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Duplex Mills (in Roll Forming)

Two cantilevered mills facing each other are called a duplex mill. Duplex mills have one common base and drive. They can form both edges of narrow or wide products leaving the center flat. The minimum strip widths depend on how close the opposing rolls can be pushed together, and the maximum widths usually depend on how far the two mills can be moved from each other. The width of the formed duplex mill with one or two adjustable row products can be changed quickly by adjusting of stands. Duplex mills have the same advantages and disadvantages as the cantilevered mills, except that the shaft end connecting pieces cannot be used. Some duplex mills have shafts extended at the other side of the mill, which can be used to form narrow sections. Duplex mills either have one side fixed and the other one adjustable, or both sides adjustable. Adjustment of a side is usually accomplished by placing all stands on one plate, which, with proper guides, can be moved in and out, thus changing the gap between the two cantilever mills. For duplex mills with one adjustable row of stands, the centerline of the product changes with width change. In the case of duplex mills with two adjustable rows of stands, the centerline of the products remains in the same position. This arrangement is used when holes are prepunched at or around the centerline, either when the cutoff die has to be kept symmetrical or for other reasons when it is advantageous to keep the centerline in the same position. The width adjustment can be manual or motorized.

(Halmos G.T., Roll Forming Handbook, pg. 2-7, Kayra Ermutlu)

Conventional Injection Molding (in PMC)

In PMC shape processing, injection molding is used for both TP- and TS-type FRPs. In the TP category, virtually all thermoplastic polymers can be reinforced with fibers. Chopped fibers must be used; if continuous fibers were used, they would be reduced anyway by the action of the rotating screw in the barrel. During injection from the chamber into the mold cavity, the fibers tend to become aligned during their journey through the noozle. Designers can sometimes exploit this feature to optimize directional properties through part design, location of gates, and cavity orientation relative to the gate.

Whereas TP molding compounds are heated and then injected into a cold mold, TS polymers are injected in to a heated mold for curing. Controll of the process with thermosets is trickier because of the risk of premature cross-linking in the injection chamber. Subject to the same risk, injection molding can be applied to fiber-reinforced TS plastics in the form of pelletized molding compound and dough molding compound.

(Groover M.P., Fundamentals of Modern Manufacturing: Materials, Processes and Systems, pg. 337, Kayra Ermutlu)

Polysulfone

Polysulfone is a family of sulfur-containing thermoplastics. It was first introduces as Bakelite Polysulfone (Udel-TM) by Union Carbide in 2965. The family of polysulfones also includepolyarylsulfones, polyethersulfones, polyphenylsulfones, and polyarylether sulfones. Polysulfones are prepered via two different methods of condensation polymerization. The first is polysulfonylation; the second is polyetherification. The principle characteristics of polysulfones include their outstanding heat resistance, exceptional resistance to creep, rigidity, transparency, and their resistance to greases, solvents and chemicals. Additionally, they are self-extinguishing. They are among the higher priced engineering thermoplastics and so are only used in situations where polycarbonates or other cheaper materials are not suitable. Polysulfones have the highest service temperature (170C) of all melt-processible thermoplastics.

(DIANE Publishing Company, New Materials Society, Challenges and Opportunities, Vol-2, pg.8-50, Kayra Ermutlu)

Surface Processing Operations

The major categories of surface processign operations are cleaning, surface treatments, and coating and thin film deposition. Cleaning refers to industrial cleaning processes that remove soils and contaminants that result from previous processing or the factory environment. They include both chemical and mechanical cleaning methods. Surface treatments are mechanical and physical operations that alter the part surface in some way, such as improving its finish or impregnating it with atoms of a foreign material to change its chemistry and physical properties.

Coating and thin film deposition include variousprocesses that apply a layer of material to a surface. Products made of metal are almost always coated by electroplating (e.g. chrome plating), painting or other processes. Principal reasons for coating a metal are to provide corrosion protection; enhance product appearance (e.g. providing a specified color or texture); increase wear resistance and/or reduce friction of the surface; increase electrical conductivity; increase electrical resistance; prepare a metallic surface for subsequent processing; and rebuild surfaces worn or eroded during service. Nonmetallic materials are also sometimes coated. Examples include plastic parts coated to give them metallic appearance; antireflection coatings on optical glass lenses; and certain coating and deposition processes used in the fabrication of semi-conductor chips and printed circuit boards. In all cases, good adhesion must be achieved between coating and substrate, and for this to occur the substrate surface must be very clean.

(Groover M.P., Fundamentals of Modern Manufacturing: Materials, Processes and Systems, pg.668, Kayra Ermutlu)