It is a costly and slow process to continually iterate and optimise a design to re-manufacture and physically test components. With limited time and budget, HD approached the project by using engineering simulation techniques including FEA and SolidWorks Motion to virtually test design iterations.
Solidworks Motion is a Kinematic analysis tool which HD uses to virtually test and validate mechanism performance. Using this approach meant that we could rapidly tweak and test concepts in a much lower cost and efficient way. This was beneficial to the client as it kept the project within budget and delivery time constraints while improving the device’s usability to meet user needs.
A key issue was the force required to operate the device. In addition, the device wasn’t delivering sufficient audible or tactile feedback to users resulting in confusion, misuse and ultimately, issues surrounding underdosing and adherence. A key challenge of the brief was a narrow margin of changeable parameters within the existing design which could be optimised to enhance the device’s performance.
SolidWorks Motion was used to optimise the mechanical performance of mathematical CAD models. In this project, virtual springs, virtual motors and virtual body contacts were used to simulate the product in use. HD could then quickly determine why and where changes were needed to enhance and optimise performance and usability.
By running a Motion study with the mathematical model, data from an earlier physical study was replicated which not only showed that HD’s set up was accurate but, gave a benchmark to work from.
From here, the focus was to improve the product’s usability by decreasing the operation force required. Concepts were developed and modelled before being virtually tested and tweaked to develop the optimal design. By using Motion testing, the original design’s performance could be compared against the new design. Features were optimised to improve functionality, performance and provide sufficient tactile feedback to the user.
After this theoretical work, injection moulded components of the new design were manufactured and physically tested to create a further set of results which could be compared against the theoretical force profile generated in Motion – they were closely correlated. Using Motion eliminated numerous iterations of prototype designs to get to this point – saving time and reducing costs.
We also set out to determine what variable factors would cause the most significant impact on the device’s operation. I.e., what would affect the device the most;
1. Slight changes in Geometry?
2. Differences in temperature that alter the material stiffness?
3. Or, raising/lowering the coefficient of friction by using alternative materials?
By using a combination of CAD, FEA, further Kinematic Analysis and material property research, HD were able to virtually demonstrate the impact of each variable. With these results, HD then concluded which variable had the largest impact to determine which of the 3 factors the device was most sensitive to.
The findings were documented and delivered in a sensitivity study which gave some insight into the overall robustness of the design.
Having collated the data from these different studies, HD were able to compare them against the original benchmark study and determine which variable the design was most sensitive to. With this information, the client was able to specify materials and tolerances accordingly.
Simulation can often be overlooked as a software add-on to SolidWorks. It’s highly versatile so can be used to validate early concepts, reduce prototype iterations and optimise designs to suit key usability parameters.
The team at HD have used this process to optimise the usability of other drug delivery device projects too for example, to calculate auto-injector cap pull off forces as well as profiles required from springs and other components to drive complex auto-injectors mechanisms. Using simulation effectively, especially alongside some physical test data, can significantly reduce development costs and time whilst improving usability.
If you need any advice or guidance on the effective use of FEA to speed up your product or medical device development process, please get in touch and we will be glad to help.
Senior Design Development Engineer
Danny graduated from Aston University with a BSc degree in Industrial Product Design. Prior to HD, Danny worked in engineering roles, designing products varying from plastic vehicle bodies to sheet metal fabrication, gaining valuable experience of manufacture in the production environment. Within HD, Danny is an advocate for developing skills and capabilities within the team to broaden HD’s services. Danny also assists with project management activities and is our Mental Health First Aider.
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