Design Rules Revolution: DMLS Requires New Thought Process

By Heather Thompson, Senior Editor, Medical Design and Outsourcing

As product development speeds up, the design rules are changing. Nowhere is this more apparent when looking at the industrial 3D printing process of direct metal laser sintering (DMLS). Direct metal laser sintering is an additive manufacturing technology with significant potential in the medical device space. But it requires a new way of thinking even at the early design phases. In many ways it represents the transition designers must face when looking at new technologies to make medical device design and manufacturing faster and more innovative. 

Internal channels that are impossible to machine are achievable with DMLS.

There are several benefits of DMLS explains Tommy Lynch, metals project manager at Proto Labs Inc., primarily that designers can prototype designs in unusual shapes at both time and cost savings. “DMLS is different from other 3D printing because you are using real metal. Many of these materials have been used for industrial applications for decades.”

Lynch says designers like the process because they can experiment with organic shapes that can’t be readily machined. For example, one intriguing opportunity is the ability to build implantable body parts that are custom fit to the recipient. “These implants would normally need to be delicately built on a 5-axis machine at a high expense,” he says. “Technology exists to scan a person’s actual bone structure, and print a direct DMLS replacement.”

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3D-Printed Molds vs. Aluminum Tooling

Industrial 3D printing has made a tremendous impact on the manufacturing world. Rapid prototypes are possible within a day, material selection continues to grow stronger and parts with un-manufacturable designs have found their happy place. Recently, some companies have begun using this important technology to produce injection molds.

Molds made with thermoplastics-based 3D printing are kind of like the plastic storage sheds some of us put in our back yards. They’re a little cheaper than metal sheds. They go up quickly and are fine under light loads. Pile too much snow on them, however, and they’ll collapse like a house of cards.

A 3D-printed Digital ABS mold built in an Objet Connex machine.

Still, printed molds have their place, and some shops have had good success with them. Proponents argue that 3D printing produces molds up to 90 percent faster and 70 percent cheaper than using traditional moldmaking processes. And while this may be true in some circumstances, it’s important to understand the pros and cons of printed plastic molds compared to those machined from metal.

Quality is king. 3D printing builds parts in layers. Because of this, printed parts can exhibit a stair-step effect on any angled surface or wall. Printed molds are no different, and require machining or sanding to remove these small, jagged edges. Holes smaller than 0.039 in. (1mm) must be drilled, larger holes reamed or bored, and threaded features tapped or milled. All of these secondary operations eliminate much of the “print-to-press” speed advantage associated with printed molds.

Size matters. Part volumes are limited to 10 cubic inches (164 cm3), roughly the size of a grapefruit. And although modern additive machines have impressive accuracy, they cannot compete with the machining centers and EDM equipment at Proto Labs, which routinely machine mold cavities to +/- 0.003 in. (0.076mm) and part volumes up to approximately 59 cubic inches, about six times larger than parts made with 3D printing.

The heat is on. To make material flow properly, injection molding requires very high temperatures. Aluminum and steel molds are routinely subjected to temperatures 500°F (260°C) or greater, especially when processing high-temperature plastics such as PEEK and PEI (Ultem). Aluminum tools can easily produce many thousands of parts, and can also serve as bridge tooling until a production mold is available. Molds produced with SL and similar 3D printing technologies use either photoreactive or thermoset resin, which is cured by ultraviolet or laser light respectively. These plastic molds, though relatively hard, break down fairly quickly when subjected to the demanding thermal cycles of injection molding. In fact, printed molds typically become ineffective within 100 shots of soft, hot plastic such as polyethylene or styrene, and may produce only a handful of parts from glass-filled polycarbonate and other tough thermoplastics.

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EYE ON INNOVATION: Vertebrae Implants More Proof of 3D Printing’s Place in Med Tech

3D printing and other rapid manufacturing methods continue to transform the med tech industry, as illustrated recently by an Australian neurosurgeon who, in late 2015, removed cancerous vertebrae in a patient and implanted, in their place, printed vertebrae.

The 3D-printed part that would replace the patient’s cancer-ridden vertebrae. Photo: and ABC News.

Dr. Ralph Mobbs, a neurosurgeon at the Prince of Wales Hospital in Sydney, called the procedure a “world first.” The surgery was performed on a patient with chordoma, a rare form of cancer that occurs in the bone of the skull and spine. As Wired UK reports, the 60-year-old patient was affected in the two vertebrae responsible for turning the head — meaning that, if the 15-hour surgery had failed, he would have been left paralyzed.

Because of the position and function of these vertebrae, however, they’re extremely hard to replace — they must be an exact fit. Mobbs decided to 3D print the replacements instead, and worked with Anatomics, an Australian medical device manufacturer, to design and build the implants, which were made from titanium. The company also printed exact anatomical models of the patient’s head for Mobbs to practice on before the surgery. Continue reading

3D Printing Methods for Medtech Prototypes

Being able to quickly produce prototype parts is critical to creating an environment of innovation that can lead to medical device market success. By removing inefficiencies, manufacturers should expect to have prototype parts in a few days, not months. The prototype method must be fast enough to allow multiple iterations in a condensed time frame, and possess the scale to allow for multiple iterations at the same time.

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Rapid manufacturing methods like 3D printing are leveraged to help drastically reduce development time for medical devices.

Additive manufacturing (AM), also called 3D printing, enables quick evaluation of new medical product designs without making compromises due to complex part geometries. Using AM offers easier design changes and at a low cost. When prototyping via 3D printing, designers should not expect a finished part, although it should be noted 3D printing processes can yield finalized products. Stereolithography, for example, has a number of post-secondary finishing processes and direct metal laser sintering produces fully dense end-use metal parts.

There may be limits to color and texture choices, and in certain instances, thermoplastic-like materials will differ from the final production material used in process like molding and machining. If the surface finish, texture, color and coefficient of friction vary from the end material, it is difficult to accurately assess the subtle needs and benefits of these properties.

The main advantage of 3D printing is that it provides accurate form and fit testing. The build process of additive technology can accurately produce the form and size of the desired part, making it very useful for early evaluation of new medical parts. It is best used to identify design flaws, make changes, and then make second-generation machined parts or invest in tooling to create injection-molded parts. This article reviews that various AM printing methods commonly used in prototyping.

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EYE ON INNOVATION: Regrowing Damaged Nerves Using 3D Printing Technology

A national team of researchers has developed a 3D-printed guide or pathway that helps regrow complex injured or damaged nerves, and successfully tested the guide in rats.

Researchers say that this groundbreaking research holds the potential to help more than 200,000 people annually who experience nerve injuries or disease. The researchers are from the University of Minnesota, Virginia Tech, University of Maryland, Princeton University and Johns Hopkins University. The team’s study was published this month in the journal Advanced Functional Materials.

Image courtesy of Michael McAlpine, University of Minnesota College of Science and Engineering.

Researchers used a combination of 3D imaging and 3D printing techniques to create a custom silicone guide or pathway implanted with biochemical cues to help nerve regeneration. Continue reading