View
16
Download
1
Category
Preview:
Citation preview
LOGO
Dr. Juma Y. Alaydi
Engineering Measurement
Lecture 14Surface Finish
April 12, 2014 Engineering Measurement2
Surface Finish
April 12, 2014 Engineering Measurement
Outline
Importance of Surface Roughness1
3
Surface Texture2
Surface Roughness3
Surface Roughness Measurement4
5
uOne of the first thing one notice is the surfacefinish
uThe nominal surfaces appear as absolutelystraight lines, ideal circles, round holes, and otheredges and surfaces that are geometrically perfect
uActual surfaces of a part are determined by themanufacturing processes used to make it
April 12, 2014 Engineering Measurement4
April 12, 2014 Engineering Measurement5
During machining processes roughness can be found due to:
1.Mechanical vibration in the machine
2.Fixing both of W/P and cutting tool (eccentricity)
3.Metallurgical deficiencies (material defect)
4.Cutting procedure (cutting depth, feed rate….)
April 12, 2014 Engineering Measurement6
Why Surfaces are Important?ØSurfaces affect safetyØ Friction and wear depend on surfaceØ characteristicsØSurfaces affect mechanical and physical
propertiesØAssembly of parts is affected by their surfacesØSmooth surfaces make better electrical contacts
April 12, 2014 Engineering Measurement7
Surface Texture
April 12, 2014 Engineering Measurement8
April 12, 2014 Engineering Measurement9
The topography and geometric features ofthe surface
•When highly magnified, the surface isanything but straight and smooth
•It has roughness, waviness, and flaws•It also possesses a pattern and/or directionresulting from the mechanical process thatproduced it
Four Elements of Surface Texture
April 12, 2014 Engineering Measurement10
1. Roughnesssmall, finely-spaced deviations from nominal
surfaceØDetermined by material characteristics and processes thatformed the surface
2. Wavinessdeviations of much larger spacingØWaviness deviations occur due to work deflection,
vibration, heat treatment, and similar factorsØRoughness is superimposed on waviness
April 12, 2014 Engineering Measurement11
3.Laypredominant direction or pattern of the surface texture
4.Flawsirregularities that occur occasionally on the surfaceØIncludes cracks, scratches, inclusions, and similar defects in the surfaceØAlthough some flaws relate to surface texture, they also affect surface
April 12, 2014 Engineering Measurement12
Evaluation of Surface Roughness
April 12, 2014 Engineering Measurement13
April 12, 2014 Engineering Measurement14
RMS Value, Rq
Rq is the Root Mean Square of the distance of the filtered or unfiltered Roughness Profile from its mean line.
April 12, 2014 Engineering Measurement15
Center Line Average(CLA), Ra
Ra is the Arithmetic Average of the distance of the filtered or unfiltered Roughness profile from its Mean Line
Advantages: Statistically very stable parameter. Easy and cheap to implement into instrumentation. Good for random type surfaces (Processes like grinding)
Disadvantages:
April 12, 2014 Engineering Measurement16
April 12, 2014 Engineering Measurement17
Maximum Peak to valley height, Rt or Rmax
ØRt is the highest Peak to the lowest Valley in the assessmentlength
ØRp is the highest Peak in the assessment lengthØRv is the lowest Valley in the assessment length.
April 12, 2014 Engineering Measurement18
Average peak to valley height, Rz
April 12, 2014 Engineering Measurement19
April 12, 2014 Engineering Measurement20
Surface Roughness Specification
Surface texture symbols in engineering drawings: (a) the symbol,(b) symbol with identification labels.
April 12, 2014 Engineering Measurement21
April 12, 2014 Engineering Measurement22
April 12, 2014 Engineering Measurement23
Surface Finish Process• Grinding• Lapping• Honing• Buffing• Barrel Tumbling• Barrel rolling
April 12, 2014 Engineering Measurement24
April 12, 2014 Engineering Measurement25
LOGO
Dr. Juma
April 12, 2014 26Engineering Measurement
Recommended