Industrial Processes II INDUSTRIAL PROCESSES II INDEN 3313 Lecture 2 – Grinding and Finishing.

Industrial Processes II

INDUSTRIAL PROCESSES IIINDUSTRIAL PROCESSES II

INDEN 3313INDEN 3313

Lecture 2 – Grinding and Lecture 2 – Grinding and FinishingFinishing

OVERVIEWOVERVIEW

• Questions to StartQuestions to Start

• GrindingGrinding– Process Description– Parameters/Impact on Surface Finish

• FinishingFinishing– Process Descriptions– Parameters/Impact on Surface Finish

QUESTIONSQUESTIONSTO START ??TO START ??

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

GRINDINGGRINDING• Illustration of ProcessIllustration of Process

Kalpakjian, Figure 25.3, p. 785

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

GRINDINGGRINDING• Review of Metal Cutting (Shear) Review of Metal Cutting (Shear)

ProcessProcess

Kalpakjian, Figure 20.1a, p. 606, Figure 20.13 p. 608

GRINDINGGRINDING• Analogous to Milling (Grains vs. Teeth)Analogous to Milling (Grains vs. Teeth)

Kalpakjian, Figure 23.8b, p. 723

GRINDINGGRINDING• Illustration of ProcessIllustration of Process

Kalpakjian, Figure 25.3, p. 785

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

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

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

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

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

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

– 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”

– 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

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)

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)

GRINDINGGRINDING• Types of Machines/EquipmentTypes of Machines/Equipment

– Surface Grinders

Groover, Figure 26.9, p. 668

– Cylindrical Grinder

– External Centerless Grinding

– Internal Centerless Grinding

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

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

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

GRINDING WHEELSGRINDING WHEELS

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.)

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

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)

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)

FINISHINGFINISHING

• Types (cont.)Types (cont.)– Polishing– Buffing– Electro-Polishing– Magnetic Float Polishing (Ceramic Ball

Bearings)– Barrel Finishing– Abrasive Flow– Abrasive Jet (Chapter 26 -Kalpakjian)

BELT GRINDINGBELT GRINDING• IllustrationIllustration

Kalpakjian, Figure 25.28, p.813, Groover Figure 26.17, p 674

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.)

WIRE BRUSHINGWIRE BRUSHING• IllustrationIllustration

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

HONINGHONING• IllustrationIllustration

Groover Figure 26.19, p 675

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

LAPPINGLAPPING• IllustrationIllustration

Kalpakjian, Figure 25.31, p.815

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

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

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

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

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

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

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

FLOAT POLISHINGFLOAT POLISHING• IllustrationIllustration

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

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.

BARREL FINISHINGBARREL FINISHING• IllustrationIllustration

BARREL FINISHINGBARREL FINISHING• Illustration Of Pellet ShapesIllustration Of Pellet Shapes

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”

ABRASIVE FLOWABRASIVE FLOW• IllustrationIllustration

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

ABRASIVE JETABRASIVE JET• IllustrationIllustration

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

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)

Industrial Processes II INDUSTRIAL PROCESSES II INDEN 3313 Lecture 2 – Grinding and Finishing.

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