We invented the roto molded traffic door in 1976. Since that time we have sold over half a million doors. What we do is unique and the Durulite product is known throughout the industry as the toughest door on the market and by which all others are measured.
Molding a full-size double acting impact door is very different from traditional impact traffic door construction methods. Most products, including our Proline and Chase SC3000 double acting doors, are based on a frame and skin or a multi-layer lamination method of construction. While fine for light to medium duty applications, many of these designs are inadequate in heavy-duty traffic situations. The adhesives and mechanical fasteners used to attach materials to frames or create “laid up” composites of wood, plastics and metals have minimal ability to stretch on impact causing material stress that can lead to damage or complete breakage after repeated impacts over time.
Formed as a monolithic, one-piece hollow shell, a roto-molded traffic door does not have seams, does not use adhesives or mechanical fasteners for its structure. High-density cross-linked polyethylene is a naturally resilient material with a surface that has resistance to solvents and adhesives. The panel is also lighter in weight than its’ laid up counterpart because no internal framing is required.
The process of rotational molding or the more common term roto-molding is an art and a science. It starts by placing a specific amount of colored plastic resin into the bottom half of a two piece aluminum mold. The mold is closed and then attached to a long arm on an automated molding machine. The machine may have multiple molds on three to five of these arms which radiate from a central, motorized wheel. The mold arm first moves into an oven chamber. As the mold slowly spins on two axes the resin melts and adheres to the inside of the hot mold. After the proper amount of “cooking time”, the mold swings to the next station where air is used to cool down the mold, allowing the material to set while it continues to spin to assure an even wall thickness. When it is completely cooled it swings to the original station where the mold is opened and a hollow door shell is removed. The rotational speed, heating and cooling times are all controlled throughout the process.
After cooling is complete, the hollow panel is put into a hydraulic press where it is injected with non CFC urethane foam, which completely fills the cavity inside of the hollow door shell. The foam provides a variety of benefits, including thermal insulating characteristics and increased shock absorbency. The panel then moves to the floor for trimming, finishing and addition of windows and ordered options before being packaged with its’ installation hardware. The impact traffic door is then ready to be packaged and shipped.
Our modern, 82,000 square foot manufacturing facility in Redmond, Oregon is dedicated to the rotational molding of our Durulite door products and extruding our flexible PVC strip material. We are long time members of the Association of Rotational Molders International (ARM).