1. For: Bosch Rexroth – Rineer Hydraulics
GRINDING BASICS
Presented by Dale Savington
For:
Bosch Rexroth – Rineer Hydraulics

2. Cylindrical Grinding Processes
Machine Requirements (Utilizing CBN)
Abrasives
Properties of Abrasives

3. Superabrasives
Bonds
Mechanics of Grinding
Coolant
Truing & Dressing

4. CYLINDRICAL PROCESSES (GRINDING BETWEEN CENTERS)

5. Conventional Plunge / Face Grinding
Down-Feed (face bump grind)
Q’ (Prime) 2.14 (0.2) +
Wheel Velocity
S.F.P.M. 8,500 +
m/sec. 43 +
High volume of coolant to get into grinding zone

6. Conventional Traverse Grinding
Cross –Feed (Traverse) only
Stock Removal (in-feed depth)
0.0” to mm (0.0007”)
≥ 10% of abrasive Ø / pass
Traverse rate
10 – 25% of wheel width per rotation of part
Wheel Velocity
S.F.P.M. 8,500 +
m/sec. 43 +
Finish Grinding

7. Peel (“Quick Point”) Grinding
Multiple grinding functions
Wheel face configuration
Wheel Velocity
S.F.P.M. 17,000 +
m/sec. 86 +
Easier coolant delivery into grinding zone (narrow contact area)

8. Cylindrical Grinding Plunge
Q Prime (Q’) = work piece diameter x 3.14 (π) x in-feed rate
Example:
Work piece diameter = 25.4mm (1”)
In-feed rate = 4.039mm/min. (0.159”/minute)
Q’ then equals:
(25.4 x 3.14 x 4.039)/60 = 5.37 mm3/mm· sec.
1 x 3.14 x = 0.5 in3/in· min.
Therefore:
(5.37/(3.14 x 25.4)) x 60 = 4.039mm/min.
0.5/(3.14 x 1”)= 0.159”/min. infeed rate
Note: (mm3/mm· sec.) to (in3/in· min.) conversion of 10.75

9. Surface Grinding

10. Conventional Grinding
Wheel Speed = S l o w
Stock Removal = Light
Fast

11. Creep Feed
Wheel Speed = S l o w
Stock Removal = Heavy
S l o w

12. HEDG (High Efficient Deep Grinding)
Wheel Speed = Fast
Stock Removal = Heavy
Fast

13. Surface Grinding Example: In-Feed per pass= 0.0508mm (0.002”)
Q Prime (Q’) =In-feed rate/pass x Traverse rate/min.
Example:
In-Feed per pass= mm (0.002”)
Traverse rate per min.= 3,810mm (3.81m)/min. (150” (12.5’)/minute)
Q’ then equals:
( x 3,810)/60 = mm3/mm· sec.
0.002 x 150 = 0.3 in3/in· min.
Therefore:
(3.225/(0.0508) x 60 = 3,810mm/min. traverse rate
0.3/(0.002”)= 150”/min. traverse rate
Note: (mm3/mm· sec.) to (in3/in· min.) conversion of 10.75

14. MACHINE REQUIREMENTS

15. Parts will Mirror Machines Rigidity
Machine Rigidity
Slides
Spindle’s
Centers
Head Stock
Tail Stock
Base
Parts will Mirror Machines Rigidity

16. Kilowatts! Wheel Spindle POWER!
Wheel spindle power per 25.4mm (1”) of wheel to work contact
Conventional Abrasives = 3.75 Kw (5 H.P.)
CBN Abrasives = 7.5 Kw (10 H.P.)
(HEDG) = Kw (25 H.P.)
Peel – depends on contact area, material and stock removal

17. Spindle Integrity
Run-Out
Out of Balance

18. Wheel Balance (Dynamic vs Static)
Dynamic Balance – real time
Static Balance
Wheel Balance (Dynamic vs Static)
Portable Dynamic Balance

19. Wheel Balance (Dynamic vs Static)
Static Balance allows balance in stationary position off the spindle.
Dynamic Balance is continuous balance on the spindle at working rotating speeds.
Wheel Balance (Dynamic vs Static)

20. Acoustic Sensors Dressing:
Sound of dresser touching wheel through coolant.
Complete contact = dressed wheel
Other uses:
Picture of grinding process
Crash prevention
Acoustic Sensors

