CASE STUDY: STERIFRE AURA (IN DEVELOPMENT)
Sterifre AURA Coming Soon: Automated Device Disinfection at the Point of Care
Sterifre Medical had an initial design for their AURA product, an automated point-of-care disinfection device, when they selected Simplexity as their engineering development partner to take over the design. AURA takes a new approach to device disinfection for the medical device industry with the simple press of a button. It is the first automated, point-of-care device that can disinfect handheld diagnostic and therapeutic devices from stethoscopes to sensors, meters, pumps, and communications devices. Even staff and patient personal items like cell phones, keys, and badges can be safely and effectively disinfected. AURA offers broad material compatibility with broad-spectrum efficacy with no chemical residue, device damage, environmental impact, or employee chemical exposure like currently available wipes and sprays. Unlike UV systems that offer an incomplete solution, AURA will be fully EPA regulated as a hospital disinfection device.
Introducing Sterifre AURA
Sterifre selected Simplexity to complete a simplification assessment and optimization of the full product design prior to final production ramp. In parallel, Simplexity would also execute a build of initial commercial units for near-term EPA testing based on the current product specifications and design.
The initial commercial design had three major areas that were critical to address during the simplification assessment to meet Sterifre’s goals. These were:
- Noise. The initial units were registering at around 55 dBA and the goal was 35 dBA.
- Weight. Sterifre had an aggressive weight target of 9.1 kg, but the initial commercial units were weighing over double that amount, 18.3 kg.
- Cost. The cost to manufacture the units needed to be lowered by 38% to meet market pricing goals.
These were challenging targets that would require Simplexity’s multi-disciplinary team of simplification experts to develop creative solutions and take a disciplined approach in analyzing and implementing them prior to scaled production ramp.
“We appreciate the depth of talent that they have. Some of the other folks we looked at just do medical products. We didn't view that as crucial for us. What was important to us was that the talent was there to tackle the job no matter what the issue was. Drawing from all the experience they have on different kinds of products, not just medical, is a big bonus. We went through our check list of attributes and I think we picked a winner.”
CEO at Sterifre Medical
To determine potential for noise reduction improvements, one of the initial AURA units was converted into a Noise Breadboard. The amount of noise generated at 1 meter from the unit was measured as a baseline. The team took a systems approach to brainstorming ideas for reducing the noise of the unit. Then each idea was prototyped and the effect on noise was measured.
Based on this analysis and testing, the following modifications are recommended to reduce system noise:
- Line the case parts with acoustic insulation.
- Use a minimum ratio of 2 ½ inlet diameters of smooth ducting leading to the inlet of the blower.
- Add a muffler on the blower outlet.
- Mount the blower using vibration damping grommets between the mounting bracket and the frame.
- Block off bulk access between the airflow through the system and the exhaust filter, replacing it instead with a thin connection such as a length of tubing to maintain the desired pressure in the system.
- Reduce flow restrictions in the ducting and key sub-assemblies to enable running the blower at lower speeds while achieving the desired airflow through the system.
By incorporating the six modifications described above, the estimated noise would be decreased to 36.6 dBA. Because this estimate uses worst-case assumptions for the effects of the case/duct/chamber mass reduction, and because the duct smoothing should provide noise savings that are unaccounted for, there is a clear path to reduce system noise emissions below 40 dBA. However, other assumptions have not yet been tested, so more work is required to determine whether the final units will be able to achieve the goal of being below 35 dBA.
The weight of the Sterifre AURA system is important both from a practicality and regulatory standpoint. Too heavy of a device will make handling for sales personnel and transport difficult. There are also regulatory requirements to allow for the unit to be wall mounted. The initial AURA design was over twice as heavy as the goal.
Simplexity started the analysis of weight by creating a Pareto chart, categorizing which components had the greatest weight contributions. This resulted in understanding that much of the weight is made up of molded plastic or sheet metal components. The case parts, airflow system, and chamber make up nearly 80% of the mass of the system, so much of the effort to design a lighter system focused on those subassemblies.
Mass can be reduced in the case parts by reducing wall thickness on the case and doors. The nominal wall thickness can be reduced from 3 mm to 1.5-1.8 mm while still maintaining structural rigidity. The back panel can also be integrated into the main case, eliminating a double layer of case parts on the back of the unit.
