Good night and sweet dreams!

In this case study of reverse engineering and rapid prototyping we will look at a company that developed an initial prototype of an anti-snoring device based on many years of research in the field of dentistry. The company’s main dental advisor is a pioneering dentist in the research and development of mandibular advancement devices to treat snoring and obstructive sleep apnea (OSA). He designed and created a functional device that comfortably and healthily helps cure snoring. 

The challenge came after the initial anatomical design and fabrication work was done, when modifications were needed to make the device more functional. The first version tested the shape and size, but the company wanted a way to quickly prototype different features into the base design. They also wanted to try different FDA-approved resins for improved functionality and comfort. And, as is typical for a one-of-a-kind prototype, the company did not have CAD files of the part. The development schedule allowed for flexibility, but the company wanted to move forward to get its anti-snoring device into production and on the market. 

A consultant assisting the device company with product development and production had worked with GKS Inspection Services in the past and found their expertise in rapid prototyping and product design invaluable. “I was very satisfied with the work GKS had done for another company, so I recommended them to my current client to help with the final design of the anti-snoring device,” the consultant explained. He knew GKS could laser scan a part in three dimensions directly to the CAD file type used for rapid prototyping, saving significant time and money. 

The consultant sent GKS the basic anti-snoring device to be scanned. The company had scanned small medical devices in the past with great success, so it had plenty of experience producing the best possible scan results.

The original design kept the jaw in a position where the throat stays open to prevent snoring, but needed to add some ribs to the bite to create “positive positioning,” which holds the device in place without sliding. “In addition to digitizing the device to a CAD model, the customer wanted us to help design these functional ribs," explains Larry Carlberg, GKS service bureau manager. "GKS eventually made the patent drawing for the device with these design modifications. We also referred him to both a rapid prototyping company and a manufacturing company."

A Laser Design Surveyor WS-2030 (work envelope of 20” x 30” x 20”) was used to perform the scan on the anti-snoring device. This highly automated 3-D laser scanning system uses Laser Design’s SLP-250 laser line scanning probe. This probe integrates with Wenzel’s coordinate measuring machine (CMM) technology and includes both a Renishaw PH-10 programmable indexing head along with a rotary fourth axis stage. This system has full conventional probing capability when combined with traditional hard probes and OpenDMIS inspection software.

The irregular soft surfaces and ridges of the device were captured very accurately and completely without distorting the shape. Since laser scanning is non-contact, nothing touched or applied pressure to the pliable resin. The laser scanning system projects a line of laser light onto all of a part’s surfaces while cameras continuously triangulate the changing distance and profile of the laser line as it sweeps along, greatly reducing the problems of missing data on an irregularly shaped surface. The laser line moves back and forth over the part’s surface until the entire area is captured. The system measures details and complex free-form geometry so the object can be exactly replicated digitally. Laser scanners measure articles quickly, picking up to 75,000 coordinate points per second. They generate a large quantity of data points without the need for special templates or fixtures.

The Surveyor WS-2030 laser scanning software and Surveyor Scan Control (SSC) took only a few minutes to set up with the scan parameters. Part extremities were quickly scanned into the software and the desired scan density was entered (the scanner supports up to 100,000 points per square inch). Scanning the anti-snoring device was automatic and done unattended except for one flip of the special magnetic fixture that allows both sides of the part to be scanned. After scanning, the data was automatically combined into one high-density point cloud with a common coordinate system. Only 45 minutes of scan time were required to scan the entire device.

Laser scanning is ideal for reverse engineering complex parts like this anti-snoring device into CAD models because the whole surface of the object is scanned, not just a limited sample of discrete points as would have been the case with contact measurement. Parts can be modeled “as is” for exact replication or the original design intent of the prismatic shapes can be extracted even if the as-built prototype part is warped or misaligned. When taken into a solid modeler software package, the “history” of the model is available to designers, so any version may be referred to at any time in the remodeling process. Design changes or variations can then be easily made and documented.

For this project, Geomagic Studio and SolidWorks were used to create a solid model of the scan data. Geomagic Qualify Inspection software was used to compare the scan of the part to the CAD model showing discrepancies in a 3-D color error map. While in this case the scan data was used for adding the rib geometry to the CAD model for reverse engineering and rapid prototyping, this same scan data could also be used for inspecting manufactured parts against the intended perfect CAD model for ensuring manufacturing tooling and production processes.

After the laser scanning, data editing, and modeling were complete, GKS sent the product engineers at the device company a digital model (version 1) of the part. Carlberg advised them to produce some rapid prototypes of various materials using Fused Deposition Modeling (FDM) technology. Two more digital model versions were made and evaluated by Carlberg and the company’s engineers. Carlberg recommended some elegant solutions to the design problems based on his years of experience in working with scans and design of medical devices. The rapid prototypes led to other rework of the final design (version 4), which GKS engineers modeled and from which they eventually made the patent drawing.

To create the prototypes for user testing, GKS recommended another frequent business partner, Protomold. Protomold affordably makes injection molding prototypes for limited manufacturing runs and can provide custom plastic parts in as little as one business day.. This combination of speed and a short run was perfect for the anti-snoring device. With Protomold, they could create real, production quality parts using several different FDA-approved resins for testing with actual users. This approach allowed the company to analyze the different resins before going into full production.

Results

The ultra-precise Wenzel CMM measuring capability (± 0.0002”) combined with the high-speed laser scanning technology made the scanning process fast, automated, and less expensive than other measurement methods. If the device had been measured only by traditional contact measurement methods, the process would have taken several hours and yielded only several hundred data coordinates. With laser scanning, millions of coordinates from the free-form shape were gathered in minutes. The total topography of the part was recreated and modeled, and thus, could be accurately modified to meet the design needs after testing. 

With one of the scan files analyzed by Protomold, it was determined that some features were missing, so GKS quickly did some clean-up, filling in missing data from the model. With the revised digital design model from GKS, Protomold had no problem making the mold. A few dozen devices were made in different resins so testers could determine the best material. The company was able to narrow the field to two choices and then consult with their dental advisor to make sure the alternatives were viable.

The iterative process with GKS played a big role in the development and improvement of this product. Several rounds of designs, prototypes, revisions, and new designs were completed to create the final anti-snoring device. GKS provided the 3-D laser scanning to create the original CAD model. The CAD model was revised based on the prototypes until the design was optimized and the material was selected. GKS also recommended E&O Plastics, a high-volume injection molding company to make the devices when they go into mass production.

Once the pre-production mold was made, E&O consulted Protomold before building full production molds. Protomold was instrumental at making suggestions on moldability. Their ability to create parts in different materials for field testing saved the company thousands of dollars and weeks of unnecessary testing and evaluation.

Work is also in progress to produce instructional materials on how to use the anti-snoring device, as well as to start a user group to determine which device ultimately works the best for the most people.

“The project is moving along nicely,” says the consultant. “We have had a lot of productive exchanges with GKS and everyone was extremely helpful. GKS’s expertise and professionalism made for a very good design and development process. They provided support in all phases of the project, from start to finish.” 

About The Author