Sphere measurement by laser displacement sensor. 5-axis On-machine Laser Measurement
On-machine measurement on a machine tool is typically used either for post-machining measurement of finished workpiece or pre-machining measurement of workpiece setup.
 
 
A contact-type, touch-triggered probe is often used for such on-machine measurement. By employing a laser displacement sensor, continuous measurement can be done, which significantly improves the measurement efficiency.
 
 
For pre-machining measurement of part blank on five-axis machine tools, it is more important to measure the three-dimensional position and orientation, or three-dimensional geometry, of part blank. For such a measurement, it is significantly more efficient to continuously perform the measurement with tilting a sensor (or a workpiece) by driving the machine tool's rotary axes (see Fig.1).
 
 
Clearly, major contributors to measurement uncertainties of on-machine measurement schemes are error motions of the machine tool itself. In this project, a simulator is developed to evaluate the influence of the machine's geometric errors of rotary axes on the measurement uncertainty. Such a simulator is essential to evaluate the measurement uncertainty of the present on-machine laser measurement system.
 
 
This project is partly supported by Mori Seiki Co., Ltd. The on-machine laser measurement system, "S-Quad," is commercially available from Mori Seiki. (April, 2013)
 
 
>> Publications: JE35, JE33, CE53, CJ70, CJ66
 
 
 
 
 
 
5-axis scanning measurement.
 
Figure 1: Five-axis on-line measurement by using a laser displacement sensor significantly improves measurement efficiency.
 
 
 
On-machine laser measurement of a blade.
 
Figure 2: On-machine measurement of a turbine blade by the laser measurement system (photo from Mori Seiki).
 
 
 
Laser measurement test of a flat surface.  
Figure 3: Measurement test of a flat surface.
 
 
 
Laser measurement test of a precision sphere.
 
Figure 4: Measurement test of a precision sphere. By measuring the sphere of the pre-calibrated geometry, the on-machine measurement system's uncertainty was investigated.
 
 
 
Measured profiles of precision sphere.
 
Figure 5: Measured trajectories of the precision sphere by the laser measurement system. The laser beam direction is controlled normal to the spherical surface. It was shown that the machine's geometric errors are dominant contributors to the measurement error. Their influence can be predicted by using the proposed kinematic simulator.