21. Machine Requirements (Maximizing Grinding Process)
Rigidity
Coolant Flow
Spindle power
Smooth Transitional Plumbing
Wheel Velocity
Coolant Tank Capacity
Rotary Dresser
1. In process gaging
2. Automatic loading
3. Chillers
4. Coolants should be Water soluable oil (.3%) or straight oil
5. Coolant flow meters, temperature monitors, (Discuss Searcy Project)
Coolant with lubricity
Acoustic Sensors
Dynamic Balancing

22. ABRASIVES

23. What affects Abrasive Decision?
Ferrous Materials
Non-Ferrous Materials
Fatigue Concerns
(Potential thermal damage)
Dimensional Tolerances
Process Controls
Production Numbers

24. Types of Abrasives Aluminum Oxide Silicon Carbide
Cubic Boron Nitride (CBN)
Diamond

25. Abrasive Selection Ferrous Materials Non-Ferrous Materials
Cubic Boron Nitride (CBN)
Diamond
Silicon Carbide
Aluminum Oxide

26. PROPERTIES OF ABRASIVES

27. Aluminum Oxide (Al2O3) For Grinding Ferrous Materials
Thermal Conductivity
(W/mOK) = 29
Hardness on Knoop Scale
(kg/mm2) =

28. Non-Ferrous Materials
Silicon Carbide (Si,C)
For Grinding
Non-Ferrous Materials
Thermal Conductivity
(W/mOK) = 400
Hardness on Knoop Scale
(kg/mm2) = 2700

29. Cubic Boron Nitride (CBN) (B,N)
For Grinding
Ferrous Materials
Hardness on Knoop Scale
(kg/mm2) = 4500
Thermal Conductivity
(W/mOK) = 1300

30. Non-Ferrous Materials
Diamond (C)
For Grinding
Non-Ferrous Materials
Thermal Conductivity
(W/mOK) = 2000
Hardness on Knoop Scale
(kg/mm2) = 8000

31. Review Knoop Thermal Hardness Conductivity Aluminum Oxide 1400-2100 29
Silicon Carbide
Cubic Boron Nitride (CBN)
Diamond

32. The Puzzle Why Not Diamond?
Diamond + Ferrous Material + Heat =
REACTION
Note: Silicon Carbide has similar reaction

33. SUPERABRASIVES

34. What are Superabrasives?
Diamond
Cubic Boron Nitride (CBN) Borazon
Show overhead on make up of Diamond and CBN

35. What makes Superabrasives Super?
Hardness - (Resistance to wear)
Thermal Conductivity- (The ability to absorb heat)
Flexibility- (one wheel for many applications)
Be prepared to show overh ead of Properties of Superabrasives
Hardness for CBN =4700Knoop
Diamond =7000 Knoop
Alumimum Oxide = Knoop
Silicon Carbide =2700 Knoop
Thermal Conductivity for CBN =1300
Diamond =2000
Aluminium Oxide =29
Silicon Carbide =400
Grinding Ratio for M2 Steel =229
Volume of Work / Volume of wheel T15 Steel =150
D2 Steel =217
Wheel Life- (100 + times Conventional Abrasives)

36. Some Advantages (For Superabrasives)
Decreased Cycle Time
Reduced Dressing
Reduced Gaging
More Consistent Parts (Less Scrap)
Reduced Time for Wheel Changes
Reduced Coolant Changes
Reduced Filter Changes
Reduced Coolant Disposal Costs
Less Swarf Contamination

37. Conventional Abrasives Construction
Conventional Layer = full area of wheel
Vitrified Bond
Resin Bond
Rubber Bond
Shellac Bond
Wheel
1. If a grinding wheel is 24 inch in diameter with a 12 inch hole
The entire wheel from O.D. to hole is conventional abrasive
compared to the 1/8 to 1/4 inch section for Superabrasives.
2. This small section is going to last from time a conventional wheel

38. Superabrasive Construction
Superabrasive Layer = 3mm (1/8”) to 12.7mm (1/2”)
Wheel
Core
Resin Bond
Metal Bond
Vitrified Bond
1. If a grinding wheel is 24 inch in diameter with a 12 inch hole
The entire wheel from O.D. to hole is conventional abrasive
compared to the 1/8 to 1/4 inch section for Superabrasives.
2. This small section is going to last from time a conventional wheel

39. BONDS

40. Grinding Matrix Vitrified Wheel
Grain
Pore
Bond
Chip

41. Grinding Wheel Bond Systems
Sintered Vitrified
Resin , Metal & Bonds
Abrasive + Bond = Wheel

42. Grinding Wheel Bond Systems
Open Structure (Low fired) Vitrified Bonds
Abrasive + Bond + Pores = Wheel

43. Grinding Wheel Bond Systems
Plated Wheels (Single Layer)
Wheel body
Cathode (-)
Electrolyte
(Nickle Solution)
Abrasive
Anode (+)
Plated Wheel
Cut-A-Way

