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Examination of drilling manufacturing operation made

by environmentally conscious way

Gyula Varga1, a

, Illes Dudas 2, b

1, 2

Department of Production Engineering

University of Miskolc

H-3515, Egyetemvaros a gyula.varga@uni-miskolc.hu,

b illes.dudas@uni-miskolc.hu

Abstract Drilling is one of the most commonly used machining operations. A twist drill has

numerous geometrical data such as angle of the tip, chisel edge angle, cutting lip length,

chisel edge length and helix angle. Each one of these data has affect on the cutting forces and

drilled hole qualities in different ways. Measurements were performed using different amount

of coolants and lubricants when inner and outer coolants admission. We measured the thrust,

torque, cutting tool wear, macroscopic and microscopic geometrical properties of the

machined surfaces. The drilling tool was examined by physical modelling. In this research the

measurement tasks, problems of the different parameters are examined. Furthermore, it

contains a mathematical model based on the roundness error.

Keywords: Drilled surface quality; minimal lubrication; hole roundness error;

environmentally conscious drilling

1. Introduction

Near Dry Machining is defined as the dispensing of cutting fluids at optimal flow rates,

small quantities of cutting fluid are allowed to the cutting zone directly [1, 2]. Papers relating

to Near Dry Machining are limited.

Near Dry Machining offers the following advantages: decreased use of metal working

fluids, reduced costs as compared to flood applications, reduced industrial hygiene hazard,

opportunity to employ more benign fluids (e.g., vegetable oils) and improved process

performance as compared to dry machining [3].

2. Literature review

Dowling and his co-authors [4] suggested the use of least squares method. Varghese and

his co-authors [5] proved that the least squares algorithm serves a good solution. Sun and his

co-authors [6] proposed a framework based Design of Experiment method for verifying the

estimation of circularity form errors. They based on the correlation among the controllable

factors, such as sampling method and form evaluation method. Jywe his co-authors [7], Roy

and Zhang [8], Samuel and Shunmugam [9], and Rajagopal and Anand [10] presented various

methods based on computational geometry, non-linear optimization, and using artificial

intelligence- based methods for the evaluation of the circularity.

Finally, a new model is proposed which can be used for both suggesting an inspection

plan given the value of acceptable error in the measurement of the circularity and for

estimating the circularity at the case of different parameters.

3. Circumstances of experiments

At our experiments we used the following circumstances [11]:

Machine tool: Manufacturing centre, type: MKC-500,

Lubrication: Oil: ÖMV-Öl X-Ultra-CF (without chlorine).

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Cutting tool: twist drill (with right hand side flute) having inner cooling channels

(Ø 10,0 K20 GÜHRING VHM) with TiAlN coating

Further parameters can be found in Table 1.

Table 1. Values of some research parameters.

Coating of twist drills: TiAlN MoS2

Values of cutting speeds: 80 m/min 120 m/min

Feeds: 0,2 mm/rev 0,315 mm/rev

Coolants and lubrications: Minimal volume of lubricants Dry

hcmVoil /0 3 hcmVoil /10 3 hcmVoil /28 3

Criteria for drilling:

At least 15 m drilling length,

VBCorner max ≤ 0,5 mm, or till the damage of the twist drill

At measurements (at all twist drill clamping) we inspected the run out of the twist drill,

and when its value was smaller than 0,05 mm, we could begin the drilling.

4. Evaluation of measurement data

Each measurement was repeated at least three times when the same parameter setup

during executing our experiments. The evaluation was done by using mathematic statistics.

We determined the average, standard deviation, and relative deviation as well. The average

values of measured results were demonstrated as the function of the drilled length.

4.1. Results of measurements of roundness error

At the case of drilling experiments, after the given length of drilling (0.03m, 10m, 20m,

30m) we have examined the roundness errors of the drilled holes. The measuring was done on

the measuring equipment type TALYROND-73 made by TAYLOR-HOBSON (Fig. 1a). The

test specimens were clamped by a magnetic prism. We have drawn diagrams of roundness

error after each measurement. Here we are concentrating only on the roundness error of the

drilled holes. In order to make the possibility of comparing of the results, we measured the

same place of the holes of the roundness error. The measurements were done at the beginning

of the hole, and at the end of the hole, which is shown on Fig. 1b. The whole results of the

measuring activity is summarised in the research reports [12].

We used two different filters:

Switch B: the diagram contains the differences between the real and the theoretical

shape of the profile.

