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

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Presentation on theme: "Industrial Processes II INDUSTRIAL PROCESSES II INDEN 3313 Lecture 2 – Grinding and Finishing."— Presentation transcript:

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

2 Industrial Processes II OVERVIEW Questions to StartQuestions to Start GrindingGrinding –Process Description –Parameters/Impact on Surface Finish FinishingFinishing –Process Descriptions –Parameters/Impact on Surface Finish

3 Industrial Processes II QUESTIONS TO START ??

4 Industrial Processes II GRINDING 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

5 Industrial Processes II GRINDING Illustration of ProcessIllustration of Process Kalpakjian, Figure 25.3, p. 785

6 Industrial Processes II GRINDING 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

7 Industrial Processes II GRINDING Review of Metal Cutting (Shear) ProcessReview of Metal Cutting (Shear) Process Kalpakjian, Figure 20.1a, p. 606, Figure p. 608

8 Industrial Processes II GRINDING Analogous to Milling (Grains vs. Teeth)Analogous to Milling (Grains vs. Teeth) Kalpakjian, Figure 23.8b, p. 723

9 Industrial Processes II GRINDING Illustration of ProcessIllustration of Process Kalpakjian, Figure 25.3, p. 785

10 Industrial Processes II GRINDING 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

11 Industrial Processes II GRINDING 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

12 Industrial Processes II GRINDING 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

13 Industrial Processes II GRINDING Spacing of Abrasive Determines StructureSpacing 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

14 Industrial Processes II GRINDING Spacing of Abrasive Determines StructureSpacing 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

15 Industrial Processes II GRINDING 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

16 Industrial Processes II GRINDING 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”

17 Industrial Processes II GRINDING 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

18 Industrial Processes II GRINDING Grinding – Process’s Impact on WorkpieceGrinding – 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)

19 Industrial Processes II GRINDING 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)

20 Industrial Processes II GRINDING Types of Machines/EquipmentTypes of Machines/Equipment –Surface Grinders Groover, Figure 26.9, p. 668

21 Industrial Processes II GRINDING Types of Machines/EquipmentTypes of Machines/Equipment –Cylindrical Grinder Groover, Figure 26.12, p. 670

22 Industrial Processes II GRINDING Types of Machines/EquipmentTypes of Machines/Equipment –External Centerless Grinding Groover, Figure 26.13, p. 671

23 Industrial Processes II GRINDING Types of Machines/EquipmentTypes of Machines/Equipment –Internal Centerless Grinding Groover, Figure 26.14, p. 671

24 Industrial Processes II GRINDING 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

25 Industrial Processes II GRINDING Application GuidelinesApplication 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

26 Industrial Processes II GRINDING 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

27 Industrial Processes II GRINDING WHEELS Groover, Figure 26.4, p. 661

28 Industrial Processes II GRINDING WHEELS Conventional WheelsConventional Wheels –ANSI Standard B 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 ( ) 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.)

29 Industrial Processes II GRINDING WHEELS Diamond and Cubic Boron Nitride WheelsDiamond and Cubic Boron Nitride Wheels –ANSI Standard B 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 ( ) 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

30 Industrial Processes II FINISHING 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)

31 Industrial Processes II FINISHING TypesTypes –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)

32 Industrial Processes II FINISHING Types (cont.)Types (cont.) –Polishing –Buffing –Electro-Polishing –Magnetic Float Polishing (Ceramic Ball Bearings) –Barrel Finishing –Abrasive Flow –Abrasive Jet (Chapter 26 -Kalpakjian)

33 Industrial Processes II BELT GRINDING IllustrationIllustration Kalpakjian, Figure 25.28, p.813, Groover Figure 26.17, p 674

34 Industrial Processes II BELT 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.)

35 Industrial Processes II WIRE BRUSHING IllustrationIllustration

36 Industrial Processes II WIRE 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

37 Industrial Processes II HONING IllustrationIllustration Groover Figure 26.19, p 675

38 Industrial Processes II HONING 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

39 Industrial Processes II LAPPING IllustrationIllustration Kalpakjian, Figure 25.31, p.815

40 Industrial Processes II LAPPING 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

41 Industrial Processes II POLISHING 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

42 Industrial Processes II POLISHING 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

43 Industrial Processes II BUFFING 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

44 Industrial Processes II BUFFING 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

45 Industrial Processes II ELECTRO-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

46 Industrial Processes II ELECTRO-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

47 Industrial Processes II FLOAT POLISHING IllustrationIllustration Kalpakjian, Figure 25.32, p.816

48 Industrial Processes II FLOAT 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

49 Industrial Processes II BARREL 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.

50 Industrial Processes II BARREL FINISHING IllustrationIllustration Groover, Figure 32.2, p. 816

51 Industrial Processes II BARREL FINISHING Illustration Of Pellet ShapesIllustration Of Pellet Shapes Groover, Figure 32.3, p. 817

52 Industrial Processes II BARREL 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”

53 Industrial Processes II ABRASIVE FLOW IllustrationIllustration Kalpakjian, Figure 25.33, p.818

54 Industrial Processes II ABRASIVE 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

55 Industrial Processes II ABRASIVE JET IllustrationIllustration Kalpakjian, Figure 26.20, p.847

56 Industrial Processes II ABRASIVE 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

57 Industrial Processes II QUESTIONS OR CLARIFICATIONS ??? Reminder : Location and Timing of Thursday Class Location and Timing of Thursday Class Correction in Reading for Thursday (No Chapt. 25)


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