DESIGN AND MANUFACTURING OF

DYNAMOMETER

ByESSAM AL-YASSIN

Supervised byDR. TARQI AL-HOSSAINY

PRESENTATION OUTLINE

• INTRODUCTION

• DYNAMOMETRY

• DESIGN AND CONSTRUCTION OF A DYNAMOMETR FOR CENTER LATHE

• CALIBRATION AND EXPERIMENT

• MULTIPLE REGRESSION ANALYSIS

AND DESIGN OF FACTORIAL

• Conclusion

INTRODUCTION

Machine tools should be designed and constructed Machine tools should be designed and constructed according to their purposes if they are to be used according to their purposes if they are to be used effectively. Mechanical structures of a machine tool effectively. Mechanical structures of a machine tool should support the forces acting on them and the should support the forces acting on them and the auxiliary devices without permanent deformation. auxiliary devices without permanent deformation. Rather, during metal cutting, the resulting cutting Rather, during metal cutting, the resulting cutting forces should not deform the machine tools, cutting forces should not deform the machine tools, cutting tools and tool holders. For a long machine tool tools and tool holders. For a long machine tool service life, it is essential to protect the moving parts service life, it is essential to protect the moving parts of the machine tool against wear. of the machine tool against wear.

In order to prevent tool breakage due to the excess In order to prevent tool breakage due to the excess cutting forces, mechanical properties of the cutting cutting forces, mechanical properties of the cutting tool should be known and therefore care should be tool should be known and therefore care should be taken to prevent this.taken to prevent this.

Force measurement in metal cutting is essential Force measurement in metal cutting is essential requirement as it is related to machine part design, requirement as it is related to machine part design, tool design, power consumptions, vibrations, part tool design, power consumptions, vibrations, part accuracy, etc. accuracy, etc. It is the purpose of the measurement It is the purpose of the measurement of cutting force to be able to understand the cutting of cutting force to be able to understand the cutting mechanism such as the effects of cutting variables mechanism such as the effects of cutting variables on the cutting force, the machinability of the work on the cutting force, the machinability of the work piece, the process of chip formation, chatter and piece, the process of chip formation, chatter and tool wear.tool wear.

DYNAMOMETRY As progress has been made in the machine tool

field, parallel progress has characterized the development of cutting force-measuring systems. The cutting forces developed in machining operations may be estimated indirectly by obtaining the power consumed or directly from metal cutting dynamometers; mechanical, hydraulic, and pneumatic or several types of electro-mechanical dynamometers.

Knowledge of cutting forces is essential to machine tool builders in calculating power requirements and frame rigidity.

At the design of tool that have sufficient strength capable to remove chip at the desired quantity from the work piece and to calculate power of tool driver system, cutting forces acting on the tool must be measured.

The need for measurement of all cutting force component arises from many factors, but probably the most important is the need for correlation with the progress of tool wear. This can be the reason for the dynamometer to be a good indicator in detecting tool wear.

Due to the complex tool configurations/cutting conditions of metal cutting operations and some unknown factors and stresses, theoretical cutting force calculations failed to produce accurate results and therefore, experimental measurements of the cutting forces became unavoidable. For this purpose many dynamometers have been developed.

A dynamometer is an important and fundamental instrument to measure the cutting forces during metal cutting.

Design and construction of a dynamometer for center lathe

1) Shape:

For designing the dynamometer, the acting forces statically and dynamically should be known. In our case the forces applied to ( dynamometer ) is dynamic forces so that we will consider this forces and design the (dynamometer )under static and dynamic load. (Forces = 0→3000 )N

A two-component strain gauge dynamometer was used for measuring the cutting forces. The dynamometer was designed for measuring tangential and axial forces. It consists of two main parts attached to each other with 6 bolts:

A) A part acts as a tool holder, where the cutting tool is secured in its place by means of two perpendicular bolts (cress-section # C).

B) The main body of the dynamometer, where the strain gauges are mounted. The square part is held in the tool post of the machine.

We select this shape to be consist of two ends, The first shape is circular (cress-section # B ) to ensure that the stress will be distributed all over the tool. The other shape is square (cress-section # A) to ensure the best fixture of the in the machine.

2) Material:• Steel Structural (Steel 36) • бy =250Mpa (yield strength) • бu = 400Mpa (Ultimate strength)

* Then the design (Shape and Material and

Dimensions) dynamometer are suitable for this application.

