EME 050 W26 Habibi Midterm

Machining

Removing material and modifying the workpiece surface

Cutting

Removing material through shearing off chips; machining with geometrically defined cutting edge

Turning

Cutting parts with rotational/helical symmetry by feeding a single-edge tool into a rotating workpiece

Drilling

Cutting a hole

Milling

Cutting parts by feeding the workpiece along translational or rotational axes into a rotating multi-edge tool

Peripheral milling

Tool axis parallel to milling surface

Face milling

Tool axis perpendicular to milling surface

Primary/cutting motion

Motion which without feed motion leads to only one chip formation, generally rotational OR motion responsible for chip formation

Subsidiary/feed motion

Leads to multiple chip removal, generally translational

Boring

Turning to enlarge a hole

Reaming

Finishing operation for holes to produce a high precision inner surface with high surface quality

Broaching

Cutting with a profiled tool that has progressively larger teeth

Sawing

Cutting with a thin metal blade or disk that has a multi-toothed edge

Feed

Distance of tool in direction of feed motion per workpiece revolution

Feed rate/velocity

vf, instantaneous velocity of feed

Cutting speed

vc, instantaneous velocity of primary motion on the cutting edge relative to the workpiece

Material removal rate

Volume of material removed divided by time

Up/conventional milling

Peripheral milling with feed direction against rotation direction, can cut more than desired

Down/climb milling

Peripheral milling with feed direction same as rotation direction, used for finishing and can cut less than desired

Circular saw, band saw, and hack saw

Sawing methods

Sawing restrictions

Tooth orientation patterns in saw blades

Trochoidal milling

Constant circular movement used to produce required slot width

Hob

Complex tool used to produce gears

Idealized wedge engagement

Orthogonal cutting, approximates a turning process

Clearance angle

Angle between vertical and flank face

Rake angle

Angle between horizontal and rake face

Nose radius

Viewed from top of the tool, minimum feed must be greater than this

Wedge angle

Angle between rake face and flank face

Chip control, surface finish/integrity, force/power required, tool life

Four factors of machinability

Fracture (force) and temperature (plastic deformation of sharp edge)

Main types of tool failure

Material, interface, tool, and machine

Main factors of tool wear

Abrasion

Harder material shears small particles from softer work material

Adhesion

Fragments of softer work material adhere to harder tool. These fragments can separate and tear away pieces of the cutting tool

Diffusion

Atoms from the tool migrate to the workpiece, softening the tool. Caused by high temperatures

Oxidation

Reactions between the air and the cutting tool or work material

Crater/rake wear

Caused by abrasion, diffusion, and oxidation

Flank wear

Dominated by abrasion, more important as it affects surface quality

Tool wear, machine errors, structural errors

Systematic manufacturing errors

Unknown material source, tool breakage, chatter, machine vibration

Stochastic manufacturing errors

100% control

Every part is inspected for quality control

Statistical control

Every n component is inspected for quality control

Random control

Random components are inspected for quality control

Precision

Repeatability, not necessarily correct

Accuracy

Correct but not necessarily repeatable

IT number

Describes tolerance grade

Letter

Describes fundamental deviation

Shaft fundamental deviation

Lowercase letter for fundamental deviation

Hole fundamental deviation

Uppercase letter for fundamental deviation

Clearance fit

A gap between parts

Transition fit

Some dimensional overlap

Interference fit

Always dimensional overlap

Basic size

Nominal size of both members

Allowance

Minimum clearance or maximum interference

Machining distortion

Deviation of part from original intent after being released from a fixture

Lay

Direction of dominant pattern of surface roughness

Topography, hardness, residual stresses, material structure, and chemical behavior

Factors of surface integrity

Resolution

The smallest change in value that a measurement instrument can detect