Rotational molding is a three step process. The first step is to load a mold cavity with a plastic material, liquid or powder. Next the mold is moved, or indexed, to the heating chamber where it rotates on its horizontal and vertical axes. Finally the mold is then indexed to the cooling chamber where it again rotates biaxially until it is cooled.

In the first phase of the process the mold, either cast aluminum or fabricated sheet metal, is charged with a rotationally moldable material. The most commonly used materials are polyethylene, polyvinylchloride, nylon or polycarbonate. Materials are also available with flame-retardant characteristics. The mold is then bolted or clamped back together and moved to the heating chamber.

Once in the heating chamber the mold begins to turn biaxially. As the mold turns the heat begins to cause the material to stick to the wall surface of the mold. Once the material reaches its melt index a puddle forms. The mold now begins to move around this puddle causing the material to coat the mold with layer upon layer of material. Finally the plastic begins to densify into a uniform wall of material.

Now that the heating, or curing, process is complete the mold continues to rotate and is indexed automatically to the cooling chamber. The mold is cooled using either air blown from fans and/or a water mist. Once the mold is sufficiently cooled it is moved to the load and unload area and the process begins again

The entire three step process takes approximately 45 minutes to complete. This longer process time allows rotational molders the ability to offer their customers added value other processes can not. Metal inserts can be molded into the parts eliminating the need for costly secondary operations. In mold graphics can be applied directly to the mold surface.

Rotationally molded parts have more consistent wall thickness than parts made by other processes. In fact rotational molding produces parts with an increased wall thickness in outside corners - an obvious advantage when part strength is an issue.

Rotationally Molded Spineboard Wins Eleven Awards of Excellence at ICE '98
Case History: Custom Pultrusions. Spinalboard Wins Best In Market Award.
Board Strength: Spineboard, rotationally molded by Formed Plastics, Inc., was shown, in independent laboratory testing, to withstand a distributed load of 2,500 pounds without structural failure.

This revolutionary new spineboard optimizes the benefits of composites. Used for immobilizing and transporting patients from the scene of an accident, the spineboard was designed with both the patient and rescuer in mind. This innovative design won Best of Market in the medical category at The Society of Plastics Industry's Composite Institute Product Showcase.

The design team from Strongwell developed a pultruded carbon fiber stiffening tube for dimensional stability. Utilizing a proprietary "Insert Rotational Molding" process, the pultruded stiffening tubes are completely sealed in high density polyethylene (HDPE). This eliminates drilling holes to insert the stiffening tubes and plugging the ends. Watertight composite materials and the one-piece sealed construction minimize contamination and maximize fluid resistance.

High strength composites were essential to the load requirements. In laboratory tests, the Spineboard has been shown to withstand distributed loads of greater than 2,500 pounds without structural failure. This far exceeds the performance of other similar products.

The Spineboard is an FDA Class I Medical Product. The all-composite structure does not interfere with x-rays or other medical imaging procedures used in diagnosing spinal trauma.