ManufacturingManufacturingRounded Shapes IIRounded Shapes II

Manufacturing Manufacturing ProcessesProcesses

OutlineOutline

Specialized Turning OperationsSpecialized Turning OperationsHigh-Speed MachiningHigh-Speed Machining

Ultraprecision MachiningUltraprecision Machining

Hard TurningHard Turning

Cutting Screw ThreadsCutting Screw Threads

KnurlingKnurling

Boring and Boring MachinesBoring and Boring Machines

Drilling and DrillsDrilling and Drills

Reaming and ReamersReaming and Reamers

Tapping and TapsTapping and Taps

Chip CollectionChip Collection

High-Speed MachiningHigh-Speed Machining

Decreases cutting time by increasing cutting Decreases cutting time by increasing cutting speedspeed

Approximate Range of Cutting Speeds:Approximate Range of Cutting Speeds:- High Speed: 2000-6000 ft/minHigh Speed: 2000-6000 ft/min- Very High Speed: 6000-60000 ft/minVery High Speed: 6000-60000 ft/min- Ultrahigh Speed: >60000 ft/minUltrahigh Speed: >60000 ft/min

Decreases total energy required:Decreases total energy required:- Power for high-speed machining ≈ .004 - Power for high-speed machining ≈ .004

W/rpmW/rpm- Power for normal machiningPower for normal machining ≈ ≈ .2-.4 W/rpm.2-.4 W/rpm

Most important when cutting time is a Most important when cutting time is a significant part of the manufacturing timesignificant part of the manufacturing time

High-Speed MachiningHigh-Speed Machining

Factors:Factors:- Stiffness of the machine toolsStiffness of the machine tools- Stiffness of tool holders and Stiffness of tool holders and

workpiece holdersworkpiece holders- Proper spindle for high speeds Proper spindle for high speeds

and powerand power- Sufficiently fast feed drivesSufficiently fast feed drives- AutomationAutomation- A proper cutting tool for high A proper cutting tool for high

cutting speedscutting speeds- Ability to hold the piece in Ability to hold the piece in

fixtures at high speedfixtures at high speed

UltraprecisionUltraprecisionMachiningMachining

Used for very small surface finish Used for very small surface finish tolerances in the range tolerances in the range of .01 of .01 µµmm

The depth of cut is in the range The depth of cut is in the range of nanometersof nanometers

Machine tools must be made Machine tools must be made with high stiffnesswith high stiffness

UltraprecisionUltraprecisionMachiningMachining

Factors:Factors:- Stiffness, damping, and geometric Stiffness, damping, and geometric

accuracy of machine toolsaccuracy of machine tools- Accurate linear and rotational motion Accurate linear and rotational motion

controlcontrol- Proper spindle technologyProper spindle technology- Thermal expansion of machine tools, Thermal expansion of machine tools,

compensation thereof, and control of the compensation thereof, and control of the machine tool environmentmachine tool environment

- Correct selection and application of Correct selection and application of cutting toolscutting tools

- Machining parametersMachining parameters- Performance and tool-condition Performance and tool-condition

monitoring in real time, and control monitoring in real time, and control thereofthereof

Hard TurningHard Turning

Used for relatively hard, brittle Used for relatively hard, brittle materialsmaterials

Produces parts with good Produces parts with good dimensional accuracy, smooth dimensional accuracy, smooth surface finish, and surface surface finish, and surface integrityintegrity

May be used as an alternative to May be used as an alternative to grindinggrinding

Hard TurningHard TurningProcedureProcedure

Hard TurningHard TurningStatisticsStatistics

Heat dissipated by chips

Tool forces: radial force is greatest

Hard TurningHard TurningChip FormationChip Formation

Brittle materials form segmented chips, which cause a large force against the cutting edge

Hard TurningHard Turning

Advantages (as an alternative to Advantages (as an alternative to grinding)grinding)

- Lower cost of machine toolsLower cost of machine tools- Ability to machine complex parts in Ability to machine complex parts in

a single setupa single setup- Ability to create various part styles Ability to create various part styles

or small part numbers efficientlyor small part numbers efficiently- Less industrial wasteLess industrial waste- Ability to cut without fluids Ability to cut without fluids

(eliminates grinding sludge)(eliminates grinding sludge)- Easily automatedEasily automated

Hard TurningHard TurningSurface FinishSurface Finish

NO YES

A hard journal bearing surface should have a surface with deep valleys and low peaks

Cutting Screw ThreadsCutting Screw Threads

Cutting threads on a lathe is Cutting threads on a lathe is slower than newer methodsslower than newer methods

- Die-Head ChasersDie-Head Chasers

used to increase production used to increase production rate of threading on a latherate of threading on a lathe

