DESIGN AND MANUFACTURING OF DYNAMOMETER By ESSAM AL-YASSIN Supervised by DR. 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 according to their purposes if they are to be used effectively. Mechanical structures of a machine tool should support the forces acting on them and the auxiliary devices without permanent deformation. Rather, during metal cutting, the resulting cutting forces should not deform the machine tools, cutting tools and tool holders. For a long machine tool service life, it is essential to protect the moving parts of the machine tool against wear.

In order to prevent tool breakage due to the excess cutting forces, mechanical properties of the cutting tool should be known and therefore care should be taken to prevent this. Force measurement in metal cutting is essential requirement as it is related to machine part design, tool design, power consumptions, vibrations, part accuracy, etc. It is the purpose of the measurement of cutting force to be able to understand the cutting mechanism such as the effects of cutting variables on the cutting force, the machinability of the work piece, the process of chip formation, chatter and 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 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 part acts as a tool holder, where the cutting tool is secured in its place by means of two perpendicular bolts (cress-section # C). 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 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 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.

Cutting force Thrust force D v (ch1) Reading (prove) 5 20 11 42 16 62 79 26 103 31 121 35 138 161 49 190 53 208 Dh (ch2) Reading (prove) 6 23 10 42 14 59 19 79 25 102 30 124 34 148 36 165 40 184 208 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.

From these curves the following equations were deduced: SLOPE=4.858552 SLOPE =3.89051 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 17 284.359 355.266 0.304 20 417.96 15 12 250.905 250.776 0.5 98 18 376.164 217.451 132 14 292.572 334.368 27 22 451.629 459.756 32 535.264 668.736 36 602.172 752.328 26 21 434.902 438.858 1.5 30 626.94 35 585.445 731.43 25 418.175 29 606.042 34 33 568.718 689.634 47 786.169 49 819.623 982.206 65 1087.255 1358.37 43 719.261 710.532 2.5 898.614 59 60 986.893 1253.88 40 669.08 45 42 752.715 877.716 58 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

b. Main cutting force

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) 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 Pearson Correlation 1 0.976 Sig. (2-tailed) . N 27 * Correlation between Fv and Fh is significant at the 0.01 level.

2) Univariate Analysis of Variance Tests of Between-Subjects Effects Dependent Variable: FV 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 5.148 418.296 209.148 3.526 0.13 240.778 4.059 59.315 D 5434.741 2717.37 43.108 0.001 287.258 4.557 63.037 V * F 3.926 4 0.981 1.828 0.217 4.296 8 0.537 V * D 18.815 4.704 8.759 0.005 F * D 235.481 58.87 109.621

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 1088.889 544.444 5.452 0.071 405.881 4.064 99.861 D 4290.889 2145.444 21.413 0.007 409.916 4.091 100.194 V * F 5.556 4 1.389 2.381 0.138 4.667 8 0.583 V * D 6.889 1.722 2.952 0.09 F * D 396.222 99.056 169.81

The analysis of variance is show in table Since α=0 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.

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