Chapter 25 (grinding)

4,227 views

Published on

Published in: Education, Business
1 Comment
0 Likes
Statistics
Notes
  • Be the first to like this

No Downloads
Views
Total views
4,227
On SlideShare
0
From Embeds
0
Number of Embeds
36
Actions
Shares
0
Downloads
531
Comments
1
Likes
0
Embeds 0
No embeds

No notes for slide

Chapter 25 (grinding)

  1. 1. GRINDING AND OTHER ABRASIVE PROCESSES 1
  2. 2. Material Removal Processes A family of shaping operations, the common feature of which is removal of material from a starting workpart so the remaining part has the desired geometry. Machining – material removal by a sharp cutting tool, e.g., turning, milling, drilling. Material Removal Nontraditional processes various energy forms other than sharp cutting tool to remove material, e.g. electrochemical and thermal energy processes. Manufacturing Processes Prof Simin Nasseri Abrasive processes – material removal by hard, abrasive particles, e.g., grinding.
  3. 3. Machining Processes Traditional Chip Removal • • • • • • Turning Milling Drilling Boring Reaming Shaping Manufacturing Processes Prof Simin Nasseri  Sawing Broaching  Planing  Grinding Honing Lapping    Nontraditional Machining          Ultrasonic Electrical Discharge Electro-arc Optical Lasers Electrochemical Chem-milling Abrasive Jet Cutting Electron Beam Machining Plasma Arc Machining
  4. 4. Abrasive Machining  Material removal by action of hard, abrasive particles usually in the form of a bonded wheel  Generally used as finishing operations after part geometry has been established by conventional machining  Grinding is most important abrasive process  Other abrasive processes: honing, lapping, superfinishing, polishing, and buffing Manufacturing Processes Prof Simin Nasseri
  5. 5. Why Abrasive Processes are Important  Can be used on all types of materials  Some can produce extremely fine surface finishes, to 0.025 m (1 -in)  Some can hold dimensions to extremely close tolerances Manufacturing Processes Prof Simin Nasseri
  6. 6. Grinding Material removal process in which abrasive particles are contained in a wheel that operates at very high surface speeds. Manufacturing Processes Prof Simin Nasseri
  7. 7. Wheel Structure The grinding wheel: is usually disk-shaped and precisely balanced for high rotational speeds. Consists of abrasive particles and bonding material. • Abrasive particles accomplish cutting. • Bonding material holds particles in place and establishes shape and structure of wheel. Figure 25.1 Typical structure of a grinding wheel. Manufacturing Processes Prof Simin Nasseri
  8. 8. Abrasive Material Properties     High hardness Wear resistance Toughness Friability - capacity to fracture when cutting edge dulls, so a new sharp edge is exposed Manufacturing Processes Prof Simin Nasseri
  9. 9. Traditional Abrasive Materials Aluminum oxide (Al2O3) - most common abrasive Silicon carbide (SiC) - harder than Al2O3 but not as tough Used to grind steel and other ferrous high-strength alloys Used on aluminum, brass, stainless steel, some cast irons and certain ceramics Manufacturing Processes Prof Simin Nasseri
  10. 10. Hardness of Abrasive Materials Abrasive material Aluminum oxide Silicon carbide Cubic boron nitride Diamond (synthetic) Manufacturing Processes Prof Simin Nasseri Knoop hardness 2100 2500 5000 7000
  11. 11. Surface Finish Most grinding is performed to achieve good surface finish Best surface finish is achieved by:  Small grain sizes  Higher wheel speeds  Denser wheel structure = more grits per wheel area Two main categories of grinding:  Surface grinding  Cylindrical grinding Manufacturing Processes Prof Simin Nasseri
  12. 12. Four Types of Surface Grinding Figure 25.7 (a) Horizontal spindle with reciprocating worktable, (b) horizontal spindle with rotating worktable, (c) vertical spindle with reciprocating worktable, (d) vertical spindle with rotating worktable. Manufacturing Processes Prof Simin Nasseri
  13. 13. Surface Grinder Figure 25.8 Surface grinder with horizontal spindle and reciprocating worktable (most common grinder type). Manufacturing Processes Prof Simin Nasseri
  14. 14. Cylindrical Grinding Figure 25.9 Two types of cylindrical grinding: (a) external, and (b) internal. Manufacturing Processes Prof Simin Nasseri
  15. 15. Other Abrasive Processes  Honing  Lapping  Superfinishing Manufacturing Processes Prof Simin Nasseri
  16. 16. Honing Abrasive process performed by a set of bonded abrasive sticks using a combination of rotational and oscillatory motions. Creates a characteristic cross-hatched surface that retains lubrication. Grit sizes range between 30 and 600. Figure 25.16 The honing process: (a) the honing tool used for internal bore surface. Manufacturing Processes Prof Simin Nasseri Surface finishes of 0.12 m (5 -in) or better.
  17. 17. Honing Common application is to finish the bores of internal combustion engines. Manufacturing Processes Prof Simin Nasseri
  18. 18. Lapping Uses fluid suspension of very small abrasive particles between workpiece and lap (tool). Lapping compound - fluid with abrasives, general appearance of a chalky paste. Applications: optical lenses, metallic bearing surfaces, gages. Figure 25.17 The lapping process in lens-making. Manufacturing Processes Prof Simin Nasseri
  19. 19. Superfinishing Similar to honing - uses bonded abrasive stick pressed against surface and reciprocating motion Differences with honing: * Shorter strokes * Higher frequencies * Lower pressures between tool and surface * Smaller grit sizes Figure 25.18 Superfinishing on an external cylindrical surface. Manufacturing Processes Prof Simin Nasseri

×