2009 Casting Competition: Polaris achieves core vision with frame casting: motorcycle developers at Polaris designed a minimalist yet complex cast aluminum frame, which Craft Pattern and Mold engineered, tooled and delivered in less than five weeks.

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The 2009 Casting of the Year embodies nearly every advantage the casting process has over other manufacturing processes, h is a consolidation of more than 20 parts into a single component. It reduces weight and tooling costs. And it incorporates the complex shapes and thin and thick sections needed to meet the application's function, all while making the part look clean and simple. It's no wonder the achievement won the enthusiasm of the customer. "With the casting process, I didn't feel like there was any restriction on what we could do," said Greg Brew, Polaris Core concept motorcycle developer.

The other eight prize winners in the 2009 Casting Competition boast similar success stories for customers in the aerospace, dental, agriculture, wind power, mining and military industries.

The Polaris Victory Core concept motorcycle started as a sketch dreamed up a few thousand feet in the air on a flight from Arizona to Minnesota. Michael Song, Polaris lead industrial designer for Victory Motorcycle, had been visiting with motorcycle enthusiasts who were riding stripped down versions of the Polaris Victory Vision touring bike. Song, who was building his own custom bobber--a raw, basic bike in which everything not needed to run is eliminated--was inspired by the transformation of Polaris' complex touring bike into a simple bare-bones machine.

Back at Polaris' industrial design department in Medina, Minn., Greg Brew, director of industrial design at Polaris Industries, was easily sold on the idea.

"We were interested in the minimalistic approach because it is really hard to do," Brew said. "It's easy to make something look modern when it is complex." Polaris wanted to produce a modern-looking bike that was at the same time stripped of the excess.

Part of the answer to achieving the minimalist design was hidden within the Victory Vision touring bike. The large production bike features a cast aluminum frame, and the design team knew the casting process was capable of incorporating further part integration, which would be just the ticket for a bobber-style bike.

"The Victory Vision was our first application of a cast frame, but the Victory Core incorporates five or six more things," Brew said. "We wanted to show there was a lot more you could do with casting technology."

With the help of Craft Pattern and Mold, Maple Plain, Minn., an experienced supplier of prototype plastic and metal components, Polaris was able to make the Core idea a reality. The backbone frame casting--one of five castings that makes up the concept motorcycle's cast aluminum frame--serves as the main structural component and incorporates the gas tank, air inlet, air intake box, electrical routing, and seat and motor mounts. The casting process afforded the bike superior design opportunities over typical steel fabrication and assembly, leading the backbone part to be named this year's Casting of the Year by Metal Casting Design and Purchasing and the American Foundry Society.

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Complexity Made Simple

Before Brew and Song could think about sourcing the Polaris Core's cast components, however, they had to convince the powers-that-be that the parts should be cast in the first place. Steel fabrications and tubing weldments are the standard for much of what Polaris makes--from its snowmobiles to its ATVs and motorcycles.

"It was a big jump for the company to go from a welded fabrication to a casting, and it took a lot of pushing from the design and engineering team," Brew said. "But tube frames have a high part count and are difficult to weld and assemble. We wanted to show the aesthetic of the metalcasting process. Also, it is one of the least expensive manufacturing methods."

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The backbone casting consolidated what would have been a 20-piece steel fabrication into a single part. The integration resulted in a 30-35% weight savings, as well as significant cost savings in tooling and piece price. "It would take, for instance, $1.2 million to tool a gas tank," Brew said. The tooling for the backbone casting, which incorporates the gas tank, along with several other critical features, was engineered and produced by Craft Pattern and Mold for less than $15,000.

"The process and cost-savings are really intriguing," Brew said. "The impact of it is that the Core looks like a custom bike--everything is hidden in the frame--yet it could be the least expensive bike in our lineup."

Craft Pattern and Mold's team of machinists were able to fixture the casting and control critical part features and tolerances using CAD-CAM technology and CNC machining techniques, all of which led to improved downstream secondary processing and assembly efficiency.

"Casting reduces the tolerance variation, so we start with a more accurate base," Brew said.

In addition to part consolidation and cost savings, the cast aluminum frame increased the rigidity of the bike, improving its resistance to the twisting force pulling on the front and rear wheels. According to Brew, tube frames have more flex, so when the bike is taking a hard corner, the frame bends, causing the two wheels to move in different directions from each other. The cast frame's inherent rigidity prevents that from happening.

"The other thing I love about the casting is that it gives fantastic validity to the front end of the bike," Brew said. "It has a certain mass and polished spine that is really just amazing. Only because we cast the bike were we able to do that. The overall feel of the cast frame is very powerful and solid."

