KANNAPOLIS, NC — Like most auto manufacturers, NASCAR race teams are motivated to make vehicle parts better, cheaper and faster. Hundreds of the leading Fortune 500 brands are highly visible on the evocative vehicle paint schemes, pointing to continued healthy investment in the sport.
Yet prudence prevails at any smart company and race teams are looking for creative ways to save money. That includes within their machine shop operations. One of the ways Stewart-Haas Racing is achieving that is by applying Dynamic Motion toolpaths featured in their Mastercam CAD/CAM software (CNC Software Inc., Tolland, CT).
Stewart-Haas Racing is the title-winning NASCAR team co-owned by three-time Monster Energy NASCAR Cup Series Champion Tony Stewart and Gene Haas, founder of Haas Automation, the largest CNC machine tool builder in North America.
The organization fields four entries in the Monster Energy NASCAR Cup Series—the number 4 Ford Fusion for Kevin Harvick, the number 10 Ford Fusion for Aric Almirola, the number 14 Ford Fusion for Clint Bowyer and the number 41 Ford Fusion for Kurt Busch. The team also competes in the NASCAR XFINITY Series by fielding a full-time entry—the number 00 Ford Mustang for Cole Custer and one part-time entry, the number 98 Ford Mustang. Based in Kannapolis, NC, Stewart-Haas Racing operates out of a 200,000 ft2 (18,580 m2) facility with about 370 employees.
A very active 4000 ft2 (372 m2) of that space is the company’s machine shop. Stewart-Haas Racing has been bolstering its manufacturing strategies to make more of the parts itself that were formerly outsourced. That provides the team with better quality control, improved delivery times and added protection for proprietary designs. Doing more has led Stewart-Haas to streamline its facilities list (with predominantly Haas machine tools), manufacturing processes and procedures, and CNC part programming—specifically with the new Dynamic Motion toolpaths.
While these advanced CAM toolpaths have been in the last several Mastercam versions, and were first launched about 10 years ago, they are still new to many in manufacturing and are continually being improved and integrated into more product features for both milling and turning.
Here’s a brief explanation: Typically, conventional CNC programs are based on geometric boundaries. They have the tool enter the material and then embark on one direction until it encounters a wall or some other obstacle, and then it changes direction. The tool covers all of the area as dictated by the part model, cutting whatever is in its path. Sometimes that is material and sometimes it is inefficient air.
Now, the more recent Dynamic Motion toolpaths have the tool behave rather unconventionally. The tool motion is governed by a highly engineered set of rules that takes into consideration both the area from which metal is to be removed and also the changing condition of the material throughout the various stages of machining. The proprietary algorithms foresee what is next, weigh the alternatives, and automatically modify feeds, stepovers and cutting motions in response to the changing material conditions as the part is being cut.
The objective is to remove material more efficiently by controlling lateral forces to avoid excesses that generate heat. Often referred to as “constant chipload machining”, the smoother, safer motions—constantly in the cut—alleviate stresses on cutting tools and machines, increasing their longevity.
“The biggest transformation I’ve seen in the last year in our shop is the full adoption of Mastercam’s dynamic toolpaths,” said John Simmons, CNC machine shop manager at Stewart-Haas Racing.“They are very powerful. We can make complete parts straight from a large billet now, rather than having to do smaller components and welding them together,” he said. “The dynamic toolpaths give us a lot more tool engagement which cuts down on us having to optimize the roughing toolpaths and allows us to get to the finish operations much faster.”
As an example of just how much faster, Simmons cites a steering center link component as one of the many part applications that are benefiting from the Dynamic Motion toolpaths. The steering link is the connection from the steering box to the wheels, a very important component. The part starts out on its Haas model VF6 TR (for trunnion) 50-taper vertical CNC milling machine as a solid 150-lb (68-kg) bar of alloy steel approximately 4″ wide × 5″ high × 23.5″ long (102 × 127 × 597 mm). The roughing process used to take 12 hours, now it’s down to seven hours by applying the “material aware” toolpaths.
“I would say we are 60–75% more efficient and that’s not only cutting time, but we are also getting significantly more tool life using dynamic motion,” said Simmons.Subsequent 3D contour milling operations finesse the critical dimensions. The tolerances, finish geometry and part weight were undisclosed by Simmons for competitive reasons. However he provided the main causes for the boost in cutting efficiency in the rough machining process with the advanced toolpaths:
–Minimal stepovers to avoid heat buildup and excessive lateral force;
–Smooth motions that alleviate stresses on tools and the machines;
–High spindle speeds;
–Maximum flute engagement for cuts that remove the most material;
–Continual material engagement (climb milling) to minimize air cutting;
–Dynamic adjustments of stepovers to keep tool load constant;
–Tool entry strategies that present the tool to the material at the safest angle;
–Material “awareness” that keeps the tool in a consistent, safe cutting condition regardless of the contour geometry (it modifies the path so that chips will be the same size);Micro-lifts that raise the cutter away from the part’s floor or away from walls so that heat does not build up when cutting speeds are being adjusted during repositioning.
–Micro-lifts that raise the cutter away from the part’s floor or away from walls so that heat does not build up when cutting speeds are being adjusted during repositioning.
In addition to the heavy-duty Haas VF6 TR VMC, the Haas shop has 14 other machine tools. Haas CNC turning centers with live milling heads have been the most recent additions as Simmons said that it was primarily turned parts that were once outsourced but now brought in-house. In addition to machining operations, the shop area has a fully equipped quality control department that checks each part carefully for defects.
“As complex technology becomes more pervasive in our shop, the support we receive from our various suppliers is of paramount importance,” said Simmons. “It’s more than just having the technology, we want to ensure that we are getting the most out of our investments to ultimately save money, improve efficiencies and make competitive vehicles.
“For example the evolution to the dynamic toolpath way of thinking, while worth it for the benefits, can be tricky to navigate,” he added. “You have to remember, I was a CNC programmer for almost 15 years of my career. The light went on much quicker with the assistance of CNC Software’s applications engineers and their reseller in my area, Barefoot CNC.”
Edited by Motorized Vehicle Yearbook Editor Bill Koenig from information supplied by CNC Software.
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