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How Polaris Designs Aggressive Looking Snowmobiles with solidThinking Software

By Jeffrey Heimgartner, February 24, 2014

Altair Engineering was founded in 1985 and today is a software company that produces product design, engineering, and cloud computing software. While the company has a myriad of CAE (computer-aided engineering) software products in its lineup, in this article I focus on two, solidThinking Inspire and OptiStruct.

About solidThinking Inspire

solidThinking Inspire is for design engineers, product designers, and architects to create and test structurally efficient 3D design concepts quickly and early in the design process. In essence, it validates certain designs before the final design stage or even manufacturing the part on the shop floor. The company figures this saves time and money because users can zero in on proven designs and then optimize them.

Inspire accomplishes the optimization by generating material layouts (or shapes) within a defined design space, to which the designer applies specific criteria, such as dimensions, loads, supports, and material properties. Inspire is positioned to design structural parts correctly earlier, thereby reducing cost, development time, material consumption, and product weight (see figure 1, right).

About OptiStruct

Altair positions OptiStruct as a modern structural analysis solver for linear and non-linear structural problems under static and dynamic loads. It is based on finite element and multi-body dynamics technology. Through the application of advanced analysis and optimization algorithms, OptiStruct helps designers and engineers develop innovative, lightweight and structurally efficient designs rapidly.

OptiStruct is used by thousands of companies worldwide to analyze and optimize structures for their strength, durability and NVH (noise, vibration and harshness) characteristics (see figure 1, left).

Figure 1: Optimizing shapes of parts

Shape Optimization: Parametrics Vs Topology

Generically speaking, both Inspire and OptiStruct are meant for shape optimization. They evaluate different parts and their properties to come up with the best shape that yields the greatest strength with the least amount of material. Using less material means the parts weigh less and cost less, lowering the price of raw materials and the later, cost of energy.

To better understand how they work, we first need to understand the difference between parametric shapes and topology shapes, the latter also known as free-form shapes.

Figure 2: Inspire optimizing materials based on loading conditions

In cases where the shape optimization leads to a shape that might be cost prohibitive or difficult to manufacture, manufacturing constraints can be added to the process to ensure standard manufacturing practices.

Designing Polaris Off-road Vehicles

For the practical side of this article, I interviewed Polaris staff engineer Rick Kerner to hear his thoughts on using Inspire and OptiStruct for CAE and shape optimization at their organization. Polaris engineers and manufactures an array of off-road vehicles, motorcycles, electric motorcars and snowmobiles at a number of locations in North America. Kerner is part of the Polaris Snow Group.
The Polaris engineering department has been using CAD and FEA (finite element analysis) for quite some time. They implemented solidThinking Inspire and Altair OptiStruct to add topology optimization to the tools they were using currently.

While optimizing snowmobile designs, one of Kerner’s main concerns in the past was the time it took to get acceptable results using the FEA programs they had. "Typically, we’d go through 10 to 12 iterations to get the last degree of acceptability from the result," he said. In describing the existing process, he explained that it took "significant resource time to create a valid concept." Going from the opportunity phase to concept selection took approximately four months; subsequently, the concept selection to design review stage was taking close to seven months. Basically, it took the design team a year to go from the blank napkin sketch to a mature design.

After implementing solidThinking Inspire and Altair OptiStruct, Polaris cut the number of iterations required in half. "This translates into cost savings. Rather than creating three generations of prototypes, as we previously did, we typically get by with one now," Kerner stated (see figure 3).

Figure 3: Polaris used similar steps in Inspire in optimizing for material, strength, and size

Besides being able to generate good, credible designs in early phases of the design process, solidThinking and OptiStruct allow the Polaris team to identify integration and design space issues earlier - as opposed to later on when rework would be required. With good inputs, load data, and boundary conditions, Polaris now produces two to three iterations of a reasonable design solution in a short amount of time: two days, as opposed to nearly a week via the old method that employed detailed CAD drawings. All this makes collaboration much more efficient as early designs can be proven to be functionally proper. Rick stated that, "It is easier to agree and improve on concepts that have integrity built in up front."

solidThinking is used to develop designs based on a given design space defined by given loads or constraints. A design space is basically a given area or volume in which the desired design can exist or fit, such as the driver of a snow mobile or the engine under the hood. Assembly, packaging, and tool accessibility are types of criteria used when defining the design space (see figure 4).

Figure 4: Optimizing weight by finding volumes where material is not needed

From there, the Polaris team uses OptiStruct for topology shape optimization. In one project, it reduced an assembly with 17 components weighing 3.5KG and taking 15 minutes of welding, down to an assembly of only three components, that weighed under 3KG, and used six bolts - and no welding.

"Inspire gives us the basic shape and engineering, and then we move to OptiStruct to refine the shape for manufacturability and stress requirements," Kerner explains.

During this project, Polaris also used Inspire and OptiStruct for evaluating how substituting aluminum for steel would affect weight reduction in subassembly structures. (Aluminum has half the weight but only 1/3 the strength of steel.) "In Inspire, we removed all the steel except for anchor points," Kerner said, "and let Inspire come up with a support shape using aluminum. Then we assessed the shape, determining where we wanted to retain steel tubes and where it looked that aluminum was feasible. This allowed us to create designs from aluminum and marry them to steel, producing an assembly that met our weight and load requirements."

Conclusion

By reducing the number of design iterations and time it takes to arrive at these iterations, Polaris gets its designs to manufacturing and subsequently to the market much quicker than before. In addition, being able to significantly reduce the weight of their designs allowed them to reduce material costs in the manufacturing process.

Polaris has been able to produce two to three iterations of a reasonable solution in about two days by using Inspire and OptiStruct, with good input/load data and boundary conditions - as compared to nearly a week of a detailed CAD concept. This means that design collaboration time is much more efficient when the initial solutions are functionally proper, making it easier for designers to agree on and improve concepts already proven early in the process. As Kerner stated, "Detailed CAD follow-up also is faster, as it is very easy to explain/share/import the finished geometry into other CAD systems."

Polaris reduced the typical concept-design-FEA cycle from eight to ten iterations over three to six weeks, down to two to three weeks using Inspire and OptiStruct - in conjunction with a solid design and analysis team. Essentially, these tools have helped to reduce the time from concept to design verification with prototype components and assemblies by 30 to 50 percent.

Success in the manufacturing industry is affected by the ability to maximize efficiencies and eliminate waste during the process of bringing a product to the market. Inspire and OptiStruct allow Polaris to do this by identifying problem areas and ruling out inferior designs early in the process, without having to produce prototypes or flush out problems on the shop floor.

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About the Author

Jeffrey Heimgartner has over 20 years of industry experience. He manages Advanced Technical Services for CapStone's CAD division. He has a bachelor's degree in Industrial Technology with an emphasis in CAD from Wayne State College in Wayne, Nebraska. More...

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