A Non-Contact Measuring System for In-Situ Surface Characterization Based on Laser Confocal Microscopy.

Shaowei Fu,Fang Cheng,David Butler,Tegoeh Tjahjowidodo,Yu Zhou

doi:10.3390/s18082657

Abstract

The characterization of surface topographic features on a component is typically quantified using two-dimensional roughness descriptors which are captured by off-line desktop instruments. Ideally any measurement system should be integrated into the manufacturing process to provide in-situ measurement and real-time feedback. A non-contact in-situ surface topography measuring system is proposed in this paper. The proposed system utilizes a laser confocal sensor in both lateral and vertical scanning modes to measure the height of the target features. The roughness parameters are calculated in the developed data processing software according to ISO 4287. To reduce the inherent disadvantage of confocal microscopy, e.g., scattering noise at steep angles and background noise from specular reflection from the optical elements, the developed system has been calibrated and a linear correction factor has been applied in this study. A particular challenge identified for this work is the in-situ measurement of features generated by a robotized surface finishing system. The proposed system was integrated onto a robotic arm with the measuring distance and angle adjusted during measurement based on a CAD model of the component in question. Experimental data confirms the capability of this system to measure the surface roughness within the Ra range of 0.2–7 μm (bandwidth λc/λs of 300), with a relative accuracy of 5%.

Highlights

Surface topography measurements play an important role in product quality assessment for manufacturing process evaluation
We propose a non-contact in-situ surface topography measuring system and the paper is organized as follows: Section 2 compares stylus-based and confocal-based methods for surface roughness measurement
The objective of this study is to explore roughness measurement technology which can be used in the manufacturing environment instead of the measurement technology which can be used in the manufacturing environment instead of the traditional desktop measurement in laboratories

Summary

Introduction

Surface topography measurements play an important role in product quality assessment for manufacturing process evaluation. In most applications, compared to contour measurements, surface topography measurements require higher resolution and accuracy [1,2], and the process typically relies on laboratory equipment. This makes an in-situ surface topography measurement and roughness analysis [3,4] very challenging as it has to meet the compactness and robustness requirements, especially in a relatively harsh manufacturing environment. Contact measurement is limited to a relatively low measurement speed (

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