Surface Roughness Parameters - Jenoptik
Precise roughness measurementSurface texture parametersin practice
Surface texture measurementSurface texture measurement with JenoptikSurface texture is very important where it has a direct influence on the quality of the part. Therefore, it has to be definedas precisely as possible with the help of standardized surfacetexture parameters.This leaflet gives you an overview of the most important definitions, standards, and parameters of surface texture measurement.We manufacture a wide range of roughness measuring systemsproviding you with a large variety of evaluation possibilities – inthe measuring lab as well as on the production line.One particularly important aspect is the continuous monitoringof the roughness measuring systems for optimum accuracy.Our DAkkS-DKD calibration laboratory can calibrate yourstandards based on different surface texture parameters. Forparameters not requiring accreditation, we offer an in-housecalibration certificate.Division of a surfaceUnfiltered P-profileFiltered W-profileFiltered R-profile2
Surface texture measurementSurface profiles – total height of the profileSurface profile is measured two-dimensionally using the tracingsystem.The unfiltered primary profile (P-profile) is the actual measuredsurface profile. Filtering it in accordance with ISO 11562/ISO16610-21 produces the waviness profile (W-profile) and theroughness profile (R-profile). The variable for determining thelimit between waviness and roughness is the cut-off λc.Following ISO 4287, all parameter definitions are valid for boththe roughness profile as well as for the primary and wavinessprofiles. The profile type is identified by the capital letters P, Ror W.The total height Pt, Wt or Rt of the respective profile type is themaximum height between the highest peak and the deepestvalley of the evaluation length profile.Evaluation lengths – cut-offStart-up lengthRoughness profileRun-off lengthThe traverse length (lt) is the total length of the probe movement during the scanning process. It must be greater than theevaluation length ln in order to be able to form the roughnessprofile with the profile filter.With the exception of Rt, Rmr(c) and RPc, the roughnessparameters are defined within an evaluation length ln, which isdetermined using an average of five sampling lengths lr.The sampling length lr corresponds to the cut-off λc.3
Measurement conditionsSelection of the cut-off (profile filter) according to ISOThe cut-off is selected depending on the workpiece surfaceeither according to the valley spacing, or the expected roughness values. At the same time the total evaluation length andPeriodic profilese.g. turning, millingMeasurement conditionslrlnltλcλsrtipΔXRSmsampling lengthevaluation lengthtraverse lengthcut-offshortwave profile filterstylus tip radiusdigitization distance 1)λc lr (mm)ln (mm)lt (mm) 0.013.0.040.080.40.48 0.04.0.130.251.251.5 0.13.0.40.844.8 0.4.1,32.512.515 1.3.484048RSm (mm)Application exampleIn a periodic profile the mean width of the profile elements RSm is used. Withan RSm between 0.4 and 1.3 mm the following measuring conditions result:λc 2.5 mm / ln 12.5 mm / lt 15 mm / rtip 5 µm / λs 8 µm.* At Rz 2 μm the stylus tip radius is 2 μm, at Rz 2 μm it is 5 μm.The distance between two measuring points is 0.5 μm.Measurement conditions for Motif parameters accordingA* (mm)B* (mm)Traverse length (mm)0.020.10.640.10.53.20.52.5162.512.580* If not otherwise specified, the default values are A 0.5 mm and B 2.5 mm, respectively. The defined limit A4
Measurement conditions4288:1998 and ISO 3274:1998the corresponding traverse length are defined according tostandards. Deviations are necessary if the workpiece does notallow the required traverse length. See drawing entries.Aperiodic profilese.g. grinding, erodingThe digitizationdistance is also stan dardized. This is setautomatically by mostroughness measuringinstruments.1)Rzrtip (µm) λs (µm)Ra (µm)22.5 (0.006) 0.02 (0.025) 0.122.5 0.02 0.1 0.1 0.52 or 5 *2.5 0.1 2 0.5 1058 2 10 10 501025 10 80 50 200Rz (µm)Shortened standard evaluation lengthIf the actual possible traverse length on the workpiece surface is not enough forlt, the number of sampling lengths is reduced accordingly and specified in thedrawing.If the actually available traverse length is less than a sampling length, the totalheight of profile Pt of the primary profile is evaluated instead of Rt or Rz.to ISO 12085Evaluation length (mm)λs (µm)Max. stylus tip radius (µm)0.642.52 0,53.22.52 0,51685 1802510 2determines in this case that the measured AR parameters are always smaller than 0.5 mm.5