- Solid Threading DiesSolid Threading Dies

used for cutting straight or used for cutting straight or tapered threads on the ends of tapered threads on the ends of pipes or tubingpipes or tubing

Cutting Screw ThreadsCutting Screw Threads

Cutting Screw ThreadsCutting Screw Threads

Die-Head Chasers and Die-Head Chasers and Solid Threading Dies Solid Threading Dies

Straight chaser cutting die (top)Straight chaser cutting die (top)

Circular chaser cutting die (bottom left)Circular chaser cutting die (bottom left)

Solid threading die (bottom right)Solid threading die (bottom right)

Screw MachineScrew Machine

Screw MachineScrew Machine

Cutting Screw ThreadsCutting Screw Threads

Design Considerations:Design Considerations:- Threads should not be required to reach Threads should not be required to reach

a shouldera shoulder- Avoid shallow blind tapped holesAvoid shallow blind tapped holes- Chamfer the ends of threaded sections to Chamfer the ends of threaded sections to

reduce burrsreduce burrs- Do not interrupt threaded sections with Do not interrupt threaded sections with

slots, holes etc.slots, holes etc.- Use standard thread tools and inserts as Use standard thread tools and inserts as

much as possiblemuch as possible- The walls of the part should be thick The walls of the part should be thick

enough to withstand clamping and cutting enough to withstand clamping and cutting forcesforces

- Design the part so that cutting operations Design the part so that cutting operations can be completed in a single setupcan be completed in a single setup

KnurlingKnurling

Used to create a uniform roughness Used to create a uniform roughness pattern on cylindrical surfacespattern on cylindrical surfaces

Performed on parts where friction is Performed on parts where friction is desired (knobs, grip bars etc.)desired (knobs, grip bars etc.)

Types:Types:- Angular KnurlsAngular Knurls

create a pattern of diamond-shaped create a pattern of diamond-shaped ridgesridges

- Straight KnurlsStraight Knurlscreate a pattern of straight create a pattern of straight longitudinal ridgeslongitudinal ridges

Knurling ResultsKnurling Results

Knurling OperationKnurling Operation

Boring andBoring andBoring MachinesBoring Machines

Boring produces circular internal Boring produces circular internal profilesprofiles

Small pieces can be bored on a Small pieces can be bored on a lathe; boring mills are used for lathe; boring mills are used for larger workpieceslarger workpieces

Boring OperationBoring Operation

Boring OperationBoring Operation

Boring andBoring andBoring MachinesBoring Machines

Design Considerations:Design Considerations:- Avoid blind holes when Avoid blind holes when

possiblepossible- A higher ratio of the length to A higher ratio of the length to

the bore diameter will cause the bore diameter will cause more variations in dimensions more variations in dimensions because the boring bar will because the boring bar will deflect moredeflect more

- Avoid interrupted internal Avoid interrupted internal surfacessurfaces

Drilling and DrillsDrilling and Drills

Types of drillTypes of drill- Twist drill (most common)Twist drill (most common)- Gun drillGun drill- TrepannerTrepanner

Pilot HolesPilot Holes

Sometimes, when drilling Sometimes, when drilling large-diameter holes, it is large-diameter holes, it is necessary to drill a smaller necessary to drill a smaller hole first to guide the large drillhole first to guide the large drill

Types of DrillsTypes of Drillsand Drilling Operationsand Drilling Operations

Drill TerminologyDrill Terminology

Drill Point AngleDrill Point Angle

Point Angle

118° Standard

135° Harder Materials

stainless steel, titanium

Minimizes burring

90° Softer Materials

plastic

TrepannersTrepanners

Drills and DrillingDrills and Drilling

Deep HolesDeep Holes

Complications may occur when Complications may occur when drilling a hole longer than 3 drilling a hole longer than 3 times the drill diametertimes the drill diameter

ProblemsProblems- Chip removalChip removal- Coolant dispensing to the Coolant dispensing to the

cutting edgecutting edge- Tool deflectionTool deflection

Drills and DrillingDrills and Drilling

Small HolesSmall Holes

Small drillsSmall drills

.0059-.04 in.0059-.04 in

MicrodrillingMicrodrilling

.0001-.02 in.0001-.02 in

MicrodrillsMicrodrills

Pilot HolesPilot Holes

Drills and DrillingDrills and Drilling

Forces and TorqueForces and Torque

Thrust force:Thrust force:

acts perpendicular to the axis of the acts perpendicular to the axis of the hole; large forces can cause the hole; large forces can cause the drill to bend or breakdrill to bend or break

