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How Long Do You Need Your Machine Tools to Last?

Bill Malanche
By Bill Malanche Chief Operations Officer, Mitsui Seiki USA Inc.

In the aerospace industry it’s common for OEM contracts and programs with their component suppliers to extend from 10 years to as many as 40 years. Many, if not most, aerospace parts demand efficient and productive metal removal rates—in tough materials, with tight tolerances, and with a reliable, robust, automated process. Dialing in the system can take many months. There’s a huge investment by all parties to ensure that all aspects are operating as designed and built, essentially being able to press a button and walk away. And that’s exactly how it is for one to four years. All is well. Until it isn’t.

Maybe a tolerance becomes troublesome to hold. Maybe machine tool service technicians have to be called in frequently. Maybe the “system down” condition is bordering on unacceptable. Meanwhile, the supplier is barely into the decades-long program! Now what? Keep repairing and retrofitting? Buy new again and hope it lasts this time? That ROI report would certainly be cringe-worthy, wouldn’t it?

We see this scenario play out often. There is a solution, but it must be considered long before the supplier officially gets the order: a long contract warrants a long view of the manufacturing technology required to fulfill it. Otherwise, a supplier and its stakeholders will be exposed to risk.

There are key differences in machine tool construction and design. There are good solutions that can perform well in the short term. And then there are solutions crafted for the long haul and, ideally, designed for a particular application with the appropriate spindle, table and cutting tools, as well as a proven-out process. Yes, those dedicated machines have a heftier initial price tag, but they actually cost less to operate over time based on zero to minimal downtime for machine failure, longer tool life and less scrap—along with a predictable, reliable work flow and process.

For example, optimal hard-metal machining (typically required in the aerospace industry) is based on the ability of the machining system to perform low-frequency machining without chatter at low spindle speeds and to extend cutting tool life. The system also needs to hold tools tightly with heavy-duty tool tapers. The system’s design and construction must be directed at increasing machine stiffness to resist heavy cutting loads.

It also must deliver the power necessary to take large, rough cuts—meaning adequate spindle horsepower, torque and large servomotor drives on the ballscrews. As such, the machines must have the structural design to machine at low amplitude ranges. Hand scraping the way surfaces and spindle-mounting surfaces is the only way to achieve predicable frequency control.

Further, all of the materials in the machine structure must stay within a specific range of static and dynamic stiffness and resiliency so that when cutting, the spring memory of the machine is highly repeatable. This repeatability is vital for tightly controlling the cutting edge as it passes through these hard materials. To aggressively cut titanium, for example, the machine needs high-torque motors and spindles with a large taper interface. Also, high-pressure, high-volume coolant systems are mandatory when cutting titanium. Choosing the right cutting tools is also vital. Considering these requirements, a horizontal platform is well suited to these large heavy parts.

A Machine Tool that Lasts for Decades

The right machine tool will last for decades. And if a supplier has a multi-year contract, that’s what is needed to mitigate the risks of failing a customer, neglecting stockholders, and forsaking the employee profit-sharing plan. There’s too much at stake to take the short-term view in a long-term relationship.

 

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