0.01– ~20mm (thickness)
Laser guided by
total internal refection
5 – 50mm
50 – 800bar
20 – 400 W
WATER-JET LASER GUIDANCE
TECHNOLOGY MINIMIZES HEAT DAMAGE TO PARTS
Laser technologies are enabling the design and manufacture of higher-performance gas turbine engines. As aerospace manufacturers strive to improve engine effciency
and reduce fuel consumption, they are redesigning turbine
components and developing new materials to withstand
ever-higher temperatures. When compared to using traditional dry lasers in machining such materials, Synova’s
Laser MicroJet (LMJ) technology features a water jet-guided laser to reduce heat-affected zones.
The Laser MicroJet
When officials with GE Aviation and GE Power talk about big investments in new technol- ogy, they prefer describing it as a calculated but necessary
risk. GE Aviation, an operating unit of GE, has an industrial backlog of more than $150 billion. This translates into
more than 15,000 jet engines, most of which will be supplied to Airbus and Boeing. As a result, jet engine developers are looking into improved designs and new materials for improving performance.
Increasingly, laser technologies are overcoming the
limitations of conventional machining in processing turbine components. For example, lasers can pierce through
thermal coatings to drill holes in turbine parts. Using electronic discharge machining (EDM), coolant holes have
to be drilled prior to the application of thermal coatings,
resulting in additional operations. While lasers are suited
for machining extremely hard materials, the heat generated by a laser beam may have undesirable side effects.
For aerospace turbine parts, metallurgical quality is
important. Two effects caused by laser heat can impact
the life cycle of an engine component:
Recast layer, which is formed by molten material that
adheres to the part during machining, and
Laser technologies are best suited for machining such
ultra-hard materials. Synova’s Laser MicroJet (LMJ) pro-
cess is capable of precision laser machining without any
heat damage from a high-power laser beam (SIDEBAR). In
the LMJ system, a laser beam, passing through a pres-
surized water chamber, is focused into a nozzle.
The low-pressure water jet emitted from the nozzle guides the
laser beam by means of total internal reflection at the water/air interface. The water-jet diameter is usually between 30 and 80µm, and
the laser power required is between 10 and 200W. While the principle looks simple, years of experimentation and optimization were
required to fine-tune the process.
The technology behind LMJ is based on creating a laser beam
that is completely reflected at the air-water interface, using the difference in the refractive indices of air and water (FIGURE 1). The laser