ABRASIVES

About SG grains:

SG Grains AlO Grains

SG is a premium ceramic abrasive made up of billions of micro crystals. The grain

fracture occurs at micro level, resulting in extremely low wheel wear and self-sharpening

of the grains. The above photograph is a magnified snap of the grains. Schematically it

can be shown as follows:

AlO Grain SG Grain

Due to this microcrystalline structure, the grain dulling/glazing some time after dressing

occurs as follows:

AlO (Before) AlO (After) SG (Before) SG (After)

Some features/Benefits of SG are as follows:

ABRASIVES• Higher Material Removal Rates: This implies faster production, lower labour costs

and better machine utilization.

• Cool cutting: SG grains produce lesser heat during grinding than conventional

grains. This results into better finish, reduced rejects and no metallurgical damages.

• Reduced dressing: Lesser down time, better dresser life.

• Longer Life: This yields into reduction in down time (for wheel changes) and hence

reduction in cost/component.

• Hold form better

> Can handle complex shapes and forms with ease > Cuts down cost per part > Consistent form holding. > No special Equipment > Keeps total grinding cost low

Improve operating Efficiency > Reduce grinding cycle time > Increase productivity and machine utilization > Reduce metal damage > Better process reliability > Make grinding easy on difficult to grind material

Improve cost efficiency > Reduce over all cost per part.

ABRASIVES

Plunge cylindrical grinding using premium abrasive option – “SG”

Case 1 Trial of the SG wheels was conducted at XYZ co, in the shafts division for the plunge grinding operation. definite need for finish improvement. Process Conditions:

Machine HMT Cylindrical grinder 7.5 HP at 33 m/s

Component Steel shaft (SM76) 12.3 mm dia and 71 mm long Material: Alloy Steel 50 to 55 HRC

Process parameters • Stock – 300 microns • Cycle time – 55 to 60

sec • Dressing frequency -

40 with existing (to reduce taper)

• Dresser – Multipoint diamond “Star DG11)

• Coolant – Emulsion (5%)

Finish of 0.6 to

0.7 mic Ra First trial specification: SG80-20M8VH. Parameters Cumi SG80-20M8VH Dressing after X Components 3X Components Finish 0.6 to 0.7 mic Ra 0.4 to 0.5 mic Ra MRR Acceptable More than twice The result was very encouraging. XYZ co required better finish (bHence #120 was tried out to further optimise the performance.

Tool : 500x100x254Old : Cumi A60L5V10

Output • High productivity • Consistent size and

finish (0.4 mic Ra) • Low dressing

frequency • Low or nil

metallurgical damages

Tool : 500x100x254 New : SG120-20

elow 0.4 mic Ra).

ABRASIVES Second trial specification : SG120-20M8VH The finish was measured at regular intervals to evaluate the effect of dressing frequency changes.

Surface Finish at 35 sec Cycle Time (SG120)

00.10.20.30.40.5

1 15 30 45 60 75 90 105

120

Job No

Surf

ace

Fini

sh

1

Taper higher than 5 microns

Surface Finish trend below 0.4 for 15 jobs after actual dressing.

Graph 1

The above trend indicates that the SG120 wheel is capable of grinding consistently at 35 sec cycle time at a dressing frequency of 120 with consistent finish below 0.4 mic Ra. Parameters CUMI GNL Specification A60L5V10 SG80-20M8VH SG120-20M8VH SG120-20M8VH

Cycle Time (sec) 60 32 60 35 Volume Ground 406.4 406.4 406.4 406.4 MRR (c.mm/sec) 6.773 12.700 6.773 11.611 No of jobs/dressing 40 120 150 120 Finish (mic Ra) 0.57-0.75 0.467-0.66 0.3 0.35

Table 1 1. The above table indicates the performance superiority of SG 120 wheel over the

conventional A abrasive of competition. 2. Along with improved finish, we were able to demonstrate reduction in cycle time and

improved life and consistent average Cp value of 1.4. Based on the results obtained from the tests carried out at xyz, the following inferences can be derived:

ABRASIVES

Surface Finish x MRR

00.10.20.30.40.50.60.7

5 7 9 11 13MRR

Fini

sh (u

Ra)

15

CUMI A60 CYCLE TIME =60 SG80 CYCLE TIME =32

SG120 CYCLE TIME = 35

With CUMI Wheel increase in MRR detoriates the finish

With SG80 ,increase in MRR doesn't worsen the finish as grain remains sharper for longer time and cuts freely

SG120 gives finish well within required limits with marginal increase in cycle time as compared to SG80 but nearly 71% improvement over existing CUMi wheels

