Laser scanning and CAD conversion accuracy correction of a highly curved engineering component using a precision tactile measuring system

¹ Qcontrol, GR 17675, Athens, Greece
² International Hellenic University, 14km Thessaloniki - N. Moudania, Thermi GR57001, Greece
³ National Technical University of Athens, School of Mechanical Engineering, Athens, GR15780, Greece
⁴ Western Macedonia University of Applied Sciences, Department of Mechanical Engineering and Industrial Design, Kila Kozani GR50100, Greece

^* Corresponding author: d.tzetzis@ihu.edu.gr

Abstract

Impellers are used in various mechanical applications and they usually operate under severe conditions. Very often a replacement of an impeller is required after certain operation hours due to material failure. Since it is a critical and expensive spare part, accurate manufacturing, following the design requirements of the part, is necessary. In order to avoid any dimensional manufacturing defects, quality control procedures are used based on reverse engineering. The aim of the current paper was to evaluate the overall accuracy of the reverse engineering procedure, when a laser scanner is used for digital data capturing. The specified accuracy of the laser scanner was of ±0.084mm and the scanned data were converted to a Computer Aided Design (CAD) file using commercial design software. In order to assess the accuracy of the laser scanning and the CAD conversion procedure, a highly accurate coordinate measuring machine was used with a touch trigger probe and specified accuracy of ±0.006 mm. The results have shown that the deviation produced by the laser scanning and the associated reverse engineering methodology was up to 1mm, mostly observed at the edges of the freeform surfaces. It was concluded that such large deviations are caused from the inaccuracy of the laser scanner, possible errors created by the mesh – polygonal model creation, but most importantly from the errors when creating the B-splines.