Five-Axis Machining Lifts Shop’s Part Productivity and Quality

Coldwater, Mich.-based Sport Truck USA (Sport Truck), a division of Fox Factory Holding Corp., knows a thing or two about automotive suspensions. Since 1991, the shop’s been designing, manufacturing, marketing and distributing high-quality aftermarket off-road suspension components, such as lift kits, for pickup trucks and 4x4s through its family of brands that includes BDS Suspension, Zone Offroad Products, JKS Manufacturing and 4×4 Posi-Lok. But as consumer demand grows for suspension lift kits for today’s newer, more sophisticated models, so too does the need for more complicated parts necessary for those kits.

A key part Sport Truck makes for its lift kits is the steering knuckle, which also happens to be the most complex component and one that takes the longest to make. The part is critical because it keeps a vehicle’s upper A-arm in the stock location while being lifted – and the quality and supply of knuckles are critical to the shop’s continued success.

At one point in its manufacturing operations history, Sport Truck machined some knuckles on one of its 4-axis horizontal machining centers and outsourced the production of the rest overseas. But quality and lead time issues forced most of the knuckle machining production back in house at Sport Truck, according to Design Manager Jared Ball. 

“Today, we machine most knuckles in house so we can control the quality to our high standards,” Ball said. “When we outsourced, and performed our quality testing, we were finding only about 80% of the finished product met our standards. The fit of the knuckles is critical to the overall performance of our kits and to meeting customer expectations, so how they’re machined is equally as critical.”

But more manufacturing change was on the horizon for Sport Truck in 2015. That’s when the shop received a project for the new model year Ford F150 pickup truck, and the vehicle’s new design required a more complex knuckle, in particular, one with a compound-angle design.

“We asked ourselves if there was a different, more efficient way to make the part,” Ball explained. “That’s when we began our search for a machine technology that could do more and give us higher levels of efficiency to produce those complex parts in fewer operations.”

As a satisfied, long-time Mazak customer, it didn’t take long for Sport Truck to contact its Mazak distributor, Addy Machinery, to help identify a solution. The shop knew it wanted an easy-to-use machine that would combine operations and reduce setup times so the shop could quickly and efficiently deliver products to market faster and keep up with the trend of more sophisticated – and frequent – vehicle suspension design changes.

That solution turned out to be a Mazak VARIAXIS i-800 5-axis Vertical Machining Center with rotary/tilt table and 50 taper spindle. It was perfect for the shop because of its advanced multiple-surface, simultaneous machining capabilities that include milling, drilling and tapping – ideal for the knuckles’ profiled surfaces. As a result, the shop was able to eliminate three operations, reduce production lead times, improve machining accuracy and lower operating expenses.

“We were already using the 4-axis Mazak HCN-6000 Horizontal Machining Center,” said Ball. “One of the good things about it is that it's the same machine that our other suppliers use when they make parts for us. And it’s the reason we got the 5-axis VARIAXIS – we already trusted  Mazak machines and knew they’re reliable and user friendly in addition to being able to make quality parts.

The shop saw immediate boosts in production efficiency and accuracy. According to Ball, competitors were using a horizontal plane, three chuckings and multiple operations to produce a single knuckle. On its VARIAXIS i-800, Sport Truck now machines the same part, completed and ready-to-ship, in one setup made possible by Mazak’s DONE IN ONE® technology. Operators only touch parts twice – once to load and again to unload – as opposed to moving parts around the shop to multiple workstations.

“For us, this is a huge deal. I’ve been on the technical support side in the years I’ve been at Sport Truck, and something you never, ever want to hear from a customer is that a part isn’t meeting their expectations,” said Ball. “One of the things about Mazak machines, and the VARIAXIS i-800 in particular, is that they can make the same identical part every single time, without quality issues, which results in a better customer experience.”

The machine also features extra tooling capacity for longer unattended operation. Its higher feed and speed capabilities generate smooth surface finishes, while a high-pressure coolant system helps extend tool life.

When paired with an optional two-pallet changer, the machine provides additional unmanned operations and off-cycle part setup. This simple, efficient form of automation allows the shop to load, unload and inspect parts on one pallet while the machine works on the other. The machine’s MAZATROL SmoothX CNC offers easy 5-axis programming and, according to Ball, the control’s touch-screen functionality linking program, process list and 3D tool path display enables him to take 3D models of the fixturing and use the screen to easily program the job.

Sport Truck began in 1982 as a retail store specializing in lifted suspensions. Through a series of acquisitions over the next few years, the company broadened its product offerings until, in 1994, it began focusing solely on suspension products. The shop prides itself in making high-quality parts and backs them up with one of the industry’s best customer care programs.

Today, the employee-owned company has around 275 workers. The shop’s production operations include machining, laser cutting, sheet metal fabricating, CNC robotic welding and manual welding. For its suspension kits, the shop produces, in addition to the knuckles, control arms and shock bodies.

“The biggest thing in our business is being first to market, so part production cycle time is important. When a new model truck comes out, we want to be the first to get a kit for it out in the market,” said Ball. “Being first to market with a quality kit has driven our business and resulted in consistent growth over the years.”

Ultimately though, he adds, it all comes down to taking care of customers. “If you don’t, they're not coming back to you – they’ll go to your competitor. The reason our customers keep buying from us is because we make excellent products, they’re confident in our quality and they know they’re getting the best support. It’s a model that has worked for us and one that wouldn’t be possible without our Mazak partnership.” 

About Mazak Corporation

Mazak Corporation is a leader in the design and manufacture of productive machine tool solutions. Committed to being a partner to customers with innovative technology, its world-class facility in Florence, Kentucky produces over 70 models of turning centers, Multi-Tasking machines and vertical machining centers, including 5-axis models, Hybrid Additive processing machines and Swiss Turning Machines. Continuously investing in manufacturing technology allows the Mazak iSMART Factory™ to be the most advanced and efficient in the industry, providing high-quality and reliable products. Mazak maintains eight Technology Centers across North America to provide local hands-on applications, service and sales support to customers. For more information on Mazak's products and solutions, visit or follow us on social media.