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INDUSTRIAL PROCESSES II INDEN 3313 PowerPoint PPT Presentation


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INDUSTRIAL PROCESSES II INDEN 3313. Lecture 2 – Grinding and Finishing. OVERVIEW. Questions to Start Grinding Process Description Parameters/Impact on Surface Finish Finishing Process Descriptions Parameters/Impact on Surface Finish. QUESTIONS TO START ??. GRINDING. Definition

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INDUSTRIAL PROCESSES II INDEN 3313

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Industrial processes ii inden 3313 l.jpg

INDUSTRIAL PROCESSES IIINDEN 3313

Lecture 2 – Grinding and Finishing

Industrial Processes II


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OVERVIEW

  • Questions to Start

  • Grinding

    • Process Description

    • Parameters/Impact on Surface Finish

  • Finishing

    • Process Descriptions

    • Parameters/Impact on Surface Finish

Industrial Processes II


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QUESTIONSTO START ??

Industrial Processes II


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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


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GRINDING

  • Illustration of Process

    Kalpakjian, Figure 25.3, p. 785

Industrial Processes II


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GRINDING

  • Shearing 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


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GRINDING

  • Review of Metal Cutting (Shear) Process

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

Industrial Processes II


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GRINDING

  • Analogous to Milling (Grains vs. Teeth)

    Kalpakjian, Figure 23.8b, p. 723

Industrial Processes II


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GRINDING

  • Illustration of Process

    Kalpakjian, Figure 25.3, p. 785

Industrial Processes II


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GRINDING

  • 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


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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


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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

      • 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


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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


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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


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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


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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


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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


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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


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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


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GRINDING

  • Types of Machines/Equipment

    • Surface Grinders

      Groover, Figure 26.9, p. 668

Industrial Processes II


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GRINDING

  • Types of Machines/Equipment

    • Cylindrical Grinder

      Groover, Figure 26.12, p. 670

Industrial Processes II


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GRINDING

  • Types of Machines/Equipment

    • External Centerless Grinding

      Groover, Figure 26.13, p. 671

Industrial Processes II


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GRINDING

  • Types of Machines/Equipment

    • Internal Centerless Grinding

      Groover, Figure 26.14, p. 671

Industrial Processes II


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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


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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

      • 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


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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


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GRINDING WHEELS

Groover, Figure 26.4, p. 661

Industrial Processes II


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GRINDING WHEELS

  • Conventional 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


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GRINDING WHEELS

  • Diamond and Cubic Boron Nitride Wheels

    • 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


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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


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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


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FINISHING

  • Types (cont.)

    • Polishing

    • Buffing

    • Electro-Polishing

    • Magnetic Float Polishing (Ceramic Ball Bearings)

    • Barrel Finishing

    • Abrasive Flow

    • Abrasive Jet (Chapter 26 -Kalpakjian)

Industrial Processes II


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BELT GRINDING

  • Illustration

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

Industrial Processes II


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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

      • Abrasive Material, Grit Size

      • Backing Material

      • Adhesive Used (Bond)

      • Belt Speed, Control (Platen, etc.)

Industrial Processes II


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WIRE BRUSHING

  • Illustration

Industrial Processes II


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WIRE BRUSHING

  • Comparison 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


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HONING

  • Illustration

    Groover Figure 26.19, p 675

Industrial Processes II


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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

      • Abrasive Material

      • Grit Size

      • Pressure Used

      • Adhesive Used (Bond)

      • Hone Speed

Industrial Processes II


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LAPPING

  • Illustration

    Kalpakjian, Figure 25.31, p.815

Industrial Processes II


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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

      • Abrasive Material

      • Grit Size

      • Slurry Consistency

      • Lap/Work Speed

Industrial Processes II


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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


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POLISHING

  • Comparison 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


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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


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BUFFING

  • Comparison 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


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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


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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


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FLOAT POLISHING

  • Illustration

    Kalpakjian, Figure 25.32, p.816

Industrial Processes II


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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

      • Abrasive Material

      • Grit Size, Slurry

      • Strength of Magnetic Field

      • Rotational Speed

Industrial Processes II


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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


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BARREL FINISHING

  • Illustration

    Groover, Figure 32.2, p. 816

Industrial Processes II


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BARREL FINISHING

  • Illustration Of Pellet Shapes

    Groover, Figure 32.3, p. 817

Industrial Processes II


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BARREL FINISHING

  • Comparison 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


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ABRASIVE FLOW

  • Illustration

    Kalpakjian, Figure 25.33, p.818

Industrial Processes II


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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


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ABRASIVE JET

  • Illustration

    Kalpakjian, Figure 26.20, p.847

Industrial Processes II


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ABRASIVE JET

  • Comparison 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


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QUESTIONSOR CLARIFICATIONS ???

Reminder :

Location and Timing of Thursday Class

Correction in Reading for Thursday (No Chapt. 25)

Industrial Processes II


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