Perfect and On-Time

As a manufacturer of prototype metal and plastic components, Craft Pattern and Mold is geared toward working on complex parts with tight deadlines and the Polaris Core concept bike was no exception.

The industrial design team at Polaris handed over the order for the frame component, as well as 8-10 other castings and machined parts needed for the concept two-wheeler, shortly after Thanksgiving '08. The deadline: before Christmas. Polaris planned on showing the bike at several shows throughout 2009, starting with one held mid-January. The bike required a week of assembly and photography for the launch and another week for delivery to the show.

"Those guys [at Craft Pattern and Mold] were fantastic," Brew said. "It wouldn't have happened if they just acted like a supplier. But they were more like a partner. It's pretty staggering how quickly they turned it around."

Tony Cremers, president of Craft Pattern and Mold, estimates his team spent three days engineering the casting and tooling before CNC cutting the patterns and coreboxes for the nobake sand molding process. Tool development took about a week, and the castings were poured the next day.

One of the biggest challenges in engineering the tooling and casting design was determining where to locate the cores and hold them in place without inducing casting defects.

"There weren't many exit holes in the casting," Cremers said. "So we incorporated chaplets to keep the wall thickness of the interior walls accurate."

Craft Pattern and Mold's engineering and tooling professionals worked with Polaris staff on developing a design that offered the best opportunity for success considering the accelerated timeline. Adding material to thin wall sections between core cavities and the addition of internal chaplet markers were readily accepted by Polaris engineering and incorporated into the design.

Because Craft Pattern and Mold was several other prototype parts for the Core motorcycle, first-pour casting success was critical to the project moving forward without delays due to part redesign and tool revisions.

"The backbone casting was the hinge of the whole project, so when it was poured 100% correct the first time, it was a relief," said Steve Shade, Craft Pattern project manager.

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Craft Pattern produced two prototype units, which were heat treated to a T6 condition and machined, before delivering the parts to Polaris on time and ready for assembly. The castings fit up with the other mating components flawlessly the first time.

Up to the Customers

While Polaris has been pleased with the cost and look of the cast frame, its customers ultimately will decide the late of the Core concept bike and future cast frame applications. In the past, Polaris had received criticism from customers who did not like the look of the plastic tanks on the company's cruiser models. Polaris' industrial design team was curious to see if the public would accept a bike with a raw cast surface finish.

So far, the bike has scored high on customer interest, gaining attention at various shows, as well as via the Polaris website. Brew said that the first four days the Core concept bike was introduced on the website, traffic doubled. The company has received a large international response, as well.

After the round of shows, the development team will work with Craft Pattern to finalize the fuel system for the bike, which is the last thing to develop before the bike is operational. From there, Brew said it is hard to say whether Polaris will put the whole bike in production of take elements from it and incorporate them into other series.

"No matter what, it is a preview of what we could be doing with future bikes," Brew said.

Casting of the Year

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Polaris Motorcycle Frame Casting

Craft pattern & Mold Inc., Maple Plain, Minnesota 

Material: 356 aluminum with T-6 heat treat.

Process: Nobake sand.

Weight: 51 lbs.

Dimensions: 12 x 18.75 x 45.5 in.

Application: Structural frame component for concept motorcycle.

Converted from: Steel fabrication.

* The casting replaces an assembly of more than 20 parts and serves as the main structural frame component for the Polaris Victory Core concept motorcycle. The design incorporates the gas tank, air inlet, air intake box, electrical routing, and seat and motor mounts.

* The prototype casting was delivered as a machined component in four and a half weeks.

* The casting design reduced weight by 30%. Additionally, the tooling investment required for the nobake casting process was significantly lower than the costs of multiple stamping, forming and bending dies, as well as welding fixtures. Structurally, the cast frame is more rigid and precise in shape and form than the fabricated steel frame and offers reduced dimensional variation.

Best-In-Class

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Refueling Manifold

Alum-Alloy Co, Inc,, Ontario, California 

Material: A356 with T-6 heat treat.

Process: Sand casting.

Weight: 9.5 lbs.

Dimensions: 25 x 19 x 8 in.

Application: Connects to multiple fuel tanks for in-flight refueling.

* The refueling manifold is integrated into a modification kit that is installed on U.S. Air Force aircraft. The manifold mounts to the airframe with four bolts, and all the fuel connections are made with quick-disconnect flexible hoses.

* The end-user received a commendation from the U.S. Air Force for the design of the refueling manifold and installation kit.

* The sand casting process is ideal for this application because quantity requirements are low (10 pieces per year). Delivery of the raw castings can be as quick as four to six weeks after receipt of order.

Best-In-Class

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Cam

Signicast Investment Castings, Hartford, Wisconsin 

Material: 8620 steel.

Process: Investment casting.

Weight: 1 lb.

