A New Art- to- Part Model is Emerging

This technical information has been contributed by
Sensable Technologies
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Surgical guide for dental implant placement (in orange), showing implants (grey, near top right corner) and abutments (blue) that will retain a finished crown
Image courtesy of Pro Precision Guides

Service bureaus are leveraging advances in design software to serve new and highly specialized "rapid markets"

By Kevin Atkins
Product Manager, Sensable Technologies, Inc.

Service bureaus have democratized the rapid prototyping and rapid manufacturing industries and accelerated the reach of additive fabrication technologies into exciting growth markets. Just a few years ago, additive fabrication was only viewed as a rapid prototyping technology. Recent advances in materials and quality have created a host of new markets for rapid manufacturing. Today, just about anyone can access design, prototyping, and innovative manufacturing approaches, including 3D printing, laser melting, direct metal printing, stereolithography, and laser sintering, via service bureaus without the investment, expertise, and staffing requirements.

Service bureaus allow smaller organizations to access technologies that were previously out of reach, and they help larger organizations meet the needs for specialized materials or small scale production runs. This easy accessibility has helped speed uptake of new digitally-driven design and manufacturing approaches in sectors not typically associated with novel manufacturing approaches, and fueled the emerging "maker market" of hobbyists and prosumers. And service bureaus aren't just for output these days. Many of these centers provide 3D scanning, as well as design services--or very specific art-to-part services within an industry.

As opposed to the traditional service bureau model, where it's a "send us your file, we'll send you your part" business, a new crop of specialized service bureaus is emerging to serve some very specific niche markets in dental, medical, and tooling. These next-gen service bureaus are better considered rapid product development firms, and are a perfect fit in industries where a buyer needs strategic, highly specialized services in limited runs. For example, patient-specific implants, dental restorations, and surgical guides are still primarily made by hand by small labs, and organizations usually can't support volume demand for digital fabrication devices to justify their cost. In contrast, service bureaus can allow organizations to create custom tooling that might formerly have cost $10,000 for as little as $2,000.

Next-gen service bureaus are allowing small companies to establish their businesses with a relatively minimal investment, because organizations can rely on the service bureau for deliverables that formerly required intensive capital investment and highly trained staffs. A key market driver is that design tools are incorporating different and more representational modeling schemes, and greater interoperability between CAD software, for far greater speed and efficiency. At last, after many years of the industry offering rapid prototyping and rapid manufacturing solutions, there is now something "rapid" at the start of the process.

Wanted: A 'Swiss Army Knife' for Service Bureaus

Additive fabrication technologies open up new design possibilities, as well as economic benefits. No longer do you have to be limited to shapes that can be made using traditional manufacturing techniques and their inherent limitations, e.g. mold with draft, machining with jigging and tool path limitations, or expensive wasted excess material. This opens up many design possibilities, including organic shapes, hollow structures, honeycombed structures, and forms with undercuts, for example.

Yet traditional CAD solutions were designed for regular geometry and for modeling shapes that could be made with the manufacturing limitations of the day. And even then, traditional CAD has its issues--for example, shelling complex models and calculating complex mold shut-out surfaces.

Another headache for service bureaus is taking customer models, which are not ready for manufacture, and editing them so that they can be manufactured. A model that looks right on a computer may be very different from a model that is indeed all right for manufacturing, particularly since most additive manufacturing requires watertight STL models. CAD modelers with surfacing techniques often produce STL models with open faces or overlapping coincident faces, instances that must be corrected for additive manufacturing.

Like most product developers, service bureaus maintain a toolkit of 3D design solutions to meet the wide variety of needs that come in to their business—from simple scan cleanup to full product design and prep for manufacturing and final production. Traditional CAD is important to them, but may not get their designs where clients want them to go—or support the compressed turnaround times that are implicit for an on-demand service business.

That's where "rapid design" software comes in. Service bureaus today are embracing multi-functional design software that, like a Swiss army knife for design, can be easily used to clean up scans, fix files for rapid prototyping, prepare for manufacturing, and create highly organic shapes that are perfect for rapid manufacturing.

Below are two examples of how next-generation service bureaus are providing design services to assure exceptional products.

Enabling CT Scan-Guided Dental Surgery

Surgical guides are an excellent application for new digitally-driven additive manufacturing processes. Doctors and dentists use biocompatible guides when medical drills must place the desired component--such as a pin, screw, or retaining bar--at a location and an angle of insertion that is difficult to achieve by eye alone. The ready availability of digital scans now can allow the process to go digital, so that the creation of a custom surgical guide is based on a highly precise source file, and the resulting surgical guide is a perfect fit.

Pro Precision Guides (http://proprecisionguides.com), of Gainesville Fla., specializes in surgical guides for dental implant surgery for complex cases. The structure of a dental implant includes an anchor-like screw (gray implant in graphic at left) that is surgically placed into the bone in the space left by the missing tooth. This implant holds an abutment (blue, in graphic), onto which the dentist affixes the tooth-like crown as an over-structure. The surgical guide (orange, in graphic) helps the surgeon drill the hole for the implant in the exact required location. Precise placement of the implant is paramount to stability, comfort, and life expectancies, particularly when the space in the patient's mouth for the implant is slightly smaller than the manufacturer design recommends, or there are several implants located together, further complicating the surgery.

