INCREASING THE WORKING EFFICIENCY OF ABRASIVE GRAINS IN MACHINING SKD11 STEEL BY USING NEWLY DEVELOPED INCLINED SEGMENTED GRINDING WHEEL

INCREASING THE WORKING EFFICIENCY OF ABRASIVE GRAINS IN MACHINING SKD11 STEEL BY USING NEWLY DEVELOPED INCLINED SEGMENTED GRINDING WHEEL Tien Dong Nguyen* Hanoi University of Science a

INCREASING THE WORKING EFFICIENCY OF ABRASIVE GRAINS IN MACHINING SKD11 STEEL BY USING NEWLY DEVELOPED

INCLINED SEGMENTED GRINDING WHEEL

Tien Dong Nguyen*

Hanoi University of Science and Technology, No 1, Dai Co Viet, Hai Ba Trung, Hanoi, Viet Nam

ABSTRACT:

In this paper, newly developed inclined

segmented grinding wheel (ISGW), which have

segments on the working surface; angle between

these segments and a shaft of grinding machine

β=15º, were used to grind SKD11 steel which is

popular material in mold making technology The

percentage of discontinue on wheel surface

symbolized by η, is defined as the ratio between

the area does not containing abrasive grains and

the total area of wheel surface Four ISGWs, with

different percentage of discontinue η (16.37,

18.19, 20.01 and 21.83%) and a conventional

wheel with η = 0% were used in experimental

process The number of abrasive grain in contact

with sample surface per unit area per second ,

was calculated to evaluate the efficiency of abrasive grains by wheel rotation speed, feeding speed and percentage of discontinue η Surface roughness of ground sample was employed When the number of abrasive grain increase or

the feeding speed S decrease, the surface roughness of surface ground by conventional grinding wheel decrease, but it obtained the same values by using ISGWs It seems that the surface roughness does not depend on number of abrasive grain participate in the grinding process

In other word, the working efficiency of abrasive grains can increase up to 20% as increasing of the feeding speed from 12 m/min to 15 m/mm using inclined segmented grinding wheels.

Keywords: inclined segmented grinding wheel (ISGW), SDK11 steel, roughness, abrasive grains

1 INTRODUCTION

In the last few years, grinding process is a

strategic process for machining new materials

with tough characteristics, such as hard and brittle

materials, ceramics, etc, which required a good

accuracy and a high quality of surface roughness

Grinding process can be used to combine high

removal rate with high accuracy [1] Alternatively,

grinding can be employed with moderate removal

rates to produce high accuracy parts in large

volumes In manufacturing mold plate, spherical

grinding plays an important role because it is the

simplest and least expensive process for

machining materials which is popular in mold

making technology To increase the productivity

and quality of grinding process, researchers not

only spend time to optimize the parameters on

machine, apply new materials but also present

new design of wheels to reduce average force

and temperature to have better surface

roughness, such as cup-type

diamond-grinding-wheels with hexagonal pattern were used to grind

effective working abrasive grains in comparison with conventional grinding wheels [2] According

to the previous researches, smoother surface can

be obtained by decreasing speed rate or decreasing cutting depth [3-14], but speed rate or cutting depth have the limit depending on ground samples or grinding machines

In this work, newly developed inclined segmented grinding wheels - ISGW with different number of segments on the wheel surface are used to grind SKD11 steel, which is applied widely in manufacturing mold plate and base The effects of abrasive grains and surface roughness

of ground sample are evaluated This paper reveals a new mechanism of grinding process by the proposed ISGWs

2 EXPERIMENTAL

Newly developed inclined segmented

grinding wheel

Figure 1 Inclined segmented grinding wheel

which has outside diameter D = 350 mm, inner

diameter d = 127 mm, wide of segment

w = 10 mm, height of segment h = 15 mm,

thickness B = 40 mm and inclined angle β=15

These wheels are characterized by number

of segment Z, and inclined angle of segment

β=15º All the wheels have outside diameter of

350 mm, inner diameter of 127 mm, wide and

height of segment are 10 mm and 15 mm

respectively Percentage of discontinue η, is

defined as the ratio between the area does not

containing abrasive grains and the total area of

wheels Four inclined segmented grinding wheels

with different η (16.37, 18.19, 20.01 and 21.83%)

and a conventional wheel with η = 0% were used

as shown in Table 1

Table 1 Number of segment Z and % discontinue

η of grinding wheels

Z Z = 0 Z = 18 Z = 20 Z = 22 Z = 24

η 0% 16,37% 18,19% 20,01% 21,83%

Experiment procedures

Samples are SKD11 steel with dimensions of

Length x Wide x Height = 60x30x10 mm A

sample was placed at the center of machine table

so that long edge was perpendicular to the shaft

of machine Conventional and inclined segmented

grinding wheels (Cn46 MV2 350x40x127-35m/s)

experiment, grinding wheels were dressed by industrial diamond grinding stone with grinding conditions of 0.1 mm cutting depth, 450 rpm wheel rotation speed in order to obtain flatness on the wheel surface

