Pneumatic Non-Contact Roughness Assessment of Moving Surfaces

Abstract

All machined surfaces inherently have roughness. The level of control of this surface is dependeat on the specifications outlined for its intended use. In strictly controlled situatiom, the monitoring and characterization of these surfaces becomes increasingly important to ensure that each component conforms to specifications. For this reason, the need for in-situ monitoring systems has increased in order to optimize manufacturing time and minimize generated scrap for companies to remain competitive in industry. Current in-situ roughness monitoring systems, such as optical methods, are limited by the harsl: environments in which these systems are required to operate and the requirement for highly reflective materials. Accordingly, the need to develop a more robust system is required. The objective of this work was to develop and test a noncontact surface roughness characterization system which can be implemented into a machining center in order to provide in-situ measurements where currently available methods are rendered inappropriate. Through the use of a pneumatic technique, a non-contact surface assessment tool has been developed and tested for use in a machining center. The development began offline for characterization of surfaces created by different machining operations and was then introduced in to a turning center for in-situ evaluation. The developed system is capable of distinguishing surfaces created from different machining operations with the same Ra values, characterize milled and turned surfaces down to R^a values of 0.8 μm that are comparable with stylus measurements, impervious to external influences on the measurement process such as cutting fluid, capable of characterizing moving surfaces with surface speeds up to 100 m/min, provides surface characterization around the entire workpiece instead of along a single line, and can be operated in-process to monitor the entire workpiece or be used to make spot checks for important surface features. The developed system is capable of providing a method for in-situ monitoring of machined surfaces where currently available techniques fall short. The limitations caused by the harsh environment in which these in-situ monitoring devices operate and the limitations of workpiece materials have been eliminated and the developed system has been proven to provide results comparable to stylus measurements that are the industrial standard. This work is the basis for the development of a non-contact, in-situ surface roughness assessment tool. Limitations of the current device are also presented. Further research and development avenues are identified to expand the operating envelope of the developed pneumatic system.