Grand Valley State UniversityPadnos School of EngineeringEGR 367: Manufacturing ProcessesLaboratory Exercise 4:Effect of Variables on Injection Molding of Polymers10-8-02Dale SlotmanPartners:Hung NygungDan ShirkeyAdam VerbeekAbstractBlah blah blah.IntroductionInjection molding is a versatile process that can be used with most polymeric materials to create parts of a range of complexities. Injection molding of a polymeric material involves the melting of the material, the injection of the material into a mold, thesolidification of the material, and the removal of the part from the mold. Injection molding is the most commonly used molding process for thermoplastics (Groover 275). Reasonable tolerances can be achieved using injection molding, at a fraction of the time cost of machining parts. This makes injection molding an economical choice for production.The objective of this laboratory exercise was to investigate the effects of molding conditions to the quality of polymeric parts made using injection molding. The conditions to be observed were material composition, injection temperature, cycle time, and air pressure.Experimental ProcedureThe first material tested in the injection molding machine was high density polyethylene. The injection molding machine was brought to a barrel temperature of 407 deg F and a nozzle temperature of 425 deg F. The air pressure was set to 6000 psi at the air inlet. Residual plastic was purged from the machine by placing high density polyethylene into the hopper located on top of the machine and shooting hot plastic onto a flat sheet until only high density polyethylene was emitted from the nozzle.A small amount of mold release was applied to the mold cavity and to the nozzle of the injection machine. The hopper was refilled with high density polyethylene.An injection was performed using a dwell of 5 seconds. Another injection was performed for 10 sec. A third injection was performed for 2 seconds.After the third sample, the injection molder would not produce usable parts. Not enough plastic was being injected to fill the mold. The plastic coming out of the injectionmolder was chunky and looked like it had not been melted properly.The barrel temperature was turned up to 410 deg, and a sample was taken with a dwell of 4 seconds.The air pressure was turned down to 4500 psia and a sample was taken with a dwell of 5 seconds.Width measurements were taken on all samples at three corners. Mass measurements were also taken on all samples, including flash mass
View Full Document