CALIBRATION AND EXPERIMENT

1) Calibration:

The strain gauges were arranged in the dynamometer such that four strain gauges will

form a bridge for measuring the horizontal component in the feed direction, while the

other strain gauges form a bridge for measuring the vertical component in the

cutting direction. The outputs of the Wheatstone bridges were connected to a

multi-channel, digital strain measuring bridge .

Wheatstone bridges for vertical and horizontal components.

View y-y The acting forces.

The output of the bridges was fed to the digital strain bridge while the deflection of the proving ring was read directly on a dial indicator. fig.

The set-up for calibration.

After converting the ring readings into forces by multiplying them by the ring constant, the calibration curves for both cutting and thrust forces were plotted.

D v (ch1) Reading (prove)

5 20

11 42

16 62

20 79

26 103

31 121

35 138

42 161

49 190

53 208

Thrust force

Dh (ch2) Reading (prove)

6 23

10 42

14 59

19 79

25 102

30 124

34 148

36 165

40 184

42 208

Cutting force

Thrust force

0

50

100

150

200

250

0 20 40 60

Dv (ch1)

Rea

ding

(pro

ve)

SLOPE =3.89051

Cutting force

0

50

100

150

200

250

0 10 20 30 40 50

Dh(ch2)

Rea

ding

(pro

ve)

SLOPE=4.858552

From these curves the following equations were deduced:Fv= 16.727 x Dv = Fv (N) Fh= 20.898 x Dh = Fh (N)

Where Dv Dh are the bridge readings corresponding to the forces Fv

and Fh respectively.

EXPERIMENTAL EQUIPMENT : 1- Engine lathe

2- Workpiece materials (aluminum)

3- strain meter (device for measuring)

4- dynamometer

PROCEDURE :• Fig. shows the block diagram

• Before cutting operation, the two bridges are adjusted and zero balanced. As cutting operation starts, a load is applied through the tool to the dynamometer. Bridge readings corresponding to the forces Fv and Fh respectively are recorded for different cutting conditions.

• In this experiment we used three velocities (66, 98, 132) m/min, three feed (0.1, 0.2, 0.3)mm/rev and three depth of cut (0.5, 1.5, 2.5) mm and workpice 60 mm from aluminum . as shown in table.

General set-up

d (mm) V (m/min) f (mm/rev) Dy Dh Fv (N) Fh (N)

    0.102 16 13 267.632 271.674

  66 0.205 17 17 284.359 355.266

    0.304 17 20 284.359 417.96

    0.102 15 12 250.905 250.776

0.5 98 0.205 16 17 267.632 355.266

    0.304 17 18 284.359 376.164

    0.102 13 12 217.451 250.776

  132 0.205 15 14 250.905 292.572

    0.304 16 16 267.632 334.368

    0.102 27 22 451.629 459.756

  66 0.205 32 32 535.264 668.736

    0.304 36 36 602.172 752.328

    0.102 26 21 434.902 438.858

1.5 98 0.205 32 30 535.264 626.94

    0.304 35 35 585.445 731.43

    0.102 25 20 418.175 417.96

  132 0.205 32 29 535.264 606.042

    0.304 34 33 568.718 689.634

    0.102 47 35 786.169 731.43

  66 0.205 49 47 819.623 982.206

    0.304 65 65 1087.255 1358.37

    0.102 43 34 719.261 710.532

2.5 98 0.205 47 43 786.169 898.614

    0.304 59 60 986.893 1253.88

    0.102 40 32 669.08 668.736

  132 0.205 45 42 752.715 877.716

    0.304 59 58 986.893 1212.084

Fig. show the variations of cutting force with various cutting condition. The curves show an increasing effect of main cutting and thrust force with the increase feed at different depths of cut. while the curves show also a decreasing effect of main cutting and thrust force with the increase of cutting speed.

a. Thrust force d=0.5 (mm)

0

50

100

150

200

250

300

0.102 0.205 0.304

f (mm/rev)

Fv (

N) V=66

V=98

V=132

d=1.5 (mm)

0

100

200

300

400

500

600

700

0.102 0.205 0.304

f (mm/rev)

Fv

(N

) V=66

V=98

V=132

d=2.5 (mm)

0

200

400

600

800

1000

1200

0.102 0.205 0.304

f (mm/rev)

