Small is the new BIG
Newport Motion Solutions for Laser Micromachining
IDL Linear Motor Stage
is, therefore, entirely contained within the water jet as a cylindrical
beam, similar in principle to an optical fiber.
The LMJ process works in two stages. The energy of the laser
pulses vaporizes the workpiece material by heating while the water
cools and cleans the surface in the interval between the pulses.
Through a scanning process, a trench is formed that becomes
deeper with each pass.
In contrast to traditional dry lasers, the LMJ wet laser technology
cuts with a parallel beam, with a working distance that can extend
up to several centimeters (FIGURE 2).
This is not the case with conventional lasers, where the focused
laser beam has a limited working range of just a few millimeters
from beam divergence. The beam converges at a focal point and
then diverges, so a focus distance control is required and the working distance is short.
The LMJ process offers several advantages. There is no need for
focal adjustment, which enables parallel kerf sides. There is minimum HAZ, thanks to the cooling effect of the water. Finally, there
is a high removal rate with debris washed from the kerf.
The water jet eliminates the complexity and process variations of
maintaining the laser in focus typically associated with dry laser
systems. Using water to guide the laser to the workpiece yields
Water guides the laser. The application becomes insensitive to
the focal plane of the laser. A cylindrical laser beam is created,
resulting in perfectly parallel walls and tight kerf widths. It also
enables the user to cut thick or non-flat parts without having to
worry about being in focus.
Water cools the material. Heat is generated during laser ablation. When using a conventional dry laser system, the surrounding
material absorbs a lot of laser energy, creating an unwanted HAZ.
With LMJ, much of the heat dissipates into the water, so there is
little HAZ on the workpiece. Stress-induced conditions such as
micro-cracking, oxidation, thermal damage, or deformation are
Water cleans the surface. When using a conventional dry
laser, a portion of a laser-ablated material tends to redeposit
and solidify, creating unwanted slag. With LMJ, the water dis-
places that material before it solidifies, translating into much
cleaner entrance, wall, and exit surfaces without particle deposition or burrs.
Diffuser hole geometries
Film cooling in all of its various formats has become a mainstay of
turbine cooling technology. The primary focus of most research
has been on the use of discrete holes, or rows of holes, on the
hot gas path surfaces of the turbine, as seen in the vane and
blades (FIGURE 3).