Dimensions: 1.625 in. diameter, 4.84 in. long.

Application: Commercial industry.

Converted from: Machined from solid billet.

* The casting supplier was able to produce the cam tracks and spline, a series of projections that fit into slots on a corresponding part, in near-net-shape. Signicast also provided the star shape on the end of the casting that was previously a secondary component pressed onto the original machined part.

* Elimination of machining, broaching of the spline, and assembly involving the secondary component significantly reduced overall costs and lead time.

* Part performance was improved due to a reduction in weight, which resulted in less rotational inertia.

Best-In-Class

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ClassicSeries CVR Dental Pump

Piad Precision Casting Corp., Greensburg, Pennsylvania 

Material: A020 aluminum bronze.

Process: Semi-permanent mold.

Weight: 15.4 lbs.

Dimonsions: 10 x 10 x 4.5 in.

Application: Dental suction pump.

* The casting design features cast-to-size holes, diameters, and internal ports and passages. Some internal passages and overflow ports could not be formed through the extraction of steel cores, so the casting supplier used two expendable sand cores.

* Customer Matrix by Midmark selected A020 alloy for its high strength, mechanical properties and wear resistance. The high tensile and yield strengths of the material allowed the casting supplier to cast the housing with minimum wall thicknesses, keeping part weight and material costs down.

* The casting design also incorporated three mounting feet into the housing, which reduced the net casting weight by 7% and overall cost by 14% compared to purchasing the housing and mounting baseplate separately.

Best-In-Class

Agriculture Hitch

Bremen Castings Inc., Bremen, Indiana 

Material: 80-55-06 ductile iron.

Process: Green sand casting.

Weight: 25.24 lbs.

Dimensions: 15 x 9 x 5 in.

Application: Hitch coupling for an agriculture implement.

Converted from: Five different hitches fabricated out of steel plate.

* The hitch is a replacement that consolidates five different hitches into one. Each original hitch was made of multiple steel pieces that were bent and welded together.

* The consolidation of hitches into a single casting reduced the number of parts and allowed commonality of products for the customer, as well as the consumer.

* The part is provided machined complete by the casting supplier. The new casting design provided the customer an annual savings of $20,000.

Honorable Mention

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Aerospace Valve

Aristo-Cast Inc., Almont, Michigan 

Material: 356 aluminum.

Process: Investment casting.

Weight: 700 g.

Dimensions: 3 x 4 x 2 in.

Application: Aerospace.

* To fully understand the complex core geometry required in the part, the casting supplier produced cores using fused deposition modeling. These models helped the casting engineers spot trouble areas that would require special attention.

* A low pressure semi-pneumatic device was used to fill the core passageways and eliminate air pockets that could cause core breakage or failure.

Snubber Arm Casting

P&H Mining Equipment, Milwaukee

Spokane Steel Foundry, Spokane Valley, Washington 

Material: AISI 4320 modified steel.

Process: Nobake sand.

Weight: 207.72 lbs.

Dimensions: 33 x 9 x 14 in.

Application: Large above ground electric mining shovel.

Converted from: Steel fabrication.

* The casting slows the 25,000-1b. dipper door from opening and closing too fast. A full dipper load on the door is 227,000 lbs.

* Codesigned between the OEM P&H Mining and Spokane Steel Foundry, the cast part resulted in a 40% reduction in machining time, a 15% reduction in weight and a per unit savings of 46% ($81,178 annually).

Honorable Mention

Wind Power Tail Fin

LA Aluminum Casting Co., Hayden Lake, Idaho 

Material: A356 aluminum.

Process: Permanent mold.

Weight: 3.7 lbs.

Dimensions: 23 x 5.5 in.

Application: Wind power generation.

* The customer for the rail fin part of a 1 MW wind generator was experiencing a 50% fall-out rate. Converting it to a permanent mold casting reduced the rate to less than 1%, saving the customer $470,000 annually.

* The sand blasted permanent mold version for use on land exhibited a denser surface structure than the previous version, providing a better surface finish after sand blasting.

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U.S. Military Target Location Device

Precise Cast Prototypes & Engineering

Commerce City, Colorado 

Material: AZ91D magnesium.

Process: Plaster casting.

Weight: 1.6 lbs. (for the upper and lower housing combined).

Dimensions: 10 x 10 x 4 in.

Application: Target acquisition and location for defense industry.

Converted from: Composite/thermoplastic/carbon fiber.

* Other materials considered for the part were carbon fiber and thermoplastic, but they would have required extensive lead times for tooling. Using magnesium castings shaved months off development and reduced overall cost.

* The casting supplier had to overcome thick sections surrounded by thin areas. Some cross sectional thicknesses are as little as 0.04 in.

Shannon Wetzel

Managing Editor