Surface texture parametersRa according to ISO 4287Center lineRa – arithmetical mean deviationRa is the arithmetic mean roughness value from the amountsof all profile values. Ra does not differentiate between peaksand valleys and has therefore a relatively weak informationcharacter.Rz, Rz1max, Rt according to ISO 428Rz – maximum height of profileAverage value of the five Rz values.Rz1max – maximum height of profile (ISO 4287:1997)Greatest Rz value from the five sampling lengths lr.Rt – total height of profileRt is the distance between the highest peak and the deepestvalley of the profile of the total evaluation length ln.6
Surface texture parametersRSm according to ISO 4287Center lineRSm – mean width of the profile elementsRSm is the arithmetic mean value of the width of the roughnessprofile elements within the sampling length and requires thedefinition of height discriminations (c1, c2) matching the function of the surface. If not specified otherwise, the sum of theheight discriminations should add up to 10 % of Rz.RPc according to EN 10049/ISO 4287Center lineRPc – standardized number of peaksRPc corresponds to the number of local peaks, which successively exceed an upper section line c1 and a lower sectionline c2. The number of peaks is related to a length of 10 mmirrespective of the evaluation length selected.7
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Surface texture parametersRmr(c) according to ISO 4287Reference lineReference section height c0Section height cMaterialratio curveEvaluation length InMaterial ratio Rmr (c)Rmr(c) – material ratio of the profileRmr indicates what ratio the totaled length in the material hasassumed relative to the evaluation length (in %). The comparison is made in the specified section height c and the total evaluation length ln. The material ratio curve indicates thematerial ratio as a function of the section height.Profile valley sectionRvkCoreRpk*„Peak surface“Material ratio curve„Valley surface“Rvk*Profile peak sectionRkRpkRk, Rpk, Rvk, Mr1, Mr2according to ISO 13565-2Material ratioRk – core roughness depthDepth of the roughness core profile.Rpk – reduced peak heightMean height of the peaks protruding from the roughness profile.Rpk* – highest profile peak height (not ISO 13565-2)Rvk – reduced valley depthMean depth of the valleys reaching into the material from the core.Rvk* – deepest profile valley depth (not ISO 13565-2)Mr1, Mr2 – material ratioSmallest (Mr1) and greatest (Mr2) material ratio (in %) at thelimits of the roughness core area.9
Surface texture parametersMotif standard according to ISO 12085AR1HmHm-1HjH j 1H1H2H3The principle of the Motif standard consists of looking for localpeaks and valleys in the primary profile, and associating onevalley with the closest preceding and following peaks in orderto create a Motif. Several iterative combinations of two Motifseach assure that the most important Motifs, the width of whichfall below the limit A, are considered. If not otherwise specified,the default value is A 0.5 mm (see measurement conditionspage 4/5).The limit A has a similar function as the cut-off in the Gaussianfiltering. The 16 % rule generally applies.AR nAR iThe most important Motif parameters:R – Mean depth of roughness MotifsR is the arithmetic mean value of the depths Hj of the roughness Motifs within the evaluation length.AR – Mean spacing of roughness MotifsAR is the arithmetic mean value of the lengths ARi of theroughness Motifs within the evaluation length.Rx – Maximum depth of profile irregularityThe deepest depth Hj within the evaluation length.10
Surface texture parametersWDSm, WDt, WDc –Dominant waviness according to VDA 2007The primary profile is checked for none, one or two dominantwavinesses. Narrow band filtering of the primary profile withthe waviness creates the WD-profile that is used for calculating the parameters. The evaluation length ln is chosen eitheraccording to ISO 4288 (as for surface roughness measurements)or on the basis of the drawing entry.Period lengths are checked for dominant wavinesses inthe range of 0.02 mm WDSm ln/5. To catch dominant wavinesses at WDSm ln/5, it is n ecessary to enlarge the evaluation length.WDtWDSmEvaluation length lnP-profileWD-profileWDSmMean horizontal value of the profile elements, calculated fromthe amplitude spectrum (mean periodic length of the dominantwaviness).WDtVertical difference between the highest and the deepest pointof the WD-profile within the evaluation length. Z1 Z2 Z3 ZN-1 ZNEvaluation length lnP-profileWD-profileWDcMean value of the peaks of the profile elements within theevaluation length.11
EvaluationEvaluation of measurement resultsAccording to ISO 4288 the surface measurement shouldbe made where the highest values are to be expected (visualdetermination).Maximum value ruleThe surface is considered good when the measured values of aparameter do not exceed the fixed maximum value. In this case,the parameter is identified by the suffix „max“, e.g. Rz1max.16 % ruleIf the suffix „max“ is not specified, the 16 % rule applies,which states that the surface is considered “good” if not morethan 16 % of the measured parameter values exceed the fixedmaximum value. You will find further information about thisrule in the standard ISO 4288:1997.Special rule VDAThe 16 % rule is not used. VDA 2006 assumes that the dispersion of the parameters is taken into account in the definition ofthe limit values. The maximum value rule applies generally evenwithout the „max“ index in the designation. The use of the λsfilter is prohibited.At Rz 2 μm the stylus tip radius is 2 μm, at Rz 2 μm it is5 μm. The distance between two measuring points is 0.5 μm.The cone angle is either 60 or 90 . If not otherwise specified,it is 90 .12
