17-03-2014, 09:40 PM
Abstract
Nowadays, reverse engineering has been used more
often for inspection and manufacturing in industry, such
as the freeform part widely used in the engineering areas
of automotives, aerospace and shipbuilding. However,
due to the entire process is complicated and largely
human intervened, the efficiency is low and the cost is
very high. In this research, we propose a robotic 3D
scanning system for parts having freeform surfaces that
significantly reduce the time. Two scanning modes are
designed for measuring different kinds of part
automatically in this system. The scan plan and the robot
scan program are also described. The system can be
integrated in mechanical machining. An industrial
application is presented.
1. Introduction
Reverse engineering (RE) is an efficient approach to
significantly model the product and reduces the product
development cycle [1-3]. Currently, the coordinate
measuring machine (CMM) and the three-dimensional
(3D) laser scanner are widely used in the fields for shape
reverse engineering and quality inspection [4]. The typical
CMM has a trigger probe, it acquires point data by
touching the probe to the part which is called contact
type. However, it cannot measure part made of soft
materials and part with complicated shape. Furthermore,
using CMM to digitalize the part, the measuring speed is
low and the amount of the acquired point data is small.
For this purpose, an alternative approach is represented by
the non-contact digitization of surfaces based on optical
techniques, which is much more efficient in terms of
speed and reduces the human labor required [5]. With the
accuracy of the laser scanner improved more recently,
laser scanners are adopted widely for many applications
in industry.
In recent years, a large amount of work has been
performed to develop systems for reverse engineering of
complicated and freeform part using laser scanner. Son
developed an automated laser scanning system for reverse
engineering and inspection but it is under the assumptions
of the CAD model of the part is known [4]. Carbone
developed a scanning system of combination of a vision
system and a coordinate measuring machine for the
reverse engineering of freeform surfaces [5]. Chen
proposed a vision-aided reverse engineering system to
reconstruct freeform surfaces [6]. Valkenburg used a
structured light system for accurate 3D measurement [7].
Xie developed a multi-probe system of integrated a
structured-light sensor and a trigger probe with a
coordinate measuring machine (CMM) for complete 3D
measurement of complicated and freeform surfaces in
reverse engineering [8]. All the systems mentioned above
are for the purpose of reducing human intervention and
improving the level of automation of the scanning process
and they are not considered about integrating with the
machining system. Due to apply industrial robot holding
the part, the system proposed in this paper could not only
perform the automated scanning work but also integrated
the system in machining directly.
In this research, a robotic scanning system is
developed. The system mainly consists of a laser scanner
mounted on fixed position and an industrial robot that can
provide proper location and orientation for measurement.
Rotation mode and Four-view mode are designed for
measuring freeform parts with different characteristic.
The system can automatically scan the part using the scan
plan. The scanned point data could be registered in one
coordinate system automatically to shorten the cycle time
of modeling. The reconstructed CAD model could be
used in mechanical machining integrated with the
industrial robot, such as the robotic turbine blade grinding
system.