NEW SOMOS® 10120 WATERCLEAR™ ENABLES FUNCTIONAL TESTING AND FASTER SPEED-TO-MARKET FOR SELF CONTAINED BREATHING APPARATUS
23 July 2001 - DSM Somos

Somos® 10120 WaterClear™ is a unique new composite of many desirable engineering properties mimicking the flexural strength and modulus of polycarbonate, the notched izod impact strength of Nylon 66 and the tensile strength of ABS. Ideal applications for this epoxy-based photopolymer include: flow visualization, complex assembly analysis, form/fit analysis and functional testing.

According to Bill Noack, president of MTI, “Somos® 10120 WaterClear™ provides optical clarity that allowed our client to test their product design earlier than used to be possible. The result was a time savings of many valuable weeks in getting the product to production tooling and making it a more functional product due to an enhanced ability to modify the design. We found Somos® 10120 WaterClear™ to be robust enough to perform select functional testing and excellent for handling of components that require form/fit applications. Additionally, for certain applications, not only have early prototypes been used to test product, but that same part is then used in the production of RTV Tooling for urethane reproductions. This has resulted in a large cost-savings to our clients and reduced lead times.”

MTI’s client manufacturers all components that go into a complete SCBA including the regulators, pack frame, face shield and fitting components around the face. These products are, literally, the lifeline for those who wear them...ranging from industrial uses such as cleaning the inside of storage tanks to fire fighting...basically any environment where atmospheric conditions are inhospitable to a human.

Because the environments in which SCBA’s are worn are so potentially harsh, testing standards for these units are extensive and rigorous. The single-most important attribute is that of product reliability. Unlike other products, if a SCBA fails at the wrong time the consequences have the possibility of being tragic. In addition, it is imperative that the fit be very comfortable due to the fact that the user will often be wearing the SCBA for an extended period of time.

Understandably, a tremendous amount of testing is involved in designing and prototyping new units. Prior to six years ago, many SCBA components would be hand made and then fitted to a human model, adjustments made and the process repeated. That was a time-consuming process with significant margin for errors.

In the past 5-6 years, with the great advancements in CAD, this ‘hand’ process has been eliminated by the precision of CAD models and highly accurate rapid prototypes. Now, the process has been accelerated and many more iterations of the design can be produced prior to committing to production tooling. This ability to modify designs has lead to greater reliability and more experimentation of the designs in order to overcome any potential problems. MTI’s ability to simulate the production parts in their appearance and their durometers has also meant near real-life testing of the SCBA’s.

Until recently, however, there remained the challenge of finding a prototyping resin that could meet the many demands of the testing process. Resins were available to create molding masters that would, in turn, be used in the production of clear urethanes for the face shield and also mold masters for the creation of the face masks and nose cups that are a lower durometer urethane. This led to masters of acceptable dimensional stability providing stiffness that was adequate to finishing to a high level, thereby achieving production-looking urethane reproductions.

The drawback was the time factor involved. Low-durometer components usually are built around the face shield, and to accurately test the face shield it is necessary to have a clear material. Making clear urethanes is, under the best of circumstances from start-to-finish, a 1-1/2 to 2 week process involving building an SL master, finishing it to a high level of polish, creating an RTV Tool and then shooting a clear urethane material. Only after the first article has been produced, can other testing begin.

The release of DSM Somos® 10120 WaterClear™ resin has significantly reduced the time constraints of this process. It is now possible to produce a highly accurate, yet clear part, in approximately the same time required to finish an RTV master. MTI was are able to finish WaterClear™ parts to an optically clear end-result. Consequently, MTI’s SCBA-manufacturing client now has the ability to produce an SL part, test it for form/fit and then decide if additional parts are required or if changes to the files need to be made. Using Somos® 10120 WaterClear™ in this particular application has allowed near-production testing of the unit and this in turn has generated more accurate feedback from the individuals who wear the mocked-up masks.

Moreover, the advantages of this resin go beyond optical clarity. MTI has found Somos® 10120 WaterClear™ to be a strong, robust resin able to withstand moderate flexing and functional testing. This is advantageous for its ability to work in applications where a part might be functionally tested or handled frequently.

MTI has determined that Somos® 10120 WaterClear™ also works very well as mold masters for RTV Tooling. This has meant that not only can MTI use a particular part for form/fit and limited functional testing, but can then use that same part as a mold master once it has been returned from the client.

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