Precision CNC Machining Performance Enables Hardmilling Innovation at Fallbrook Technologies

If you visit Fallbrook Technologies Inc. in Cedar Park, Texas, and meet David Markley, the vice president of technology development, ask him if he can explain what his company does. You just might be surprised by his reply:

“Sure. Go ride this bike.”

That’s because it’s easier for Markley to let you experience Fallbrook’s revolutionary NuVinci® continuously variable planetary (CVP) than it is to try to explain it—it’s that far removed from anything riders would have previously experienced from the seat of a bicycle. Born from the mind of a man who was working to break the land-speed record for bicycles and who realized that traditional bicycle gearing was a significant limitation, the NuVinci N360™ hub replaces the cogs of gears and derailleurs that have been standard issue on multi-speed bicycles for decades. Unlike conventional transmissions, the NuVinci hub enables riders to continuously, seamlessly and silently change the bike’s drive ratio. Exclamations from those who experience it turn quickly to, “Wow, that’s smooth!”

Fallbrook began commercializing this transmission in bicycles, and when the company first demonstrated it at the Interbike trade show in 2004, it caused quite a stir. “Everyone thought that it was cool, but it was clear from talking to people in the booth that only 5 to 10 percent of people really understood what it meant for the industry,” explained Mark House, engineering manager for the prototype shop. “Before they ride it, people want to know things like ‘What’s the efficiency?’ After they ride it, they want to know ‘How much is it?’ and ‘Where can I buy one?’”

But what’s equally appealing as a ride on a NuVinci-equipped bike is the wide range of applications where the innovative transmission can be used. Everything from lawnmowers to heavy equipment, from automobiles to electric vehicles can use a version of this transmission. What’s more, it can provide not only a continuously variable forward-ratio range but also reverse with an infinitely variable planetary configuration—all without using a single gear.

It was in working through the R&D required to develop solutions for these additional applications, as well as further innovation in the original design for bicycles, that Fallbrook found its prototype shop pushing the limits of its machine tools. Like many manufacturers, Fallbrook brought the designs coming out of its R&D department to life as prototype parts produced on commodity production vertical machining centers.

Since introducing the NuVinci CVP almost a decade ago, Fallbrook has been on the leading edge of mechanical power transmission, and the company is further pushing the envelope with its new designs. Over the years, Fallbrook relied on the creativity of its operators to overcome commodity machine limitations in order to produce prototype parts for testing. Some of Fallbrook’s new designs and larger transmission sizes started exceeding its machining capabilities.

With the nature of the traction-drive principle used in the NuVinci CVP, surface finishes for its parts are vital and profile accuracy is required for proper operation. Further complicating matters—because the transmission essentially also serves as a large bearing—it requires hardened materials, typically 52100 alloy steel hardened to HRC 62, making tool life a significant concern as well. This situation was untenable, since the company needed its R&D team to produce quality parts in order to prove that its newest design innovations were commercially viable for production. Fallbrook knew it had reached the limits of what creative processing could get from its commodity vertical machines and decided to seek out a precision hardmilling solution.

Markley explained, “We were limited by the equipment we had, but we became masters of using it to get the parts that we needed.”

House said, “We got incredibly creative in overcoming the machine limitations in order to meet the specifications that we needed to achieve, but we finally hit the wall. We had to be able to machine the hard materials to take the next step.”

Outsourcing was not the best option, according to Markley. “We looked at outsourcing the work to a mold-making shop, but we would be coming in with such small numbers, one to 10 of something, that there was no way we would be able to get any attention or the quick turnarounds we need.”

He added, “Had we not been able to do things on our own schedule—often under tight timeframes—in order to make it to all the different industry shows and events we have done, we wouldn’t be here today. There’s simply no way we could outsource it.”

Looking to Mold-Making Technologies

It’s that kind of productivity on short lead-times that has fostered in Fallbrook’s leadership a significant respect for the value that the R&D shop provides to the company. House summed it up: “We have incredibly creative people working here, and the ability to quickly take the engineers’ imaginative solutions and develop a part to put on a bike and ride in the parking lot is the value our R&D department provides. With our machining talent, we can evaluate the benefits and drawbacks of a design in real-world terms almost immediately.”

Based on specifications for one of its most challenging parts and desired cycle times, House conducted extensive research into precision CNC machining technologies that could handle Fallbrook’s requirements with ease. Typical of the out-of-the-box thinking at Fallbrook, the search was not limited to the usual production machines.

House added, “Focus remained largely on prototyping, but we needed to demonstrate quality typical of production solutions. In keeping the complicated simple, we realized that processes previously tried had potential if they were refined and utilized on capable equipment.

“We needed a path to production in the tens of thousands. Our R&D team could make tens of things or handle any one-off designs, but we needed to move into what we called medium volume production. Higher volumes also demand cost reduction, increased surface finish and repeatable accuracy. We needed something more than our current prototype practices provided. We made the most of hard milling and hard turning, but this is where we hit the limitations of the machines in terms of tool life, surface finish and ultimately part cost.”

