Stereolithography and the Internet – DePuy Speeds Down the Information Highway
The Challenge
Through the use of modern technology, DePuy has developed a better way to manage available resources. Combining stereolithography and the Internet, DePuy
operates a global, three-dimensional fax machine, transferring files rapidly and accurately.
Only moments before his flight left from Manchester, England, to Chicago, Illinois, the
bio-engineer received a request for a modified reamer, a device used to drill a hole in a patient's
bone so that an implant could be attached. He needed a stereolithography (SL) model to show
a surgeon the next day.
What to do? His solution was to model the reamer in Leeds and request that a copy of the
modeling file be transferred over the Internet to a sister company in Warsaw, Indiana. As the
engineer flew over the Atlantic, the file was already being transmitted and the stereolithography
apparatus (SLA) put into action. When he arrived in Warsaw, waiting for the engineer was a
model of the reamer exactly like the one he had modeled in Leeds. The American company had
built the model in just a few hours on its SLA system.
Routine Procedure
Transferring SL files from Leeds to Warsaw has become standard operating procedure for
DePuy, one of the world's largest suppliers of orthopedic appliances and surgical tooling. DePuy
International Ltd. of Leeds has one SLA 250 system while DePuy Inc. in Warsaw has two.
"If Leeds wants something cast in metal using the QuickCastTM build style, many times it is quicker
to make the model in the States and send it to the casting vendor in the U.K. than it is for Leeds
to generate the model themselves and ship it to the U.S. casting vendor," says Bart Huffman,
senior product designer in Warsaw.
Huffman explains that since there are more qualified casting vendors in the United States, the
British company often finds it expedient for the North American company to assign the job. He
says downloading model files off the Internet is preferred over shipping a model by a delivery
service. Overnight services sometimes have difficulty clearing packages through customs. So it
could take two or three days for the model to arrive. Since some customers may require a
specialized appliance in just a few days, DePuy seeks to save as much time as it can.
Accessing the Internet
The process of transmitting a file begins when DePuy in Leeds uploads either an
".ems" (engineering modeling system file) or an ".stl" (SL file) on its Sun Spark 10 server. Phil Kilburn, a
Leeds research and development engineer, then notifies Huffman by phone that the file is
available.
To access the file, Huffman has his personal computer's modem dial up the Internet. He enters
the Internet address of the Leeds company and, using a file transfer protocol (ftp), downloads the
file. Files for small models run about 0.2 megabytes, while larger models can take up to 3
megabytes. Depending on its size, downloading of a file can last up to 20 minutes, says Huffman.
Industry Innovator
Founded by Revra DePuy a hundred years ago in Indiana, DePuy has long been recognized as an innovator
in the development and distribution of orthopedic devices. Among them: one of the first hip prostheses. But
it didn't stop there. "We manufacture about every joint in the body," explains Huffman. "We use SL quite a
bit to design instruments, cutting grinders, screwdrivers, rasps. We also use SL to design trial
implements to run joints through all the motions before the actual implant is put in. "SL
has enabled us to get to market faster and it has shortened the design cycle considerably."
Faster Development, Better Products
"Prior to the SLA 250 system, we had been making prototypes in a model shop on wire rotor machines with computer numeric
controls. Just a redesign on a femoral component could take us 2-1/2 weeks to get our first prototype. But when we did it on the
SLA system, it was ready the next day."
Phil Kilburn, R&D Engineer, DePuy International Ltd.
Kilburn estimates his company is realizing a cost savings of 25 to 30 percent with SL
compared to the prior modeling process. Using SL also shrinks development time for new
products. Modeling of appliances often calls for several iterations before a surgeon is satisfied with the result. With SL, a development process that once could last as long as a
year now takes only eight to ten months.
Surgeons like the ease of working with SL models, notes Kilburn. "The surgeon can hold it
in his hand," Kilburn points out. "The surgeon knows the shape of the product. Sometimes surgeons will modify the models themselves
with just a metal file." Previously a surgeon had to describe what the problem was or do a rough sketch of the
correction he wanted and then hope the model makers understood. "It is quite expensive to make a model and
then discover it is not what the surgeon expected," says Kilburn.
DePuy often combines SL models and spray metal tooling to save time and money when
introducing a new product line, Huffman explains. The model is sprayed over with an
aluminum zinc compound. The liquid metal is no hotter than shaving water, but rapidly hardens over the resin, creating a die tool from which a cast is made. Appliances
manufactured with spray metal tooling can quickly get to market. If the company decides
the product line is viable, permanent hard tooling is created.
A Unique QuickCast Build Style
DePuy employs the QuickCast build style mostly for appliance research and development.
"With QuickCast build style, we don't need to build a metal tool," Huffman explains. "The
model goes directly to the foundry, where they do shell investment casting." The resulting metal model then can be sectioned and tested for stress.
QuickCast build style also is ideal for modeling unique appliances for patients. Huffman
says that the bones in some patients have become so deteriorated that items from
DePuy's standard inventory are not acceptable. But with SL and spray metal tooling, an
appliance designed specifically for a particular patient is ready in a matter of days.
Although 100 years old, DePuy has stayed forever spry by adopting the latest technologies. SL and the QuickCast build style
are helping create new appliances and tooling more quickly. And combining SL with the Internet guarantees that DePuy can
react even more rapidly to the needs of its customers around the world.
