Wiseco's Near-Net Piston Forging Process Explained

October 2, 2019 / by Mike Rithjin

Near-net forging is a proprietary manufacturing process that allows precision features such as valve reliefs and oil drain-backs to be formed without additional machining. Wiseco's Tracker Series V-Twin pistons are one of Wiseco's latest products using this technology. We take you through all the technical details of Wiseco's proprietary near-net forging process here.

Hooligan Sportsters are all the rage these days. The lightweight Harley is a great customizing platform–an 883cc Sportster can be picked up cheap and it’s ideal for flat-tracking fun on the weekend for guys looking to break into the sport. However, perhaps the best part about the 883 is that it can easily be bumped up to a 1200cc racer, quickly transforming the lackluster performance into a go-fast, turn-left, dirt-spewing machine by upping the performance ante with some new pistons that don’t break the bank. For guys looking for a competitive edge without reducing the weight of their wallet… well, that’s a no-brainer. And the solution is Wiseco’s Tracker Series pistons.

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The desire for more power will perhaps never fade, but with new forms of racing becoming more popular as well, reliable and affordable parts for performance Harley builds are in demand.
Photo: Justin George Photos

Near-Net Forging Process

Wiseco Tracker Series pistons are manufactured using Near-Net forging technology. Near-Net forging is the process of optimizing the forge tooling to create an almost finished product right out of the forging press. When pistons are forged, a metal puck is physically smashed against a forging to form the base shape of the piston, which creates better grain flow resulting in a part yielding higher tensile strength. From there, standard pistons will go through multiple operations of finish machining to create features such as valve pockets and oil drain backs. When pistons are forged using a Near-Net forging, the piston only requires minimal additional machining because many features are created in the forging itself. This reduction in required machining operations has a direct effect on reducing cost.

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Notice the difference in the appearance of the material on the crown. The textured surface reflects the material shaped straight out of the forge.

“Near-Net shape forging is where we form most of the geometry on the top of the piston [with the forging]. The crown and the valve pockets are forged into the part,” explains Wiseco engineer Dave Sulecki. “Those areas are machined in most piston manufacturing processes. You forge out the aluminum and get the slug. Then you have to machine all of that metal away to get the valve pockets and the crown to achieve whatever specific design you’re trying to hit, or the compression ratio for the specific engine. Wiseco is forging those features into the piston. When our Near-Net-forged pistons come off the presses, they need less finishing and machining as they go through the factory. The whole crown area comes right off the press and looks like a finished product. It’s a really unique way to form a piston.” 

Get even more details on Tracker Series here.

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Adding crown features to the forging design allows precision features to be forged directly into the piston without having to go through additional machining steps.

Want to find Tracker pistons for your bike? Use our vehicle search here, or check out the different applications here.

Design

The process of designing a piston made from a Near-Net forging is a multi-step process completed by Wiseco’s design engineering department. The first step is to gather all design criteria to achieve a finished product meeting all consumer requirements such as bore sizes, ring package, compression ratios, wrist pin size, valve size, valve lift, and others. Using these design inputs, the engineering team creates a three-dimensional solid model file of each product and performs Finite Element Analysis (FEA) checks to ensure the piston has the desired strength for the intended application. After creating the finished piston design, the engineer then works backward to design as many surfaces or features to be finished through the forging process such as dome, valve pockets, oil drain backs and other features to reduce machine time, thus creating a Near-Net piston for the Tracker Series line of piston kits.

Want more specifics on Tracker Series designs? Check this out.

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Manufacturing pistons with the near-net forging process requires careful designing, including working backward to translate typically-machined features to the forging.

Strength in Grain Flow

Now let’s delve deeper into the importance of grain flow strength. Basically, the crown shape, valve reliefs, and oil drain backs are forged into the piston instead of machined. The grain flow of the alloy aligns with the shape of those features, essentially providing improved tensile strength throughout every shape and feature of the piston. While some power-hungry enthusiasts are looking to increase bore size and compression ratio in their V-twins, they may want to rethink their strategy, as this ultimately adds additional stress on the pistons. The strength benefits of near-net forging help combat those stresses, especially when equipped with ArmorGlide, a proprietary skirt coating allowing tighter piston to wall clearances, quieter operation, friction reduction and extended service life. This coating consists of a Moly Teflon component, which is a proven solution for piston skirt to cylinder wall interface.

Learn more about increased strength through forging here.

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Forging aluminum aligns the grain structure of the alloy for greater tensile strength. Combined with ArmorGlide skirt coating, this creates a reliable performance package.

Overall, Near-Net forging technology offers an efficient approach to piston manufacturing while still retaining superb quality. Because manufacturing times are drastically reduced, the cost savings is then passed on to the end user. “The consumer benefits on Near-Net design by receiving a high strength forged piston designed for the intended use and longevity, while keeping exceptional value in mind,” says Scott Highland, director of powersports for Wiseco. “This is great for performance street use. The consumer only had cast piston options at this price point in the past, so this gives the rider an upgrade to their engine.”

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At the end of the day, utilizing the near-net forging and design process translates to lower manufacturing cost, meaning a more appealing price point for the rider or builder.

Topics: featured, PISTONS 101, Powersports, Tech

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Written by Mike Rithjin

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