Figure 2 Grinding machine AMADA WASINO

SE63

Figure 3 Surface roughness Mitutoyo SJ-301

Grinding wheel rotation speed 450 rpm for the whole experiment process On each grinding wheel, experiment was carried out on 3 different cutting conditions with cutting depth was 0.02 mm per pass, feeding speed were 12, 15 and 20 m/min alternatively The wheels were redressed before each grinding experiment The coolant water was sprayed into the contact zone between grinding wheel and sample during grinding process Grinding conditions are listed in Table 2 The surface roughness, was measured using roughness tester Mitutoyo SJ-301

Table 2 Specifications of grinding wheels,

grinding conditions and sample

Grinding wheels Grinding

condition

Sample

Inner diameter:

127 mm

Outside diameter:

350 mm

Thickness: 40mm

Segment wide: 10

mm

Segment height:

15 mm

Inclined angle: 15º

Cn: Corundum

abrasive

46: Size of

abrasive grain

MV2: Hardness

Rotation speed: 450 rpm

Cutting depth:

0.02mm and 0.05mm Feeding speed: 12,

15 and 20 m/min

Material:

SKD11 Length:

60mm Wide:

30mm Height:

10mm

3 RESUTS AND DISCUSSION

Figure 4 Sample surface roughness R a as

function of number of segment Z at S = 12 m/min,

a = 0.02 mm on SKD11

Figure 5 Sample surface roughness Ra as

function of number of segment Z at S = 15 m/min,

Figure 4 and 5 show surface roughness R a

as function of number of segment Z for different feeding speed S = 12 and S = 15 m/min

respectively The same trend of the surface roughness on sample ground by ISGW with 2 different feeding speeds can be observe

Discussion

With small change in number of segment Z, depth of cut a or feeding speed S It is difficult to

recognize the differences of input parameter between different cutting conditions Number of abrasive grain participate in grinding process is possible choice in this situation

Figure 6 Peripheral surface of conventional

grinding wheel

Number of abrasive grain in contact with sample surface per unit area per second on conventional grinding wheel:

= ∙ (grain) (1)

Where grinding wheel revolution to complete the grinding process along the length of workpiece in the experiment; is a number of abrasive on working surface of grinding wheel, in the conventional wheel used in the experiment

= 109900 grains

 = 12 m/min = 200 mm/s Time need to complete the grinding process along the length of workpiece:

= = = 0.3 (s) (2)

Grinding wheel revolution to complete the grinding process along the length of workpiece:

= ∙ V = 0.3 ∙ 24.17 = 7.251 (rev)

(3)

Number of abrasive grain in contact with sample surface per unit area per second by conventional grinding wheel:

= ∙

= ∙ = 332

 = 15 m/min = 250 mm/s Time need to complete the grinding process along the length of workpiece:

= =

= 0.24 (s) (5)

Grinding wheel revolution to complete the grinding

process along the length of workpiece:

= ∙ V = 0.24 ∙ 24.17 = 5.801 (rev)

(6)

Number of abrasive grain in contact with sample

surface per unit area per second by

conventional grinding wheel:

= ∙

= 5.801 ∙ = 266

(grains) (7)

The number of abrasive grain in contact with

sample surface per unit area per second on ISGW

can be calculated due to percentage of

discontinue η on table 1

Table 3 Number of abrasive grain in contact with

sample surface per unit area per second on each

grinding wheels at S = 12 m/min and S = 15

m/min

TT Z

% discontinu

e η

Number of abrasive grain

1 Z = 0 0 332 266

2 Z = 18 16,37% 278 222

3 Z = 20 18,19% 272 218

4 Z = 22 20,01% 266 213

5 Z = 24 21,83% 260 208

Figure 7 Number of abrasive grain in contact

with sample surface per unit area per second as

function of surface roughness R a at a=0.02m/min

Figure 7, illustrate the relation between number of abrasive grain in contact with surface

sample per unit area per second X S and surface

roughness R a On conventional grinding wheel,

the surface roughness R a decrease when the number of abrasive grain in contact with sample surface per unit area per second increase or

the feeding speed S decrease This result is in

accord with metal cutting theory, which has been published in many researches about grinding operation, there are clear differences in surface roughness among different number of abrasive grain [4-6] However, on ISGW, the desired surface roughness can be achieved at the cutting conditions with less number of abrasive grain To put it differently, on ISGW, surface roughness does not depend on number of abrasive grain participate in the grinding process

