VDI 3400 Surface Finishes Definition, VDI 3400 Depth

Charmilles_VDI3400

VDI 3400 Surface Finish – is a scale often used by German machine manufacturers and quite widely used in Spark and Wire Erosion (Verein Deutscher Ingenieure, the Society of German Engineers)

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EDM Surface Finish Scale

RA

MICRO-METER

RA

MICRO INCHES

RMS

-2

.08

3.14

3.90

-1

.09

3.54

4.40

0

.10

3.94

4.90

1

.11

4.33

5.50

2

.12

4.72

5.90

3

.14

5.51

6.90

4

.16

6.29

7.90

5

.18

7.09

8.90

6

.20

7.87

9.90

7

.22

8.66

10.80

8

.25

9.84

12.3

9

.28

11.02

13.80

10

.32

12.60

15.80

11

.35

13.78

17.20

12

.40

15.60

19.50

13

.45

17.6

22.00

14

.50

19.60

24.50

15

.56

21.60

27.00

16

.64

25.00

31.30

17

.72

28.10

35.20

18

.80

31.20

39.00

19

.91

35.50

44.40

20

1.01

39.40

49.30

21

1.12

43.70

54.60

22

1.28

49.90

62.40

23

1.44

56.20

70.30

24

1.60

62.40

78.00

25

1.81

70.60

88.20

26

2.03

79.10

98.90

27

2.24

87.40

109.20

28

2.54

99.10

123.90

29

2.84

110.80

138.50

30

3.15

122.9

153.70

31

3.6

140.40

175.50

32

4.05

158.00

197.50

33

4.50

175.50

218.80

34

5.10

198.90

248.60

35

5.70

222.30

277.90

36

6.30

245.70

306.20

Measurement of surface finishes is done with instruments called profilometers. Experience proves that measurement of surface finishes by comparison using a surface finish gauge does not give an error above 2 CH classes. The criteria of roughness are the Ra (Europe) – CLA (UK) – AA (USA) To obtain a grading of roughness, Charmilles has defined a CH scale, which is however cross referenced with the standards that are in common use.

Definition of Roughness criteria

No CH = 20 log (10 Ra) (µm)

Some significant rules and figures

1 µm Ra = CH20

10 µm Ra = CH40 If Ra = Ra x 2 CH = CH+6 ex: 1 µm Ra = CH20

  1. µm Ra = CH26
  2. µm Ra = CH32

The ratio

between 2 successive CH units is 1.12

The difference

between 2 successive CH units is 12.2%

The MAX Rt: roughly equal to 8 x Ra

The mean Rt: is the arithmetic mean of the 5 Max Rt recorded on the 5 sample lengths selected.

(For establishing the technology: 0.8mm)

Mean Rt = 5 x the Ra value

Note:

In surface finish measurements a tolerance of + 2 CH units is accepted.

Further note:

The American and English standards admit the following relationship between the values V(RMS) and V(Ra):

V(RMS) = 1.11 V(Ra)

The French standard NF 05051 is tied in with the ISO 1302 standard concerning classes of surface finish.

Please contact with : info@Upmold.com for more informations or helps

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