Graph 2

Conclusion : SG120 A120

Price (Rs) 15080.9 4689.38 Dress frequency 120 40 Life (shafts) 100000 36000 Tool cost (Rs/shaft) 0.150809 0.130261 Cycle time 35 sec 60 sec Down time cost 0.012 0.033 Machine cost 1.45 2.5 Labour cost 0.45 0.75 Total cost per shaft 2.1 3.4 Cp 1.44 0.9 - 1 Capacity increase 79 % Cost reduction by 39 %

ABRASIVESCase Study 2 Trial of the SG wheels was conducted at ABC Ltd, in the shafts division for the race plunge grinding operation. The customer currently uses 510 x 8 x 304.8 DA120L5V10 or 19A120L8VH9 for the inner track outer race grinding application for the shaft. This was always a constraint for production due to ‘8’ mm thickness. Process Conditions : Machine Mode: Centerless OD Plunge. Make and model: Izumi, KN311B. Condition: Good. Power: 5.5 hp.

Stock: 0.5 mm.

Process RPM: 1500. Feedrate: Rough=5 mm/min and Finish=5 mm/min Spark out time: 2 sec.

Dress frequency: 5 shafts. Dress depth: 0.02 mm. Coolant: Koolcut 70(conc.=1:70). Material: En53100. Hardness: 58-60 HRc.

Wheel 510 x 8 x 304.8 19A120LVH9/19A120L5V10

Trial - SG120-20M8VH and SG120-20N8VH.

Output Size: +_ 0.006 mm Taper: +_ 0.006 mm Surface finish: 4.0 Rmax Roundness: 0.004 mm Radius: +_ 0.012 mm

ABRASIVESTrial Results:

DA120L5V10/ 19A120L8VH9 (DA120)

SG120-20M8VH (M)

SG120-20N8VH (N)

DRESSING FREQUENCY

5. 20. 30.

OUTPUT (Shafts/hour)

214. 244. 248.

The data given along with shows that the process capability of SG wheels in N grade is the best over the

conventional abrasive.

PROCESS CAPABILITY COMPARISON

Parameter M grade N grade DA120 Size 16.665 14.215 16.665 Average 16.662 14.204 16.661 Min 16.65 14.205 16.658 Max 16.675 14.215 16.665 Range 0.025 0.01 0.007 Tol 0.012 0.012 0.012 6(sigma) 0.00259 0.00266 0.0083 Cp 0.8 1.2 0.75

The variation in size within the pair, finish and out of roundness values were checked and found to improve with SG wheels. QUALITY PARAMETERS COMPARISON

Variation in size between the two tracks

0

2

4

6

19A M N

MIC

RO

NS

Series1

The diameter difference between two tracks. In a normal monitoring over the specific skip the variation is from 0 to values mentioned in the graph. For all graphs the skip for 19A is 5 for M grade is 20 and N grade is 30.

ABRASIVES

0

2

4

6

19A M N

Rmax after grinding

Series1Series2

Limit – 4 mic Rz

ROUNDNESS

0

1

2

3

4

M N

Series1Series2

Limit – 4 mic

The above graph shows maximum and minimum values of Rmax & roundness achieved on the track. (Sample size – 5) Cost comparison analysis COST COMPONENT

EXISTING

SG120-20M8VH

SG120-20N8VH

ABRASIVE COST 0.283 0.180 0.138

MACHINE COST 0.70 0.61 0.60

LABOUR COST 0.21 0.18 0.18

DRESSING COST 0.06 0.018 0.012

COST OF DOWN TIME

0.013 0.003 0.002

TOTAL COST/COMPONENT

1.266 0.991 0.932

ABRASIVES NOTES 1) ABRASIVE COST = WHEEL PRICE/SHAFTS PER WHEEL. 2) MACHINE COST = HOURLY MACHINE RATE / SHAFTS PER HOUR. 3) LABOUR COST = HOURLY LABOUR COST h/ SHAFTS PER HOUR. 4) DRESSING COST = DRESSER PRICE / (EXPECTED DRESSING CYCLES) x (RINGS PER

DRESS). 5) COST OF DOWNTIME = (TIME FOR WHEEL CHANGE) x (HOURLY LABOUR +

HOURLY MACHINE COST)/SHAFTS PER WHEEL. ASSUMPTIONS 1) HOURLY MACHINE COST= Rs.150/- 2) HOURLY LABOUR COST= Rs.45/- 3) SHAFTS PER WHEEL CALCULATED ON DRESSING FREQUENCY, DRESSING

COMPENSATION AND DISCARD DIAMETER. 4) DRESSER COST= Rs.300/- Based on the number of shafts produced, the actual savings can be calculated. For production of 1.5 Lac shafts per month and 100% SG usage, the cost saving for customer (consumption - 12 Lacs per year. A bulk evaluation order of 6 wheels in SG120-20M8VH has been executed and customer is in the process of conversion to SG.

