Kinematic Restraint Fixturing Mechanics for Injection Molded Thermoplastics Metrology
Kinematic restraint fixturing isolates molded thermoplastic part geometry by arresting six spatial degrees of freedom without introducing bending strain.
Injection Molded Thermoplastics
Meaning
Polymer materials change from a solid to a liquid state when heated and return to a solid state upon cooling within a high pressure mold. The category of injection molded thermoplastics includes substances like polypropylene or nylon which can be reshaped multiple times. This process allows for the mass production of complex geometries with high repeatability.
It remains the dominant method for creating plastic housings and mechanical components in the automotive sector.
Production Yield
High volume manufacturing relies on the stability of the raw resin. Any variation in the melt flow index can alter the cooling time for injection molded thermoplastics.
Thermal Processing
The cycle begins when raw pellets enter a heated barrel and become a viscous melt. Modern injection molded thermoplastics require precise temperature control to avoid degrading the molecular chains of the polymer. Once the material enters the cavity, it must cool quickly to minimize the cycle time.
Cooling channels in the tool pull heat away from the part. If the temperature is uneven, the part may warp or develop internal stresses. This cooling phase represents the longest portion of the manufacturing cycle.
Material Property
Mechanical strength and chemical resistance vary widely between different grades of resins. Engineers choose specific injection molded thermoplastics based on the environmental demands of the final application. Some materials offer high impact resistance while others prioritize clarity or heat deflection.
The addition of glass fibers can increase the stiffness of the component.