Transcript ADVANCED MANUFACTURING SYSTEMS INDEN 5303

INDUSTRIAL PROCESSES II
INDEN 3313
Lecture 2 – Grinding and Finishing
Industrial Processes II
OVERVIEW
• Questions to Start
• Grinding
– Process Description
– Parameters/Impact on Surface Finish
• Finishing
– Process Descriptions
– Parameters/Impact on Surface Finish
Industrial Processes II
QUESTIONS
TO START ??
Industrial Processes II
GRINDING
• Definition
– Shearing Process Which Uses Abrasive
Grains to Remove Material
• Cutting Action
– Abrasives Act Like “Tiny Cutting Tools”
• Process Characteristics
– High Speed, Temperature
– Low Depth of Cuts, MRR
– High Specific Energy Requirements
• Ratio of Plastic and Elastic Deformation vs Cutting
Industrial Processes II
GRINDING
• Illustration of Process
Kalpakjian, Figure 25.3, p. 785
Industrial Processes II
GRINDING
• Shearing Action in Grinding
– Each Grain is a Cutting Tool
• Grains Usually Embedded in a Grinding Wheel
– Cutting Angles Vary
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Back Rake Angle (Positive and Negative)
Sharpness of Cutting Edge
Side Rake Angle
Clearances
• Grains are Metal Oxides, Diamonds
• Wheels are Self-Sharpening
– Friability
» Abrasive Crystals Break
– Bond Strength
» Abrasive Grain is Torn From Bonding Material
Industrial Processes II
GRINDING
• Review of Metal Cutting (Shear) Process
Kalpakjian, Figure 20.1a, p. 606, Figure 20.13 p. 608
Industrial Processes II
GRINDING
• Analogous to Milling (Grains vs. Teeth)
Kalpakjian, Figure 23.8b, p. 723
Industrial Processes II
GRINDING
• Illustration of Process
Kalpakjian, Figure 25.3, p. 785
Industrial Processes II
GRINDING
• Why Used?
– Produce “Better” Surface Finish
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Smooth – Lower Coefficient of Friction
Smooth – Tighter Fit
Smooth – Less Eddy Currents/Corrosion
Smooth – Less Surface Area (Corrosion)
Rough – Better Adherence (Paint, Non-Skid)
– Produce More Dimensionally Accurate Parts
– Produce Sharp Edges
– Break Sharp Edges
Industrial Processes II
GRINDING
• Bond Types (Wheels/Stones)
– Vitrified (Clays)
• Most Common
• Hard, High Hot Hardness
• Mixed, Pressed, Heated to Fuse (Glass)
– Resinoid
• Phenolic (Thermosetting Compounds)
• Mix, Heat to Set
• More Flexible than Vitrified
– Rubberoid
• Vulcanized Rubber and Abrasive Particles
• More Flexible than Resinoid
Industrial Processes II
GRINDING
• Bond Types
– Metallic
• Made via Powder Metallurgy
• Usual Bond for Diamonds
– Metal better Adhesive for Diamonds
• Bond Type Determines Wheel Grade
– Grade is “Hardness” of Wheel
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Determined by Bonding Material and Amount
Strength of Bonding of Abrasive
NOT Related to Hardness of Abrasive
Harder Wheels are More Brittle/Subject to
Fracture
Industrial Processes II
GRINDING
• Spacing of Abrasive Determines
Structure
– Structure is Density of Abrasive
• Distance Between Abrasive Particles
• Corresponds to Tooth Gullet (Broach, Mills)
– “Clogging” of Grinding Wheel
• Also Referred to as Porosity of Wheel
• Determines Number of Cutting Edges (Teeth)
– Size of Abrasive Known as Grit
• Larger Grit
– Rougher Surface (Grain Variance)
– Larger Structure
– Higher MRR
Industrial Processes II
GRINDING
• Spacing of Abrasive Determines
Structure
– Structure is Density of Abrasive
• Distance Between Abrasive Particles
• Corresponds to Tooth Gullet (Broach, Mills)
• Also Referred to as Porosity of Wheel
– Size of Abrasive Known as Grit
• Larger Grit
– Rougher Surface (Grain Variance)
– Larger Structure
– Higher MRR
Industrial Processes II
GRINDING
• Grinding Parameters
– Size of Grit
• Smaller Grit, Smoother Finish
• Number of Cutting Edges
– Reduces “Tooth Marks” (Feed Marks)
– Reduces Waviness
• Limits Depth of Cut
– Size of Grain
• Smaller Grains are less Friable
• More Negative Rake Angles, More Burnishing
– Higher Specific Horsepower Needed
– Runs Hotter
– Lower G (Grinding Ratio)
