H3D Employs Machining and 3D Printing to Develop Gamma Ray Spectrometer

Posted On October 23, 2017 By Proto Labs
H3D radioisotope identification device
H3D’s state-of-the-art RIID helps users easily identify sources of radiation in a variety of applications.

Founded in the Department of Nuclear Engineering and Radiological Sciences at the University of Michigan, H3D, Inc. offers high-performance gamma-ray spectrometers and imagers for the defense, nuclear power, chemical, and medical industries. The company consists of just over 20 employees, with about half holding doctoral degrees in nuclear engineering.

We interviewed David Barron, mechanical engineer at H3D, to learn how he takes technology developed by the company’s nuclear experts and incorporates it into a user-friendly product. And to hear how he worked with Proto Labs to develop the company’s latest product, a radioisotope identification device (RIID) called Apollo.

Can you give a quick explanation as to what a RIID is used for and how the H3D RIID improves upon past designs?

A RIID is used for finding and identifying sources of radiation in many different scenarios including border crossings, advanced police teams, hospitals, etc. The current state-of-the-art RIIDs primarily use scintillators as the radiation detection technology, which only provide low-fidelity energy resolution; other RIIDs use high-purity germanium (HPGe) to provide high energy resolution at an expensive price point, but HPGe is fragile and must be cooled to cryogenic temperatures. Neither of these technologies directly provide users with the data they really want to know—where the radiation is coming from. 

We are packaging our robust, large-volume, 3D-sensing Cadmium-Zinc-Telluride (CZT) crystals into a handheld unit centered around a high-resolution screen displaying 3D arrows to quickly indicate the location of detected radioisotopes. Other RIIDs do not provide an indication of direction, which forces the operator to play a “hotter or colder” game to find sources of radiation. The operator of an H3D RIID will simply follow the arrow to find the source. In addition to the 3D directionality, the system provides HPGe-like energy resolution of <1.0% FWHM (at 662 keV). 

What was the primary development challenge you encountered while designing the RIID?

The key development challenge was packaging the CZT and electronics into a handheld system that is comfortable and intuitive for the operator to use in a host of non-ideal environments. We wanted the smallest and lightest packaging possible for the product, while maintaining sealed, temperature-stabilized compartments for the CZT and electronics.

As you worked towards a final design, how many iterations did the product go through?

We created three distinct generations of prototypes of the Apollo RIID. The first was a fast-to-fail handheld to prove H3D’s large-volume CZT could be robustly packaged into a handheld device. For our second and third prototypes, we focused on refining the design to create an ergonomic form factor, setting up the design to be manufacturable for injection molding and to provide samples to early adopters for ergonomic and interface feedback.

Inside a PolyJet 3D printing machine
With PolyJet technology, H3D built several prototypes of its operator interface to experiment with various button layouts and sizes.

Did Proto Labs’ design for manufacturability feedback help improve your design?

Proto Labs’ automated design analysis was used extensively for DFM feedback on our injection molding design. Also, the customer service engineers did an excellent job providing quick quotes for both prototypes and budgetary quotes for tooling.

What Proto Labs process did you use for producing parts?

Our RIID prototype design consists of multiple Proto Labs parts using both machining and 3D printing.

We used Proto Labs’ machining service to manufacture aluminum logo plates that remove heat from the electronics bay, preventing the device from overheating and damaging the electronics. This part also gives us a spot to feature the company logo and product name.

We also 3D-printed a several parts with Proto Labs; one was an operator interface panel to experiment with various button sizes and locations. Using Proto Labs’ PolyJet 3D printing process, we could combine multiple materials into a single part design. In this instance, we combined black and clear in both flexible and rigid durometers to simulate a variety of overmolding designs. Another part 3D printed by Proto Labs was one half of the overall housing, this was made with clear rigid material and black flexible seals. This part allows us to visually inspect for water ingress during IP testing without disassembling the system. When we reach production, these components are planned to be overmolded PC+ABS parts.

We chose Proto Labs for these 3D-printed parts due to their willingness to set up the correct mix of materials in the Connex machines, the quick and easy quoting process, and the ability to provide secondary operations. Specifically, the finishing of the clear portion of the operator interface panel to see the screen were quite intricate, and executed very well by Proto Labs.

Q&A is a regular column featuring quick conversations with designers, engineers, and other professionals developing products with rapid manufacturing.