Page 11 - Industrial Technology EXTRA - 22nd June 2020

not necessarily the same thing, the motion of both the likelihood of communication jitters that could
is typically controlled by a CNC system. The reason desynchronise PLC- and CNC-based processes on
for this lies in the simplicity of programming motion the same machine.
control trajectories with computer numerical
controllers and their G-Code language. A holistic approach
This programming language is distinct because To address these issues, factory automation
it instructs machines on where and how to move component and system manufacturers are
based on computer-aided design/manufacturing beginning to invest in motion control technologies
(CAD/CAM) images and files. G-code reads that cross the boundaries between PLCs and CNC
CAD/CAM files for the intended end products and systems to create integrated machine controllers
converts them into trajectories and directions for that combine key functions from both solutions.
CNC servo drives within the cartesian coordinate A good example is Mitsubishi Electric's MELSEC
robot. As a result, highly accurate, precise and iQ-R motion controller and its G-Code add-on
reproducible movements can create even the most library. By choosing this solution, machine builders
complicated and unusual 2D shapes and contours. can use general-purpose servos and MELSEC iQ-R
While CNC solutions work well as robot series PLCs to implement CNC capabilities, if
controllers, they cannot monitor and guide other needed, by installing the G-Code library. This allows
components, such as solenoid valves, clamps and the programming of highly accurate complex cutting
air hoses – to do so, the unit needs a PLC. This trajectories and profiles in G-Code without the need
could theoretically handle tight tool control and for computer numerical controllers.
feedback for all the different automation parts, More precisely, the add-on function helps the
eliminating the need for CNC systems. However, system to follow PLC-specific programming
writing motion control code for cartesian coordinate instructions, such as Motion SFCs (sequential
robots with any of the five PLC languages would be function charts), as well as automatically generate
quite challenging. Consequently, machine builders and read motion profiles from CAD/CAM files. The
and users need to use these two different control G-Code programmes, available in text format, can
systems for one machine. be edited easily on Mitsubishi Electric's HMIs or
This solution is however far from ideal: with any generic editor.
additional hardware will only increase the total cost By eliminating the need for separate PLC and
of ownership for the machine and can also affect CNC component hardware, the MELSEC iQ-R
build / commissioning time. In fact, two separate system can synchronise the different processes
control units need to share time-critical information, within one machine and reduce cycle times.
thus increasing potential cycle times and increasing Furthermore, the possibility to use one single
solution for various applications, including CNC
machining and easily switch between them allows
machine builders to use it to control a complete
production line. As a result, businesses can benefit
from a highly flexible, fast and cost-effective system
that truly streamlines their industrial processes
whilst delivering quality and consistency.
gb3a.mitsubishielectric.com

June 2020 • INDUSTRIAL TECHNOLOGY EXTRA! • p11