Design of the surgical guide requires an accurate impression of the patient's oral cavity, as well as the invisible anatomy, including the bone and nerves. This requires two different data sets to be captured and accurately aligned. Capturing the digital model of the oral cavity is easily achieved either using an intra-oral optic scanner, or with a traditional plaster impression that is then laser scanned. Capturing the anatomy is also easy with CT scans. But CT scans of anatomy are notoriously noisy and often of a relatively low resolution, so that automatic alignment of the two data sets via common elements, such as teeth, is not sufficiently accurate. One way to overcome this accuracy problem is to use the impression of the oral cavity to make a custom fit mouth piece that has radiographic markers in it. The patient then wears this appliance during the CT scan, and the radiographic markers are clearly visible and accurately captured on the resulting scan. Using the radiographic markers for the alignment results in accurate location of the data sets.

The scanned data then moves through a digital work flow of file assembly. The ProPrecision designer converts the intra-oral scan into an STL and imports it into Freeform^®, a 3D modeling system developed by Sensable Technologies (www.sensable.com), Wilmington, Mass., for use in design and manufacturing. As a voxel-based modeling solution (think of voxels as 3D pixels, readily moved and reshaped like grains of sand), Freeform is tailored for organic, highly sculptural shapes, such as those found in the human body.

The patient's CT scan is converted from DICOM (digital imaging and communication in medicine) data into an STL file, and imported into Freeform as well. The designer can now place the implant and abutment assembly into the bony anatomy. Next, the designer selects from a set of digitally scanned teeth that ProPrecision guides has compiled as its own digital library. Using Freeform's digital clay, the designer pulls, tugs, and moves the tooth into the perfect tooth for the given shape and angle of the abutment. Freeform is unique in that users manipulate the design by holding a touch-enabled haptic device, instead of a computer mouse. Being able to sculpt digitally just as they would in wax or plaster allows a degree of speed and precision typically not possible with geometrically oriented CAD and 3D design tools.

Once the digital implant, abutment, and crown are placed and designed, ProPrecision creates the companion surgical guide, which would be overlaid like a mouth guard. Freeform's Boolean functions allow the designer to subtract the intra-oral anatomy from the mouth guard design to achieve a perfect fit, with the hole accurately guiding the surgeon's drill.

John Pellerito, an executive at ProPrecision Guide, estimates that the company now designs custom surgical guides at least 60% faster with Freeform. Once design is finalized, the Freeform STL file is sent directly to an Objet Geometries 3D printer for creation in the FullCure 720 material, an FDA-approved biocompatible resin, to be printed in about an hour.

Design and RP for Small Business

The ready availability of low-end 3D modeling packages has allowed the prosumer and the inventor to design what they might dream of making—and turn to service bureaus to directly make tooling on rapid prototyping (RP) machines. Yet manufacturing the dream can challenge the service bureau as well. For example, traditional NURBs modeling packages are good for mechanical components but may not be the fastest with complex, organic shapes, or with design modifications that are necessary to prepare designs for manufacturing but also balance aesthetic concerns. Also, low-end 3D graphics packages often do not share the tools that the higher end, more powerful and expensive packages have for making models manufacturable—models that look right versus models that are right.

Having the Swiss Army Knife of 3D design solutions is imperative to serving this market and accessing higher-margin opportunities, such as 3D-printed tooling and direct digital manufacturing.

Mydea Technologies (www.mydeatechnologies.com) is an Orlando Fla.-based service bureau where an inventor recently sought design and consulting help to produce a tool for manufacturing a soft foam grip for a cane in the shape of a creature's head. The grip would be placed over top of a cane as a more comfortable ergonomic shape to hold.

At the request of the inventor, Mydea began by having a sculptor design a physical clay model. Once the inventor approved it, Mydea laser scanned it, converted the scan into an IGES file, imported this into SolidWorks, and performed basic Boolean operations to make the two tool halves. Yet there were areas of the model requiring shaping, as well as other tasks that in past projects the team had found to be time-consuming when done in SolidWorks.

Mydea's designer saved the design as an STL file, imported it into Freeform, and in minutes, the designer was able to do what would take far longer in SolidWorks. He added digital clay to the back end of the creature and also added rounds to support moldability. He did a final smoothing of the creature's shape, and then adjusted the design with an eye to making sure all areas were manufacturable. The team sent several iterations of the design to the inventor until he felt the look of the creature was just right.

Because the mold was larger than the print area of the ZCorp 3D printer on which it would be created, Freeform also helped Mydea's designer split the mold in half and test for undercuts to make sure the resulting product would not contain design flaws.

With the final design approved, the tool of the creature-headed grip is then output on a ZCorp printer, infiltrated with epoxy, and made as a rigid tool. It is then cast with an expanding urethane foam for actual manufacturing.

About the Author

Kevin Atkins is a product manager with Sensable Technologies, Inc., provider of the Freeform^® organic 3D design and manufacturing application. For over 25 years, he has been involved with leading digital modeling technology, both as a user and as a software designer. His experience covers a wide range of models, from complex medical implants and surgical procedures, to organically sculpted toys, stylized product design, and functional engineering.

This technical information has been contributed by
Seaway Plastics Engineering
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