Current vs. proposed case part design
The four 2/2 flapper valves from the initial design can be consolidated into two 3/2 butterfly valves and integrated into the ducting. The duct walls can also be reduced in thickness which will lead to additional weight savings.
The main structure in the initial design is a stainless steel sheet metal bracket that weighs 1.3 kg (2.9 lb). By mounting the subassemblies directly to the chamber in the proposed optimized design, this panel can be removed and replaced by two smaller aluminum sheet metal parts, weighing a combined 0.3 kg (0.7 lb). This would be a 77% weight reduction for this subassembly.
Current stainless steel support structure vs. optimized aluminum brackets
The chamber is a major area opportunity for mass reduction. The body of the chamber in the initial design consists of 6 panels, each nominally 6.35mm thick. This can be reduced to one larger part with a nominal 1.5mm wall thickness. Reducing the wall thicknesses so substantially on parts in this subassembly saves 2.38 kg (5.24 lb) of weight.
Current vs. proposed chamber design
Total Weight Savings
The new proposed design reduces the weight from 18.3 kg to an anticipated 9.5 kg, a 48% weight savings. Additional weight savings will continue to be explored to see if an additional 0.4 kg can be reduced to make it to the goal.
One of the first tactics employed in the cost reduction activity was to analyze the entire Bill of Materials in the current design to remove, combine, and/or simplify parts. Getting rid of unnecessary parts is almost always more effective than trying to make a part cheaper to make. An example of one of the cost reductions recommended is to decrease the chamber body from 10 custom parts (7 unique) to 1 part designed for injection molding. Another example is to replace an expensive bearing linear guide with simple, inexpensive parts that can be cleverly engineered to perform the same function at a fraction of the cost.
Based on the cost reduction analysis and proposed optimized design, it is estimated that the total part count can be reduced by 36%, from 180 to 115 unique parts.
Another key tactic to cost reduction is evaluating and replacing off-the-shelf components with less expensive ones that also meet the technical specifications. The top candidates for cost reduction are listed below.
On the electrical engineering side, the design of the custom PCAs have been reevaluated for optimization, while still meeting specifications and safety requirements. Options considered include:
- Merging two MCUs into one
- Designing custom circuitries instead of purchasing off-the-shelf modules/components
- Minimizing unnecessary redundancies
The scope of this project also includes Simplexity writing the embedded firmware to control, run, and monitor performance of the device. While lines of code are not as easy to visualize from a cost reduction standpoint, they do affect the size of processor that is needed. Thus, the firmware is also optimized to require as small a processor as possible.
In addition to the significant unique part and component cost savings, it is necessary to include the expenses of manufacturing and assembly to yield an estimate of the total delivered unit cost. Simplexity uses a series of calculations based off volume, design complexity, location, and other NPI factors to estimate assembly and contract manufacturing (CM) costs. These calculations are estimates until formal pricing can take place with prospective contract manufacturers.
The result of this cost reduction analysis is that we believe the aggressive cost reduction target of 38% can be met. In fact, the data is currently showing a cost reduction of 48% if the above changes are implemented, which gives more margin to Sterifre to generate a compelling pricing strategy in addition to their technological breakthrough.
“Simplexity has a very disciplined, systematic approach in the way they work. They provide us with options for solutions and make sure we understand trade-offs as we make decisions. All of these things come together to meet our design challenges.”
VP of Quality & Regulatory Affairs at Sterifre Medical
Sterifre AURA Customer Testimonial
Sterifre AURA Initial Commercial Unit Build
In addition to the design and analysis for the optimized units, an important part of the work includes building, debugging, and testing the initial commercial units that were intended for additional microbial efficacy testing. Simplexity was sent the parts from the other vendor who designed the initial units. Simplexity engineers then analyzed where reliability issues may be present and wrote the embedded firmware to control, run, and monitor performance of the devices. They performed additional design optimization and built the early commercial units.
Our Project Managers, Mechanical, Electrical, Firmware, Systems, NPI, and Quality Engineering teams are all working together with the client’s team on Sterifre AURA to meet key milestones during this critical development time. This includes documenting the project in Simplexity’s ISO 13485-certified Quality Management System so key decisions and milestones are well tracked.
We appreciate Sterifre Medical’s willingness to let us share this case study as a work-in-progress based on the design improvements we’ve realized to date. Stay tuned for additional updates as we progress through the design, engineering, and NPI work on this project.