ABRASIVES

Crankshaft pin grinding using SG abrasives

Case 3 SG for crank pin grinding at ABC Co. Process Conditions :

Trial R Parame

Two piDress Two piDress Three Dress

Machine Make : Toyoda Opn no : IE-30-20-1 Power : 22 KW Rated speed : 60 m/s (constant surface speed)

Process parameters • Job rpm : 200 (shoulder

& rough) & 10 during finishing

• Stock – 250 micron on sides and 60 microns on pin diameter

Feed rates – Shoulder 27 mm/min 1st Rough 12 mm/min 2nd rough 07 mm/min 1st Fine 2.5 mm/min 2nd fine 0.8 mm/min Micro-finish 0.14 mm/min • Dressing frequency –

Once every pin • Dressing depth – 30

microns on diameter • Dresser – Roller (87.5

mm dia) • Dresser feed rate – 0.26

mm/rev

esults:

ters Finish on Pin4

Finish on Pin1 Finis

ns/Dress depth 0.03 mm

2.40 2.91 ** 2.56

ns/Dress depth 0.025 mm

2.49 2.71 ** 2.67

pins/Dress depth 0.03 mm

2.25 2.60 2.94

Component Crank pin grinding MX crankshafts Material : C70 at 235 to 280 BHN (Forged)

Output expected • Dress frequency - 3• Consistent size and

finish below 3.2 Rmax

• Good cut rate • Low or nil

metallurgical damages

• Cycle time of 40 sec

H

h

Tool TDV 223/60 New : SG80-20M8V

on Pin2 Finish on Pin3 2.77

2.48

** 2.61

ABRASIVESSkip dressing of 3 was achieved. The power trend is stable pointing to possibility of further optimisation.

Cost per component

41

73

1224

151

5572

12 12

150

36

73

12 8

129

0

20

40

60

80

100

120

140

160

Rs. Rs. Rs. Rs. Rs.

Abrasive cost Machine cost Labour cost Dressing cost Total Cost

Cost components

Valu

e in

Rs

'000

DA (skip 1)SG (skip 2)SG (Skip 3)

Conclusion : SG was found cost justifying over DA wheels by 14 % with additional benefit of 30 % increase in productivity.

Case Study 4

Customer: XYZ LTD

Operation: OD Cylindrical plunge.

Trial size/specification: 500 x 20 x 203.2 SG100-20L8VH

As shown in the above figure, the pins are ground using cylindrical plunge operation.

The trial was carried out for grinding pin-2.

Pin-2

Pin-1

ABRASIVESExisting wheel used is AA100K5V10.

Objective of trial:

• To reduce cost/component.

• To optimize the grinding process using latest technology offered by Saint-Gobain

Abrasives.

Trial description:

Initial trial was conducted on the machine when the peripheral speed was 28 m/s. At

this speed, the surface finish obtained was found to be deteriorating after 25-30 jobs

after dressing. The finish was above 12 micro inches after 25 jobs (maximum allowed

surface roughness is 12 micro inches) The wheel face was found to be glazed. At 28

m/s, the SG grains were not undergoing micro-fracture, thus causing grain dulling and

poor surface finish. After discussion with the customer personnel, it was agreed upon

that the optimum output can be obtained out of SG trial wheel if the machine RPM is

increased.

The machine pulley was changed to increase peripheral speed to 34 m/s. After increase

in speed, Field instrumentation System (F.I.S) was used to compare the performance of

CUMI wheel and SG trial wheel. Some of the terms used for analysis are as follows:

Material Removal Rate (MRR) = Volume of material ground/cycle time

Q’ = MRR/wheel-work contact width

Power = Peak power – Idle power

The following graph depicts the data for CUMI wheel as well as GNL’s SG trial wheel.

Both the wheels were tried at two MRR’s. viz. regular MRR (0.3 cc/min) and higher MRR

(0.7 cc/min). The power was calculated using FIS and the same was plotted against

MRR’ as follows:

ABRASIVES

Power v/s MRR' Comparison

y = 0.13x + 0.37

y = 0.2x + 0.1

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

Low MRR' High MRR'MRR' (cc/min/cm)

Pow

er c

onsu

med

(KW

)

CUMI SG

From the above graph, it can be seen that the gradient of CUMI line is higher than SG

wheel. This indicates that due to micro-fracture of SG grains, the cutting edge of the

grains remains sharp and ensures smooth cutting. This can be seen in the number of

components ground between two dressings. For CUMI wheel, the dressing frequency is

90-100 components, whereas for SG wheel it is about 200 components.