As shown in Figure 8, Curve (I) for feeding

speed S = 12 m/min and Curve (II) for feeding speed S = 15 m/min in figure 7 By multiplying

0.75 to the value of for the feeding speed S =

12 m/min, Curve (I) of feeding speed S = 12

m/min superposes on Curve (II) for feeding speed

S = 15 m/min as shown in Figure 9 In other

words, working efficiency of abrasive grain on ISGW can increase by 25% by increasing the feeding speed from 12 m/min to 15 m/min

Figure 8 Surface roughness, versus number

of abrasive grains X S Curve (I) for feeding speed

S = 12 m/min and Curve (II) for feeding speed S =

15 m/min

Figure 9 Surface roughness, R a versus number

of abrasive grains X S Curve (I) of feeding speed

S = 12 m/min is superposed on Curve (II) of

feeding speed S = 15 m/min by multiplying 0.75 to

the value of X S of feeding speed S = 12 m/min

4 CONCLUSIONS

In this work, samples made by SKD11 steel

are ground by a conventional and newly

developed ISGWs The abrasive grain efficiency

and surface roughness were evaluated The

following can be concluded:

 Surface roughness of sample ground by

conventional wheel decrease as the

number of abrasive grain increase

 On ISGWs, surface roughness obtained

the same values when feeding speed S

are changed from 12 m/min to 15 m/mm

alternately In other words, surface

roughness does not depend on number of

abrasive grain participate in the grinding

process

 It is possible to increase the working

efficiency of abrasive grain on ISGW by

25% by increasing the feeding speed

from 12m/min to 15m/min

REFERENCES

[1] W B Rowe, Principles of Modern Grinding

Technology, Massachusetts: Elsevier, 2013

[2] Tien Dong NGUYEN, Koji MATSUMARU,

Masakazu TAKATSU and Kozo ISHIZAKI,

"Abrasive Grain Efficiency And Surface

Roughness For Machining Ceramics By

Newly developed Cup-Type

Diamond-Grindings-Wheels," Advantage in

Technology of Material and Material

Processing, vol 10, pp 77-84, 2008

[3] S Malkin, Grinding Technology Theory and Applications Machining with Abrasives, Chichester, England: Ellis Horwood Limited

Publication, 1989

[4] M C Shaw, Principles of Abrasive Processing, USA: Oxford Science Publications, 1996

[5] J E Mayer and G P Fang, "Effects of Grinding Parameters on Surface Finishing of

Ground Ceramics", Annals of the CIRP, vol

44, 1995

[6] G Warnecke and U Rosenberger, "Basic of Process Parameter Selection in Grinding of

Advanced Ceramics", Annals of the CIRP,

vol 44, 1995

[7] J Pe´rez, S Hoyas, D.L Skuratov, Yu.L Ratis, I.A Selezneva, P Ferna´ndez de Co´rdoba, J.F Urchueguı´a eHeat “Transfer analysis of intermittent grinding processes”, International Journal of Heat and Mass Transfer 51 (2008) 4132–4138

[8] Taghi Tawakoli, Bahman Azarhoushang* (2011) “Intermittent grinding of ceramic matrix composites (CMCS) utilizing a developed segmented whell”

[9] Xiarui Fan, Michele Miller, Force analysis for segmental grinding, chining Science and

Technology, 10 (2006), 435-455

[10] Agarwal S, Venkateswara Rao P, “A new surface roughness prediction model for ceramic grinding”, Proc Inst Mech Eng, B J

Eng Manuf, 219 (11) (2005) 811–821

[11] Young HT, Liao HT, Huang HY, “Surface integrity of silicon wafers in ultra precision

machining”, Int J Adv Manuf Technol,

29(3–4) (2006) 372–378

[12] W H Tuan, J C Kuo, “Effects of grinding parameters on the reliability of alumina”,

Materials Chemistry and Physics, 52 (1998)

41-45

[13] R Gupta, K S Shishodia, G.S Sekhon,

“Optimization of grinding process parameters using enumeration method”, Journal of

Material Processing Technology, 112 (2001)

63-67

[14] G F Li, L S Wang, L B Yang, “Multi-parameter optimization and control of the cylindrical grinding process”, Journal of

Material Processing Technology, 129 (2002)

232-236