Jackson Mark. Machining with Abrasives

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radial movement of the abrasive segments without signiﬁcant movement in the

circumferential direction, thus reducing the maximum circumferential stress in the

abrasive segment and in the adhesive bonding layer. This means that segmented

vitriﬁed and electroplated single-layer grinding wheels can be used at much higher

operating speeds than conventional and reinforced grinding wheels.

3.9 Conclusions

The levels of stress in a cylindrical grinding wheel due to centripetal loading can be

reduced by using a reinforced center made from a material that is rigid, lighter, and is

stronger than the abrasive material. Replacing the continuous layer of abrasive with

a layer of discontinuous segments can reduce the levels of stress due to centripetal

loading further. The depth and number of segments has a signiﬁcant inﬂuence on the

Fig. 3.48 Fringe plot of large cup shaped grinding wheel spinning at 45 m/s (P ¼250, F ¼50).

Used with permission from Inderscience Publishers (2010)

3 Grinding Wheel Safety and Design 175

Fig. 3.49 Fringe plot of large cup shaped grinding wheel spinning at 45 m/s (P ¼250, F ¼75).

Used with permission from Inderscience Publishers (2010)

Fig. 3.50 Fringe plot of large cup shaped grinding wheel spinning at 45 m/s (P ¼275, F ¼50).

Used with permission from Inderscience Publishers (2010)

176 M.J. Jackson

levels of stress in a rotating grindin g wheel. As a general rule, increasing the number

of segments and reducing the depth of the abrasive segments can reduce stress levels.

The maximum stress in an abrasive segment due to centripetal loading is in the radial

direction. Stress factors in high-speed segmented grinding wheels can be reduced

further by reducing the mass of the wheel by redesigning the center section of the

wheel using the new “porous” design. Stresses can be reduced even further when

using single-layer abrasive grinding wheels. It appears that carbon ﬁber is suited to

high speed gri nding operations (in excess of 100 m/s), whilst steel and aluminum

bodies can be used at much lower peripheral speeds. For small recessed grinding

wheels, the following conclusions are applicable:

1. For both parallel-sided wheels and recessed cup wheels, the maximum principal

stress acted circumferentially at the bore of the grinding wheel;

2. For the recessed cup-shaped grinding wheels, the factor of safety varied from 1.6

to 18 depending on their rotational speed;

Fig. 3.51 Fringe plot of large cup shaped grinding wheel spinning at 45 m/s (P ¼325, F ¼75).

Used with permission from Inderscience Publishers (2010)

3 Grinding Wheel Safety and Design 177

Table 3.4 Mechanical property data concerning the operating conditions for various grinding

wheels with varying geometry and rotational speeds

Cup

geometry

(mm)

Maximum

circumferential

stress (MN/m

)

Factor of

safety x y f

Calculated

bursting

speed (m/s)

Experimental

bursting

speed (m/s)

Rotational speed ¼45 m/s

P ¼200,

F ¼25

9.92 5.65 0.39 0.25 1.16 243 233

P ¼200,

F ¼50

10.2 5.5 0.39 0.5 1.17 242 238

P ¼250,

F ¼25

8.75 6.4 0.49 0.25 1.24 235 241

P ¼250,

F ¼50

13.5 4.1 0.49 0.5 1.29 231 225

P ¼250,

F ¼75

14.1 4 0.49 0.75 1.29 231 225

P ¼275,

F ¼50

12 4.7 0.54 0.5 1.35 226 233

P ¼325,

F ¼75

13.9 4 0.64 0.75 1.42 220 212

Rotational speed ¼60 m/s

P ¼200,

F ¼25

17.6 3.18 0.39 0.25 1.16 243 233

P ¼200,

F ¼50

17.5 3.2 0.39 0.5 1.18 242 238

P ¼250,

F ¼25

17.8 3.15 0.49 0.25 1.3 235 241

P ¼250,

F ¼50

24.1 2.3 0.49 0.5 1.4 231 225

P ¼250,

F ¼75

23.2 2.4 0.49 0.75 1.39 231 225

P ¼275,

F ¼50

21.3 2.6 0.54 0.5 1.47 226 233

¼325,

F ¼75

24.7 2.3 0.64 0.75 1.46 220 212

Rotational speed ¼90 m/s

P ¼200,

F ¼25

39.7 1.41 0.39 0.25 1.16 243 233

P ¼200,

F ¼50

40.1 1.4 0.39 0.5 1.18 242 238

P ¼250,

F ¼25

35 1.6 0.49 0.25 1.3 235 241

P ¼250,

F ¼50

54.1 1.04 0.49 0.5 1.4 231 225

P ¼250,

F ¼75

52.1 1.07 0.49 0.75 1.39 231 225

P ¼275,

F ¼50

47.8 1.17 0.54 0.5 1.47 226 233

P ¼325,

F ¼75

55.5 1.01 0.64 0.75 1.46 220 212

(continued)

178 M.J. Jackson

3. The measured fracture toughness for the 80-grain size cup wheel was 2.14 M Pa

m, and 1.8 M Pa m for a 36-grain size cup wheel. The standard deviation was 10

and 12%, respectively.