• Reduces Vibration/Chatter
Industrial Processes II
GRINDING
• Grinding Parameters
– Wheel Speed (RPM, Surface Feet/Minute)
• Higher Speed – Less Waviness
– Less Rotation/Feed ‘til Next Grain/Edge
• Higher Speed – Less Depth of Cut
– Less Feed ‘til Next Grain/Edge
• Higher Speed – Runs Hotter
– Grater Ration of Deformation Ploughing/Burnishing
to Shearing
• Higher Speed – Higher Tendency to Clog
– Hotter (Softer) Wheel and Workpiece Material
• Higher Speed – Higher Dynamic Loading
– More Easily Broken, “Fly-Apart”
Industrial Processes II
GRINDING
• Grinding Parameters
– Feed Rate
• Increasing Feed – Higher Production Rates
– Higher Material Removal Rates (MRR)
– How to Calculate
• Increasing Feed – Higher Forces on Grain/Edge
– Higher Wheel Wear (Attrious Wear)
– Loss of Grains(Grain Fracture)
• Increasing Feed – Rougher Surface
– Greater Waviness
• Increasing Feed – Less Dimensionally Accurate
– Greater Deflection
Industrial Processes II
GRINDING
• Grinding – Process’s Impact on
Workpiece
– Heat Affects
• Tempering
– Localized High Temperatures followed by Rapid
Cooling
• Burning
– Rapid Oxidation on Workpiece Surface
– “Sparks” during Grinding are Oxidizing Chips
» High Surface Area to Mass Ratio
• Residual Stresses
– Countering the Heat
• Use Grinding Fluids (Like Cutting Fluids)
Industrial Processes II
GRINDING
• Types
– Surface (Flats/Planar)
– Cylindrical (O.D. of Parts - Held Between
Centers)
– Thread (Precision (Instrument) Threads)
– Internal (I.D. of Parts)
– Centerless (O.D. of Parts, No Centers)
Industrial Processes II
GRINDING
• Types of Machines/Equipment
– Surface Grinders
Groover, Figure 26.9, p. 668
Industrial Processes II
GRINDING
• Types of Machines/Equipment
– Cylindrical Grinder
Groover, Figure 26.12, p. 670
Industrial Processes II
GRINDING
• Types of Machines/Equipment
– External Centerless Grinding
Groover, Figure 26.13, p. 671
Industrial Processes II
GRINDING
• Types of Machines/Equipment
– Internal Centerless Grinding
Groover, Figure 26.14, p. 671
Industrial Processes II
GRINDING
• Design Considerations
– Hold Securely (Vibration, Precision)
– Avoid Shock Loading
• Avoid Surface Discontinuities
– (Dynamically) Balance Wheels and Parts
• Vibration, Bearing Wear, Break Loose
– Maximize Fillets and Radii of Parts
• Wheel Shape/Cross Section
– Match Abrasive and Part Material
• Materials
• Grit Size
• Wheel Hardness, Structure
Industrial Processes II
GRINDING
• Application Guidelines
– For Smoother Finish
• Use Smaller Grit and Denser Wheel Structure,
Higher Wheel Speed, Lower Work Speed, Smaller
Depths of Cut, Larger Wheel Diameters
– For Higher MRR
• Select Larger Grit Size, More Open Structure, and
Vitrified Bond
– Match Materials
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Steel and Cast Iron, Grind with Aluminum Oxide
Non-ferrous, Grind with Silicon Carbide
Hardened Alloys – Grind with Boron Nitride
Ceramics, Carbides, Grind with Diamond
Industrial Processes II
GRINDING
• Application Guidelines (cont.)
– For Soft Metals
• Use a Large Grit, Harder Wheel
– For Hard Metals
• Use Small Grit, Softer Wheel
– Minimize Heat Stress
• Dress Wheel, Lower Depths, Lower Wheel Speeds,
Faster Work Speed, Use a Fluid
– If Wheel Glazes
• Use Softer Grade, More Open Structure
– If Wheel Breaks Down
• Use Harder Grade, Denser Structure
Industrial Processes II
GRINDING WHEELS
Groover, Figure 26.4, p. 661
Industrial Processes II
GRINDING WHEELS
• Conventional Wheels
– ANSI Standard B74.13-177
• Prefix (Manufacturer’s Symbol for Abrasive –
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Optional)
Abrasive Type - A (Aluminum Oxide), C Silicon
Carbide, …
Grain Size – Coarse (8-24), Medium (30-60),
Fine (70-180), Very Fine (220-600)
Grade -- A (Soft) to Z (Hard)
Structure – 1 (Very Dense) to 15 (Very Open)
Bond Type – B (Resinoid), E (Shellac), R (Rubber),
S (Silicate), V (Vitrified)
Manufacturers Record (Optional by Mfgr.)
