Metrology Lab Report

Manufacture & Materials 3 Metrology Lab Report Autocollimator Sam Rutherford S1221186

Introduction: An autocollimator is a device for the precise measuring of angles and can also be used to determine the straightness of a surface by measuring the angular deflection of a plane reflector mounted on the surface in question.

Aim: The aim of this report is to determine the straightness of a surface using a microptic autocollimator and determine if the machine is suitable for continued use.

Equipment: The equipment used in this experiment was an autocollimator, a reflector carriage and the straight edge of a milling machine.

Procedure: First, I aligned the autocollimator to the edge of the surface and checked that it could receive a reflected image along the full length of the machine. Next, I took a reading from each of the 9 positions along the length of the milling machine noting down the times for each one. This was done by sliding the reflector carriage along the surface stopping at each point and taking a reading from the reflected image sent back to the autocollimator. I then repeated the previous step in reverse until the carriage was back at its original starting point and took the average result for each of the positions along the machine. Finally, I checked over the results to make sure there were no large errors for any of the readings. Once I was satisfied with the data, it was put in to a table and the respective rows and columns were filled out using the information gathered.

Results: For the results in the table and graphs, I used the average time value for each position and calculated the rest of the results from these values.

Readi ng 0 1

Positio n 0 1

Minut es 0 4

Secon ds 0 28.15

Differen ce 0 0

Conve rt 0 0

Cumulative

Adjust

Error

0 0

0 11.4528

2

2

4

16.9

11.25

5.625

5.625

3

3

4

16.7

11.45

5.725

11.35

4

4

4

7.65

20.5

10.25

21.6

5

5

4

3.5

24.65

12.32 5

33.925

0 11.452 8 22.905 6 34.358 4 45.811 2 57.264

17.2806 23.0084 24.2112 -23.339

6

6

4

3.7

24.45

12.22 5

45.15

7

7

3

52.1

36.05

18.02 5

64.175

8

8

3

52.5

35.65

17.82 5

82

9

9

3

46

42.15

21.07 5

103.075

68.716 8 80.169 6 91.622 4 103.07 5

23.5668 15.9946 -9.6224

0

* Cumulative, Adjust and Error are all measured in micrometres (μm).

Cumulative Error v Position Graph

120 100 80 Cumulitive Error (μm)

60 40 20 0 1

2

3

4

5

6

7

8

9

10

Position

This graph shows a steady incline of the error, however, we can also see that as we get to the end positions the graph becomes steeper, showing that the errors for those points are greater.

Actual Error v Position Graph

0 1

2

3

4

5

6

7

8

9

10

-5 -10 Actual Error (μm) -15 -20 -25 -30 Position

The graph shows that the end positions of the surface have little to no error and it gradually increases as we reach the middle point. From this we can say that the middle positions have the largest errors.

Conclusion: In conclusion, the graphs follow the trend which was expected of them and the table shows no gross errors from the readings taken during the experiment. However, it should also be noted that human error may be involved in taking the readings from the autocollimator which would affect the values calculated. There is general wear and tear on the surface from use which can be expected. The machine is not suitable for use as there are values outside the 0.02 mm/m limit. The surface should be replaced and steps should be taken to ensure that it remains in working condition. The machine should be checked regularly to see if there are any major peaks or troughs upon the surface that could affect the machining done on the surface or the safety of those using it. To reduce general wear, a lubricant could be applied so that when in use, less damage is inflicted on the surface giving it a longer working life which also makes it a more economical machine.