Usually horizontal and side-acting, an extrusion press form shapes by forcing metals or plastics through a die or series of dies. The resulting extrusions can be thick or thin, solid or hollow, and can even be tapered or stepped depending on the tooling. Metals can be extruded cool or heated to “billets” above the recrystallization temperature of the metal. Cool extrusion adds strength and hardness to the metal stock. Plastics are almost always extruded in a molten form. The most commonly extruded thermoplastics include nylon, polycarbonate, polyethylene, and polyvinyl chloride (PVC).
As the demand for stronger, lighter composite materials increases, manufacturers are looking for new ways to create large parts that have traditionally been formed using metal dies, stampings, or welded assemblies. Such is the case when a manufacturer of composite railroad ties explained their unique injection molding process to Beckwood’s application engineers.
The resulting side-acting extrusion press features a gravity-feed system which allows the material to gravity-drop directly into the pressing chamber. A spherical “plunger” attached to the press cylinder rod compacts and extrudes the material through the heated nose cone into a mold positioned on the outfeed side of the machine, and a mold latching system around the nose cone ensures that the mold is flush to the surface of the nose cone in order to reduce potential material waste. This out-of-the-box design has been successful in revolutionizing the way manufacturers processes their raw material into a finished product.