Polaris Produces Powertrains With Exacting Quality

Polaris products that are being equipped with drive trains being produced at the firm's Osceola plant include snowmobiles (the Indy 500 model shown top), personal watercraft (the '97 SL700, middle), and all-terrain vehicles (the '97 Scrambler 500, bottom). (Photo:Polaris Industries)

Polaris layout inspector Connier McClay using the Zeiss Eclipse ST to audit the surface flatness on the crank case assembly for a 700-cc snowmobile engine.

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Polaris Industries' plant in Osceola, Wisconsin underwent an expansion last year; a drive train facility, for clutch and engine production, was added. The plant was already performing seat assembly, exhaust assembly, tube bending and stamping to support the production of Polaris snowmobiles, all-terrain vehicles (ATVs), and personal watercraft (PWC) that are marketed worldwide. The Osceola plant will also build engines for the new cruiser-class Polaris motorcycle that's scheduled to become available next spring.

Two- and three-cylinder snowmobile and PWC engines, previously purchased from a Japanese supplier, are among the things produced in the new drive train facility. Not only were bricks and mortar involved, but also a full complement of design, support and production employees. And machinery, too. Among the equipment: a computer-controlled coordinate measuring machine (CMM) sourced from Carl Zeiss IMT Corp. (Minneapolis, MN), an Eclipse ST. It is assigned around-the-clock to accommodate the measurement complexities of tight-tolerance drive train components and assemblies. Quality manager at Polaris, Brad Clark, describes the CMM as being an automated unit "with the accuracy and flexibility to handle complex part measurement routines, roving assembly line audits, SPC sampling of out-sourced materials, and new tooling verification."

Clark points out that the demand for product improvement within recreational and utility motorsports manufacturing closely resembles the pace automakers are on to continuously enhance performance, quality, and manufacturability. "Polaris competes in markets where consumer demands require the steady introduction of new models offering improved performance," says Clark. "Customers always want faster and lighter machines with more muscle. New product development makes these things happen, but breakthroughs in design and engineering also lead to increased manufacturing complexity. Responding to those challenges across four major product lines means that we are always working on systems and processes that will lead to improved cost-control and quality."

The CMM has an X, Y, Z measuring envelope of 28 × 28 × 20-in. This has the capacity needed to handle Polaris drive train work-pieces, which range from 1-in. diameter O-rings to pistons, cylinders, and crankcase assemblies. These components have tolerances that require accuracy to a stringent 0.0002 in.

Because drive train quality technicians conduct inspections and audits continually on all three shifts, Polaris requires versatility along with peak speed and accuracy performance.

Speed? The Eclipse ST takes readings at a rate of one per second. Complete inspection of a complex part—or a multiple-piece assembly—frequently requires several probe types, lengths or stylus configurations. The CMM features automatic probe changing; probes are stored on a tool rack.

Automatic probe changing comes into play, for example, when Polaris conducts roving line audits at critical stages of engine assembly to monitor the impact of progressive assembly processes. Says Clark: "Applying incorrect torque to a crank case can cause bore crash, which leads to bearing failure to premature wear of internal parts. We also need to determine whether the case is being twisted. If a crank case loses parallelism, the result can be an engine burning down or a piston scuffing." So they need to check with the CMM.

He adds, "An inspection can involve a probe extension to reach into a deep cavity like the cylinder, followed by a star probe configuration to measure the cylinder in multiple directions. The automated probe changing system enables us to write a measurement program, often involving four and five probe changes, that will complete a multi-phase inspection routine uninterrupted. The results are inspection streamlining and CMM throughput that would not be available to us if we had to swap probes manually."

Sourcing Checks

A variety of components are sourced by Polaris from an array of suppliers. There is a wide range of material types, dimensions, shapes, and contours. Almost every incoming part is subject to a critical characteristic audit at receiving. The CMM plays an important role during this incoming audit: parallelism of piston heads and the tapers on crankshafts, for example, are among the checks.

Not all parts checked are metal. Gaskets and rubber O-rings are examples of the types of parts that leverage the "force-free" characteristic of the Zeiss ST probe system. The probe system can acquire data with a measuring force of less than 0.01 N. This means that the force necessary to generate a pulse back to the computer is so minimal that the probe won't bend or distort even soft gasket material. This sensitivity also helps assure that measurements are directionally independent. According to Clark, "The pulse is actually sent before a deflection occurs, so results aren't impacted during a cylinder inspection if the probe is bent to the left during one routine and to the right during the next. There is constant accuracy in all probing directions without the need to perform special calibrations."

Ease of Use

"It would be counter productive, within our operation, if the CMM required an engineering background in order to understand, program and execute the dozens of measurement tasks we do," says Clark. The machine is running a diversity of inspection and quality control duties at Polaris five days a week, three shifts a day.

So to be certain that they can run the machine, Polaris selected U-Soft, a Zeiss pictorial software, to drive and control the Eclipse ST. U-Soft is an integrated program that gives Polaris flexibility on the production floor to probe a simple geometric shape, build a comprehensive statistics report, and digitize 2D and 3D contoured parts. Not only is it easy to use, but Clark notes that the software helps assure that the speed of the CMM is being used to the utmost. He observes, "Our CMM operators are skilled technicians who are extremely comfortable with the software. They have excellent success using the system to get the results that are needed."