Delivering these exacting parts became even more challenging when, over a five-year period, Tell Tool's customers switched from specifying castings and forgings to requiring parts machined directly from solid aluminum billet. This switch provides several advantages. The aluminum billet parts have superior material integrity, design changes can be made to the toolpath instead of the casting and, compared to the castings, the aluminum billet parts have shorter lead times and have a lower cost.

During these changing times, Tell Tool was upgrading its machining technology. As one of a handful of niche aerospace and defense part suppliers in the country, Tell Tool faces some stiff competition and upgrades regularly to stay competitive.

"Moving to aluminum 'hog-outs' requires 80 percent metal removal and high accuracies," says Mark DiLorenzo, Tell Tool's president. "We saw high-speed machining as the way to meet these needs. In 1996, we purchased a Makino high-speed, A77 horizontal machining center with five axis capability. Based on the results it provided, we added two more A77s and a modular machining complex (MMC)."

Solving the "Innovator's Dilemma"

Finding an advanced solution to support manufacturing is not always straightforward for Tell Tool. "In the past, we have been unable to evolve our processes as quickly as we would like," says DiLorenzo. "The technology did not always exist when we needed it." Case in point: owners Paul Drewski and Bill Weber helped pioneer vertical five-axis technology with other industry leaders in the early 1970s to enhance the milling of their compound angle parts. More than 25 years later, Tell Tool still relies on itself to bridge the gap between its needs and the available technology.

"Off-the-shelf tooling simply cannot make the complex cuts we rely on to manufacture these aircraft engine components," says Bob Morin, Tell Tool's vice president of manufacturing and operations. "We have created a library of more than 20,000 tools to machine the hydraulic actuators, fuel controls, hydraulic manifold control systems and pumps we make. At least 60 percent of the tooling in these applications is custom."

Automation Increases Throughput

During Tell Tool's upgrade, the manufacturing team realized the benefits material handling technology and automation would bring, even though it is typically used for large volume jobs with less variety in the part mix.

"Material handling support has proven essential for making small volumes of our various niche parts," says DiLorenzo. "We do not make parts typically considered for lights out manufacturing. But the high-speed cell with MMC allows us to run multiple parts unattended." Russell Bigelow and Tim Nehmer, Tell Tool machine operators, almost take the MMC for granted. "The automation takes away hand work and allows you to focus on the head work," says Bigelow. "The Model C Cell Control software schedules parts and monitors tool life. The MMC shuttles pallets to and from the machines."

Nehmer notes the cell's ability to run various types of parts at the same time. "The Model C software makes changeovers possible on a pallet-to-pallet basis," he says."We simply load the pallet onto the shuttle and enter its tracking number. The MMC and the machining center switch tooling and change part programs accordingly. It takes minutes instead of hours to machine these parts using the MMC. This lets us focus on the next jobs instead of the one currently being machined. With room for 12 pallets on the MMC, and 26 pallets on hand, there is always plenty to set up. Our throughput levels have increased dramatically."

Programming the Complex

Tell Tool quickly proved out its approach with one part: a fuel control housing for a Cessna Citation Bravo. This unforgiving part resembles an uneven block of Swiss cheese, with multiple surfaces, compound angles and an array of holes throughout. But team members like Tony Roda eagerly accepted the challenge.

"A manufacturing engineer orchestrates the entire process," says Roda, a Tell Tool senior process engineer. "Once the tools and the machines that will support each job are specified, we turn customer prints into a solid model." "The parts are so complex," he adds, "that sometimes the CAM is unable to effectively program the toolpath for a complex area. We focus on these part characteristics and we create proprietary macros in Visual Basic to address these gaps."

The programming staff creates as much of the program as possible in Camax. "We aim for a zero-defect part program," says Jeff Pease, a Tell Tool senior N/C programmer. "So we send every part program through a computer simulation to ensure its quality and accuracy. This lets us optimize designs for manufacturability, automatically generate a CNC tool path from the surface model and verify that the toolpath is correct before cutting chips. This simulation is one of many quality checks throughout the application."

Tell Tool's award-winning quality system also involves the operator in the inspection of many part dimensions. "The tighter the tolerance, the more often it is inspected," says Pease. "The parts from the Makino cell are also checked by two Zeiss Prismo VAST CMMs. And after manufacturing we can pinpoint when each part was machined and other details in case anything needs to be checked."

Fuel Control Application Goes High-Speed

With 80 percent metal removal, Tell Tool also relies on an HSK spindle for extra rigidity to support its vast array of customized tooling.

"Each machining center is armed with a 244 capacity tool carousel with a mix of custom and standard tooling," says Morin. "The standard tooling is made up of end mills, drills and threading tools. The HSK combined with the machining center's five axes allows us to take advantage of the higher machining center speeds and machine as many details as possible on each part without refixturing."

The A77's metal removal rates are impressive (see FIGURE 1), relying on helical milling to eliminate tools previously used to straighten out the castings. "We are doing a lot more with each tool than we did in the past," says Morin. "By standardizing tools, we minimize the overall quantity. The machine's coolant pressure is boosted by a high-pressure chip blaster. This provides 1,000 PSI of through-spindle coolant to literally blast chips away from the work pieces and ensure thorough chip removal during unattended operation."

Figure 1

Part Snapshot	Fuel Control Housing
Operations	From 21 operations across 5 machines to 4 operations across 1 machine
Cutting Tools	From 747 cutting tools to 235 cutting tools
Roughing Speeds	16,000 RPM
Finishing Speeds	400 RPM
Roughing Feeds	12,000 IPM
Finishing Feeds	250 IPM
Machining Cycle Times	Reduced 50 percent

Using pallet tombstones has also opened up throughput. "We now put 12 fuel control parts on one pallet," says Morin. "The five-axis machining can access more of the part and the fewer set-ups eliminate stacking of tolerances. The added throughput provided by the combination of high-speed machining using the MMC, tombstones and lights out operation has been impressive."

This increased throughput gives Tell Tool the opportunity to handle more customer offloads and other jobs. "Increased throughput with less lead time reduces our inventory and increases our cash flow," says Morin. "This is a powerful equation and a competitive advantage."

Customers Continue to Evolve

Tell Tool will continue to rely on this high-speed technology advantage. "Our customers now request weekly part delivery instead of monthly to reduce their inventories," says DiLorenzo. "We could easily make more parts each month, but these parts change constantly and changes must be incorporated into them at a moment's notice.

So instead of manufacturing more parts than required each month, we hit the necessary part levels. And when changes do occur, our team responds quickly and we efficiently meet our goals."

Based on these impressive results, Tell Tool is already investing in its future. "We are investigating two more A77s and extending the MMC to support all five machining centers," says DiLorenzo. "This will give us room for 16 more pallets and expand our impressive throughput levels. We will be able to manufacture an increasingly complex and dynamic part offering. We are ready for whatever changes the industry may bring."

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