Quick Guide to Precision Measuring Instruments
Surftest (Surface Roughness Testers)
ISO 4287: 1997 Geometrical Product Specifications (GPS) –Surface Texture: Profile method– Terms, definitions, and surface texture parameters ISO 4288: 1996 Geometrical Product Specifications (GPS) –Surface Texture: Profile method– Rules and procedures for the assessment of surface texture ISO 3274: 1996 Geometrical Product Specifications (GPS) –Surface Texture: Profile method– Nominal characteristics of contact (stylus) instruments ISO 11562: 1996 Geometrical Product Specifications (GPS) –Surface texture: Profile method– Metrological characteristics of phase correct filters
Elements of Contact Type Surface Roughness Measuring Instruments
Roughness sampling length for non-periodic profiles
ISO 3274: 1996 (JIS B 0651: 2001)
Input/Output
Input/Output
Probe
ISO 4288: 1996 (JIS B 0633: 2001)
Z-axis Signal Transfer Unit
Table 1: Sampling lengths for aperiodic profile roughness
Traced profile
Stylus tip
Surface
parameters ( R a , R q , R sk , R ku , RΔ q ), material ratio curve, probability density function, and related parameters
Analysis according to ISO 4287
Profile filter λ S
AD converter
Nominal form removal
Primary profile
Amplifier
Transducer
Total profile
Sampling length l r mm
R a µm (0.006)< R a ≤ 0.02 0.02 < R a ≤ 0.1 0.1 < R a ≤ 2 2 < R a ≤ 10 10 < R a ≤ 80
Evaluation length l n mm 0.4 1.25 4 12.5 40
0.08 0.25
Measure- ment loop
Reference guide skid
Reference profile
0.8 2.5 8
Column
External disturbances
Feed device
Table 2: Sampling lengths for aperiodic profile roughness parameters ( R z , R v , R p , R c , R t )
Feed device
Measuring loop
R z R z1max . µm (0.025)< R z , R z1max. ≤ 0.1 0.1 < R z , R z1max. ≤ 0.5 0.5 < R z , R z1max. ≤ 10 10 < R z , R z1max. ≤ 50 50 < R z , R z1max. ≤ 200
Drive Unit
Sampling length l r mm
Evaluation length l n mm
Probe (pickup)
Stylus (contact element)
Stylus Shape A typical shape for a stylus end is conical with a spherical tip. Tip radius: r tip = 2 µm, 5 µm or 10 µm Cone angle: 60°, 90° In typical surface roughness testers, the conical angle of the stylus end is 60˚ unless otherwise specified.
0.08 0.25
0.4 1.25 4
Workpiece
0.8 2.5 8
12.5 40
Base
Fixture
1) R z is used for measurement of R z , R v , R p , R c , and R t . 2) R z1max. only used for measurement of R z1max., R v1max., R p1max., and R c1max..
Table 3: Sampling lengths for measurement of periodic roughness profile roughness parameters and periodic or aperiodic profile parameter R sm
60°
60°
60°
Relationship between Cutoff Value and Stylus Tip Radius The following table lists the relationship between the roughness profile cutoff value λ c, stylus tip radius r tip , and cutoff ratio λ c/ λ s.
Sampling length l r mm
Evaluation length l n mm 0.4 1.25 4 12.5 40
Rsm mm
0.013 < R sm ≤ 0.04 0.04 < R sm ≤ 0.13 0.13 < R sm ≤ 0.4 0.4 < R sm ≤ 1.3 1.3 < R sm ≤ 4
0.08 0.25
90°
90°
90°
Maximum r tip µm
λ c mm 0.08 0.25
λ s µm
λ c/ λ s
Maximum sampling length µm
0.8 2.5 8
2.5 2.5 2.5 8
30 100 300 300 300
2 2 2 5 10
0.5 0.5 0.5 1.5 5
0.8 2.5 8
*1
Procedure for determining a sampling length if it is not specified
*2
Static Measuring Force
25
*2
*1 For a surface with R a >0.5 µm or R z >3 µm, a significant error will not usually occur in a measurement even if r tip = 5 µm. *2 If a cutoff value λ s is 2.5 µm or 8 µm, attenuation of the signal due to the mechanical filtering effect of a stylus with the recommended tip radius appears outside the roughness profile pass band. Therefore, a small error in stylus tip radius or shape does not affect parameter values calculated from measurements. If a specific cutoff ratio is required, the ratio must be defined.
Estimate R a , R z , R z1max. , or RS m according to recorded waveforms, visual inspection, etc.
Nominal radius of curvature of stylus tip: µm
Static measuring force at the mean position of stylus: mN
Tolerance on static measuring force variations: mN/ µm
2 5 10
0.75
0.035
Estimate the sampling length from an estimated value and Tables 1 to 3
0.75 (4.0) *
0.2
Surface Profiles
ISO 4287:1997 (JIS B 0601: 2013)
* The maximum value of static measuring force at the average position of a stylus is to be 4.0 mN for a probe with a special structure including a replaceable stylus.
Measure R a , R z , R z1max. , or RS m according to the estimated value of the sampling length
Primary profile
100
Metrological Characterization of Phase Correct Filters
Roughness profile
Waviness profile
50
ISO 11562: 1996 (JIS B 0632: 2001)
Change to a longer or shorter sampling length
Does each measured value meet the parameter range of Table 1, 2, or 3?
No
A profile filter is a phase-correct filter without phase delay (cause of profile distortion dependent on wavelength). The weight function of a phase-correct filter shows a normal (Gaussian) distribution in which the amplitude transmission is 50% at the cutoff wavelength.
λ s
λ c
λ f
Yes
Wavelength
Primary Profile Profile obtained from the measured profile by applying a low-pass filter with cutoff value λ s.
No
Change to a shorter sampling length
Has a shorter sampling length been tried?
J
Data Processing Flow
Yes
Definition: Profile that results from the
Surface profile on the real surface
intersection of the real surface and a plane rectangular to it.
Measure the parameter according to the final sampling length
Measurement
Fig.1 Procedure for determining the sampling length of an aperiodic profile if it is not specified.
Definition: Locus of the center of the stylus tip that traces the workpiece surface.
Traced profile
Estimate RS m from a measured roughness profile
AD conversion
Roughness Profile Profile obtained from the primary profile by suppressing the longer wavelength components using a high-pass filter of cutoff value λ c.
Definition: Data obtained by quantizing the traced profile.
Total profile
Estimate the sampling length from an estimated value and Table 3
Suppresses irrelevant geometry of the surface such as inclination of a flat feature and curvature of a cylindrical feature using the least squares method.
Low-pass filter of cutoff value λ s
Measure RS m according to the estimated value of the sampling length
Primary profile parameters
Primary profile
Waviness Profile Profile obtained by applying a band-pass filter to the primary profile to remove the longer wavelengths above λ f and the shorter wavelengths below λ c.
Change the sampling length so as to meet the condition of Table 3
No
Does the measured value meet the condition of Table 3?
High-pass filter of cutoff value λ c
Band-pass filter that passes wavelengths between cutoff values λ c and λ f
Yes
Roughness profile
Waviness profile
Measure the parameter according to the final sampling length
Roughness profile parameters
Waviness profile parameters
Fig.2 Procedure for determining the sampling length of a periodic profile if it is not specified.
J-17
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