processing materials and processes needed for fiber
With its minimal heat input, the femtosecond
laser is suitable for cutting small features in small
parts with good edge quality and feature definition.
Figure 3 shows some examples of femtosecond
The majority of stents and tubing are metal. However, Food and Drug Administration-approved polymer stents and scaffolds are now on the market,
which can be cut only with a femtosecond laser. The
fiber laser does not absorb well enough in the polymer to make quality cuts. The femtosecond laser
has such great photon density that it is absorbed by
the polymer material through a process known as
multiphoton absorption, which makes cutting possible. This cutting can be further enhanced by using
a green wavelength over 1 micron, which provides
better cut quality, faster speeds, and a larger processing window.
Software, Controllers, and Mechanicals. New
digital motion controllers and improved system acceleration enable manufacturers to follow the programmed tooling path with fewer errors and at fast
speeds. In most tube cutting applications, the limiting factor for cycle time is the motion, specifically
the rotary axes, and so mechanicals and controller
performance improvements are a key part of maximizing production.
As part of day-to-day operation, the interaction of
the operator with the control software can optimize
efficiency in setup and process monitoring. The
use of large-screen monitors has facilitated single-screen, operator-oriented interfaces.
In addition, inline sensors, gauges, digital flow-meters, and valves can report on the status of all
process-critical parameters, including assist gas
pressure, water flow, and pressure. Not only are
these vital process conditions monitored, but values also can be set with alarms and error states for
low levels to avoid wasted material stock, equipment damage, and downtime.
Water System. In many legacy laser designs, the
water system was a weak point, requiring constant
attention and maintenance to keep the machine
running. Such issues as small water tank sizes,
pumps with short lifespans, and lack of internal
flow monitoring contributed to systems that could
be looked upon as somewhat unreliable. Compounding these issues was the fact that it was often
difficult to change the water filters.
Today newer systems have a 10-gallon tank size,
four-level debris filtering, intelligent programmable
flow valves, multiple solenoid switches to prevent
large water leaks, and drawer-mounted hardware
that enables filter changing in seconds. The user
interface gives the operator all the necessary information, along with precutting safeguards and go/
no-go limits, to ensure that all is well.
Automated Tube Loaders. The standard stent
and tube cutter is loaded manually with tubing
that is typically up to 3 meters long. The cutter then
cuts parts and advances the tube according to the
program. When most of a tube has been cut, the re-
mainder is removed and a new tube is loaded.
With more pressure to improve productivity and
minimize labor costs, many manufacturers are now
using automated tube loaders to feed the laser cutting machine. While it is not recommended that
these machines be operated in a “lights-out” mode,
they can be helpful in reducing labor allocated to
Open-architecture System Design
A key part of any system is making the hardware
usable for the operator every day. One feature that
helps to accomplish this is composite over granite
for better vibration damping. Because the com-
posite has a uniform internal structure, it can be
mechanically modeled and optimized for vibration
isolation, load-bearing capacity, and deflection un-
der load. These features enable a cantilever arm to
support the focus optics and movement across the
axes. As a result, this type of machine has an open
design, and the operator can access the work area
easily (see Figure 4).
Better Technology, Better Parts
The design and cutting performance of the latest-generation stent and tube cutting systems offer
significant advantages and capability over legacy
machines. Fabricators that take advantage of these
technology advances can look forward to increased
productivity with these newer user-friendly and reliable tools.
Geoff Shannon is manager, advanced technology,
Amada Miyachi America and David Van de Wall is
manager, Amada Miyachi Europe, 626-303-5676,
An operator can easily access the work area of this laser tube cutting machine. Pullout drawers that help to make
changing water filters very straightforward are an example of the equipment features that support ease of maintenance.
A femtosecond laser was used to cut these fine features. Pictured (from left to right) are a 50-micron slot in 250-mi-
cro-OD nitinol tubing; 50-micron relief holes for flexible tubing; and a nitinol stent that has received only an ultrasonic bath cleaning.