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INDUSTRIAL PROCESSES II INDEN 3313

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

  2. OVERVIEW • Questions to Start • Grinding • Process Description • Parameters/Impact on Surface Finish • Finishing • Process Descriptions • Parameters/Impact on Surface Finish Industrial Processes II

  3. QUESTIONSTO START ?? Industrial Processes II

  4. 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

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

  6. 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

  7. GRINDING • Review of Metal Cutting (Shear) Process Kalpakjian, Figure 20.1a, p. 606, Figure 20.13 p. 608 Industrial Processes II

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

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

  10. 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

  11. 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

  12. 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

  13. 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

  14. 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

  15. 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

  16. 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

  17. 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

  18. 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

  19. 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

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

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

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

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

  24. 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

  25. 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

  26. 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

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

  28. 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

  29. 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

  30. 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

  31. 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

  32. 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

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

  34. 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

  35. WIRE BRUSHING • Illustration Industrial Processes II

  36. 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

  37. HONING • Illustration Groover Figure 26.19, p 675 Industrial Processes II

  38. 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

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

  40. 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

  41. 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

  42. 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

  43. 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

  44. 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

  45. 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

  46. 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

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

  48. 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

  49. 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

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

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