EXPERIMENT 6 : Roughness Test of Machine Component

Name:Muhammad Hisham Bin Amirruddin Matric:115751 Experiment Date:26/9/14

1.0 Introduction Roughness is something that we calculate from the texture of the specimen and entire thing. In this world have the roughness but in different value of roughness. The surface for specimen are not always been smooth even the mirror have the roughness. The roughness can be qualified by the deviation, higher deviation higher the roughs the surface.

In this experiment, the arithmetic mean value (Ra¿ of surface roughness is given by the following equation:

Ra=1.22×105M f 1.004V c−1.252μm

where Ra is the average surface roughness, M=r−0.714BHN−0.323 is the constant to account for the influence of tool nose radii and work piece hardness, f is the feed rate, BHN is the Brinell hardness number for the work piece and V c is the cutting velocity. For turning process, cutting velocity, V c, is related to work piece diameter D, and the spindle revolution rate N. This relation is given by

V c=πDN .

2.0 Experimental MethodTwo cylindrical workpieces, cutting tool and machine tool are prepare. The cutting

parameters for the experiment(Vc,a,f) and the tool nose radii are determined. Turning process are performed using the speed and federate that are obtained from previous step and the surface roughness obtained are measured. Surface roughness as function of cutting speed and as a function of feedrate are plotted.

3.0 Results3.1.1 Effect of federate on surface rouhgness

Diameter of Workpiece, D (mm) 24Length of Workpiece, L (mm) 100Cutting Speed, (m/min) 90.43Spindle Rotation, N (rpm) 1200Tool Nose Radii, r (mm) 0.8Workpiece Brinell Hardness Value, BHN 80Depth of Cut, a (mm) 0.5Feedrate, f (mm/rev) 0.05 0.10 0.16 0.20 0.25 0.30

Experimental Roughness Value, (μm)

1 0.41 0.44 0.64 0.99 1.17 1.252 0.45 0.43 0.64 0.88 0.93 1.143 0.49 0.48 0.82 1.12 1.49 1.81

Average 0.45 0.45 0.70 1.00 1.20 1.40

Theoretical Roughness Value, (μm) 0.1801 0.3612 0.5791 0.7245 0.90641.088

5

Table 1:Effect of Feed Rate On Surface Roughness

3.1.2 Effect of cutting speed on surface roughness

Diameter of Workpiece, D (mm) 24Length of Workpiece, L (mm) 100Tool Nose Radii, r (mm) 0.8Workpiece Brinell Hardness Value, BHN 80Feedrate, f (mm/rev) 0.2Depth of Cut, a (mm) 0.5Spindle Rotation, N (rpm) 180 260 370 540 800 1200 1700

Cutting Speed, (m/min) 13.57 19.60 27.90 40.72 60.32 90.48128.1

8

Experimental Roughness Value, (μm)

1 0.6 0.76 1.33 0.86 0.98 1.04 0.732 0.8 0.54 1.01 0.65 0.92 0.95 0.883 0.93 0.73 0.89 0.62 0.64 1.25 0.69

Average 0.78 0.68 1.21 0.71 0.85 1.08 0.77

Theoretical Roughness Value, (μm) 7.7853 4.9128 3.1586 1.9675 1.2028 0.7040

0.4681

Table 2:Effect of Cutting Speed on Surface Roughness

3.2.1 Calculation for theoretical

Effect of Feed rate on Surface roughness

M¿0.8−0.714 80−0.323

=0.2848m

V c=¿,)

=1.049×10−4m/min

Ra=(1.22 x105)(0.2848)(0.051.004)(1.049×10−4 )−1.252

Ra=0.1801μm

3.2.2

Effect of Cutting Speed on Surface Roughness

-This calculation same as the effect of feed rate on surface roughness

0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.350.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

1.60

0.1801

0.3612

0.5791

0.7245

0.9064

1.0885

0.45 0.45

0.70

1.00

1.20

1.40

Graph 1 : Roughness Value Against Feedrate

Experimental Roughness Value (Average) Theoretical Roughness ValueLinear (Theoretical Roughness Value)

Roughness Value , Ra (μm)

0.00 20.00 40.00 60.00 80.00 100.00 120.00 140.000.00

1.00

2.00

3.00

4.00

5.00

6.00

7.00

8.00

9.00

7.7853

4.9128

3.1586

1.96751.2028

0.7040 0.46810.780.681.21

0.71 0.85 1.08 0.77

Graph 2 : Roughness Value Against Cutting Speed

Experimental Roughness Value (Average) Theoretical Roughness Value

Cutting Speed , Vc (m/min )

Roug

hess

Val

ue ,

Ra (μ

m)

4.0 Discussion

Ra=1.22×105M f 1.004V c−1.252

1. Based on the equation above the value of Ra depend on the value of feed rate.The value of Rais directly proportional to the feed rate value. Higher the feed rate the surface roughness also higher.

2. Surface roughness depend on the feed rate compared to nose radius .This is because at lower feed rates the roughness become independent of feed rate and is a function of nose radius only.

3. Based on the data in table 1,as the federate increases, surface roughness is also increase.This because the cutting heat generated during machining process. This causes heat generated will increase due to friction and causing surface roughness to increase. Higher temperature cause thermal damage to the specimen and the machine. Federate also increase when the effect of feed marks will become increasingly visible which will increase the surface roughness. Discontinuous chip formation will occur when cutting speed is very low.

4. Based on the graph 1, we can see that the theoretical graph is located below experimental graph. This show that the roughness for theoretical Ra is lower than the value of experimental at any federate and constant cutting speed. The graph for experimental is not consistent because some part the chips are not continuous. This make the texture of the specimen are not not consistent.

5. Based on the table 2, when the cutting speed increases, surface roughness decreases. This is because at higher speeds and lower federate , lower surface roughness can be obtained.To improve surface finish we need to increase the cutting speed as the result the formation of chip will produce less discontinuously.

6. Based on the graph we can see that at the the graph is not consistent at cutting speed 20m/min to 40m/min. This is cause by formation of chip.The picture below show the line where is the chip discontinuos.We also can consider that the cutting tool or cutting speed is one of the factor can happen.

7. There are some errors occur and its precaution:a) parallax error

-Eye must perpendicularly to the scaleb) Thermal distortion -No lubrication during the processc) Backlash error of the lathe machine caused inaccuracy in feed rate and cutting speed.-Make sure troubleshoot the machine before use it d) Chatter or vibration e) Human error-Do with carefullyf) Machine defects- Make sure troubleshoot the machine before use it

Percentage error:

For f=0.05mm /rev % error=0.45−0.1801

0.1801×100

% error=149.86 %

For Cutting Speed,Vc=13.57m /min

% error=0.78−7.7853

7.7853×100

% error=89 %

Based on the percentage error the value for 149.86% is not unacapptable.For the percentage error for 89% is acceptable and the experiment is successful.

5.0 Conclusion

The value of percentage error for federate for f=0.04mm/rev is 149.86%.The value of percentage error for cutting speed Vc=13.57m/min is 89%. The experiment is accepted when we calculated error with another value.

6.0 Reference

1. Lab manual, EML 331/2, Engineering lab 2, by USM.2. Manufacturing Engineering and Technology by Serope Kalpakjian and Steven

R.Schmid. (6th Edition by Prentice Hall International).