Polaris Industries teamed up with Craft Pattern & Mold to solve a steel fabrication conversion design challenge on a line of custom motorcycles.

Denise Kapel, Senior Editor

(Click here to see the story as it appears in July's Modern Casting.)

Once an experimental field, with some players excelling while others succumbed to economic pressures, rapid manufacturing is hitting its stride. Additive 3-D sand printing technology enables the production of quick-turn metal castings for applications ranging from proof-of-concept prototypes to high quality preliminary runs and onward into full production. For metalcasters, the benefits of using this flexible design method are impressive.

When Polaris Industries, Medina, Minn., was evaluating ways to improve its Indian “Big Chief Custom” line of motorcycles, metalcaster Craft Pattern & Mold, Montrose, Minn., proved itself a key player.

One structural component in the redesigned girder style suspension system achieved a 30% weight savings through conversion to metalcasting. Typically a steel fabrication, the part is a prototype of the upper triple clamp for the front steering assembly on the motorcycle.

“The use of high strength aluminum alloy allowed for critical weight savings, a key driver of performance in the motorcycle industry,” said Tony Cremers, president, Craft Pattern & Mold. “The cast aluminum design is much lighter. Also, the shock mounts and the pivot arms tie in with it, so it’s incorporating three things into one component.”

Other noteworthy benefits to casting the part was Polaris’ ability to incorporate its logo directly into the part, as well as the part’s better appearance overall.

“We didn’t want to give the appearance of a true finished part,” said Steve Shade, project manager, Craft Pattern. “We’re bringing it out as that raw look the customer wants, but with new functionality.”

The Proof Is in the Printing

Polaris was updating its motorcycle suspension, which was built on a technology introduced many years ago.

“We wanted to use an air over spring shock in the front, which this component does mount, and we wanted to integrate the handlebar mounts and the pivot arms,” said Tom Hanegraaf, senior computer-aided industrial design (CAID) designer, Polaris Industries. “The industrial designer was the one to conceive how this was going to be packaged together, and I needed to come up with a design for Craft Pattern, so they could produce the molds.”

All together, the group had no more than three weeks to accomplish this part design. Craft Pattern & Mold used 3-D sand printing technology to produce the prototype sand mold for the steering clamp, now a single 6.5 x 5 x 3-in. 356-T6 aluminum casting weighing 2.6 lbs.

“We had a total of six cast parts to complete for this one-off concept bike,” Hanegraaf said. “[3-D printing] allowed me to hand off these models, making changes as needed during the prototyping process.”

“Near-net-shape castings eliminate costly machining and fabrication processes,” Cremers added. “Timeframe was a factor, and also the customer’s need for one or two pieces. Usually that is a good candidate for [rapid prototyping], where you don’t have to invest the time in producing a pattern tool, then make your sand mold and pour your parts.”

The rapid 3-D sand printing process significantly reduced cost and lead time obstacles to producing this casting conversion. Craft Pattern drew up gating and machining plans, and the parts were on their way to completion. Prototype delivery was accomplished in days rather than weeks.

Rapid manufacturing enables metalcasters to produce components for physical testing that match the castings to be created in full production using other methods. It’s a game changer in the market’s ever-increasing competition to produce lightweight, high performance components.

“I was at one of the bike shows and a lot of people were intrigued with us using the latest suspension,” said Hanegraaf. “We were mounting up the fork itself to the triple clamps. That bodes well from a marketing standpoint to have those highlighted areas, to show people the days of old versus what we’re capable of doing now.” He credits his relationship with Craft Pattern and the shop’s introduction of 3-D sand printing as key enablers to the proof of concept and straightforward production of this Polaris prototype.