Rather than start with the machine, says Boeing, start with the tooling. For titanium workpieces and other high-value parts, a simple spreadsheet of tools and operations might be the most valuable resource for machining center selection.
The demand for machining titanium is set to skyrocket in the coming years as aircraft manufacturers increasingly turn to this metal. Steve Lovendahl from Boeing highlights that the company’s 787 model alone contains more titanium than all previous Boeing aircraft combined. Similarly, the competition’s aircraft are just as titanium-intensive, and new military aircraft models are following the same trend. As these planes move into full production, the demand for titanium parts will vastly exceed the current machining capacity in the aerospace supply chain.
For machining suppliers, this presents a clear and significant opportunity. However, Lovendahl cautions that many suppliers may need to reevaluate their current methods and equipment to fully capitalize on this demand. In some cases, this may require investment in new machine tools, though he adds that such investments may not always involve costly machines.
Understanding Titanium’s Unique Machining Requirements
Lovendahl, a production specialist at Boeing’s machining facility in Portland, Oregon, focuses on the challenges of machining complex structures from hard metals. He and his team often work to solve these challenges and share their findings with suppliers. Even within Boeing, the choice of the right machine tool for titanium parts can be challenging.
For example, when working on a forward engine mount for the 787, the team initially prioritized finding the stiffest machining center available. The assumption was that titanium required heavy-duty milling, which would necessitate a very stiff machine. However, after analyzing the machining operations and employing innovative cutting strategies, they found that a standard machine within Boeing’s existing fleet was sufficient to handle the torque demands of this part.
However, the situation changed when they moved on to the aft engine mount, which required much higher torque than any of their existing machines could deliver. To meet this need, machine tool builder Mitsui Seiki modified its heavy-duty HS6A machining center to provide the necessary torque.
Lovendahl emphasizes that performing such analysis of required machine capabilities is crucial, and it’s relatively simple. By evaluating each machining operation, suppliers can identify whether they need new equipment or whether existing machines can handle the job. In the aerospace industry, where much of the equipment is optimized for aluminum, titanium often demands different capabilities—namely, higher spindle torque, better coolant delivery, and increased thrust force for drilling.
Tools Drive the Process
According to Lovendahl, the first step in determining the appropriate machine tool is identifying the cutting tools and strategies that are best suited to the job. Instead of starting with the machine, it’s more productive to begin by selecting the right tools for roughing, finishing, and drilling the titanium part, then using the cutting parameters to guide the choice of machine.
He suggests that shops don’t have to do this alone. Boeing collaborates with its suppliers on process development, and cutting tool companies can also offer valuable input. Knowledgeable suppliers can recommend high-metal-removal-rate tools and optimal methods for using them.
From there, the analysis becomes straightforward. By calculating the required horsepower, torque, and thrust force for each machining operation based on the cutting parameters, shops can develop a clear understanding of their machine requirements. This data can be compiled into a simple spreadsheet, which offers two main benefits.
First, it simplifies the search for a suitable machine, whether it’s a new purchase or an existing model in the shop. The data clearly shows the performance capabilities needed for the job. Second, the analysis may reveal areas where changes to the process could allow the use of more accessible equipment. For example, if one operation has an unusually high torque requirement, reworking that step might make it possible to use a less expensive machine.
When existing equipment isn’t sufficient, as was the case with Boeing’s aft engine mount, the analysis can also guide machine tool builders in customizing designs to meet the required performance. Mitsui Seiki refined its HS6A machine to dampen vibrations and achieve the high metal removal rates needed for Boeing’s titanium parts. The Portland facility now has five of these machines—two for roughing and three for finishing the aft engine mounts.
Finding the Right Machine
One of the main reasons shops hesitate to develop their machining processes as Lovendahl suggests is the belief that the process cannot be mapped out accurately in advance. Factors like tool wear can affect the torque needed for a particular cut, making precise predictions seem impossible. However, Lovendahl argues that absolute precision isn’t necessary.
Rather than seeking the perfect fit in a machine tool, shops are often choosing among general classes of machines with specific capabilities. While making the right choice is critical, the machine doesn’t need to be a perfect match in every detail. Even within the same performance class, machines can sometimes deliver impressive results on high-value parts.
Ultimately, the goal is to find a machine within the right range of capabilities, and this can only be achieved through analysis. Without data, choosing the right machine is a much harder task. But for shops looking to move forward and meet the growing demand for titanium parts, conducting this analysis and selecting the appropriate machine is a necessary and logical step.