere. EPM designers must look for leak paths where vapors could enter or leave the motor and initiate an explosion.

The Achilles’ heel of EPMs is usually the point where electrical and signal wires enter the motor housing. Designers typically flow a low viscosity polymer into voids to create solid contact with wire surfaces and entry-point edges to create a gas and moisturetight barrier.
Read the full article.

PEM® MICRO STANDOFFS (TYPE MSO4™)

PEM® Type MSO4™ self-clinching micro standoffs are used to stack or space internal components and provide strong, permanent, and reusable load-bearing threads in metal sheets as thin as .016” / 0.4mm. Thread sizes have been developed as small as M1 and are available in unified fastener lengths .094” and .125” and 2mm and 3mm in metric.

www.pemnet.com

Molding parts that are designed to degrade

Under normal conditions, the organs of the human body self-regulate and heal when damaged. But when the damage is more severe, it is not always easy in today’s rapidly paced society for patients to get enough rest for the body to heal fully. This is certainly the case when soft tissue such as the ligaments around joints is damaged. In these instances, it is best to implant ligament-augmentation systems to stabilize the joint, allowing the body to heal fully.

Some of these implants are only needed for short periods until they have served their purpose. This leaves the problem of what to do with the implant when it hinders full motion in the joint at a later stage. It is almost impossible to remove soft-tissue implants, which are traditionally made of fabrics or biotextiles. However, the development of specialized hyperelastic polymers makes possible soft-tissue implants which perform mechanically as required for a short period of time to stabilize the joint. They then biodegrade naturally, eliminating the need for surgical removal.
Read the full article.

The changing face of part inspection

A necessary component of the model-based definition (MBD) approach to product design is 3D geometric dimensioning and tolerancing (GD&T), a universal symbolic and tolerancing language. In the MBD approach, the 3D CAD model is the authority, providing all the detailed product information for the entire product life cycle. The method moves the 3D CAD model from design to a manufacturing orientation, and lets software automate and validate steps in simulation, manufacturing, and inspection, thereby reducing human error.

Last updated in 2009, GD&T has been rigorously studied and applied by thousands of manufacturers around the world. It is often considered essential for communicating design intent — that is, that parts from technical drawings have the needed form, fit, function, and interchangeability.
Read the full article.

New Products

One-part thermally conductive epoxy

Supreme 10AOHT-LO single-component epoxy works between 4K and 400°F, is electrically insulative, meets NASA low-outgassing specifications, and resists thermal cycling, water, oil, and some fuels. It has a thermal conductivity between 9 and 10 BTU/in/ft²/hour/°F, Shore D hardness over 75, and compressive strength over 15,000 psi.

The material cures between 250 and 300°F for 1 hour. It comes in 0.5-pt, 1-pt, 1-qt, 1-gal, and 5-gal containers.
Master Bond Inc.

Automatic hex-head driver

PEM StickScrew System inserts small hex-head screws with a lower-cost, air-powered StickShooter driver and interchangeable nose assemblies. The driver advances a 12-in. "stick" of dozens of serially screws, and the operator squeezes the trigger and places the tip of the rotating screw into the hole. The screw twists off cleanly when precise seating torque is achieved.

Thread-cutting screws come in #2-56 to #6-32 and M3 in 400 series stainless steel. Machine screws and thread-forming screws in steel, brass, and aluminum, and in thread sizes from #0-80 to #8-32 and M1 to M4 are available and can be plated, black oxidized, or hardened.
PennEngineering

Bonding brochures

The Magnet Bonding Guide and Design Guide for Electric Motors and Generators brochures provide in-depth information on adhesives and equipment specifically designed for bonding in these applications. The Magnet Bonding Guide covers adhesives for ferrite, neodymium/iron, and alnico magnets. Selector guides detail nine acid-free, noncorrosive Loctite adhesives and manual, semi-automated, and automated dispensing and curing equipment.

The Design Guide for Electric Motors and Generators covers adhesive, sealant and coating technologies used in electric motors and generators. Topics include general bonding, magnet bonding, gasketing, potting, retaining, tacking, threadlocking, thread sealing, wire reinforcement, and surface treatment. The brochure also has a product selector guide broken down by application category.

To request the brochures call (888) 427-3676 or email literature@loctite.com and ask for brochure LT-4320 (Electric motors) or LT-4914 (Magnets).
Henkel Corp.

News from MD

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