For large recessed cup wheels, the maximum principal stress acted circumferen-

tially at the bore of the grinding wheel and ranged from 8.75 to 55.5 MN/m

depending upon the operating speed. The following conclusions can be applied to

large recessed cup wheels:

1. For large recessed cup-shaped grinding wheels, the factor of safety varied from

1.01 to 6.4 depending on their rotational speed;

2. The measured fracture toughness for the 80-grain size cup wheel was 2.14 M Pa

m, and 1.8 M Pa m for a 36-grain size cup wheel. The standard deviation was 10

and 12%, respectively. And,

3. The method developed by Behrens and Kamm ler [15] proved to yield accurate

values of bursting speed when compared to experimentally determined bursting

speeds.

Acknowledgements The author acknowledges support from Vitriﬁed Technologies, Inc., and

thanks Ameya Deshpande for contributions made to the ﬁnite element analysis of the electroplated

grinding wheel design. The author wishes to thank Dr. Malcolm Bailey, Alan Jones, Roland

Wakeﬁeld and Peter Derbyshire for providing grinding wheel material and data. The author wishes

to thank Inderscience publishers for allowing the author to reproduce the author’s material from

Table 3.4 (continued)

Cup

geometry

(mm)

Maximum

circumferential

stress (MN/m

)

Factor of

safety x y f

Calculated

bursting

speed (m/s)

Experimental

bursting

speed (m/s)

Rotational speed ¼125 m/s

P ¼200,

F ¼25

27.1 2 0.4 0.25 1.16 243 233

P ¼200,

F ¼50

34 1.6 0.4 0.5 1.18 242 238

P ¼250,

F ¼25

23.7 2.4 0.6 0.25 1.3 235 241

P ¼250,

F ¼50

28.5 2 0.6 0.5 1.4 231 225

P ¼250,

F ¼75

24.6 2.3 0.6 0.75 1.39 231 225

P ¼275,

F ¼50

27.3 2 0.72 0.5 1.47 226 233

P ¼325,

F ¼75

26.2 2.15 0.8 0.75 1.46 220 212

3 Grinding Wheel Safety and Design 179

papers published in the International Journal of Computational Materials Science and Surface

Engineering and the International Journal of Manufacturing Technology and Management.

References

1. M. J. Jackson, C. J. Davis, M. P. Hitchiner, and B. Mills, High-Speed Grinding with c.B.N.

Grinding Wheels – Applications and Future Developments, Journal of Materials Processing

Technology (2001), 110, 78–88.

2. M. J. Jackson and N. Barlow, Computer Aided Design of High-Performance Grinding Tools,

Proceedings of the Institution of Mechanical Engineers (London), Part B – Journal of

Engineering Manufacture (2001), 215, 583–588.

3. M. J. Jackson, Fracture Dominated Wear of Sharp Abrasive Grains and Grinding Wheels,

Proceedings of the Institution of Mechanical Engineers (London), Part J – Journal of Engi-

neering Tribology (2004), 218, 225–235.

4. N. Barlow, M. J. Jackson, B. Mills, and W. B. Rowe, Optimum Clamping of cBN and

Conventional Vitreous-Bonded Cylindrical Grinding Wheels, International Journal of

Machine Tools and Manufacture (1995), 35, 119–132.

5. M. J. Jackson, N. Barlow, B. Mills, and W. B. Rowe, Mechanical Design Safety of Vitreous-

Bonded Cylindrical Grinding Wheels, British Ceramic Transactions (1995), 94, 221–229.

6. W. Koenig and F. Ferlemann, “CBN grinding at 500 m/s”, In ‘Ultrahard Materials in Industry

– Grinding Metals’, De Beers Industrial Diamond Company, UK (1991), pp. 58–65.

7. M. J. Jackson and N. Barlow, Computer Aided Design of High Performance Grinding Wheels,

Computer Aided Production Engineering – Transactions of the Institution of Mechanical

Engineers, London, UK (2000), 16, 243–251.

