Pleiger Plastics offers various types of urethane molding and has extensive custom molding capabilities and experience.
Open casting thermoset polyurethane is a process where the reaction occurs once the raw materials are combined and poured into a mold to set and cure. This type of molding enhances the cross-linking of the polyurethane molecule, something that cannot be accomplished in the relatively short processing time of other molding types.
Advantages: results in a greater range of physical properties and better overall performance, low mold cost, large cross sections, and best metal bonding.
Disadvantages: parts frequently require secondary post machining, loose tolerances, fine details are difficult to achieve, slow cycle time, and scrap is not reusable.
Centrifugal molding is a process where a permanent mold is rotated continuously about its axis at high speeds. The material is centrifugally thrown towards the outside mold wall and sets up.
Advantages: impurities and inclusions are pulled to the top and can be machined off, large cross sections, reduced secondary processing, low porosity, better details, tighter tolerances, and best metal bonding.
Disadvantages: more expensive molds, part sizes limited, and scrap not reusable.
Compression molding is a process where the polyurethane is placed in a heated mold and put under pressure to set up and cure. The reaction takes place while the material is placed into the mold.
Advantages: large cross sections, reduced secondary processing, reduced excess flash, waste might be reusable, and fine details are possible.
Disadvantages: more expensive molds, looser tolerances, longer cycle times, and high amounts of scrap.
Injection molding is the process of injecting melted thermoplastic polyurethane pellets into a mold cavity at high pressure where it cools and hardens.
Advantages: tightest tolerances, low cost, high volume and speed, dual injection possible, easy to automate, waste is reusable, and ability to mold complex parts.
Disadvantages: shapes are limited and must be close to same wall thickness, material properties are not as good (due to heat history), tooling is very expensive, inserts are difficult to mold in, and the part is subject to knit lines and warping.
Liquid injection molding is similar to injection molding but instead of melting pellets, liquid is directly injected into a mold cavity.
Advantages: reduced secondary processing and produces more complex shapes.
Disadvantages: tooling is more expensive, there are looser tolerances, the part size is limited, long cycles, and high amount of scrap.
Foaming is the process of casting polyurethane foam. The material is mixed and placed in a closed mold to set up and expand during the polyurethane reaction. Density is determined by the weight of the material poured into the mold relative to the mold volume. (Density is typically measured in lbs/ft3 or kg/m3.)
Advantages: the material itself is the main advantage. The final product is made of high performance, shock absorbing, resilient polyurethane foam.
Disadvantages: cosmetic imperfections, part details are difficult, and a long cycle time.
For more information on urethane molding at Pleiger Plastics, contact us today.