Because of the chemical nature of thermoplastic materials, injection molding has traditionally been the primary molding method for thermoplastics, and compression and transfer molding have been the primary molding methods for thermosetting plastics. Because of the greater molding cycle speeds and lower molding costs in injection molding, thermoplastics have had a substantial molding cost advantage over thermosets.
Advantages in equipment and in thermosetting molding compounds, however, have resulted in a rapid transition to screw-injection, in-line molding. This has been especially prominent with phenolics, but other thermosets are also included to varying degrees. The growth in screw-injection molding of phenolic has been extremely rapid. The development of this technique allows the molder to automate further, reduce labor costs, improve quality, reduce rejects, and gain substantial overall molding cycle efficiency. (Charles A. Harper, Edward M. Petrie, Plastic Materials and Processes- A Concise Encyclopedia, A John Wiley & Sons,Inc.Pub., 2003. p.560)
Powder Coating
Powder coating is a method for applying finely divided, dry solid resinous coatings by dipping products in a fluidized bed or by spraying them electrostatically on the part. The fluidized bed is essentially a modified dip tank. When charged powder particles are applied during the electrostatic spraying method, they adhere to grounded parts until fused and cured. In all case the powder coating must be heated to its melt temperature where a phase change occurs, causing it to adhere to the product and fuse to form a continuous coating.
Both thermosetting and thermoplastic powder can be applied by powder coating processes. Elaborate reclaiming systems to collect and reuse over-sprayed material in electrostatic spray powder systems boost transfer efficiency. Since the enhancement of the air quality standards this method has grown markedly. (Charles A. Harper, Edward M. Petrie, Plastic Materials and Processes- A Concise Encyclopedia, A John Wiley & Sons,Inc.Pub., 2003. p.457)
Slush Molding
Slush molding is an excellent method of producing hollow objects. A wide variety of products can be manufactured by this process, including rainboots, shoes, hollow toys and dolls, and automative products such as the protective skin coatings on arm rests, head rests, and crash pads. The basic process of slush molding involves filling a hollow mold with plastisol, exposing the mold to heat, gelling an inner layer or wall of plastisol in the mold, inverting the mold to pour out the excess liquid plastisol, and heating the mold to fuse the plastisol. The mold then is cooled and the finished part removed. Slush molding can be a simple hand operation for limited production or an elaborate conveyorized system for long runs. This process can be a one-pour method, where finished or semi-finished products can be made by one slushing, or a multiple-pour method, where two or more slushing are used. ( Michael L. Berins, Plastics Enginnering Handbook of The Society of The Plastics Industry, Kluwer Academic Pub. 2002, 5th Edition, p.491)
FAST Diagram
Fuctional Analysis System Technique (FAST) is provided alternative to the function tree that is a hierarchical functional breakdown structure starting with a system function or a system mission. The FAST diagram is drawn from left to right. We start with a system function on the left side and ask how this funtion is (or may be ) accomplished. The functions on the first level are than identified and entered into the diagram. We continue asking how until we reach the intended level of detail. The lower level functions can be connected by AND or OR relations. Functions that have to be performed at the same time may be indicated by vertical arows. ( Marvin Rausand, Arnljot Hoyland, System Reliability Theory: Models, Statistical Methods and Aplications, John Wiley & Sons, Inc. Pub., 2004, Second Edition, p.80-81)
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