And with that in mind, the investigation led him into the world of mold making. While they’re not making molds, these machines are specifically designed to deliver high speeds and feeds in hardmilling operations—exactly what Fallbrook needed to achieve the levels of accuracy and finish required for its unique products.

From Problem Parts to No Problem

Fallbrook reached out to several machine suppliers, requesting sample part runs for one of its more difficult parts, giving them very aggressive cycle-time targets to try to push throughput as far as possible, along with improving part quality. Makino was the first company to meet the part requirements and deliver a sample part, using its V56i vertical machining center.

As a part of his pre-purchase research, House visited Makino and was taken to see a mold-making customer that operates a V56i for hardmilling applications. Upon taking a tour, House noticed something odd. “I realized that they didn’t have any metrology equipment in the shop,” he said. When he asked about it, he was informed that the shop was so confident in the Makino’s ability to hold two-tenths tolerance that it didn’t need to do metrology. He was told that when there is a dispute, which doesn’t happen often, the shop’s policy is to go to a qualified third party to perform the measurement testing and resolve the issue. After Fallbrook’s research was completed and the results from the test-part runs were in, it was time to prove the ROI. “We did a cost benefit analysis of the V56i over replacing with an existing brand, looking at what could be kept in-house versus what would need to be outsourced. Through this calculation, we saw a full repayment period of two to three years,” said Markley. With leadership convinced, Fallbrook purchased a Makino V56i from its local SST representative in Texas.

In order to get the most out of the V56i and the R&D department as a whole, all operators in the R&D department were trained on the machine, and Fallbrook got to work.

Pedal to the Metal

Partnering with SST and Makino, House and his team immediately began to test the machine’s capabilities by filling customer orders. Similar to the change in thinking it took for Fallbrook to look to moldmaking technology for its prototyping needs, it realized a new perspective on the entire machining process. “We no longer have that wall—that equipment limitation which previously stopped us dead in our tracks,” House explained. “Now we have fun. For example, rather than turning on one part, we chose to helical interpolate a traction surface on a large ring and held 2 microns circularity.”

Due to the rigidity and precision CNC machining capabilities of the V56i, Fallbrook was able to increase speeds and feedrates by 35 to 65 percent on typical applications, and operators believe those numbers can eventually grow much larger with additional process optimization. “It’s the rigidity of the machine, the core cooling and the control with its ability to look ahead that’s allowing us to run at those speed ranges,” said House. “We’re still learning how to look at this as a mold maker might. As we get more familiar with the high-speed machining (HSM), we expect to see our productivity on many types of parts continue to increase. These run rates and the overall machine performance brought a huge boost in morale to our engineering machinists, Kris, Jason and Keith.”

Despite employing significantly more aggressive cutting strategies, the V56i has enabled Fallbrook to use more advanced tooling. Where previous machines would cause the floor to shake with certain tools, the V56i processes parts without any struggle— as quietly as a NuVinci N360 operates. “On the old machines, when we tried to move into more expensive tools, we would get vibration due to the lower rigidity, and as a result, we didn’t get good enough tool life to justify the investment in high performance tools,” said House. “The V56i allows the tools to perform at their upper limit, and we can barely hear the machine running. That’s all rigidity.”

And while the tools cost more than previous tooling, the rigidity and stability of the V56i have led to toollife increases in excess of 300 percent in certain applications. House pointed out: “The cost of the tools is about four times as expensive, but with the extreme gains we’ve seen in tool life and overall throughput, it’s still worth the investment.”

Previous concerns surrounding accuracy and finish were eliminated with the V56i, which has enabled Fallbrook to easily hold profile tolerances. House explained, “This machine is supposed to be able to cut within a 5-micron band and we have confirmed that.” Thus, an additional way in which the prototype shop expects to benefit from the precision of the Makino is in reducing production part costs. “With the accuracy of the V56i, we’re actually able to machine in tiny defects just to test what the effects of looser tolerances or production variations might be. We have confidence in the accuracy, so we can put in defects artificially to test what we may be able to do to open up our part tolerances without affecting performance, thus possibly reducing part cost.”

The company also has experienced improvements in cycle time. In one component transferred to the V56i from previous equipment, cycle times dropped from approximately eight hours to just two hours.

Proving Commercial Viability for New Innovations

Innovative is a word that has been used so much in business that it’s almost lost all meaning. But purely mechanical breakthroughs, truly new ideas not dependent on computers or software, are becoming more and more rare. Fallbrook Technologies was founded on a product that is unlike anything in its space and that has uses in innumerable applications. This company is the very embodiment of innovation.

For a company that’s turning power transmission on its head, it’s not enough to have designs that are good in theory. They have to be commercially viable at a cost that the market can bear. Such a company cannot deliver its products without equipment that removes the limitations on what can be produced, equipment that frees its engineers to develop anything they can imagine. The Makino V56i has made the impossible possible for Fallbrook, bridging the gap between prototyping and production readiness and proving that its innovations aren’t ahead of their time.

“Bringing innovations to market is what matters most to all of us at Fallbrook,” said House. “We’re not just here to make a profit. We want to make a positive impact on the world around us, producing lasting experiences that people can’t experience anywhere else.”