Industrial Processes II
GRINDING WHEELS
• Diamond and Cubic Boron Nitride
Wheels
– ANSI Standard B74.13-177
• Prefix (Manufacturer’s Symbol for Abrasive –
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Optional)
Abrasive Type – D (Diamond), B (Cubic Boron
Nitride)
Grain Size – Coarse (8-24), Medium (30-60),
Fine (70-180), Very Fine (220-600)
Grade -- A (Soft) to Z (Hard)
Concentration – Mfgr’s Designation (Required)
Bond Type – B (Resin), M(Metal), V (Vitrified)
Bond Modification (Optional by Mfgr.)
Depth of Abrasive (Working Depth in inch or mm
Industrial Processes II
FINISHING
• Definition
– Production of Smoother Surfaces Through
an Abrasion Process that Uses of Finer or
Less Rigidly Held Abrasives and/or Slower
Relative Movement (Speed) than Grinding
• Same Cutting Action as Grinding
– Finer Grains, More Edges, Less Depth
– Less Rigid, Lower Depths of Cut
– Slower Movement –Less Heat (Expansion)
Industrial Processes II
FINISHING
• Types
– Coated Abrasives (Sandpaper, Emory Cloth)
– Belt Grinders
• Solid Belt
• Mesh Belt (Hold Grinding Fluid via Surface
Tension
– Wire Brushing
• Wire Provides Metal Cutting/Burnishing Action
• Wire (Metal) Acts as Abrasive
– Honing (Interior of Holes)
– Lapping (Flat Surfaces)
Industrial Processes II
FINISHING
• Types (cont.)
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Polishing
Buffing
Electro-Polishing
Magnetic Float Polishing (Ceramic Ball
Bearings)
– Barrel Finishing
– Abrasive Flow
– Abrasive Jet (Chapter 26 -Kalpakjian)
Industrial Processes II
BELT GRINDING
• Illustration
Kalpakjian, Figure 25.28, p.813, Groover Figure 26.17, p 674
Industrial Processes II
BELT GRINDING
• Why Smoother than Grinding
– “Infinite” Diameter Wheel
• No Waviness
• Larger Grains Do Not Cut as Deep – Soft Backing
“Gives”
• Single Grain (controlled Grit Size) Above the
Backing Material – Uniform Depth of Cutting
Edges – Leading Grains Cut, Trailing Finish (Like
Broaching)
– Process Parameters
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Abrasive Material, Grit Size
Backing Material
Adhesive Used (Bond)
Belt Speed, Control (Platen, etc.)
Industrial Processes II
WIRE BRUSHING
• Illustration
Industrial Processes II
WIRE BRUSHING
• Comparison to Grinding
– Burnishes as well as Abrades
– Metal Bristles Softer than Grinding
Abrasives
– More “Give” to Bristles than Wheel
– Process Parameters
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Bristle Material
Bristle Stiffness (Diameter)
Pressure Used
Sharpness of Bristle Ends
Industrial Processes II
HONING
• Illustration
Groover Figure 26.19, p 675
Industrial Processes II
HONING
• Comparison to Grinding
– Universal Joints Enable Stone to “Follow the
Hole”
• Highest Pressure/Abrasion at Smallest Diameters
– Precision Hole Size, Finish
• Center Compliance Assured, Cross Hatched
Pattern – Hold Lubrication in Hole
– Process Parameters
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Abrasive Material
Grit Size
Pressure Used
Adhesive Used (Bond)
Hone Speed
Industrial Processes II
LAPPING
• Illustration
Kalpakjian, Figure 25.31, p.815
Industrial Processes II
LAPPING
• Comparison to Grinding
– Both Lap and Work Move (Same Grain Never
in Same Location on Workpiece
• Abrasives in Slurry
– Low Pressure
– Able to Move in Response to Cutting Forces
– Process Parameters
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Abrasive Material
Grit Size
Slurry Consistency
Lap/Work Speed
Industrial Processes II
POLISHING
• Description
– Fine Abrasive Powders Are Used to Coat Fabric,
Leather, Felt, … Disks or Belts
– Coated Disk or Belt Rubbed on Surface to be Finished
– Fine Abrasives Remove Material
– Friction Heating Softens and Smears Surface Layers
Industrial Processes II
