Düzlüğünün Ölçümü ( Of Flatness)
The easiest method for measuring flatness is with a height gage positioned on a surface plate. Flatness is also measured with a co-ordinate measuring machine. But neither of these methods can measure flatness more accurately than about 0.0001".
optical flats in wooden case
Another method that is commonly used with lapped parts is the reflection and interference of monochromatic light. A monochromatic light source and an optical flat are all that are needed. The optical flat - which is a piece of transparent glass that has itself been lapped and polished on one side - is placed on the lapped surface. The monochromatic light is then shone down through the glass. The light will pass through the glass and reflect off the workpiece. As the light reflects in the gap between the workpiece and the polished surface of the glass, the light will interfere with itself creating light and dark fringes. Each fringe - or band - represents a change of 1HLB in the width of the gap between the glass and the workpiece. The light bands display a contour map of the surface of the workpiece and can be readily interpreted for flatness.
For a more thorough description of the physics behind this measurement technique, see interference.
Pürüzlülüğünün Ölçümü
Surface roughness is defined by the minute variations in height of the surface of a given material or workpiece. The individual variances of the peaks and valleys are averaged (Ra reading), or quantified by the largest difference from peak-to-valley (Rz). Roughness is usually expressed in microinches. A surface that exhibits an Ra of 8 consists of peaks and valleys that average no more than 8 microinches over a given distance. Roughness may be also measured by comparing the surface of the workpiece to a known sample. Calibration samples are available usually sold in a set and usually covering the typical range of machining operations from about 125 Ra to 1 Ra.
Surface roughness is measured with a profilometer, an instrument that measures the minute variations in height of the surface of a workpiece. |