44. Mechanics of Grinding

45. Abrasive wear
Bond
Abrasive
Fracture wear
Chip
Cut a way of wheel

46. Abrasive wear Conventional Abrasive (one grain) Attritious wear
(Rubbing)
Work Piece
Abrasive wear

47. Abrasive wear Conventional Abrasive (one grain) Fracture wear
Work Piece
Abrasive wear

48. Abrasive wear Conventional Abrasive (one grain) Fracture wear
Work Piece
Abrasive wear

49. CBN
Abrasive (one grain)
Attritious wear
Work Piece
Abrasive wear

50. Standard Markings Conventional Abrasives
Abrasive Type
Abrasive Size
Abrasive (combination)
Hardness (Grade)
Structure (Pore)
Bond A C
SG30 60
120 80 24 1 2 J K L R 6 12 10 V B

51. Standard Markings Superabrasives
Abrasive Type
Abrasive Size
Hardness (Grade)
Concentration
Bond BN D
140
240
120 J k L
100 75
150 B M V
Superabrasives are always combinations 120/140, 80/100 etc.
Calculating concentration take number and divide by 4
Example 100 ÷ 4 = 25% by volume of abrasive in wheel

52. Type, Flow, Pressure & Nozzle Design
Coolant
Type, Flow, Pressure & Nozzle Design

53. Coolant Types Water, Water Soluble Oils, Straight Oils
Specific Gravity of each & traits for grinding:
Water = 1 SG (Issue – lack of Lubricity)
Water Soluble Oil = 1 SG (Issues – Foaming & bacteria)
Straight & Synthetic Oils = SG (Issues – Heat & Disposal)
( Specific Gravity (SG not a factor in calculations) )

54. Particle Distribution
Coolant Condition
Filtration &
Particle Distribution
Tank Size &
Coolant Temp.
Chemistry
(Lubricity)

55. Coolant Pressure Equal Wheel Velocity
Bernoulli’s Equation for Pressure
ΔP (Bar) = SG x Vj2 / 200
Where:Vj2 = (M/s)2
Example: Wheel velocity – 43.3M/s (8,500 S.F.P.M.)
Then: 1 x (43.3)2 / 200 = 9.4 Bar
Bar conversion Bar x = 136 psi

56. Bernoulli’s Equations

58. Copyright © 2013 [Dale Savington]. All Rights Reserved

59. Copyright © 2013 [Dale Savington]. All Rights Reserved

60. Coolant Flow
Coolant Velocity = Wheel Velocity

61. “P” Line /Rim Section

65. TRUING & DRESSING

66. The Difference Between Truing & Dressing

67. Truing Resin & Metal Bonds

68. Dressing Resin & Metal Bonds

69. Truing & Dressing Plated Wheels

70. Truing & Dressing Vitrified Bonded (CBN Wheels)

71. Examples of Rotary Dressers

72. Direction for Dressing with rotary Dressers
Preferred (opens wheel)
Closes Wheel

73. Truing & Dressing (Depth or In-Feed)
Conventional Abrasives – Aluminum Oxide
≤ mm (0.0007”) per pass
Ceramic Abrasives – Seeded Gel (SG)
≤ 0.005mm (0.0002”) per pass
CBN Abrasives
≤ mm (0.0001”) per pass
Truing & Dressing (Depth or In-Feed)

74. Truing & Dressing (Traverse Rate)
Starting Parameters
0.1mm (0.004”) per revolution of wheel
Assuming 0.5mm (0.020”) radius dresser
Truing & Dressing (Traverse Rate)
Faster traverse rate creates rougher finish
Slower traverse rate creates finer finish

75. CBN vs Conventional (Surface Finish – plunge grinding only)
Conventional Grinding Surface Finish = Grit Size
CBN Grinding: Surface Finish = Diamond Overlap
CBN vs Conventional (Surface Finish – plunge grinding only)

76. “Automotive Valve Seats”
Nozzle increased production by 42% (762mm/min to >1,065mm/min.) + decrease dress amounts.
“Automotive Valve Seats”
508mm x 458mm x 304.8mm
Vitrified CBN wheel
Thru-Feed Grinding
Metal bond rotary dresser
Dr. Webster Nozzle
Each orifice is an oval 4mm
19 total orifices

77. Hard Tuning Shafts to see if it was cost affective
Cost was prohibitive because of tool life and change times

78. the end