Published 10/16/2024

Five-Axis Machines Speed NASCAR Engine Production

Moving from an aging set of five-axis mills to more advanced machines enabled Hendrick Motorsports to dramatically improve its engine production.

Eli Plaskett

Senior Associate Editor, Modern Machine Shop

The Driving Force Behind Engine Engineering

Producing the highest-quality engine is vital to Hendrick’s reputation, as the engine shop works for more than just the four NASCAR teams owned by the company – it provides the General Motors engine for several other teams, and it takes this job seriously. “We lease the same engine we use in our own cars,” Tummond says. “We don’t want any of our customers to feel like they’ve lost before the flag falls.” The engineering team at Hendrick is constantly iterating and redesigning engines to meet the highest standards physically attainable, a task that requires both comprehensive quality testing and excellent machining capabilities.

The QA lab tests engine designs to measure both power output and durability using isolated testing chambers equipped with numerous sensors. One test, for example, uses a water-brake dynamometer to measure engine performance, with sensors keeping track of other factors such as the power-to-friction ratio to judge the viability of engine designs. “Because this equipment is so sophisticated,” Tummond says, “we know if an engine is going to be an improvement over our current engines before we get to full testing on the track.” Source: Hendrick Motorsports

Each engine block arrives as a raw casting from GM. From that point, the shop machines the cylinder bores, lifter bores, sealing surfaces and oiling features, among others. Additionally, the shop performs a number of operations on cylinder heads and manifolds. For the cylinder heads, this means machining the combustion chamber, intake, exhaust, and valve features, removing roughly 10 pounds of material. For all three parts, this involves milling, drilling, boring and tapping, with a tolerance as low as 0.0002 inch on critical features.

Unfortunately, the older horizontal machining centers in the shop were starting to show their age. Decades of work had allowed slight errors to creep into their kinematics, and while the engine shop’s experienced machinists could compensate for it and hit the necessary tolerances, these efforts drained their time and energy. “With the old machines, we really had to fight to hit tolerance,” Tummond says. “Luckily we have talented people working here.” Eventually, however, he and others in the engineering team managed to convince management that upgrading to newer five-axis machines would make life easier on the shopfloor personnel and improve production.

Racing Past Expectations

Tummond had a clear idea of what the replacement machines needed: five-axis milling machines with high rigidity and accuracy, plus the repeatability needed to maintain that accuracy over long machining cycles. After months of research, the team at the engine shop purchased two G350A five-axis HMCs from Grob in Bluffton, Ohio, for machining cylinder heads and manifolds, as well as a G550A HMC for machining the engine blocks.

The most important qualities in replacement milling machines were rigidity and repeatability. “We aren’t pumping out thousands of parts a year,” Tummond says. “Accuracy was much more important to us than speed.”
Source: Hendrick Motorsports

The Grob machines had several selling points that appealed to the engine shop team. First and foremost, they were highly rigid, owing in part to the arrangement of the three linear axes, which is designed to minimize the distance between the guides and the machining point. Additionally, the machines use liquid coolant throughout their structures to maintain thermal consistency during machining operations. “There is no thermal growth that we’ve seen,” says Tummond, and that consistency makes repeatability much more attainable.

The HMCs came with 90-tool magazines and flood coolant for chip control. “We didn’t even know we needed this kind of chip management,” Tummond says, “but we’d never go back.” And the compact footprints with comparatively large work envelopes were perfect for the space in the engine shop.

The Grob milling machines provided the rigidity and repeatability the engine shop needed in a small footprint. However, the shop further benefited from features that led to reduced machining time and faster setups. Source: Hendrick Motorsports

After installation, the machines more than lived up to the team’s expectations. “[Grob] advertises six-micron accuracy, and it hits that no problem,” Tummond says. “We used to have to fight for tolerance, but if you tell the Grob to take a tenth off, it will cut a tenth. We don’t have to do anything special for it to work.” Other benefits were unexpected, such as the time saved from superior kinematics and reduced travel thanks to the compact work envelope. “The difference in speed is remarkable. What was a 15-hour machining time is now under an hour.”

While not exactly a high-production shop, the time saved from moving to a more modern line of milling machine enabled the team to dedicate more time toward iterating engine designs for testing and reduced the time crunch involved in prepping engines for races. However, some of the most important improvements were realized in the setup process.

Controlling Setup

One of the biggest changes from the perspective of the machinists was moving to the Siemens Sinumerik 840D. Initially, the old hats expressed some hesitancy when it came to learning the newer controls, but they soon warmed up to it. “[The controls] are very accurate and a whole lot easier than I thought they’d be,” says Jay Grubbs, machinist and programmer at the shop. “The Dynamic Work Offset cut setup in half by itself.”

Engine Engineering Manager Michael Tummond operates one of the Grob 350A HMCs purchased by Hendrick Motorsports. While there was initially a degree of caution about the Siemens controls, machinists at the shop now sing the praises of features like Dynamic Work Offset. Source: Hendrick Motorsports

Dynamic Work Offset (DWO) is a feature that enables users to significantly shorten the process of zeroing the part. It adjusts the machining program to match the actual location of the part, reducing the need for manual centering. “We used to have to put end adapters on and shim it manually to match the program,” Grubbs says. Now, between the DWO and the Vero-S vise — a modular workholding system from Schunk that boasts a repeat accuracy less that 0.005 millimeters — setup time has fallen dramatically and manual shimming has disappeared. “The first time we used the new control and fixturing, the setup was off by 0.0001" in one direction,” Tummond says.

This reduced setup time has improved job satisfaction in the engine shop, reducing the need for tedious manual tasks and providing machinists like Grubbs more time for more creative work. “We have to develop a new program every time the engine designers come up with something,” Grubbs says. Spending less time shimming parts means more time programming the toolpaths for cutting-edge engine designs, providing more value to the team and more engaging tasks for machinists like Grubbs.

While the constant march of incremental progress can seem gradual on the small scale, over time these improvements have added up to modern machine tools capable of incredible precision and speed. Machinists used to older models may doubt the need for high-tech solutions, but the results speak for themselves: dramatically reduced setup and machine time combined with accessible programming and the chance to cut tedious manual labor out of the work day. Those benefits can keep any shop on track.