Original roughness profile

with 5 to 36 mm band-pass-filtered profile

long-wave component of the
power spectrum 

Sheet surfaces can have undesirable long-wave textural components. Their analysis and evaluation involve scanning the surface topography over unusually large lengths or areas with high-precision reference plane measuring systems. Long-wave textural components in rolling direction, so-called chatter marks, may be present as shape or thickness deviations. Since their amplitudes amount to only a few micrometers, they are hardly identifiable on the sheet due to the shorter-wave surface roughness. Normally they become visible after 'stoning' of the surface. When the surface texture is scanned, the chatter marks can be visualised by means of suitable filter methods and analysed ac-cording to amplitude and wave length. Scanning of the sheet top and opposing bottom side enables a separate analysis of the shape and thickness deviations that are present.
The analysis of the formed surface topographies represents an important basis for determining their causes (see "Plant and System Engineering")




Long-wave textural components of sheet affected by chatter marks
 
    a) scan of a stoned sheet surface,
    b) top view and
    c) side view of the three-dimensionally scanned and visualised chatter
        marks