Power injection molding

Polycarbonate can be readily injection molded. Polycarbonates typically require only a short injection molding cycle time, because the polymer flows into the mold easily and solidifies rapidly. We injection mold polycarbonate to produce a wide variety of commercial goods, including compact disks, jewel cases, aircraft windows, kitchen utensils, and clear refrigerators drawers. Polycarbonates are also found in a wide range of disposable medical devices, such as the flow locks on intravenous tubes and the hard, disposable components of dialysis machines. Impact resistant polycarbonate is used to manufacture sports and other safety helmets. Glass fiber reinforced polycarbonate is used in the housings for power tools. 

Poly(butylene terephthalate) (PBT) (1) resins are semicrystalline thermoplastics used in a wide variety of applications, most commonly in durable goods that are formed by injection molding. Applications include electronic and communications equipment, computers, televisions, kitchen and household appliances, industrial equipment, lighting systems, gardening and agricultural equipment, pumps, medical devices, food handling systems, handles, power and hand tools, bobbins and spindles, and automotive parts in both under-the-hood and exterior applications. Additionally, PBT is very widely used to form electrical connectors. PBT, through its many blended products, can be tailored to suit numerous applications. 

Pj hydraulic back pressure for an injection-molding plasticator (Eq. 10.22) maximum power rating for the motor in watts Pr pump ratio for a two-stage screw... 

An injection molding machine is operated by hydraulic power and equipped with an dectric motor and hydraulic pump. The maximum hydraulic oil pressure is ca 14 MPa (2000 psi). A hydraulic cylinder opens and closes the mold and holds the mold dosed during injection another cylinder forces the screw forward, thereby injecting the mdt into the mold. A separate hydraulic motor turns the screw to plasticate, homogenize, and pressurize the mdt. Control of these movements is a combined function of the hydraulic and electrical systems (35—37). 

Sample balancing problem. Let us consider the multi-cavity injection molding process shown in Fig. 6.54. To achieve equal part quality, the filling time for all cavities must be balanced. For the case in question, we need to balance the cavities by solving for the runner radius R2. For a balanced runner system, the flow rates into all cavities must match. For a given flow rate Q, length L, and radius R, solve for the pressures at the runner system junctures. Assume an isothermal flow of a non-Newtonian shear thinning polymer. Compute the radius R2 for a part molded of polystyrene with a consistency index (m) of 2.8 x 104 Pa-s" and a power law index (n) of 0.28. Use values of L = 10 cm, R = 3 mm, and Q = 20 cm3/s. 

Fig. 13.26 Experimental flow curves for PS and ABS. Lines represent fits with a Carreau, for PS, and Power Law, for ABS, constitutive equations. [Reprinted by permission from E. Vos, H. E. H. Meijer, and G. W. M. Peters, Multilayer Injection Molding, Int. Polym. Process., 6, 42 (1991).]...

Kuo, J.-K. et al., A novel Nylon-6-S316L fiber compound material for injection molded PEM fuel cell bipolar plates, J. Power Sources, 162, 207, 2006. 

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