Grinding Fundementals
Grinding Fundementals
Grinding Fundementals
A
Abrasive Abrasive Type Type
46
Grit Size Grit Size 8, 10, 12, 14 8, 10, 12, 14 16, 20, 24, 30 16, 20, 24, 30 36, 46, 54, 60 36, 46, 54, 60 80, 100, 120 80, 100, 120 150, 180, 220 150, 180, 220 240, 280, 320 240, 280, 320 400,600,800 400,600,800
K
Grade Grade
10
Cumi Cumi Symbol Symbol
SiC SiC
Black C Black C Green GC Green GC Zirconia ZA Zirconia ZA
G G K K O O S S X X
H II H L M STRUCTURE Bond System L M STRUCTURE Bond System VG VVR V6 VG VVR V6 P Q P Q T U T U V7 V7 Y Z 1 2 3 4 5 V -- Vitrified Y Z 1 2 3 4 5 V Vitrified V30 V10 VL V30 V10 VL 6 B -6 B V8 V8 ..............Upto Resinoid ..............Upto Resinoid V2018 VF8 V2018 VF8 .....................3 R -- Rubber .....................3 R Rubber VMPA VMSA VMPA VMSA 5 5 BN BR BFW BN BR BFW RT R RB RT R RB
WHAT IS AN ABRASIVE ?
A Mineral Crystal with Hardness much higher than that of work piece
TYPES OF ABRASIVES
Natural Corundum, Emery, Diamond Synthetic > Aluminium Oxide - Conventional Abrasive > Silicon Carbide - Conventional Abrasive > Cubic Boron Nitride - Super Abrasive > Diamond - Super Abrasive
PROPERTIES OF ABRASIVES
Friability - Ability to Fracture under load Thermal Conductivity - Ability to Conduct Heat Hardness - Resistance to Penetration Toughness - Ability to Withstand Load
SEMIFRIABLE (SA)
Brown in colour % Of titanium oxide is less than 2% Friability index falls between A & AA
GRAIN COMBINATION
Combination of different grit sizes in predetermined percentages Ex. A463 l5 V10 - combination of 46,54 & 60 grits. Primary grit 46 will be at higher percentage.
BOND
BINDING MATERIAL WHICH HOLDS THE ABRASIVE GRAINS TOGETHER IN A WHEEL.
BOND TYPES
Vitrified bond (V) Resinoid bond (B) Rubber bond (R) Shellac bond (S) Oxychloride bond (Oxy) Magnesite bond
VITRIFIED BOND
Vitrification Bond mix melts /partly wets the abrasive Abrasive grain pulled together by surface tension Titanium rich phase from A disbursed in to the surrounding matrix - it turns blue
VITRIFIED BOND
More strength Water resistance Chemical resistance No shelf life Bond fractures induced by mechanical forces during grinding Very brittle Decreased bending strength Better form holding stability
RESINOID BONDS
Grains mixed with phenolic thermo-setting resins and plasticizers Baking at 150 to 200 deg. C High strength Ability to withstand shock loads Shelf life 1 - 2 years Low chemical & thermal resistance
WHEEL WEAR
A) Grain Fracture B) Bond Fracture C) Attritious Wear
WHEEL SELECTION
WHEEL SELECTION
FACTORS AFFECTING WHEEL SELECTION
MATERIAL TO BE GROUND STOCK TO BE REMOVED WHEEL SPEED AREA OF GRINDING TYPE OF OPERATION - WET (OR) DRY GRINDING MACHINE SURFACE FINISH
o sc o sc o sc
60 0.5
80 0.4
120 0.2
180 0.13
240 0.1
320 0.08
400 0.05
GRADE SELECTION
MATERIAL HARDNESS ARC / AREA OF CONTACT TYPE OF OPERATION FORM HOLDING WHEEL SPEED WHEEL WIDTH TYPE OF DRESSER TYPE OF COOLANT
GRADE SELECTION
MATERIAL HARDNESS
Wheel Grade M L K J I Soft 50 Rc Medium 50 - 57 Rc Hard 58 - 63 Rc
STRUCTURE SELECTION
STOCK REMOVAL THERMAL CONDUCTIVITY OF WORK MATERIAL MATERIAL REMOVAL RATE
STRUCTURE SELECTION
STOCK REMOVAL
STRUCTURE SELECTION
MATERIAL REMOVAL RATE
BOND SELECTION
SEVERITY OF OPERATION WHEEL SPEED FORM HOLDING SURFACE FINISH MATERIAL REMOVAL RATE