In situ non-contact measurements of surface roughness

Surface roughness measurements are often required to validate a machining process. However, when using a 3D surface roughness measuring instruments it is usually necessary to remove the part from the machine tool between two operations, potentially introducing systematic errors. Furthermore, surface roughness measuring instruments are not suited for measuring heavy and large parts such as stamping dies. This paper presents a method to measure the surface topography of a part in situ, i.e. directly on the machine tool without removing the part. After introducing the sensor technology and the data acquisition chain, the effects of geometric imperfections of the machine tool and compensation for thermal effects on the measurement results are discussed. An application of the method is then presented to assess a finishing process on a five-axis machining centre including milling and polishing operations.

► Measurement device and data acquisition chain for in situ measurement of surface roughness on machine tool.
► Compensation of the thermal expansion of the spindle due to cooling cycle.
► Repeatability study of the measurement along z-axis of the machine tool according to ISO 230-2.
► Validation of the method through groove and complex topography measurements compared to standard measuring instruments.
► Experimental investigation to assess a finishing process on a 5-axis machining center including milling and polishing operations.