Transcript Assembly, Alignment, and Maintenance of an Automated Laser Cutter

Assembly, Alignment, and Maintenance of an Automated Laser Cutter
Zhenghao Ding, Lunjun, Gabriel Spalding*
Physics Department, Illinois Wesleyan University
Background
Laser cutters allow for computer-aided design and fabrication of
complex mechanical, optical, and electrical systems. Although we
currently have a variety of fabrication facilities on campus, including
metal working lathes and milling machines, traditional machine shops
to not offer the same degree of ease and safety as laser cutters and
3D printers, which we believe will greatly expand the number of
students and faculty members engaged in design work on our campus.
Initial Results
We have assembled a kit for an automated laser cutter system, intended to play an important role
in a wide variety of student-led design projects on our campus. We began by electrically soldering
the wiring for the laser, and assembled all peripheral system (pulsed gas and water cooling). We
then aligned the (invisible) laser beam for accurate delivery with minimal optical aberration, and
completed the fabrication of test patterns (such as the Aztec calendar shown below), thereby
demonstrating successful computer automated laser cutting.
How does a laser cutter cut?
It is as if an invisible blade were cutting through the target material.
We use a powerful (60 Watt), pulsed infrared (10.6µm wavelength)
CO2 laser beam. Focusing such a laser beam yields a super-high
energy density, so when this beam is focused onto the surface of a
target material it can do something much more complex than merely
melt the material at that spot: instead, it can thermally induce
shockwaves that locally ablate a wide range of (non-reflective)
materials, throwing off a complex mix of matter.
How do you align an invisible laser beam optical system?
Given the high powers involved, careful alignment this invisible laser was required,
in part to ensure that the beam is safely contained while traversing a sequence of
three mirrors, some of which are mounted to movable armatures controlled by
computerized stepping motors, before redirection into an objective lens, which
focuses the beam to enormous energy densities on the surface of the target
material. Misalignment of the beam as it enters this final optical element results in
significant aberration of the focal spot, diminishing the effectiveness and speed of
the laser cutter, as well as the quality and resolution of the resulting cut
Mirror
Mirror
Peripheral Systems
Because any matter ejected during ablation has the potential to scatter the
incident laser, before each rapid pulse we supply a strong stream of
compressed air to clear the region above the target of vapor and debris.
When operating, the laser tube itself generates significant heat, so we also
assembled the required water-cooling system.
We also worked with the IWU Physical Plant to ensure that adequate
ventilation maintains a safe environment.
We can not use the photoelectric effect to visualize infrared light. However, we can
use thermally sensitive materials (such as a piece of paper) as a movable imaging
screen to aid in mapping out the path of the beam. After sending a pulse from the
tube, a burn mark on the imaging screen reveals the position of the laser beam,
allowing us to adjust the angle of each mirrors until full alignment is achieved.
Ideally, this alignment should be sustained as the motorized armatures rapidly
redirect the beam to different regions of the material to be optically etched or cut.
As an initial demonstration of the quality of our alignment, we successfully carved
test patterns (such as the one shown above) onto wood or plastic.
How can you utilize the laser cutter to fabricate your designs?
The laser cutter is connected to a computer, which has design software installed for driving the laser cutter.
To a user, the process is transparent: you can download pictures from any source, paste them into the
software and carve out these patterns with the laser cutter. However, we wish particularly promote coming
up with your own original designs, using any form of computer-aided design or drawing software. If you can
design it, then it is a simple matter to order the machine to cut or etch it!