Manufacturing Exam 1

what are some examples of mechanical properties

strength, ductility, elasticity, hardness, fatigue, crepp, toughness, fracture

what are some examples of physical and chemical properties

density, melting point, specific heat, thermal conductivity, thermal expansion, electrical conductivity, corrosion, oxidation

what is fatigue

the failure of material after repeated cycles of load

what is specific heat

the energy required to raise the temperature of a unit of mass by one degree

what is thermal conductivity

the rate at which heat flows within and through a material

what materials have the largest thermal expansion values

polymers

what is machining

the subtractive process involving the removal of material from a workpiece in the form of chips

what is feed

the distance the tool travels per unit revolution of the workpiece

how do you calculate the depth of cut (d)

D₁-D₂/2

how do you calculate the feed rate (v)

fN

what is feed rate

the linear speed of the tool along workpiece length

how do you calculate the max surface speed of workpiece

πD₀N

how do you calculate the average surface speed of workpiece

πDavgN

how do you calculate MRR

πDavgdfN

how do you calculate torque

FcDavg/2

how do you calculate power

Tω with ω=2πN

what are the units for feed rate

mm or in/min

what are the units for surface speed

m or ft/min

what are the units for MRR

mm³ or in³/min

what are the units for torque

Nm or lbft

what are the units for power

kW or hp

what are the recommended cutting conditions

high depth of cut and hardness, lower speed

what is strength

a measure of the extent of a material’s elastic range (toughness)

what is hardness

the measure of how resistant solid matter is to various kinds of permanent shape change when a force is applied

what is ductility

the extent of plastic deformation that the material undergoes prior to fracture

what are the types of chips produced by metal cutting

continuous, built-up edge, serrates or segmented and discontinuous

on a tool wear curve what is the pattern of velocity/initial wear and time

the initial wear is very fast then evens out to a more gradual pattern until the limit is reached, after that it substantially increases

why is a chip breaker helpful

long chips can interfere with the tool and present a safety hazard

what is hot hardness

maintained hardness at the temps encountered in machining operations

what is thermal shock resistance

the capability of resistance against the rapid temp change

what is the relationship between hardness and temperature in machining

as temp increases, hardness decreases

why are coated tools beneficial

they provide shock resistance, high wear resistance, cutting-edge strength, resistance to oxidation and thermomechanical stability

what are the purposes of cutting fluids

reduce friction and wear, cool the cutting zone, reduce forces and energy consumption, flush away chips, protect surface from environmental corrosion

what are the types of cutting fluids

various water-based and petroleum-based coolants

where is the appropriate application of cutting fluids on the workpiece

where the cutting is happening, where tool and workpiece meet

how do you calculate the MRR for drilling

(πD²/4)fN

what are normal drilling problems and their causes

-drill breakage: dull drill, chip clogging

-poor hole surface finish: dull drill, ineffective fluid, improper alignment

-oversize/tapered hole: misaligned or bent drill, machine spindle, side force

-excessive drill wear: high cutting speed, ineffective fluid, high rake angle, lost strength during sharpening

what is important in deep hole drilling

the depth to diameter ratio (beyond 3:1 is deep)

what is milling

a number of highly versatile machining operations taking place in a variety of configurations with the use of a milling cutter

what is a milling cutter

a multitooth cutter tool that produces a number of chips in one revolution

what are important parameters for milling

the cutting speed, feed per tooth, cutting time and MRR

what are the types of milling

conventional, climb, face and end

how do you calculate the cutting time

(l+lc)/v where lc is the extent of the cutter’s first contact with the workpiece

how do you calculate the MRR for milling

wdv

what are some problems in milling

tool breakage, excessive tool wear, rough surface finish, burr formation, breakout, back striking

what is the objective of abrasive machining and finishing

to create smooth surfaces

what is an abrasive

a machine capable of removing small amounts of material from a surface by a cutting process that produces tiny chips

what are some issues in grinding

temperature rise, sparking, tempering, burning, heat checking, residual stresses, wheel wear

what is dressing in milling

the process of conditioning, producing sharp edges on worn grains on the grinding surface of a wheel

what do grinding fluids do

reduce temp rises, improve part surface finish, improve the efficiency of the operation

what is belt grinding

coated abrasives are used for high-rate material removal with good surface finish

what is honing in grinding

an operation that is used primarily to improve the surface finish of holes produced by processes such as boring, drilling, and internal grinding

what is happing in grinding

an operation for finishing flat, cylindrical, or curved surfaces

what is chemical mechanical polishing (CMP) in grinding

the use of a suspension of abrasive particles in a water-based solution, with a chemistry selected to cause controlled corrosion

what are burrs

thin ridges, usually triangular in shape, that develop along the edges of a workpiece from operations

what is the relationship between time and the accuracy of machining

as time increased, accuracy increases

what is the process of casting

melting the material, pouring it into a cavity, waiting for solidification and post-processing

what are the advantages to casting

can form complex shapes, can have hollow parts, good for very large parts, intricate shaping, very versatile

basic requirements of casting

a mold cavity, a melting process and a pouring technique that allows gases and air to escape, post-processing, solidification, a reusable mold must allow removal

what is sand casting

a mold is made out of sand with clay and water as additives, the sand is packed around a pattern having the desired shape, a reusable process because of the sand

what is the downsprue in sand casting

the funnel shaped entry point for the metal to get into the mold

what is the runner in sand casting

it distributes molten metal to the gates

what are gates and ingates in sand casting

the entry point of the metal into the casting shape

what is the riser in sand casting

a reservoir of excess metal above the mold cavity serving as a feeder of liquid metal to the part as it solidifies

what is the relationship between time, temperature and density in casting

as time increases, temp decreases and density increases

what does a smaller grain structure in a casted object mean

it solidified quicker and has a higher strength

how do you calculate the time for solidification for casting

B(V/A)ⁿ

why does solidification shrinkage occur in casting

because of phase changes from liquid to solid

what are common defects in casting

hot tears, metallic projections, cavities, discontinuities, defective surfaces, incomplete casting, and incorrect dimensions or shapes

what is gas porosity

gas trapped in the solid object that was not rejected from the liquid metal

what is a shrinkage cavity

a defect in the casting where a region of liquid metal surrounded by solidified metal will cause a shrinkage cavity where the last pocket of liquid metal solidifies

how do we combat casting shrinkage

when designing the mold cavity, allowances are made

what are some design consideration in casting

most molds have a single flat parting line along which they can be split to remove the casting, and most molds are reusable

what are some way we control solidification in casting

keeping thickness changes gradual, avoiding sharp corners and avoiding thinly webbed sections

what is taylors equation for tool life

C=VTⁿ