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ORIGINAL ARTICLE
Reconfigurable robotic machining system controlled
and programmed in a machine tool manner
Dragan Milutinovic &Milos Glavonjic &
Nikola Slavkovic &Zoran Dimic &Sasa Zivanovic &
Branko Kokotovic &Ljubodrag Tanovic
Received: 11 March 2010 / Accepted: 5 August 2010 / Published online: 10 September 2010
#Springer-Verlag London Limited 2010
Abstract Industrial robots represent a promising cost-
effective and flexible alternative for some machining
applications. This paper describes the concept of reconfig-
urable robot multi-axis machining systems for machining
the complex parts of light materials with lower tolerances
having freeform surfaces. For the basic configuration of a
five-axis robotic machining system, the robot modeling
approach is shown in detail as well as the prototype of
developed control system with programming in G-code.
The experimental robotic machining system has been
verified by successful machining of several test work
pieces.
Keywords Robotic machining .Robot modeling .Control
and programming system
1 Introduction
Over the last four decades, industrial robots were used to
realize many industrial tasks like material handling, welding,
assembly, spray painting, and auxiliary machining tasks, such
as de-burring, polishing, grinding, etc. However, only 3% to
4% of the overall number of industrial robots is used for
machining [1,2]. Compared to machine tools, industrial
robots are cheaper and more flexible with potentially larger
work space.
This is why researchers, robot, and CAD/CAM software
manufactures as well as people from machining shops are
enthusiastic to replace machine tools by robots for certain
multi-axis milling applications. These include milling
materials, such as clay, foam, wax, etc. for new product
design, styling, and rapid prototyping projects [3–8].
Machining of work pieces of traditional materials, such as
wood, stone, aluminum, etc. in which dimensional toler-
ances are low or even middle also produce satisfactory
results [1,9,10].
It is widely recognized that poor accuracy, stiffness, and
complexity of programming are the most important limiting
factors for wider adoption of robotic machining in machine
shops. Quite a lot of research in the field of robotic machining
has been done to analyze the robot structure and to increase
accuracy. The major fields of interest for robotic machining
can be subdivided into kinematic, calibration, control,
programming, and process development [2,4,9,11,12].
Also, the leading world robot manufactures are developing
robotic arms specifically designed for robotic machining
application [13]. The reason for the complexity of robot
programming in machining application is in that each robot
manufacturer uses, for the most part, its own proprietary
robot programming language, because no industry standard
exists. This fact was a strong motivation for both researchers
and leading world robot and CAD/CAM software manufac-
tures to develop versatile software solutions, such as G-code
translators, specific postprocessor solutions, etc. to make the
robot programming close to the programming efficiency of
CNC machine tools [12,13].
In order to contribute to efficient use of robots for
machining applications, the reconfigurable robotic machin-
ing system controlled and programmed in machine tool
D. Milutinovic :M. Glavonjic (*):N. Slavkovic :
S. Zivanovic :B. Kokotovic :L. Tanovic
Mechanical Engineering Faculty, University of Belgrade,
Kraljice Marije 16,
11120 Belgrade, Serbia
e-mail: mglavonjic@mas.bg.ac.rs
Z. Dimic
Lola Institute,
Belgrade, Serbia
Int J Adv Manuf Technol (2011) 53:1217–1229
DOI 10.1007/s00170-010-2888-8
manner is proposed [14]. This paper describes the concept
of reconfigurable robot multi-axis machining systems for
machining the complex parts of light materials with lower
tolerances, having freeform surfaces. For the basic config-
uration of a five-axis robotic machining system, the robot
modeling approach is shown in detail as well as the
prototype of developed control system with programming
in G-code. Finally, several test work pieces were machined
to demonstrate the effectiveness of experimental robotic
machining system.
2 The concept of reconfigurable robot based multi-axis
machining system
The planned reconfigurable robot-based multi-axis machin-
ing system should provide rapid machining of larger-sized
complex parts of light materials, with lower tolerances and
with freeform surfaces generated by available CAD/CAM
systems and reverse engineering methods.
The concept underlying the reconfigurable robot-based
multi-axis machining system [14] (Fig. 1), presented briefly
in this paper, is based on:
▪The development of a specialized five-axis vertical
articulated robot (Fig. 1a): larger workspace, higher
payload, and stiffness, with integrated motor spindle,
similar to [9](http://www.staubli.com/en/robotics/
robot-solution-application/high-speed-machining-
robot/). Due to its advantages in respect of stiffness [1]
and singularities [16], such a robot would operate as a
vertical five-axis milling machine (X, Y, Z, A, B)
spindle-tilting type [15].
▪The possibilities of reconfiguring the system by
applying the modular system of additional rotation
and translation axes (Fig. 1b and c).
▪Open architecture control based, at this stage, on PC
real-time Linux platform and Enhanced Machine
Control (EMC2) software system (http://www.isd.mel.
nist.gov/projects/rcslib/,http://www.linuxcnc.org/).
▪The possibilities of programming a robot as a vertical
five-axis milling machine in G-code.
▪The possibilities of using the existing CAD/CAM
systems with implemented three- to five-axis machin-
ing for vertical milling machines (X, Y, Z, A, B)
spindle-tilting type.
▪Virtual robotic machining system configured in object-
oriented programming language Python implemented
in the control system for program simulation and
verification.
As noticeable, the basic goal of the planned system,
partially presented in this paper, is to be directly applicable
in machine shops by personnel experienced in CNC
technology and programming in G-code that is still very
widespread in industry [17].
To verify the concept and for the development of control
and programming system, a standardized six-axis vertical
articulated robot (with payload of 50 kg; Fig. 2) was used
as a testbed, in the way that the axis number 6 was blocked.
Fig. 1 a–cConceptual model of reconfigurable robot-based multi-
axis machining system
1218 Int J Adv Manuf Technol (2011) 53:1217–1229
