1. Manufacturing Process 1 Abrasive Machining Prepared By : Joshi Shubham H. ( ) GUIDED BY: PROF V N BADRAKIA SIR
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2. Chapter Outline Introduction Abrasives and Bonded Abrasives
The Grinding Process
Grinding Operations and Machines
Design Considerations for Grinding
Ultrasonic Machining
Finishing Operations
Deburring Operations
Economics of Abrasive Machining and Finishing Operations
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3. Introduction
Some manufacturing processes cannot produce the required dimensional accuracy or surface finish
An abrasive is a small, hard particle having sharp edges and an irregular shape
Abrasives is removing of small amounts of material from a surface through a cutting process that produces tiny chips
Grinding wheels can sharpen knives and tools
Sandpaper or emery cloth can smoothen surfaces and remove sharp corners
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4. Introduction
Abrasives are hard and used in finishing processes for heat-treated metals and alloys
Applications include:
Finishing of ceramics and glasses
Cutting off lengths of bars, structural shapes, masonry and concrete
Removing unwanted weld beads and spatter
Cleaning surfaces with jets of air or water containing abrasive particles.
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5. Introduction
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6. Abrasives and Bonded Abrasives
Abrasives that are commonly used:
Conventional abrasives
Superabrasives
Above abrasives are harder than conventional cutting- tool materials
Cubic boron nitride and diamond are the two hardest materials known; referred to as superabrasives
Friability defined as the ability of abrasive grains to fracture into smaller pieces
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7. Abrasives and Bonded Abrasives
Abrasive Types
Commonly found in nature are emery, corundum (alumina), quartz, garnet and diamond
Abrasives that have been made synthetically:
Aluminum oxide
Seeded gel
Silicon carbide
Cubic boron nitride
Diamond
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8. Abrasives and Bonded Abrasives
Abrasive Grain Size
Abrasives are very small when compared to the size of cutting tools and inserts
Abrasives have sharp edges and allow removal of small quantities of material
Very fine surface finish and dimensional accuracy can be obtained using abrasives as tools
Size of an abrasive grain is identified by a grit number
Smaller the grain size, larger the grit number
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9. Abrasives and Bonded Abrasives
Abrasive–workpiece-material Compatibility
Affinity of an abrasive grain to the workpiece material is important
The less the reactivity of the two materials, the less wear and dulling of the grains occur during grinding
Recommendations when selecting abrasives:
Aluminum oxide: Carbon steels, ferrous alloys, and alloy steels.
Silicon carbide: Nonferrous metals, cast irons
Cubic boron nitride: Steels and cast irons
Diamond: Ceramics, cemented carbides, hardened steels
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10. Abrasives and Bonded Abrasives: Grinding Wheels
Each abrasive grain removes only a very small amount of material at a time
High rates of material removal can be achieved when large number of these grains act together
Done by using bonded abrasives
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11. Abrasives and Bonded Abrasives: Grinding Wheels
In bonded abrasives, porosity is essential to provide clearance for produced chips and cooling
Porosity can be observed by the surface of grinding wheel
For non-porosity, it is fully dense and solid
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12. Abrasives and Bonded Abrasives: Grinding Wheels
Due to their high cost, only a small volume wheels consists of superabrasives
Bonded abrasives are indicated by the type of abrasive, grain size, grade, structure, and bond type
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13. Abrasives and Bonded Abrasives: Grinding Wheels
Cost of grinding wheels depends on the type and size of the wheel
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14. Abrasives and Bonded Abrasives: Bond Types
Common types of bonds:
Vitrified:
Consist of feldspar and clays
Strong, stiff, porous, and resistant to oils acids, and water
Resinoid:
Bonding materials are thermosetting resins
Resinoid wheels are more flexible than vitrified wheels
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15. Abrasives and Bonded Abrasives: Bond Types
Reinforced Wheels:
Consist of layers of fiberglass mats of various mesh sizes
Thermoplastic:
Used in grinding wheels
With sol-gel abrasives bonded with thermoplastics
Rubber:
Using powder-metallurgy techniques
Lower in cost and are used for small production quantities
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16. Abrasives and Bonded Abrasives: Wheel Grade and Structure
The grade of a bonded abrasive is a measure of its bond strength
The grade is also referred to as the hardness of a bonded abrasive
A hard wheel has a stronger bond and/or a larger amount of bonding material between the grains than a soft wheel
Structure of a bonded abrasive is a measure of its porosity
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17. The Grinding Process
Grinding is a chip-removal process that uses an individual abrasive grain as the cutting tool
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18. The Grinding Process Grinding Forces
Knowledge of grinding forces is essential for:
Estimating power requirements
Designing grinding machines and work-holding fixtures and devices.
Determining the deflections that the workpiece
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19. The Grinding Process
In surface grinding, undeformed chip length and thickness is approximated by equation
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20. The Grinding Process Grinding Forces
A knowledge of grinding forces is essential for:
Estimating power requirements
Designing grinding machines and work-holding fixtures and devices
Determining the workpiece and grinding machine deflections
Grain force is proportional to the process variables:
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21. Economics of Abrasive Machining and Finishing Operations
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