Hexagon helps RadiciGroup deliver high-performance parts
Claudio Ghilardi – CAE Analyst, Marketing and Technical Service, RadiciGroup High Performance Polymers | Hédi Skhiri – Technical Specialist Lead, and Marco Veltri, Business Enablement Manager, Hexagon’s Manufacturing Intelligence division
From metal to plastic: Hexagon and RadiciGroup's eBike innovation
Hexagon and RadiciGroup collaborated to develop a lightweight and durable rear swing arm for eBikes using innovative design, sustainable materials and advanced technology tools.
The company develops products for multiple industrial sectors, including automotive, electrical and electronic, consumer goods, clothing, furniture, construction, household appliances, and sports.
RadiciGroup High Performance Polymers is one of the most highly regarded multinational manufacturers and suppliers of technopolymer compounds and can rely on a global team including applications development, technical service and R&D, capable of providing their customers with the highest professional support throughout all project phases, from conceptual design to engineering and production.
Challenge: Replace a metal eBike part with a light, strong plastic
Acerbis, a leader in aftermarket motocross plastics, bike protection, and accessories, approached engineering polymers manufacturer RadiciGroup with a specific request: they wanted to replace a particular bike part — a rear swing arm then crafted from an aluminium 6061 alloy — with a piece that was lighter weight and made with strong plastic. The new swing arm design for electric, two-wheeler bicycle must deliver equivalent performance while simultaneously blending with the captivating bike’s aesthetics, with an attractive surface appearance and colour options able to resist fading under prolonged UV rays exposure.
“We needed a solution combining stiffness and mechanical strength resistance to static loads, as well as fatigue resistance,” explained Claudio Ghilardi, CAE analyst, marketing and technical service of RadiciGroup High Performance Polymers. “And due to the outdoor nature of the sport, we also needed a product that is less moisture sensitive.”
Solution: A cost-effective and lightweight eco-design
Across industries, manufacturers are increasingly seeking to replace metal parts with engineering plastic counterparts that offer equivalent functionality. While this transition to engineering polymers has been ongoing for decades, new opportunities continue to arise across all industrial sectors, extending even to parts previously not considered a target for metal replacement. Beyond the reduced production costs, environmental impact is now a key driver, from full material recycling to the lowered emissions through lightweighting.
There are numerous advantages in replacing metal parts with engineering polymers:
- Reduced production costs
- Decreased product weight
- Increased freedom in form and design
- Improved environmental sustainability
- Reduced assembly and post-processing machining time
- Enhanced aesthetics and colourability
- Diminished total cost of the part
When it comes to metal replacement, the aim is not simply the substitution of a metal part with a plastic part with the same functionality; instead, the approach is to consider how to take advantage of plastics’ unique features. To achieve this, the manufacturer must consider the part’s functional requirements, including implicit ones, and how the part interacts with other parts in a larger operating environment.
They must also consider plastic’s intrinsic properties, which are radically different from metal, meaning that manufacturers must effectively design the part so it may be used properly. To ensure the components work with the product as a whole, the manufacturer must have an overall view of the larger project, allowing them to preselect the material and then redesign the part, as illustrated in Figure 1.
Figure 1. Design optimisation of the rear swing arm.
Digimat & CAEfatigue help RadiciGroup deliver an innovative solution
RadiciGroup delivered a rear swing arm made from a special blend based on polyamide 66 reinforced with glass fibre instead of aluminium for the first time in the market. Fantic, an Italian company specialising in the production of electric motorcycles and bicycles, was the first adopting this innovative product, including it in some of the company’s trail and enduro bike models, first previewed at the Milan Motorcycle Show (EICMA) and now already in production and available for purchase.
RadiciGroup used Hexagon’s material modelling platform Digimat to bridge the gap between the manufacturing process and structural part performance. “With Digimat, RadiciGroup can provide their clients with advanced multiscale material cards that are perfect digital twins of the materials they characterise in the lab so that clients don’t have to do their own time-consuming and expensive testing,” said Hedi Skhiri, technical specialist lead at Hexagon.
