Inserts molded

Compounds based on S—EB—S usually contain polypropylene, which improves solvent resistance and processibiUty and raises upper service temperatures. Compounds intended for use in the automotive industry are able to survive 1000 hours air exposure at temperatures of 125°C with only minor changes in properties (54). Very soft compounds have been developed to replace foam mbber for interior trim parts. In this and similar appHcations, these soft compounds are usually insert molded over polypropylene or metal and then coated with flexible polyurethane paint (55). Other automotive appHcations include products intended for sound deadening, flexible air ducts, and gear shifter boots, as weU as improving the properties of sheet mol ding compounds. 

All these type assembly methods usually require the same time to perform as placing inserts in the mold, but they also lower IMM time. There are several other means of accomplishing the desired result that depend on the circumstances at hand. In any event, conventional molded-in inserts usually prove costlier. There are highly automatic injection molding machines available designed just for insert molding that will reverse the cost. 

TPEs are often employed to produce a resUient and soft ergonomic layer over a hard structural part. This could be done in a number of ways [213]. TPEs can also be overmolded onto an engineering material through insert molding or multiple-shot injection molding. 

Overmolding is the process by which two different materials are joined into one assembly without using secondary operations like gluing or welding. In case the materials are chemically compatible, chemical bonds may form between them and so mechanical interlocks are not required. There are two common techniques of overmolding—insert molding and multiple-shot injection molding. 

There are presses that include shuttle (molds in which usually two, or more, are moved so that one mold is positioned to receive material and then moves to the press permitting another mold to receive material with this cycle repeating result is to permit insert molding, reduce molding cycle, etc.), rotary or carousal system, and book opening or tilting press.4 279... 

Insert molding, or in-mold decoration, helps overcome the flow lines common to metallic colored intricate injection-molded parts. By this process a film with a uniform orientation is thermoformed and fused with the surface of the injection-molded part. 

Laminating lends itself to the manufacture of resilient products with a large flat surface area and excellent surface properties. These products can be converted to their final form by thermoforming and insert molding. This method avoids the use of paint with its negative side effects, that is, the influence of solvents on the physical properties of the injection-molded part (tension and plasticizing effect). The lamination process also circumvents the optical problem of flow and weld lines. 

FIGURE 14-49 Schematic diagram of insert molding part inserted (left), mold closes and plastic injected... 

Another way of looking at the two-shot process is to consider the technique to be a derivation of metal insert molding except that the first shot is plastic rather than a stamped or formed metal. 

Window lenses for testing equipment are molded from clear polysulfone and then insert-molded in an ABS/PC meter case. Both the case and lens resist fuel, oil and common solvents, and meet military shock and vibration standards. 

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