Manufacturing Processes Tools Manufacturing Processes

Outline Types of Tools Tool Geometry Cutting Fluids Tool Wear Effects Types Tool Wear Forms Causes Failure Modes Critical Parameters Horsepower Used Operating Temperature Feed and Speed Tool Life

Types of Tools

Tool Geometry Single Point Tools Multiple Point Tools Chip Breakers Effects of Material on Design

Single Point Tools

Multiple Point Tools

Chip Breakers

Important Tool Properties High hardness Resistance to abrasion, wear and chipping of the cutting edge High toughness/impact strength High hardness at high temperatures Resistance to bulk deformation Chemical stability (does not react or bond strongly with the work material High modulus of elasticity (stiffness) Consistent tool life Proper geometry and surface finish

Tool Materials Carbon and medium-alloy steels High-speed steels Cast-cobalt alloys Carbides Coated tools Alumina-based ceramics Cubic boron nitride Silicon-nitride-base ceramics Diamond Whisker-reinforced materials

Cutting Speeds of Tool Materials

Cutting Fluids Effects Types coolant lubricant flushes chips reduces oxidation of heated surfaces Types cutting oils emulsified oils chemical fluids

Cutting Fluid Application Flooding ≥ 3 gallons per minute per tool Misting atomized fluids a health hazard (OSHA limit = .2 mg/m3) High Pressure Systems often applied through the tool

Tool Wear Forms Causes crater wear flank wear chipping abrasion adhesion diffusion plastic deformation

Crater Wear and Flank Wear

Failure Modes Fracture Temperature Failure Gradual Wear

Critical Parameters Horsepower Used Operating Temperature

Horsepower Used Values of Unit Horsepower for Various Work Materials Brinell Hardness Unit Horsepower hpu hp/(in3/min) Carbon Steels 150-200 0.6 201-250 0.8 251-300 1.0 Cast Irons 125-175 0.4 175-250 Aluminum 50-100 0.25

Operating Temperature

Feed and Speed Speed – the rate at which the tool point moves as it rotates (in a lathe, the rate at which the cutting point on the workpiece rotates) Feed – the rate at which the tool is fed into/along the workpiece

Feed and Speed V = πDN/12 V = surface cutting speed (ft/min) D = diameter of rotating object (in.) N = rotation rate (RPM)

Feed and speed Example: Assume a high-speed steel saw with 100 teeth and a diameter of 6 inches is used to cut aluminum. Determine the proper RPM and feed rate. V (HSS, aluminum) = 550-1000 ft/min [in table] N = 12V/(πD) = 12(550-1000)/(π6) = 350-637 RPM Feed (aluminum, saw) = .006-.01 in/tooth [in table] (.006-.01)100 teeth = .6-1in (.6-1)350 RPM = 210-350 in/min Start with the lowest values. They can be increased so long as the finish is acceptable.

Taylor Tool Life Equation F. W. Taylor, 1907 Taylor Tool Life Equation vTn = C vTn = C(Tn ) ref

Cutting Performance How do we know if cutting parameters are optimal? Surface finish Tool wear Chip shape Sound Cutting time Heat

Summary Tools fail slowly with gradual wear or suddenly with fracture Cutting fluids help reduce the effects of wear and temperature failure The materials of the tool and the workpiece affect the tool shape and life Higher cutting speeds increase the operating temperature and decrease tool life It is necessary to calculate proper feed and speed to prevent excessive tool wear

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