22 Industrial Laser Solutions JANUARY/FEBRUARY 2017 www.industrial-lasers.com
application report
remove tiny specks of material with no thermal damage at extraordinary speeds, making new GDI spray hole designs possible.
Machining at the speed of light not only
promised to enable injector designs to
be cost-effectively machined, it was also
hoped that the process could remove
one of the most expensive and time-consuming challenges in a precision manu-
facturing process—post-processing to
remove defects.
“Energy efficiency is expected to
increase by 20–25% and cycle time could
decrease substantially,” the DOE wrote.
“No consumables are required, which
reduces materials costs and energy asso-
ciated with their production. In addition,
this process will eliminate post-produc-
tion and its associated chemicals use. This
technology could have broad impacts in
diverse manufacturing sectors.”
Traditional methods
The legacy technology used for fuel injector
machining was electric discharge machining (EDM), which works by eroding material in the path of electrical discharges that
form an arc between an electrode and a
tool. The existing manufacturing process,
electromechanical discharge machining,
was slow, expensive, and involved the use
of multiple chemicals to drill the holes and
to remove the defects from melting, burr-
ing, and recast that come from the heat
involved in the process.
“Traditional machining platforms are
poorly suited to produce small parts with
high accuracy requirements,” the DOE said.
“The current machining methods are often
too large, too inflexible, and lack the necessary precision to manufacture parts with
complex shapes or micron-sized features.”
Success factors
GDI spray nozzles are about 200µm in
diameter, about the same diameter as a
human hair. Edge quality, surface quality,
circularity, and taper are among the dimensions that, when properly controlled, can
deliver more combustion with less fuel.
Another challenge faced by automakers
was the ability to control the part during the
manufacturing process. The laser would
only be as precise as the motion control system used, and creating a reliable,
repeatable machine capable of micron-
level accuracy represented a major mile-
stone. “Combining a laser with high-pre-
cision manipulators would automate and
therefore expedite the machining process,”
the DOE said.
The solution
The companies sponsored by the DOE to
create a new manufacturing process for fuel
injectors included Microlution (Chicago,
IL), which builds micromachining platforms
optimized for high-precision applications
for a rapidly miniaturizing world.
Microlution built a micromachining
workstation with an integrated UFP laser
(FIGURE 3). The workstation was tasked to
control the control part movement very
precisely (to ensure micro-scale accu-
racy). Furthermore, the system was to
fully integrate the control of three key
technologies: 1) the machine motion, 2)
the UFP laser, and 3) an advanced 5D
scanner. Not only would the platform
need to control the blank fuel injector
part, it would also need to ensure stability that would not disturb a historically
very delicate laser beam in a production
manufacturing environment. Thermal
and inertial stability were big keys to
achieving high process capability index
(CPk) production standards over days,
months, and years.
Successful results
Fast-forward to 2015 and the DOE issued a
report on the project, stating that the team
“has successfully adopted the technology
to make GDI injectors.” The DOE reported
on the following program goals:
• Developed an integrated laser and scan
head that meets target rotational speed
that exceeds 200Hz at an attack angle
above 80% (completed);
• Demonstrated drilling of fuel injector
spray holes in <8s and an overall 50%
cycle time reduction in machine time,
with no degradation in quality com-
pared to existing micromachining processes (completed);
• Increased laser machining efficiency by
20–25% compared to standard micromachining processes (completed); and
• Produced fuel injectors that pass cold
start engine tests and move technology
