FOCUS ON SURFACE FINISHING
Measuring RA ( surface roughness ).
Measuring surface roughness .
A SMOOTH FINISH
Rimex UK is focused on creating a standard hairline finish for its metal part surfaces , using finishing machines from Timesavers International .
“ The friction and wear of sheet metal depends upon its surface texture , so it is important to tackle the surface roughness .”
Surface roughness measures the irregularities on the metal ’ s surface and is one of the characteristics of surface texture . The friction and wear of sheet metal depends upon the surface texture , so it is important to examine the roughness .
There are numerous parameters to measure a profile ’ s roughness , of which the Ra value is the most common . Ra measures , within a certain sampling length , the average of the peaks and valleys of the metal surface , including deviation from the mean line . This can be done with a profilometer or laser scanner . The greater the deviations , the rougher the surface so if the Ra is small , the surface is smooth .
“ The Ra will either be calculated in micrometres (µ m ) or microinches (µ in .), and is a useful , often used average . Another one is the Rz , which stands for the mean roughness depth . It is the average value of the difference between the highest peak and lowest valley from each of the five sampling lengths . The Rt value presents the total height of the profile , by measuring the difference between the highest peak and deepest valley across the entire
There are numerous parameters to measure a profile ’ s roughness , of which the Ra value is the most common
Below : Timesavers 71 series coil-to-coil line .
evaluation length ,” Dutch surface finishing specialist , Timesavers International , told ISMR .
A smooth surface
A smooth and non-absorbent surface can be cleaned more easily and has low adhesion . This makes it beneficial in industries such as the food and pharmaceutical industries where hygiene is top priority and the risk of bacterial adhesion should be minimised .
Rough surfaces , however , are harder to clean and more sensitive to friction . They also offer resistance to moving objects due to their many irregularities . Such surfaces are also suitable for design purposes because of their dull-looking finish . They also have a larger surface area , which provides good adhesion for coatings and painting .
32 | sheetmetalplus . com | ISMR May 2022