Shaped tube electrolytic machining (STEM): (Previous)
A second process, known as the shaped-tube electrolytic machining (STEM) process, was also created in response to unique challenges presented in the jet engine industry. Like the electrostream
process, STEM is also capable of gang drilling small holes in
difficult-to-machine materials However, the STEM process is generally
not capable of drilling holes smaller than about 0.02 in. STEM is
capable of making shaped holes with aspect ratios as high as 300:l.
Holes up to 24 in. m depth have been drilled. Like the electrostream
process, it uses an acidic electrolyte to minimize clogging due to
sludge buildup. The major differences between the STEM process and the
electrostream process are the reduced voltage levels (5 to 10 V dc)
and the special electrodes, which are long, straight, metallic tubes
coated with an insulator. The insulator helps to eliminate taper by
constraining the electrolytic action between the bottom of the tool and
the workpiece. Titanium is often used for its ability to resist acids.
The electrolyte is pressure-fed through the tube and returns through the
gap (0.001 to 0.002 m.) between the insulated tube wall and the hole
wall. Electrolyte concentrations may include up to 10% sulfuric acid.
Lower concentrations may be used to increase tool life.
(MATERIALS AND PROCESSES IN MANUFACTURING 10th edition, J. Temple Black, Ernest Paul DeGarmo, Ronald A. Kohser, p.507)
Shaped tube electrolytic machining (STEM): (New)(Better)(Machining)
Shaped tube electrolytic machining (STEM) is a specialized ECM technique for drilling small, deep holes by using acid electrolytes (Fig.48). Acid is used so that the disaaloved metal will go into the solution rather than form a sludge, as is the case with the salt-type electrolytes of ECM. The electrode is a carefully straightened acid resistant metal tube. The tube is coated with a film of enamel-type insulation. The acid is pressure-fed through the tube and returns via a narrow gap between the tube insulation and the hole wall. The electrode is fed into the workspiece at a rate exactly equal to the rate at which the workpiece EDM is suitable for cutting materials regardless of their hardness or toughness. Round or irregular-shape holes 0.002 in. diameter can be produced with L/D ratio 20:1. Narrow slots as small as 0.002-0.010 in. wide are cut by EDM.(Handbook of materials selection, Myer Kutz, p.917)
Electrochemical Corrosion: (Previous)
Electrochemical Corrosion is
understood to include all corrosion processes that can be influenced
electrically. Corrosion in general is the chemical reaction between the
metal and the surrounding environment. Electrochemical corrosion occurs
in corrosive environments depending on the galvanic series. There are
several types of electrochemical corrosion such as uniform corrosion,
galvanic corrosion, hydrogen induced cracking etc. these can be present
either one at a time or both in one case.
(Baeckmann, W, Handbook of cathodic corrosion protection, p.29) Electrochemical Corrosion (New)(Better)(Corrosion Type)
Electrochemical corrosion in metals in a natural enviroment, whether atmosphere, in water, or underground, is coused by a flow of electricity from one metal to another, or from one part of a metal surface to another part of the same surface where conditions permit the flow of electricity.
For the flow of energy to take place, either a moist conductor or an electrolyte must be present. An electrolyte is an electricity-conducting solution containing ions, which are atomic particles or radicals bearing an electrical charge. Charged ions are present in solutions of acids, alcalis, and salt. The presence of an electrolyte is necessary for corrosion to occur. Water, especially salt water, is an excelent electrolyte.
( Surface engineering for corrosion and wear resistance, Joseph R. Davis, p.12)
Addition Polymerization: (Previous)
Addition polymerization is the polymerization of the monomers by a chain mechanism involving active sites on the growing chain. Addition polymerization is frequently accomplished with unsaturated monomers, it is also called vinl polymerization when the unsaturated monomer contains the group -CH2=CH2-
(Charles A. Harper, Edward M. Petrie, Plastics materials and processes: a concise encyclopedia page 13)
Addition Polymerization: (New)(Better)(Synthetic Materials)
Polyethylene is the simplest polymer. It forms by making carcon-carbon bond between adjacent molecules of gaseous ethylene (C2H4). Polymerization is initiated by oxygen at high temperature and pressure, by spported metal catalysts, or by titanium-based catalysts in solution. Recall that such as a species is a free radical. The free radikal can add to the double bond of another ethylene molecule to form a new carbon carbon bond and generate an unpaired electron on the end of the growing chain. Because of the polymer forms by adding ethylene molecules to the growing chain, the process is termed addition polymerization.
(Braving the elements, Harry B. Gray,John Douglas Simon,William C. Trogler, p.226)
Poly-Ond: a new technology for plating metal (Previous)
Poly-Ond, a proprietary formulation developed in 1976, is a liquid bath process which chemically deposits nickel phosphorus, impregnated with polymers, on the surface of metal parts. This process permits the use of less expensive metals when anticorrosive materials are called for.
(Modern Manufacturing Processes, Brown, p.44)
Poly-Ond: (New)(Better)(Plating Metal)
Poly-Ond plating is basically an electroless nickel plating impregnated with a flouropolymer. This yields a öoderately hard, corrosion-resistant layer with a low coeficcient of friction. The low coeficient of friction makes it attractive to use in injection molds and on extruder screws. Luker from Killion Extruders reported [35] on tests with Poly-Ond plated extruder screws. He reported output increases from 5 to 36% for a number of different polymers.
(Polymer extrusion, Chris Rauwendaal, p.659)
Metallizing: (Previous)
Plastics are nonconductors of electricity, which allows them to be used in many unique applications, such as electronic devices, protective housings, and advanced military systems (stealth vehicles). There are many applications that demand plastic materials to be electrically conductive or highly reflective. Compact discs, automotive lightning systems, and chrome-like decorative surfaces for auto and truck grills have unique demands for plastic materials, and all of these applications require a metal layer to be somehow applied to the surface of the plastic. The use of metallizing is categorized as follows:
- Functional: Used to reflect or conduct energy, such as light or electricity, in electromagnetic interference (EMI) reduction and radio frequency interference (RFI) reduction
- Decorative: Used to create an appearance, such as auto/truck grills
- Both: Provides both a functional and decorative service
(Edward A. Muccio, Decoration and Assembly of Plastic Parts, p. 161)
Metallizing: (New)(Better)(Coating)
Metallizing is the deposition of an adherent coating of finely divided particles of metal, intermetalics, or metalic oxides upon a base metal. The corrosion protection of aliminum and zinc coating applied to low-carbon steel is considered in this paper. Panels coated with these metals were exposed to urban, industrial and marine enviroments over a nine-year period. Studied were thicknesses of coating, effect of methods of steel preparation, and effect of seal coats. Addequate corrosion protection was afforted in nearly all cases, aliminum providing slightly better protection than zinc.
Metalizing, shown in Fig. 1, is the process of depositting finely divided particles of metal, itermetallics or metallic oxides in a heated, semi-molten condition in order to form an adherent coating. Metal in the form of wire or powder is fed to a 'gun' heated by an oxy-fuel gas or plasma arc, and delivered to the work by high velocity air.
(Finishes for metals: paintability of galvanized steel, corrosion resistance, Building Research Institute, p.35)
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