8. T. Suto, T. Waida, T. H. Noguchi, and H. Inoue, “Wheel Designs for Grinding”, In ‘Ultrahard

Materials in Industry – Grinding Metals’, De Beers Industrial Diamond Company, UK

(1991), pp. 34–37.

9. H. Munnich, High Speed Grinding Wheel Design, Doctoral Thesis, Technische Hochschule,

Hanover (1956).

10. M. J. Jackson, et al., Mechanical Design Safety of Vitreous Bonded Cylindrical Grinding

Wheels, British Ceramic Transactions (1995), 94(6), 221–229.

11. H. Munnich, Beitrag zur Sicherheit von umlaufenden Schleifkoerpern von keramisch gebun-

denen Scleifscheiben, PhD Thesis, University of Hannover, Hannover (1956).

12. J. Thies, Bruchmechanische und zerstoerungsfreie Unterschungen en keramisch gebundenen

Schliefschieben, PhD Thesis, University of Hannover, Hannover (1986).

13. W. Pompe, et al., Bruchstatische Aspekte der Festigkeit von Schliefscheiben, Ceramic Forum

International (1983), 60(8), 296–300.

14. D. Mewes, et al., Die Festigkeit von Schliefscheiben als Faktor fuer die Prozessicherheit,

Maschinenmarkt (2000), 40, 38–41.

15. J. A. Behrens and M. Kammler, Numerical and Experimental Analysis of the Breaking

Behaviour of Vitriﬁed Bonded Grinding Wheels, Ceramic Forum International (2005), 82

(11), 47–52.

180 M.J. Jackson

Chapter 4

Dressing of Grinding Wheels

Taghi Tawakoli and Abdolreza Rasifard

Abstract The appropriate dressing of the grinding wheel is one of the most

important prerequisites for an efﬁcient grinding process because, besides the

generation of the required grinding wheel proﬁle, it should also produce a suitable

wheel topography. In this chapter, the terminology associated to the conditioning of

the grinding wheels and the procedures of dressing will be ﬁrst introduced.

Diamond dressing tools will be then presented, to continue with a detailed descrip-

tion of the dressing with diamond dressers, including the ultrasonic assisted dress-

ing as a new process. At the end of this chapter, the most important non traditional

conditioning processes such as laser dressing and electrolytic in-process dressing

(ELID) will be presented.

Keywords Dressing  Sharpening  Dressing tools  Diamond  Ultrasonic assis-

tance  Laser dressing  ELID

4.1 Introduction

Grinding is generally used as a ﬁnal machining step in the manufacture of

components with high demands on manufacturing accuracy and surface quality.

The grinding wheel performance has a great inﬂuence over the quality of the

workpiece and process efﬁciency. The performance of the wheel is determined by a

great variety of inﬂuencing factors. These include, among others, the preparation of

the grinding wheel. The purpose of preparation is to produce the required

T. Tawakoli (*)

Department of Mechanical and Process Engineering, Hochschule Furtwangen University,

Villingen-Schwenningen, Germany

e-mail: tawakoli@hs-furtwangen.de

M.J. Jackson and J.P. Davim (eds.), Machining with Abrasives,

DOI 10.1007/978-1-4419-7302-3_4,

Springer Science+Business Media, LLC 2011

181

geometrical and run- out accuracy as well as to generate a grinding wheel

topography that is speciﬁc to the g rinding process in question. During the grinding

process, due to the wear of the grits and the bond, the grinding whe el is subject to

macro-wear and micro-wear. Macro-wear alters the shape of the tool proﬁle, which

must always match the desired workpiece geometry. The micro-wear, however, leads

to changes in the topography of the wheel, as a result of which the cutting surface of

the wheel becomes either too smooth or too rough for the grinding task.

According to Salje

[1], preparing a grinding wheel includes two stages: balancing

and conditioning (Fig. 4.1). Balancing serves to compensate for the form-induced and

structure-induced imbalances of the rotating wheel, which cause dimensional and

geometric errors on the workpiece [2]. The other operations involved in preparing

wheels, which lead to changes in the macrotopography and/or the microtopography of

the active surface of the wheel, come under the general term conditioning.

4.2 Grinding Wheel Conditioning

The purpose of conditioning is to produce, or restore, a wheel geometry and/or

topography appropriate to the grinding task. Conditioning involves three different

sub-processes: proﬁling, sharpening and cleaning, where proﬁling and sharpening

come under the general term of dressing [1, 3].