POLISHING
• Comparison to Grinding
– Very Soft Backing Material (Cloth)
– Fine Abrasives (May be in Slurry)
– Low Pressure
– Process Parameters
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Abrasive Material
Abrasive Particle Size
Backing Material
Pressure Used
Industrial Processes II
BUFFING
• Description
– Similar to Buffing with Softer Backing
and/or Softer and/or Finer Abrasives
– Also Known as “Compounding” from the
term “Buffing Compound”
– Extremely Fine Surface Finish Obtainable
Industrial Processes II
BUFFING
• Comparison to Grinding
– Very Soft Backing Material (Cloth)
– Very Fine Soft Abrasives (May be in Slurry)
– Low Pressure
– Process Parameters
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Abrasive Material
Abrasive Particle Size
Backing Material
Pressure Used
Industrial Processes II
ELECTRO-POLISHING
• Description
– Placement of Workpiece in Electrolytic
Solution
– Application of Electrical Potential to
Workpiece
– Ions (Charge) Collects on Outer Surface of
Part
– Ions Go Into Solution (Dissolve)
– Highest Surface Goes Into Solution Most
Rapidly
Industrial Processes II
ELECTRO-POLISHING
• Comparison to Grinding
– Removal of Material via Electro-Chemical
Means (NOT Shearing/Metal Cutting)
– Process Parameters
• Electrolyte Used
• Strength of Potential (Voltage)
• Duration of Applied Potential
– Can Use a Similar Process With Metal
Grinding Wheel – Grinding Fluid is
Electrolyte and Known as Electro Chemical
Grinding
Industrial Processes II
FLOAT POLISHING
• Illustration
Kalpakjian, Figure 25.32, p.816
Industrial Processes II
FLOAT POLISHING
• Comparison to Grinding
– Pressure Supplied by Magnetic Forces
• Magnetic (Metallic Abrasives) Pulled Onto
Workpiece Via Strength of Magnetic Field
• Permanent or Electro-Magnets Used
• Used on Ceramic Ball Bearings
• Pioneered at OSU
– Process Parameters
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Abrasive Material
Grit Size, Slurry
Strength of Magnetic Field
Rotational Speed
Industrial Processes II
BARREL FINISHING
• Description
– Parts and (Dry Pellets) Abrasive are Placed
into a Container
– Container is Rotated
– As Container Rotates the Parts Shift/Slide
Against One Another (with the Abrasive
Between Them) and the Weight of the Parts
Provides the Pressure for the Abrasion
Process.
Industrial Processes II
BARREL FINISHING
• Illustration
Groover, Figure 32.2, p. 816
Industrial Processes II
BARREL FINISHING
• Illustration Of Pellet Shapes
Groover, Figure 32.3, p. 817
Industrial Processes II
BARREL FINISHING
• Comparison to Grinding
– Lower Pressure
– Slower Speeds
– Shaped (Loose) Abrasives
– Process Parameters
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Abrasive Material
Abrasive Pellet Shape
Ratio of Parts to Abrasive
Rotational Speed
– Also Known as “Tumbling”
Industrial Processes II
ABRASIVE FLOW
• Illustration
Kalpakjian, Figure 25.33, p.818
Industrial Processes II
ABRASIVE FLOW
• Comparison to Grinding
– Lower Pressure
– Slower Speeds
– Abrasive Slurry
– Process Parameters
• Abrasive Material
• Abrasive Slurry “Stiffness”
• Pressure Forcing Slurry Through/Around Part
Industrial Processes II
ABRASIVE JET
• Illustration
Kalpakjian, Figure 26.20, p.847
Industrial Processes II
ABRASIVE JET
• Comparison to Grinding
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“Soft” Backing (Air)
Small Depths of Cut (Bounce Off)
Abrasive is “Loose”
Peens Surface
– Process Parameters
• Abrasive Material
• Abrasive Particle Size and Shape
• Angle of Incidence
– Also Known as Sand Blasting, Bead Blasting
Industrial Processes II
QUESTIONS
OR
CLARIFICATIONS
???
Reminder :
Location and Timing of
Thursday Class
Correction in Reading for
Thursday (No Chapt. 25)
Industrial Processes II