The surface roughness values for all the components between dressing was checked. It

was found to deteriorate beyond 14 micro inches after 195-200 components. It was

decided to perform repeated tests for a dressing cycle of 200 components on the SG

wheel.

The detailed process parameters are tabulated below:

Parameter Unit Existing Trial

Machine Tschudin Tschudin

M/C No. 3170425 3170425

Wheel head motor power KW 5.5 5.5

Mode of Grinding Plunge Plunge

Wheel Size mm 500 x 20 x 203.2 500 x 20 x 203.2

ABRASIVESJob A/W-Crankshaft A/W-Crankshaft

Job OD mm 32 32

Job Material Steel Steel

Job Hardness HRc 40 40

Grnd allowance on OD micron 375 375

Wheel used AA100K5V10 SG100-20L8VH

Pre-grinding operation Heat Treatment Heat Treatment

Job Velocity M/s 0.6 0.6

Avg. Cycle time Sec 41 37

Feed rate Mm/sec 0.0095 0.012

Number of passes 1 1

Depth of cut per pass Microns 375 375

Type of dresser Single point Single point

Dresser traverse rate Mm/sec 0.45 0.45

Total dressing depth Microns 120 120

Reason for dressing Poor Finish Poor Finish

Parts per dressing 90 175-180

Coolant type % Water Based Water Based

vCoolant ratio 3 3

Surf. Rghness achieved Micro” 7-12 8-13

Ovality Microns 2 2

Parts per wheel 31818 40000

Parts per wheel is highly dependent on the dressing depth, which is dependent on the

operator, as dressing is done manually with a dressing attachment. The above figures

are calculated assuming the following:

Discard diameter = 290 mm

Dressing depth/dressing = 120 microns radially.

Wheel wear per component = 2 microns.

ABRASIVES

Cost Analysis

Total grinding cost can be split as follows:

• Abrasive cost = Wheel price / components per wheel

• Machine cost = Hourly machine rate / components per hour

• Labour cost = Hourly labour cost / components per hour

• Dressing cost = Dresser price / (Expected dressing cycles x components per

dressing)

• Cost of down time =

(time for wheel change in hrs.) x (hourly labour cost + Machine cost)

components per wheel

Assumptions made while doing the cost analysis are as follows:

• Machine hour rate = Rs. 150 per Hour.

• Hourly labour rate = Rs. 45 per Hour.

• Operators work with the same efficiency for both the wheels.

Cost per ring in Rs. for GNL trial wheel:

• Abrasive cost = (5272/40000) = 0.13

• Machine Cost = (175/97) = 1.8

• Labour cost = (75/97) = 0.77

• Dressing cost = [175/(228*175)] = 0.0043

• Down time cost = [1*(75+175)]/40000 = 0.00625

Total cost/ring = 2.71

Cost per ring in Rs. for CUMI wheel:

• Abrasive cost = (1700/31818) = 0.053

• Machine Cost = (175/87) = 2.01

• Labour cost = (75/87) = 0.87

• Dressing cost = [175/(353*90)] = 0.0055

• Down time cost = [1*(75+175)]/31818 = 0.00785

Total cost/ring = 2.94

ABRASIVESTotal Saving per component = Rs. 0.23/-

Cost Comparison Per Component

0

0.5

1

1.5

2

2.5

3

3.5

Costs

Valu

e (R

s.)

GNL CUMI

GNL 0.13 1.8 0.77 0.0043 0.00625 2.71055

CUMI 0.053 2.01 0.87 0.0055 0.00785 2.94635

Abrasive Cost Machine Cost Labour Cost Dressing Cost Down Time Cost Total Cost

Conclusion of the trial:

• The SG trial wheel was the second wheel tried in the same specification, after

successful trial of the first wheel. It was reported by the operator (For first trial

wheel) that when the wheel nears the discard diameter, the dressing frequency

drops down to as low as 140-150. Hence, during cost calculations, an average of

175 components was taken, although the trial was successful at dressing frequency

of 200 components. The same phenomenon is observed for CUMI wheel. This is

mainly due to the drop in peripheral speed with reducing diameter of the wheel (As

the RPM remains constant)

SG trial wheel of GNL was found to perform better than existing CUMI wheel.