8, 1998 Design News
SPECIAL MEDICAL ISSUE
From the regional editors
Steerable forceps make sinus surgery
CAD and SLA help engineers
simplify design and cut costs
John Lewis, Northeast Technical Editor
access the frontal or maxillary sinuses, surgeons navigate
through the patient's nostril with various instruments.
Depending on the sinus' location, getting in there can
be difficult and time consuming for the doctor, and
may result in tissue trauma to the patient. These challenges
led Thomas Davison, Endius Inc.'s president and CEO
and his staff, to develop steerable instruments for
use in sinus surgery.
"It's like the sinuses are rooms off of a long
hallway. You have to make sure you go through the right
doors to get where you want to go," Davison explains.
Endius' initial prototype-design had approximately 50
parts, and cost about $2,000 to build. Endius turned
to Product Genesis Inc., an engineering design and product
development firm with expertise in industrial design
and general engineering, to "productize" the
Using CAD and SLA, Product Genesis reduced the 50-component
prototype to less than ten parts, and cut the cost from
thousands to only a few dollars per device. The devices'
Faster, easier access to the surgical site
According to Chris Zirps, vice president of technical
development for Product Genesis, "We had to take
a step back from the prototype and ask ourselves if
there was an easier way to accomplish the same thing."
The main challenge was reducing cost. Going to injection
molding and simplifying design made the device as manufacturable
as possible. "In the end, we came up with something
far simpler than Endius had in mind."
"We eliminated all the adjustment devices inside
the handle, and simplified it to a three-piece assembly,"
Zirps explains. A trigger with integral spring controls
the opening and closing of the jaw, and a thumb-controlled
capstan with a plastic spring around it, controls the
radius of curvature at the tip.
"While the basic structure of the vertebrae was
pretty good," recalls Zirps, "each piece probably
cost on the order of $100 to make. Injection-molding
technology let us reduce total cost to less than 70
cents." The other big challenge was to figure out
how to design disposable jaws. These jaws make up most
of the total cost. The key to reducing cost was coming
up with a scheme to simplify the jaw-hinge joint as
much as possible. "We use a piece of nitinol wire,
soldered to the pivoting jaw to avoid a clevis and extra
hinge pin," explains Zirps.
PTC's ProEngineer was used throughout the process.
"It helped a great deal in getting to the new pre-production
prototype. We relied on SLA models, early in the design,
to make sure everything fit together. Then we went to
CNC-machined parts that were used in the clinical testing."
The machined versions were very close to the real thing.
"We took the feedback from the clinicals, and once
the design changes were approved by Endius, we went
directly to molding. Pro-E is a good tool to transfer
the information to the mold maker," Zirps adds.
When choosing an outside design firm, Davison says,
he looks at their track record for predicting costs
and the length of time the project will take. "Product
Genesis' people told us they could do it for a certain
cost and in this amount of time. We knew that for us
to do the same would take three times as long and three
times as much money," Davison explains.
According to Brian Vogel, senior vice president at
Product Genesis, "Our role included visits to vendors
and the selection of vendors, which we did together
with Endius. Later, our engineers made sure the tooling
was done properly. We worked together with the other
outside resources to make sure that we got the right
parts on time, and that they went together properly.
We also had an engineer at Endius' facility the day
the first production unit was assembled. We have learned
that if you manage the schedule, the hours and the dollars
will take care of themselves. But if you simply measure
the hours and the dollars and don't take care of the
schedule, you'll get burned."
Additional details?Contact Thomas
Davison, Endius Inc., 23 West Bacon St., Plainville,
MA 02762; (978) 695-0983