Cast Polyurethane Molding

Cast Polyurethane

Poly-Tek works collaboratively to develop custom polyurethane products to meet exactly what you want. This ensures that your part’s form, fit, and function match your application.

Polyurethane performs extremely well across a variety of applications. Even though some applications may be typical, we specialize in manufacturing custom parts. Each custom polyurethane part is designed and manufactured to meet your unique requirements. Some applications include environments where outstanding abrasion resistance is required. It is typical for polyurethane to outwear corresponding parts made of metal, plastic, or rubber by a wide margin. Other applications include situations where load-bearing is important. Polyurethanes have excellent load-bearing capability and exhibit deflection and recovery that far exceed plastic or metal. Methods of manufacturing parts from polyurethane include open cast molding, centrifugal molding, compression molding, and injection molding.

Open Cast Molding

This is the simplest of the molding methods. Polyurethane is smoothly poured into an open-top mold, or sometimes gently flowed up from the bottom of the mold. Molds for casting polyurethane parts can be made from a wide range of materials. The most important factor is that they must be impervious to moisture and not contain any moisture. Some of the main materials used to make molds include the following: polyurethane aluminum, silicones, steel, or hard thermoplastics.

Centrifugal Molding

The mold is rotated in one dimension (e.g. on the horizontal plane) while the polyurethane is poured in. The spinning action forces the polyurethane to move to the circumference of the mold, while the air is displaced towards the mold center. This method is used to mold products with complex details that would otherwise trap air bubbles. By spinning the mold in both the horizontal and vertical axes (or at an angle), three-dimensional hollow parts can be made. The mold may be rotated and rocked as an alternative.

Compression Molding

Compression molding uses a machine force to clamp together two halves of a mold using hydraulic pressure. The applied pressure forces the polyurethane into all cavities of the mold. This produces products with complex shapes, without the need for secondary machining operations. More complex compression molds can be made when there are shapes on all sides. The location of the plates is controlled by the fitting of location pins and corresponding bushings in the plates. Compression molds also apply more definitive pressure to the gelled polyurethane. This will give a less porous molding if there is any moisture foaming.

Injection molding

Injection molding automates the process with fast cycle times in a matter of seconds. The entire process takes place in one specialized, automated injection molding machine. It starts with feeding solid polyurethane pellets into the machine’s injecting barrel. The barrel contains a reciprocating screw that feeds and plasticizes the pellets forward toward the mold. The high shear action of the screw frictionally heats the pellets, fully melting the polyurethane by the end of the barrel. When enough material has accumulated at the end of the barrel, the molten polyurethane is forced at high pressure and velocity into the mold.