With proﬁling, the required geometrical and run-out accuracy of the grinding

wheel is produced. During the proﬁling, the bond and the grits are cut simulta-

neously. Therefore, the surface cutting of the grinding wheel possesses after

proﬁling little or no grit protrusion, particularly after the proﬁling of resin

bonded and metal bonded superabrasive wheels. In this condition the wheel doesn’t

posses a sufﬁcient cutting ability. Hence the desired grit protrusions and the

associated chip pockets have to be produced in the surface of the grinding wheel

during a shar pening process after the proﬁling. During the sharpening, the grits of

the top-most abrasive layer are exposed by cutting back the bond, whereby the chip

pocket needed for the grinding process is generat ed [4– 6 ].

dressing

profiling sharpening

cleaning

balancing

grinding wheel

geometry

grinding wheel

topography

conditioning

preparation of grinding wheels

Fig. 4.1 Terms of the

preparation of grinding

wheels after Salje

[1]

182 T. Tawakoli and A. Rasifard

During the grinding, some of the material being cut may be compressed and

adhered into the space between grains. This phenomenon, called wheel loading,

leads to a reduction of chip space, which can decrease the cutting ability of the

wheel. With the cleaning process, the loaded chips and loosened grit and bond

residues are removed from the wheel surface.

For conventional vitriﬁed wheels with their porous structure the term dressing is

often used for removal process carried out with a diamond tool, whereby the wheel

is simultaneously proﬁled and sharpened. In scientiﬁc work and in the relevant

specialist literature there are also other names for the terms proﬁling, sharpening

and cleaning. In the English-spea king world, the proﬁling of a grinding wheel, for

example, is also called truing. Another example is the use of the terms conditioning

and dressing for the sharpening operation [7, 8].

The conditioning processes can be classiﬁed according to the mechanism of grit

and/or bond removal during the process into two groups: the processes with the

principle of mechanical material removal and the processes with the principle of

non-mechanical material removal. In the ﬁrst group, grits and/or the bond are

removed by cutting or splitting the grits and/or the bond using a diamond or a

diamond-free dressing tool. In the second group, the dressing process is carried out

using non-mechanical forms of energy such as thermal and electrical energy. Laser

dressing and electrolytic in-process dressing (ELID) are two examples of condi-

tioning processes with the principle of non-mechanical material removal.

4.2.1 Proﬁling

In industry, the proﬁling of a wheel is carried out almost exclusively by a cutting

process with a stationary or rotary dressing tool. The tools used for proﬁling are

predominantly diamond dressers, in order to guarantee a high degree of geometric

and dimensional accuracy on the wheel that is to be dressed. Depending on the

kinematics of the dressing process, dressers can be divided into two groups:

stationary dressers and rotary dressers.

4.2.1.1 Stationary Dressers

Stationary dressers have no movement in the circumferential direction of

the grinding wheel. The wheel is dressed by axial movement of the dresser along

the contour of the grinding wheel. Dressing with stationary dressers is therefore

comparable to the turning process (Fig. 4.2). In industry, stationary diamond dres-

sers are used in different forms and with different diamond abrasive coatings or tips

(Fig. 4.3). Almost all of the stationary diamond dressers are only suitable for

proﬁling or dressing rectilinear and simple wheel proﬁles. Furthermore, because

Stationary diamond dressers contain only a small amount of diamond, when dressing

superabrasive CBN and diamond wheels they are subject to a great deal of wear.

4 Dressing of Grinding Wheels 183

Therefore, to meet the demands on geom etric and dimensional accuracy of the wheel

proﬁle, the dresser have to be changed frequently.

The generation of the wheel topography and also the wear on a stationary dresser

are inﬂuenced to a great extent by the process parameters. The inﬂuence of these

3-15°

a ≥ b/2

fad

Fig. 4.2 Process kinematics in dressing with stationary dressers [9] used with permission copyright

Winterthur Technology Group

dressing tool grinding wheel profile application

single-point

diamond

rectilinear

(cylindrical, taper)

single-profile

(convex and concave

radii)

surface, cylindrical and

centreless grinding

single and small batch

production

profile diamond

multi-profile

(complex profile with

steep sides and close

radii)

surface, external

cylindrical and

centreless grinding

single and small batch

production

multi-point

diamond

rectilinear

(cylindrical, Taper)

surface and external

cylindrical grinding

single and small batch

production

dressing blade

rectilinear

(cylindrical, taper)

single-profile

(convex and concave

radii)

single -layered

multilayered

surface, external

cylindrical and

centreless grinding

single to mass

production

Fig. 4.3 Examples of stationary dressers used with permission copyright Tyrolit Co

184 T. Tawakoli and A. Rasifard