Three weeks. It’s all Tooling Equipment International (TEI), had to design, cast, clean, heat treat, machine and inspect a motorcycle swing arm so uniquely complex it looks more like a spiderweb sculpture than vehicle part.

As a prototype casting shop, AFS Corporate Member TEI (Livonia, Michigan) is accustomed to quick turn-arounds and using technology to achieve castings that push the boundaries of traditional design. It was fastidious in its approach to the project yet confident the delivery would be made on time.

Others were more pessimistic. That first week, a customer walking through the facility saw a TEI engineer working on the mold design and declared, “you will never be able to cast that.”

TEI proved him wrong.

“We were given an extremely tough time scale to meet, and given the geometry, that was a bit of a challenge,” said Oliver Johnson, president of TEI. “We had at best two shots to get this thing right, and we got a good part the first time.”

The swingarm is for the Lightning LS-218 motorcycle produced by Lightning Motorcycle. 3D software design company Autodesk commissioned TEI to produce the prototype to prove the capabilities of its generative design methodology, which automates the design based on process-specific parameters.

The intricate yet robust part replaces a three-part billet machined into a box section. The design reduced the mass of the swingarm by 10% while increasing torsional and bending stiffness. The organic shape hints at the future of metalcasting and the growing opportunities for the industry from additive manufacturing methods, earning the casting the title of 2018. Casting of the Year from AFS and Metal Casting Design & Purchasing magazine.

Autodesk had worked on some initial designs for Lightning Motorcycle six years ago, and now the company felt it could put those ideas into reality with TEI as the metalcasting partner.

“We had done some previous work with TEI and knew that making more complex shapes was totally possible,” said Andreas Bastian, principal research scientist at Autodesk.  “We were just looking for the right project to take it for a spin.”

The biggest challenge after the design phase was figuring out how to clean the 3D printed sand mold. The two constraints to casting via 3D printed molds, Johnson said, are first must be able to clean the sand, and then you have to assemble the sand package. For the swing arm, the loose, unbonded sand would need to be cleared away from the all the tiny passages between the thin aluminum branches. But TEI has been working with this medium for many years and has experience in taking on and then meeting increasingly difficult challenges.

“We approach it maybe differently than the industry—we have journeyman patternmakers cleaning our 3D printed sand,” said Ted Kahaian, TEI process manager. “It is common for us to push the design boundaries to see what we can or can’t do, and we haven’t stumped them yet. We are making it tougher on them but because they are able to keep meeting the challenges, we are innovating.”

To ensure the sand mold was totally clean, TEI used a small endoscope to travel down every passage of the mold, referring frequently to the 3D design at the workstation. Critical to this step was the quality of the sand. Knowing this, TEI turned to AFS Corporate Member Hoosier Pattern (Decatur, Indiana) to produce the two 3D printed molds.

“It was vital that we had really good sand that could be cleaned easily,” Johnson said.

After cleaning, machining was another challenge.

“There were only three areas to machine, but the part isn’t easy to hold or access,” Johnson said. “While were working on the mold design and casting the part, in parallel we were designing and machining a fixture.”

TEI used simulation to map out the entire manufacturing process of the swingarm, including machining. The prototype mapped out the whole machining operation in a virtual simulation that simulated the cutting tools, fixtures, and the motions of the pallets.

“Everything is simulated because you don’t want to have a mess up on a job like this,” Johnson said.

The simulation paid off. The two molds both produced good parts, cleaning was successful, and machining operations were completed without a hitch. After CT scanning, white light scanning, x-ray inspection, and dimensional checks before and after heat treating, the swing arm was ready for the customer within the three-week deadline.

“One of the reasons this has been such a strong collaboration is TEI is an early adopter and strategic user of technology, particularly in simulation technology,” Bastian said. “The casting coming out right the first time was pretty phenomenal.”

The success of the cast swing arm will help Autodesk further make a case for applying generative design to not just metal printing but also metalcasting.

“Metal printing likes to show all these exotic shapes that can be produced, but we want to demonstrate casting is a technology that is quite well suited to those shapes, particularly when you are making something larger than a bread box,” Bastian said. “Metalcasting offers hundreds of materials to choose from compared to metal printing, and the manufacturing base is mature.”

Kahaian agrees and is excited for the future of metalcasting as the adoption of additive manufacturing in the industry speeds up.

“3D printed sand is a cheap medium to print in, and it’s using the same materials we have been using for hundreds of years,” he said. “It’s unlimited in size. It is the future, and realistically, there are no boundaries.”

Designs like the swing arm are great showpieces, but Johnson believes the impact can go past the exhibit floor.

“You might not see parts like the swing arm on a mass-produced vehicle, but you could apply the same approach of optimized design,” he said. “The part may only look subtly different but it still can be optimized with the appropriate constraints of conventional technology.”    

Click here to see this story as it appears in the May-June 2018 issue of Metal Casting Design & Purchasing