Torque:Torque:

the torque acting to turn the drillthe torque acting to turn the drill

These values are difficult to These values are difficult to calculatecalculate

Drill FeedDrill Feedand Speedand Speed

V = V = ππDN/12DN/12V = cutting speed in ft/min;V = cutting speed in ft/min;Velocity at which the drill edge moves Velocity at which the drill edge moves

along the workpiece surfacealong the workpiece surfaceD = diameter of the drillD = diameter of the drillN = RPM of the drillN = RPM of the drill

Feeds for drills are listed as in/rev or Feeds for drills are listed as in/rev or m/rev. Multiply these by the RPM to m/rev. Multiply these by the RPM to obtain the feed in in/min or m/min. obtain the feed in in/min or m/min. The feed cannot be controlled The feed cannot be controlled accurately on a drill press fed by accurately on a drill press fed by hand.hand.

Drill FeedDrill Feedand Speedand Speed

Drill FeedDrill Feedand Speedand Speed

Example:Example:Work Material:Work Material: AluminumAluminumTool Material:Tool Material: High Speed SteelHigh Speed SteelDrill Diameter: Drill Diameter: .5 in.5 inRecommended Cutting Speed: 200-300 Recommended Cutting Speed: 200-300

ft/min (from table)ft/min (from table)

N = 12V/N = 12V/ππDDN=12*(200-300)/(N=12*(200-300)/(ππ*.5)*.5)

=1528-2293 RPM=1528-2293 RPM

Recommended Feed for aluminum, .5in Recommended Feed for aluminum, .5in = .006-.01 in/rev (from table)= .006-.01 in/rev (from table)

ff = (.006-.01)*1528 RPM = 9.2-15.2 in/min = (.006-.01)*1528 RPM = 9.2-15.2 in/min

Drilling MaterialDrilling MaterialRemoval RateRemoval Rate

Material Removal RateMaterial Removal Rate

MRR = (MRR = (ππDD22/4)/4)f f NN

D = drill diameterD = drill diameter

ff = feed, in/rev or mm/rev = feed, in/rev or mm/rev

N = RPMN = RPM

Drilling MaterialDrilling MaterialRemoval RateRemoval Rate

Example:Example:

Drill Diameter:Drill Diameter: .5 in.5 in

Feed: Feed: .006 in/rev.006 in/rev

RPM: RPM: 1528 RPM1528 RPM

MRR = (MRR = (ππDD22/4)/4)f f NN

= (= (ππ(.5)(.5)22/4).006*1528/4).006*1528

= 1.8 in= 1.8 in33/min/min

Drilling OperationDrilling Operation

Reaming and ReamersReaming and Reamers

Used to improve the dimensional Used to improve the dimensional accuracy or surface finish of an accuracy or surface finish of an existing holeexisting hole

Types of reamersTypes of reamers- Hand reamersHand reamers- Rose reamersRose reamers- Fluted reamersFluted reamers- Shell reamersShell reamers- Expansion reamersExpansion reamers- Adjustable reamersAdjustable reamers

Types of ReamersTypes of Reamers

Reamer TerminologyReamer Terminology

Tapping and TapsTapping and Taps

Used to make internal threads in Used to make internal threads in workpiece holesworkpiece holes

Types of tapsTypes of taps- Tapered tapsTapered taps- Bottoming tapsBottoming taps- Collapsible tapsCollapsible taps

Tap TerminologyTap Terminology

Drilling, ReamingDrilling, Reamingand Tappingand Tapping

Design Considerations:Design Considerations:- Holes should be drilled on flat surfaces Holes should be drilled on flat surfaces

perpendicular to the hole axis to perpendicular to the hole axis to prevent drill deflectionprevent drill deflection

- Avoid interrupted hole surfacesAvoid interrupted hole surfaces- The bottoms of blind holes should The bottoms of blind holes should

match standard drill point anglesmatch standard drill point angles- Avoid blind holes when possible; if large Avoid blind holes when possible; if large

diameter holes are to be included, make diameter holes are to be included, make a pre-existing hole in fabricationa pre-existing hole in fabrication

- Design the workpiece so as to minimize Design the workpiece so as to minimize fixturing and repositioning during drillingfixturing and repositioning during drilling

- Provide extra hole depth for reaming or Provide extra hole depth for reaming or tapping blind or intersecting holestapping blind or intersecting holes

SummarySummary

Specialized cutting procedures Specialized cutting procedures exist for unusual materials and exist for unusual materials and requirementsrequirements

Proper procedure, securing of Proper procedure, securing of the workpiece, and feeds and the workpiece, and feeds and speeds must be considered to speeds must be considered to prevent damage and injuriesprevent damage and injuries

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