Skhiri added, “To replace the aluminium part with reinforced plastic, RadiciGroup first created the finite element model using MSC Apex and Marc, including the appropriate boundary conditions defining the applied forces based on their design requirements. Then Digimat was used to transfer the manufacturing data such as the fibre orientation and weld lines from the injection moulding mesh to the structural mesh. Finally, a coupled analysis using Marc simulation with Digimat as material solver was conducted to predict the performance of the part, taking into account the effect of the local fibre orientations and weld lines on the stiffness properties of the material.”
“Having completed the static simulation, the stress results can be used to compute the lifetime of the part using CAEfatigue coupled with Digimat. The fatigue material description is first calibrated in Digimat through limited experimental stress-life data. It can then consider the effect of the fibre density and orientation as well as the applied mean stress, which vary both with the part location and load case. CAEfatigue allows replicating both the in-service and bench-test conditions, defining the fatigue events through sequence of loadings and repetitions and computing the expected lifetime of the parts “ said Dr. Marco Veltri, business enablement manager at Hexagon.
Veltri added, “RadiciGroup realised a true multiphysics process; using the combined depth of Marc, Digimat and CAEfatigue to virtually exercise the part over different force levels and repetitions, they can make sure their designs are extremely unlikely to fail.”
Figure 2. Multiphysics process combining Marc, Digimat and CAEfatigue.
The Radistrong difference
RadiciGroup created the part from its Radistrong product due to its high mechanical resistance and low moisture sensitivity versus a standard PA66. “The component was part of the bike frame — a structural component — so we proposed a special blend based on polyamide 66 reinforced with glass fibre to ensure the design could withstand the continuous and strong stresses it’s subjected to.
Additionally, our solution’s mechanical properties — like stiffness and resistance — are less influenced by humidity absorption. We also paid great attention to the aesthetic result: the material surface looks attractive, stable against UV rays, and is designed to resist exposure to atmospheric events over time,” said Claudio Ghilardi, CAE analyst, marketing and technical service of RadiciGroup High Performance Polymers.
RadiciGroup tasked its engineering services team with the full project. The early deployment of Digimat and the use of computer assisted engineering simulation (CAE), allows the company to predict the behaviour of the material during the moulding phase, along with the mechanical response of the products already in the very early stages of their development. The ensuing deliverable engineering services include:
- Project feasibility assessment
- Validating material selection and part design and redesign
- Troubleshooting both in prototyping and regular production
- Coordination between R&D, external suppliers and software providers, ensuring new and reliable material cards for RadiciGroup products are made available for use in simulation communities
- Communicating with customers’ designers, engineers, and CAE experts in order to facilitate a positive exchange of material selection and modelling information
- Optimisation of clients designs’ geometry and technical performances
- Providing higher accuracy and reliability in predicting stiffness and failure
- Gathering a more in-depth understanding of the material behaviour
- Lead to a reduced tendency to overengineer and use high safety factors
- Reduce the need for prototype testing
Results: Simplified, shortened production times and sustainable design
Using RadiciGroup’s compound — empowered by Hexagon’s digital materials and multiphysics solutions suite — the eBike rear swing arm is now 10% lighter than the previous design. Additionally, because RadiciGroup’s technopolymers are coloured during the material extrusion phase, the component is ready for use at the end of the injection moulding phase, with no painting necessary.
RadiciGroup, Acerbis, and Fantic closely collaborated in all project phases — from product design and material formulation to mould creation and the mould injection process, up through the mounting on the eBike. Many severity tests were carried out at the customer’s laboratories, showing that the new part helped exceed the initial requirements by 2x. And to top it all, the new innovative rear swing arm contributes to lowering the environmental impact of an eBike and can be recovered and mechanically recycled at the end of its useful life. In fact, this bike part was the result of applying eco-design principles to fuel a virtuous system of nylon recycling towards the realisation of a circular economy.
“The project allowed us implementing a metal part replacement by re-engineering it and improving its function; by simplifying and shortening production times, we have increased the quantity of products placed on the market in a short time,” concluded Guido Acerbis, CEO of Acerbis.