Fv (

N) V=66

V=98

V=132

b. Main cutting force d=0.5 (mm)

0

50

100

150

200250

300

350

400

450

0.102 0.205 0.304

f (mm/rev)

Fh

(N

) V=66

V=98

V=132

d=1.5 (mm)

0

100

200

300

400

500

600

700

800

0.102 0.205 0.304

f (mm/rev)

Fh

(N

) V=66

V=98

V=132

d=2.5 (mm)

0

200

400

600

800

1000

1200

1400

1600

0.102 0.205 0.304

f (mm/rev)

Fh

(N

) V=66

V=98

V=132

1) MULTIPLE REGRESSION ANALYSIS:

• Empirical formulae were constructed, using the multiple regression analysis, for the prediction of both Fv and Fh as a function of speed, feed and depth of cut. (from table and using Regression Analysis)

699821.0228625.013842.0 ***1157 dfVF v

653197.0444143.017387.0 ***2294 dfVFh

The standard error of force estimation did not exceed 0.1 which proves the regression accuracy .

2) DESIGN OF FACTORIAL

• Many experiment involve the study of the effects of two or more factors. In general, factorial designs are most efficient for this type of experiment. By a factorial design, we mean that in each complete trial or replication of the experiment all possible combinations of the levels of the factors are investigated.

1- Correlations Correlation between Fv and Fh

    FV FH

FVPearson Correlation 1 0.976

  Sig. (2-tailed) . 0

  N 27 27

FHPearson Correlation 0.976 1

  Sig. (2-tailed) 0 .

  N 27 27

* Correlation between Fv and Fh is significant at the 0.01 level.

2) Univariate Analysis of Variance

Source  

Type III Sum of Squares df

Mean Square F P value

            Sig.

V Hypothesis 40.963 2 20.481 3.978 0.1

  Error 23.492 4.563 5.148    

F Hypothesis 418.296 2 209.148 3.526 0.13

  Error 240.778 4.059 59.315    

D Hypothesis 5434.741 2 2717.37 43.108 0.001

  Error 287.258 4.557 63.037    

V * F Hypothesis 3.926 4 0.981 1.828 0.217

  Error 4.296 8 0.537    

V * D Hypothesis 18.815 4 4.704 8.759 0.005

  Error 4.296 8 0.537    

F * D Hypothesis 235.481 4 58.87 109.621 0

  Error 4.296 8 0.537    

Tests of Between-Subjects Effects Dependent Variable: FV

Tests of Between-Subjects Effects Dependent Variable: FH

Source  

Type III Sum of Squares df

Mean Square F P value

            Sig.

V Hypothesis 53.556 2 26.778 10.593 0.016

  Error 12.755 5.046 2.528    

F Hypothesis 1088.889 2 544.444 5.452 0.071

  Error 405.881 4.064 99.861    

D Hypothesis 4290.889 2 2145.444 21.413 0.007

  Error 409.916 4.091 100.194    

V * F Hypothesis 5.556 4 1.389 2.381 0.138

  Error 4.667 8 0.583    

V * D Hypothesis 6.889 4 1.722 2.952 0.09

  Error 4.667 8 0.583    

F * D Hypothesis 396.222 4 99.056 169.81 0

  Error 4.667 8 0.583    

• The analysis of variance is show in table Since α=0.05, we conclude that there is a significant interaction between cutting force and cutting condition. It was found that the feed and cutting speed has the most effect both Fv and Fh which the depth of cut has the lowest effect on the both cutting force.

Conclusions In this project, a two component dynamometer

was designed and manufacturing for measuring the cutting force in turning operation. A calibration was formed for contracting the relation between the acting cutting forces and verifying the dynamometer. Empirical formulae were constructed, using the multiple regression analysis and also a factorial design was used for predicting the relation and correlation between the cutting force and cutting conditions respectively. It was found that:

1) There is no interference between the measured force.

2) The dynamometer succeeded in measuring the main cutting and thrust force.

3) A Multiple Regression Analysis was done for substituting relation between the cutting force and the cutting conditions.

4) The cutting force show an increasing effect with increase of the feed at different depth of cut while the cutting force show a decreasing effect with the increase of cutting speed.

5) Correlation between Fv and Fh is significant at the 0.01 level

6) From Factorial design, It was found that the feed and cutting speed has the most effect both Fv and Fh which the depth of cut has the lowest effect on the both cutting force.