Switch N1 (normal): the diagram contains the surface roughness error and the

waveness error of the profile [13].

At measurements we used the standardised measuring arm (length is l=63,5 mm).

Figure 2 demonstrates descriptively the result of examination as the function of the length

of drilling. The measurement of the roundness error was done at the distance of 2mm from the

beginning and the end of the hole. These circles are signed at Fig. 1b. On Fig. 2 the

expression “at the beginning of the hole” means that the measurement was on the signed

circle.

4.2. Evaluations of experiments done by Factorial Experiment Design

By using of Factorial Experiment Design three times 8 experiments, multiplied three

times each, were elaborated. The codes and the technological and experimental data are given

in Table 2.

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10

30

drilled surface

30

2

2

place of measurement

place of measurement

material: cast iron, (EN-GJL-200 (MSZ EN 1561))

Fig. 1. Measurements of roundness error, a) Roundness error measuring equipment type TALYROND-73,

b) Places of measuring of roundness errors of the holes on the section of the drilled specimen.

The result of the experiments can be seen on Fig. 2. Figure 2a shows the values of

roundness error when the volume of coolants and lubricants was hcmVoil /28 3 , while

Fig. 2b belongs to the case of hcmVoil /0 3 , that is for dry drilling. The evaluations of the

experiments were done by the method of full Factorial Experiment Design. Equation (1) valid

when the drilling length varies in between mLf 03,0 and mLf 30 , the volume of coolants

and lubricants from hcmVoil /0 3 till hcmVoil /28 3 , and from the beginning mlh 002,0

till the end mlh 028,0 of the hole in the workpiece. Although the length of the hole was

30mm long, but the measurements were done 2mm away from both end of the hole.

Table 2. Codes of specimen and technological and experimental data applied.

Number Length of

drilling, L0, m

Oil volume,

oilV , cm3/h

Length of hole,

lh, m

Cutting speed, vc,

m/min

1 0,03 10,0 0,002 80,00

2 30,0 10,0 0,002 80,00

3 0,03 28,0 0,002 80,00

4 30,0 28,0 0,002 80,00

5 0,03 10,0 0,028 80,00

6 30,0 10,0 0,028 80,00

7 0,03 28,0 0,028 80,00

8 30,0 28,0 0,028 80,00

hoilf

R

hoil

R

hf

R

oilf

R

h

R

oil

R

f

RR

error

lVLk

lVklLkVLklkVkLkkR

error

errorerrorerrorerrorerrorerrorerror

123

2313123210

(1)

where:

9398.440 errorRk 544.01 errorR

k 407.02 errorRk 2.9623 errorR

k

013.012 errorRk 817.2113 errorR

k 883.623 errorRk 481.0123 errorR

k

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Length of drilling, m

0 03010 20 2010 30

40

10

30

20

50

40

10

30

20

50

Ro

un

dn

ess e

rro

r, R

, m

Ro

un

dn

ess e

rro

r, R

, m

Length of drilling, m

At the beginning of the hole At the beginning of the hole

At the end of the hole At the end of the hole

a) b)

Fig. 2. errorR - Measured values of roundness error,

a) at dry drilling ( hcmVoil /0 3 ), b) at Near Dry drilling ( hcmVoil /28 3 ),

Substituting the values of the parameters into Equation (1) the roundness error of the

drilled holes can be demonstrated. On the Fig. 3, it can be seen that the roundness error of the

drilled hole was smaller when higher value of coolants and lubricants ( hcmVoil /28 3 ) were

used. The roundness was smaller always at the end of the hole than at the beginning.

R 1 R 2

Fig. 3. Comparing of measured values of roundness errors of the twist drill.

5. Summary

This paper gave some remarks of successful implementation of near dry machining and

for different experimental parameters:

At the case of drilling of grey cast iron when the twist drill had inner cooling channels

we have managed assure appropriate cutting parameters.

Ro

un

dn

ess

erro

r, R

e,

m

Length of drilling, L0, m

Length of hole, lh, m

hcmVoil /0 3

hcmVoil /28 3

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When using of at least hcmVoil /28 3 volume of lubricants we got smaller roundness

error than at the case of dry machining.

By the model we can plan the roundness error at the planning stage as well.

6. Acknowledgements

This publication was made in the frame of Hungarian – Polish Intergovernmental S&T

Cooperation Programme signed PL-2/2008, financially supported by National Office for

Research and Technology and its foreign contractual partner.

References

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ISBN: 9958-617-28-5.

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