Surface Processes Flashcards
Distinguish and describe common machine layout for surface grinding, cylindrical grinding, and centerless grinding
o Surface grinding: most common, involves the grinding of flat surfaces, for horizontal spindle grinding work is held to table, the table moves over the grinding wheel:
o Cylindrical grinding: the external cylindrical surfaces and shoulders of an object are ground, work piece is held between centers or in a chuck both wheel and work rotate
o Centerless grinding: continuously grinding cylindrical surfaces in which the work is supported by a blade not by centers or in a chuck
Distinguish and describe the processes of honing, lapping, polishing, and electropolishing
o Honing: used primarily to improve the surface finish of holes, multiple stones are mounted to a single mandrel
o Lapping: used to finish flat, cylindrical, or curved surfaces, the lap is either imbedded with the abrasive particles or they can be carried in a slurry, good for fine finish, but can take days
o Polishing: similar to lapping but coarser
o Electropolishing: process is same as electrochemical machining, however only removes tiny amounts of material, produces very fine surface finish
Describe the mechanism and the purpose for each of the following: sand blasting, shot peening, case hardening, thermal spraying, and anodizing
o Sand blasting: operation of forcibly propelling a stream of abrasive material against a surface under high pressure to smooth a rough surface, roughen a smooth surface, shape a surface, or remove surface contaminants. A pressurized fluid, typically air, or a centrifugal wheel is used to propel the media
o Shot peening: surface is impacted repeatedly with a lot of cast steel, glass, or ceramic shot, causing plastic deformation which can improve fatigue life because of residual stress
o Case hardening: induces residual stress on the surfaces because of the formation of martensite
o Thermal spraying: coatings of various metals, alloys, carbides, ceramics, and polymers applied using a spray gun with a stream heated by flame, electric or plasma arc. Done to give wear and corrosion resistance
o Anodizing: an oxidation process, surfaces are converted to a hard and porous oxide layer that provides corrosion resistance and a decorative finish. The work piece is the anode in an electrolyte cell immersed in an acid bath, which results in chemical absorption of oxygen.
Distinguish and describe the processes of electroplating, electroless plating, and electroforming
o Electroplating: the work piece (cathode) is plated with a different metal (anode), which is transferred through a water-based electrolytic solution
o Electroless plating: done without external source of electricity, uses chemical reaction, more expensive than electroplating however thickness is always uniform
o Electroforming: metal is electrodeposited on a mandrel (mold, matrix) which is then removed, thus the coating itself becomes the part, suitable for low production runs or intricate parts
Define and distinguish surface roughness parameters based on arithmetic average vs. root-mean-square, and their relative merits
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