Machine Design

Lightweight Designs Turn The Tables On The Competition

Three of the four top honors at this year's rotational molding design competition went to Mity-Lite Inc.,

Lightweight designs turn the tables on the competition

The rotationally molded IntelliCore rectangular and circular folding tables are for indoor and outdoor use and can carry loads of up to 1,600 lb.

Three of the four top honors at this year's rotational molding design competition went to Mity-Lite Inc., Orem, Utah, for their rectangular and circular IntelliCore tables. Sponsored by the Association of Rotational Molders International, Oak Brook, Ill., the contest's top award, Product of the Year, as well as Innovative State of the Art went to the 42-lb, 29-in.-high, 30 x 72-in. folding table while Conversion honors went to its 60-in.-diameter counterpart. Products in this category must be converted from some other material or process to rotational molding.

Mity-Lite uses proprietary foam sandwiched between two skin layers to give the 3/4-in.-thick tables high stiffnesstoweight ratios. Both tables comfortably hold over 1,600 lb. The skin-foam construction features molded-in stiffeners, leg mounting points, and an exceptionally flat surface. A 5-ft diameter, 10-ft-tall water-powered turbine, dubbed the Mother of All Bridgesharks, chewed up the competition in the Large Product division. The Bridgeshark, from Rotonics Manufacturing Inc. (RMI) removes debris from the bases of bridges as it rotates with the velocity of the water.

The Bridgeshark features a series of molded fins made from cross-linked polyethylene. The polymer is strong enough to handle impacts from logs and withstand severe weather. It is UV stabilized to resist sun damage. Rotational molding lets RMI mold the turbine as one unit with a single parting line. The process also easily accommodates fin wall thickness transitions of 0.25 to 0.5 in.

The Bridgeshark's interior is molded with two chambers. The upper is filled with 2 lb of polyurethane foam to make the turbine buoyant while the lower, hollow chamber fills with water to stabilize the device. This duo chamber construction lets the turbine adjust to changing water levels (including floods), while continuously rotating to deflect debris. The only secondary operation needed is welding the 16-in.-diameter PE pipe that acts as an axle to the plates bolted on either end of the Bridgeshark.

The Bridgeshark keeps flotsam from accumulating around bridge supports, thus reducing the need to manually remove it, which puts maintenance crews at risk.


Association of Rotational Molders International,
(630) 571-0611,
Mity-Lite Inc.,

(801) 224-0589,
Rotonics Manufacturing Inc.,
(310) 327-5401,

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