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

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

Industrial Processes II QUESTIONS TO START ?? Industrial Processes II

Industrial Processes II 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

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

Industrial Processes II 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

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

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

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

Industrial Processes II 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

Industrial Processes II 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

Industrial Processes II 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

Industrial Processes II 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

Industrial Processes II 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

Industrial Processes II 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

Industrial Processes II 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

Industrial Processes II 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

Industrial Processes II 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

Industrial Processes II 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

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

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

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

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

Industrial Processes II 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

Industrial Processes II 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

Industrial Processes II 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

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

Industrial Processes II 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

Industrial Processes II 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

Industrial Processes II 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

Industrial Processes II 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

Industrial Processes II 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

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

Industrial Processes II 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

Industrial Processes II WIRE BRUSHING Illustration Industrial Processes II

Industrial Processes II 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

Industrial Processes II HONING Illustration Groover Figure 26.19, p 675 Industrial Processes II

Industrial Processes II 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

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

Industrial Processes II 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

Industrial Processes II 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

Industrial Processes II 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

Industrial Processes II 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

Industrial Processes II 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

Industrial Processes II 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

Industrial Processes II 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

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

Industrial Processes II 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

Industrial Processes II 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

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

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

Industrial Processes II 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

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

Industrial Processes II 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

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

Industrial Processes II 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

QUESTIONS OR CLARIFICATIONS ??? Copyright 2000 John W. Nazemetz -- Each student enrolled in IEM 3313 at Oklahoma State University may make one copy for personal use. All other uses strictly prohibited. Spring 2000 QUESTIONS OR CLARIFICATIONS ??? Reminder : Location and Timing of Thursday Class Correction in Reading for Thursday (No Chapt. 25) Industrial Processes II