industrial processes ii industrial processes ii inden 3313 lecture 2 – grinding and finishing
TRANSCRIPT
Industrial Processes II
INDUSTRIAL PROCESSES IIINDUSTRIAL PROCESSES II
INDEN 3313INDEN 3313
Lecture 2 – Grinding and Lecture 2 – Grinding and FinishingFinishing
Industrial Processes II
OVERVIEWOVERVIEW
• Questions to StartQuestions to Start
• GrindingGrinding– Process Description– Parameters/Impact on Surface Finish
• FinishingFinishing– Process Descriptions– Parameters/Impact on Surface Finish
Industrial Processes II
QUESTIONSQUESTIONSTO START ??TO START ??
Industrial Processes II
GRINDINGGRINDING• DefinitionDefinition
– Shearing Process Which Uses Abrasive Grains to Remove Material
• Cutting ActionCutting Action– Abrasives Act Like “Tiny Cutting Tools”
• Process CharacteristicsProcess Characteristics– High Speed, Temperature– Low Depth of Cuts, MRR– High Specific Energy Requirements
• Ratio of Plastic and Elastic Deformation vs Cutting
Industrial Processes II
GRINDINGGRINDING• Illustration of ProcessIllustration of Process
Kalpakjian, Figure 25.3, p. 785
Industrial Processes II
GRINDINGGRINDING• Shearing Action in GrindingShearing Action in Grinding
– Each Grain is a Cutting Tool • Grains Usually Embedded in a Grinding
Wheel– Cutting Angles Vary
» 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
GRINDINGGRINDING• Review of Metal Cutting (Shear) Review of Metal Cutting (Shear)
ProcessProcess
Kalpakjian, Figure 20.1a, p. 606, Figure 20.13 p. 608
Industrial Processes II
GRINDINGGRINDING• Analogous to Milling (Grains vs. Teeth)Analogous to Milling (Grains vs. Teeth)
Kalpakjian, Figure 23.8b, p. 723
Industrial Processes II
GRINDINGGRINDING• Illustration of ProcessIllustration of Process
Kalpakjian, Figure 25.3, p. 785
Industrial Processes II
GRINDINGGRINDING• Why Used?Why Used?
– Produce “Better” Surface Finish• 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
GRINDINGGRINDING• Bond Types (Wheels/Stones)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
GRINDINGGRINDING• Bond TypesBond Types
– Metallic• Made via Powder Metallurgy• Usual Bond for Diamonds
– Metal better Adhesive for Diamonds
• Bond Type Determines Wheel GradeBond Type Determines Wheel Grade– Grade is “Hardness” of Wheel
• 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
GRINDINGGRINDING• Spacing of Abrasive Determines Spacing of Abrasive Determines
StructureStructure– 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
GRINDINGGRINDING• Spacing of Abrasive Determines Spacing of Abrasive Determines
StructureStructure– 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
GRINDINGGRINDING• Grinding ParametersGrinding 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
GRINDINGGRINDING• Grinding ParametersGrinding 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
GRINDINGGRINDING• Grinding ParametersGrinding 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
GRINDINGGRINDING• Grinding – Process’s Impact on Grinding – Process’s Impact on
WorkpieceWorkpiece– 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
GRINDINGGRINDING• TypesTypes
– 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
GRINDINGGRINDING• Types of Machines/EquipmentTypes of Machines/Equipment
– Surface Grinders
Groover, Figure 26.9, p. 668
Industrial Processes II
GRINDINGGRINDING• Types of Machines/EquipmentTypes of Machines/Equipment
– Cylindrical Grinder
Groover, Figure 26.12, p. 670
Industrial Processes II
GRINDINGGRINDING• Types of Machines/EquipmentTypes of Machines/Equipment
– External Centerless Grinding
Groover, Figure 26.13, p. 671
Industrial Processes II
GRINDINGGRINDING• Types of Machines/EquipmentTypes of Machines/Equipment
– Internal Centerless Grinding
Groover, Figure 26.14, p. 671
Industrial Processes II
GRINDINGGRINDING• Design ConsiderationsDesign 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
GRINDINGGRINDING• Application Guidelines 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• 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
GRINDINGGRINDING• Application Guidelines (cont.)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 WHEELSGRINDING WHEELS
Groover, Figure 26.4, p. 661
Industrial Processes II
GRINDING WHEELSGRINDING WHEELS• Conventional WheelsConventional Wheels
– ANSI Standard B74.13-177• Prefix (Manufacturer’s Symbol for Abrasive
– 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 WHEELSGRINDING WHEELS• Diamond and Cubic Boron Nitride Diamond and Cubic Boron Nitride
WheelsWheels– ANSI Standard B74.13-177
• Prefix (Manufacturer’s Symbol for Abrasive – 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
FINISHINGFINISHING• DefinitionDefinition
– 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 GrindingSame Cutting Action as Grinding– Finer Grains, More Edges, Less Depth– Less Rigid, Lower Depths of Cut– Slower Movement –Less Heat
(Expansion)
Industrial Processes II
FINISHINGFINISHING• Types 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
FINISHINGFINISHING
• Types (cont.)Types (cont.)– Polishing– Buffing– Electro-Polishing– Magnetic Float Polishing (Ceramic Ball
Bearings)– Barrel Finishing– Abrasive Flow– Abrasive Jet (Chapter 26 -Kalpakjian)
Industrial Processes II
BELT GRINDINGBELT GRINDING• IllustrationIllustration
Kalpakjian, Figure 25.28, p.813, Groover Figure 26.17, p 674
Industrial Processes II
BELT GRINDINGBELT GRINDING• Why Smoother than GrindingWhy 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• Abrasive Material, Grit Size• Backing Material• Adhesive Used (Bond)• Belt Speed, Control (Platen, etc.)
