manufacturing rounded shapes ii manufacturing processes
TRANSCRIPT
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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