Drawing entriesDrawing entries according to ISO 1302:2002cead bRz 4Material removingmachining;Rz max. 4 μmU Ra 4L Ra 1Material removingmachining; upper andlower limit value for Rademanded;Ra min. 1 μm andmax. 4 μm2/Pt 4Material removingmachining; P-profile,traverse length 2 mm;Pt max. 4 μmSpecifications for requirementsa surface parameter with numeric value in μmb second requirement (surface parameter in μm)c production methodd specification of valley directione machining allowance in mmL Rz 2.5Material removingmachining; lower limitvalue for Rz demanded;Rz min. 2.5 μmRzmax 4Material removingmachining;Rz max. 4 μm;the maximum value ruleapplies0.008-2.5/Rz1Material removing machining; transmission characteristic does not comply with standard case (cf. table)Rz max. 1 μm; filter selection λs 0.008 mm andλc 2.5 mm13
Drawing entriesDrawing entries according to VDA 2007 –dominant wavinessCase 1: No dominant waviness allowedWDc 0Material removingmachining; WDc 0 orWDt 0: no dominantwaviness allowedCase 2: Dominant wavinesses are allowed up toan upper limit2.5x5/WDt 2.5Material removing machining; inthe period range up to 2.5 mm,WDt max. 2.5 μm appliesCase 3: Dominant wavinesses are allowed in a period lengthwith an upper or an upper and lower limit0.8x16/Rz 30.2-2.5x5/WDc 1.5Material removing machining;Rz: the evaluation length is 12.5 mmand λc 0.8 mm, Rz max. 3 μm;WDc: in the period range of 0.2 to2.5 mm, WDc max. 1.5 μm applies14
surface profile. Filtering it in accordance with ISO 11562/ISO 16610-21 produces the waviness profile (W-profile) and the roughness profile (R-profile). The variable for determining the limit between waviness and roughness is the cut-off λc. Following ISO 42
surface roughness can be seen in Figures 3 through 5 as examples of the observations. Fig. 4. Example of a surface with relatively average surface roughness. (0.335 μm) Fig. 3. Example of a surface with relatively low surface roughness. (0.141 μm) Table 1. 3D Surface roughness parameters Parameters Name Definition Comments Sa Average Roughness
programmed surface roughness and non-programmed surface region are given, respectively. The AFM surface roughness value in the non-programmed surface roughness region in Fig. 3a showed a similar value as the first roughness value measured in the programmed surface roughness region (y -60mm). It means there is no Cr film at that location. This
Introduction Types of surfaces Nomenclature of surface texture Surface roughness value Machining symbols Roughness grades and symbols Surface roughness indication Direction of lay Roughness symbol on drawing Surface roughness for various machining processes SURFACE QUALITY & MACHINIG SYMBOLS 2 Engineering components are manufactured by
have neglected the effect of changing displacement height. In this experiment two surface roughness changes are investigated, both consisting of a change from upstream 3D Lego type roughness elements to downstream 2D bar type roughness. The downstream surface roughness bar height to canyon width ratio is different in each roughness change case
Three standardized (DIN 4768/ISO 4287) roughness parameters: average roughness (Ra), average roughness depth (Rz), and maximum roughness depth (Rt); and two derived numbers: peak roughness (Pr) and peak index (Pi) were calculated and compared statisti-cally. Ra is the arithmet
Fig. 6 Relationship between surface roughness/oil viscosity and friction coefficient (Blend 1) 3.2 Surface roughness Figs. 7 and 8 show the time-series variations of the surface roughness of the roller and discs, respectively, when the Blend 1 oil was used. A sharp decrease in the surface roughness of the roller was observed on the roller at an .
of average surface roughness of sand finished part, but in the range of 0.51µm - 2.5µm along different surface angles. Figure 5 shows the average surface roughness distribution, Ra after sanding. Minimum Ra sanded is 0.51μm at surface angle 00, which is reduced from 3μm. Surface angles 90 0 and 180 too have minimum average surface roughness.
BEC HIGHER AD BE 3 C The growth of outsourcing means that a number of MSSs are finding themselves drawn into the established managerial thinking of their OWOs to a point where their reputation becomes dependent on the OWO’s performance – in both positive and negative ways. This and other consequences of growth are generating calls from MSSs for both the private sector and governments to .
