Oak Ridge, TN, may be known as the “Secret City” for the classified research conducted there to develop nuclear weapons in the 1940s, but Tennessee Tool and Engineering, a company founded there in 1972 by Larry Palmer, is well known as a machine shop. Its customers include manufacturers servicing the automotive, commercial equipment, agricultural, medical, and defense industries.
As an aluminum die-cast parts manufacturer, Tennessee Tool’s main focus today is growing by investing in high-performance horizontal machining centers to produce millions of engine, transmission, and steering components for cars and off-road vehicles. “We’ve built our automotive machining reputation by taking on programs that have faltered elsewhere and making them work here,” said Pete Raulin, business development manager. “Original equipment manufacturers [OEMs] and Tier 1 suppliers ask us to solve problems no one else has been able to solve. To do that, we need machine tools that not only are highly reliable and accurate, but also come with engineering support to create the solutions customers are counting on.”
In one recent case, a major manufacturer of off-road recreational and utility vehicles asked Tennessee Tool to take over production of an electronic steering assist unit that the previous supplier produced on three machines. Raulin estimated Tennessee Tool would also need to make the parts on three machines with an average cycle time of 9.5 minutes. Raulin and his team consulted with application engineers at Makino Inc. (Mason, OH) and SST, which sells machine tools along with tooling, fixtures, and consumables. The Makino/SST team suggested running the parts on one a61nx four-axis HMC. Cycle time would be six minutes, fie seconds.
Tennessee Tool won the contract based on the cycle time reduction and purchased its first Makino a61nx in 2011. The investment enabled Tennessee Tool to implement the off-road vehicle parts program in just five months—60 days ahead of the customer’s schedule.
“We chose the a61nx because the Makino/SST application engineering group gave us an out-of-the-box concept that made ridiculous sense,” Raulin said. “Partnering with them was paramount in meeting the lead-time requirements and also reducing the cycle time by more than 30%. We would not have been able to accomplish that with another builder.”
Tennessee Tool’s production machining and assembly division comprises four buildings packed with machine tools, grinders and lathes. There’s no square footage that goes unused and 150 employees turn out parts 24/7. Aluminum die casting is done in another building elsewhere in Oak Ridge. Near-net parts are trucked across town for final processing in the sprawling machine shop. Being able to produce all of the steering component features on just the one a61nx HMC instead of on three separate platforms freed up much-needed floor space.
To accomplish this, Raulin’s team worked with Makino/SST to design fixturing that holds six parts on each side of a pallet. Philip Loaring, a Tennessee Tool project leader, trained with the machine tool manufacturer’s engineers and technicians to learn how to program new operations. Then, when production began, Loaring and Raulin discovered the full value of working alongside the Makino/SST team. Initial cycle time averaged 12 minutes—twice as long as planned.
Loaring consulted with Makino applications engineer Mike Roth to edit Loaring’s programming and learn shortcuts. Roth helped him add M codes to rotate the pallet to position workpieces during tool changes. Roth also showed him how to tweak codes for feeds and speeds, and how to accommodate additional tool changes needed for a part feature requested by the customer after the original project quote.
The result of their collaboration was achieving the promised cycle time of six minutes, five seconds, while also machining the additional part feature.
“It was a unique situation for me,” Loaring said. “We’ve never had that much cooperation from a machine tool builder in the past. Makino and SST were very interested in achieving what they had quoted we would be able to do. It all worked out very well.”
Demand for the off-road vehicle parts steadily increased, so Tennessee Tool invested in two additional a61nx machining centers. The 500-mm mills are ideal for high-volume machining of aluminum castings because of standard technologies that ensure productivity, accuracy, and machine reliability, according to company.
The a61nx machines feature 14,000-rpm, high-speed high-power spindles with 240 N•m of torque, making them well-suited for automotive part production. Non-cut times are minimized through 1g axis acceleration and a standard direct-drive motor B axis. Robust casting design and roller-type linear guides ensure that the entire a61nx work envelope can be effectively utilized. The mills also are equipped with an optional fixture hydraulic unit clamping system that speeds up parts loading and unloading.
Loaring pointed out that the off-road steering parts are challenging to machine. Their design requires holding a positioning of ±0.0002″ (0.005 mm), working between 0, 90 and 180 degrees.”Repeatability is excellent with the a61nx. I rarely have to make a positional offset and usually that’s because of variations in the castings. The a61nx machines do exactly what they are programmed to do,” Loaring stated.
In working with Makino, Tennessee Tool’s leaders found opportunities to talk with the machine tool builder’s engineers about other machining needs. Makino was designing a horizontal machining center specifically for high-volume production of aluminum parts and sought input from Raulin and others at Tennessee Tool.
They asked us what we wanted to see in a machine we could use on aluminum castings. We told them it had to be extremely fast. We wanted to make sure it was only machining near-net parts with minimal material removal,” Raulin recalled. “We also said we needed a small cube machine with a small footprint.”
Makino responded by introducing in 2014 the a40, a 400-mm, four-axis HMC purpose-built for die-cast parts production and asking Tennessee Tool to participate in a beta test program for a year. Palmer and Raulin put the a40 into production for an engine valve cover for a major OEM. The parts already where being produced on commodity machines using a modular fixturing system developed by Tennessee Tool so that Raulin’s manufacturing team could accurately compare their existing cycle times to what the a40 delivered.
“As a machine house, time is money,” Raulin observed. “The more parts we can make in the least amount of time goes right to the bottom line. What we found with the a40 is that our cycle times decreased by 20%, and that opened up 20% more capacity and, of course, profitability increased in turn.”
The speed of the a40 and its reliability so impressed the Tennessee Tool team that they invested in a second a40 after only eight months of beta testing. Uptime was 90% with the remaining 10% for setup and preventive maintenance. After the year-long test period ended, Tennessee Tool purchased the beta machine, too.
“We noticed that with the a40 cycle times decreased right away. And then the tolerancing and the repeatability of the machine itself make it possible for us to look at what we’re able to do from a dimensional standpoint and pursue more new business with tighter-tolerance parts,” Raulin said.
Working with Makino, Raulin said his team has learned the value of aligning with a machine tool builder that acts like a business partner instead of just a vendor. “Service is paramount in our mind,” said Raulin. “With the low downtime that we have with the a40s and the a61nx machines, and the service response that we get from Makino, it made the best sense for us to move forward with them.”