subcon scene focus
Multi-axis laser technology soars to new heights as subcomponents are more tightly
integrated into highly productive systems: an update of the last 10 years.
By Terry L VanderWert and Michael D Polad
Anything’s possible
Automotive prototype
parts are produced quickly
with laser, eliminating hand
tools. Typical laser
processed parts include
formed metal seat backs,
seat frames, transmission
parts, gas tank baffles,
engine cover plates and
radiator components.
Materials are typically mild
steel and aluminum.
MULTI-axis laser technology has become significant
in the manufacture of the next generation of commercial
aircraft. Critical components such as turbine engine
blades, nozzle guide vanes, shrouds, combustors, and even
air frames are increasingly dependent on this capability,
affecting manufacturing speed, quality and part costs.
In fact the technology has become important for many
product categories, from automotive prototyping to
medical components;and over the last decade an everincreasing
number of products have been designed to
reflect the benefits of laser processing. Previously,
applications tended to arise as lasers were demonstrated to
be more cost effective than established processes.
The most striking change in multi-axis laser system
technology has been in the degree of integration of
subsystems. Today’s systems have evolved from a
collection of individual components - laser, CNC, motion
devices, motors, etc.-into truly integrated machine tools
with components working together and optimised based
on an overall system perspective. One sees tight
integration of the laser, motion system, control, user
interface, sensors, CAD/CAM programming software,
etc, all based on more advanced process knowledge and
capability. For example, motion parameters are optimised
for the components being processed, capability
(processing speeds) of the laser source, and ability of
process and workpiece sensors to adaptively correct for
part-to-part variations. The result is multi-axis laser
systems that yield more consistent output.
Reflecting on the last 10 years, the workhorses of
94 MWP november 2007
industrial laser processing continue to be the flashlamp
pumped pulsed Nd:YAG, CW Nd:YAG, and CO2 lasers.
Integration of beam conditioning optics (eg beam
expanding/reducing telescopes) has provided the basis for
process improvements in laser drilling. With the ability to
change the size of the beam before it is focused, one can
change the focused spot size and therefore hole diameter,
while maintaining the advantages of drilling at focus.
There is much discussion in technical literature and at
conferences about new laser types, such as ultrashort
(picosecond, femtosecond) pulse length lasers and Ybdoped
fiber and disk lasers. These are in various stages of
development and evaluation. Those which demonstrate
reliability and performance in industrial processing may
become significant within the next few years.
Integration of sensors and software
Improved process control has accompanied integration of
sensors and software that provide capability for fully
integrated laser beam focus control. Laserdyne Systems
holds several patents for these system designs. Modern
multi-axis systems include one or more of these
workpiece/fixture sensors - typically capacitive or optical
and used to measure and automatically control the
distance between the laser processing beam and the work
piece.
In the past, automatic focus controls often used a small
motor to move the cutting/drilling nozzle directly,
thereby always moving the focusing lens parallel to the
laser cutting beam. However, in applications requiring
drilling holes at shallow angles to a surface (such as
aerospace turbine engine combustors) it’s better to move
the nozzle in other directions to maintain the correct hole
location. Today’s fully integrated multi-axis laser system
moves the nozzle by moving the main system axes,
allowing the user to specify any direction desired for the
motion.
More recent addition of a laser-based sensor (Optical
Focus Control/OFC) has addressed limitations of
capacitance sensing to ‘side sense’ or to also detect surfaces
of the part adjacent to the one being processed. OFC also
avoids errors that occur with debris buildup on the assist
gas nozzle and is applicable to surfaces that are not
electrically conductive. With OFC comes capability to
measure or map the run-out (actual vs design shape) at
several levels on a ceramic coated cylindrical part while
the part is moved in front of the OFC sensor, storing that
data to control the laser beam position when the part is
processed. Mapping of run-out can occur in two
directions with both sets of data then applied
simultaneously during processing.
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