Industrial Processes II
WIRE BRUSHINGWIRE BRUSHING• IllustrationIllustration
Industrial Processes II
WIRE BRUSHINGWIRE BRUSHING• Comparison to GrindingComparison to Grinding
– Burnishes as well as Abrades – Metal Bristles Softer than Grinding
Abrasives– More “Give” to Bristles than Wheel
– Process Parameters• Bristle Material• Bristle Stiffness (Diameter)• Pressure Used• Sharpness of Bristle Ends
Industrial Processes II
HONINGHONING• IllustrationIllustration
Groover Figure 26.19, p 675
Industrial Processes II
HONINGHONING• Comparison to GrindingComparison 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• Abrasive Material• Grit Size• Pressure Used• Adhesive Used (Bond)• Hone Speed
Industrial Processes II
LAPPINGLAPPING• IllustrationIllustration
Kalpakjian, Figure 25.31, p.815
Industrial Processes II
LAPPINGLAPPING• Comparison to GrindingComparison 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• Abrasive Material• Grit Size• Slurry Consistency• Lap/Work Speed
Industrial Processes II
POLISHINGPOLISHING
• DescriptionDescription
– 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
POLISHINGPOLISHING• Comparison to GrindingComparison to Grinding
– Very Soft Backing Material (Cloth)– Fine Abrasives (May be in Slurry)– Low Pressure
– Process Parameters• Abrasive Material• Abrasive Particle Size• Backing Material• Pressure Used
Industrial Processes II
BUFFINGBUFFING• DescriptionDescription
– 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
BUFFINGBUFFING• Comparison to GrindingComparison to Grinding
– Very Soft Backing Material (Cloth)– Very Fine Soft Abrasives (May be in
Slurry)– Low Pressure
– Process Parameters• Abrasive Material• Abrasive Particle Size• Backing Material• Pressure Used
Industrial Processes II
ELECTRO-POLISHINGELECTRO-POLISHING• DescriptionDescription
– 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-POLISHINGELECTRO-POLISHING• Comparison to GrindingComparison 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 POLISHINGFLOAT POLISHING• IllustrationIllustration
Kalpakjian, Figure 25.32, p.816
Industrial Processes II
FLOAT POLISHINGFLOAT POLISHING• Comparison to GrindingComparison 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• Abrasive Material• Grit Size, Slurry• Strength of Magnetic Field• Rotational Speed
Industrial Processes II
BARREL FINISHINGBARREL FINISHING• DescriptionDescription
– 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 FINISHINGBARREL FINISHING• IllustrationIllustration
Groover, Figure 32.2, p. 816
Industrial Processes II
BARREL FINISHINGBARREL FINISHING• Illustration Of Pellet ShapesIllustration Of Pellet Shapes
Groover, Figure 32.3, p. 817
Industrial Processes II
BARREL FINISHINGBARREL FINISHING• Comparison to GrindingComparison to Grinding
– Lower Pressure– Slower Speeds– Shaped (Loose) Abrasives
– Process Parameters• Abrasive Material• Abrasive Pellet Shape• Ratio of Parts to Abrasive• Rotational Speed
– Also Known as “Tumbling”
Industrial Processes II
ABRASIVE FLOWABRASIVE FLOW• IllustrationIllustration
Kalpakjian, Figure 25.33, p.818
Industrial Processes II
ABRASIVE FLOWABRASIVE FLOW• Comparison to GrindingComparison 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 JETABRASIVE JET• IllustrationIllustration
Kalpakjian, Figure 26.20, p.847
Industrial Processes II
ABRASIVE JETABRASIVE JET• Comparison to GrindingComparison to Grinding
– “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
QUESTIONSQUESTIONSOR OR
CLARIFICATIONCLARIFICATIONS ???S ???
Reminder :Reminder : Location and Timing of Location and Timing of Thursday ClassThursday Class
Correction in Reading Correction in Reading for Thursday (No Chapt. for Thursday (No Chapt. 25)25)