Simulate Early, Simulate Often... In Rhino
We at Pivot produktdesign set out to create higher performing, more durable and highly ergonomic snowshoes, the result is Fimbulvetr. Many manufacturers have tried to solve the traversing aspect of snow-shoeing but the solutions we saw were not sufficient. It was quickly identified that to achieve higher durability and traversing improvements a one piece unibody that combined the hinge and deck was the way forward. This presented us with an extreme challenge that we had very little reference to, using material to achieve areas of high stiffness but also of high flexibility and elasticity at temperatures in excess of -40 °C.
Why the use of CAE was essential to Fimbulvetrs survival
Before the final product we produced 3 prototypes. It was at P3 when we realized the importance of CAE to get the snowshoe to the market and it be a success. We had a good physical reference, but still needed to optimise the compliant hinge. In our eyes durability was number one so we needed to go for a softer material value but at the same time make the base of the shoe stiffer. By using Scan and Solve at this stage we could match the changes with the physical reference and get a very realistic assessment of the improvements and also pinpoint some stress accumulations we might otherwise have missed.
This is what makes Fimbulvetr innovative and award winning; we are using a compliant hinge for the movement instead of a conventional mechanical hinge. By far this was the biggest challenge, we had very little reference and so had to carve our own path and make decisions based on computed results. We experimented on a fundamental level with wave forms to find what amplitudes, wave forms and wavelengths gave the best flexibility to strength at low temperatures. Scan and solve allowed us to quickly and analytical draw the conclusions we needed to move forwards with confidence.
Experience of using scan and solve
As scan and solve does not have the same meshing technology as conventional FEA packages we were able to focus more on the aspects that matter rather than trying to optimize the model for meshing and fixing problematic areas, all scan and solves asks for is a closed polysurface. Having used other packages this is in our opinion its main strength as is takes a huge amount of hassle and headaches out of the CAE process.
Most material data is for values in the low 20 °C range, our product would be used in +5°C all the way down to -40°C with an optimum performance level at -7.5°C. Scan and Solve allowed us to easily enter the adjusted values to have full control over the variation of temperature ranges.
Loads and restraints
Scan and solve makes it very easy to set up the loads and restraints on models giving lots of options. The availability of torsion helped us draw accurate results as this was the closest representation of working the hinge. As scan and solve is based in Rhino we could quickly split faces and add geometry to steer our simulations quickly in the direction we needed to get accurate results.
As we were going to be carrying out a great deal of simulations we invested the time to adjust the resolution and plot it against the results. This allowed us to see at what resolution the graph started to flatten out, in the long run it saved us allot of computing hours and we were confident the results displayed were accurate.
Benefit of being a plug in
Fimbulvetr was modelled in Rhino and complimented with Grasshopper in both modelling and analysis. As the export and meshing complications are removed the speed of development was greatly increased. In the optimization process grasshopper was great compliment as we extracted the i-values at an intervals of x and were able to find the areas were it drastically changed and smooth theses areas out to then see in scan and solve this weak/flex point was no longer present.
Scan and solve works great as a communication tool, being able to bake as mesh with the von misses plots as a vrml allowed us to 3D print in full colour and discuss and justify changes and their affects. The bake mesh capability also helped us draw higher accuracy and confidence, as when a model is deformed the geometry is different. We were able to at a basic level run dynamic simulations by baking the mesh at 0 deflection 25%, 50% and 75% then running the simulations on these deformed models.
Due to the scan and solves ease of use and accuracy when we did our physical cyclic testing it confirmed our computed results that allow us to offer a life time warranty covering materials and workman ship within normal use.