High-Speed Machining for AEROSPACE

Manufacturing Engineering, Mar 2008 by Morey, Bruce

Rather than spindle speed, Cooper uses surface speed and feed rate as a measure of HSM. The surface speed is a function of spindle rpm and cutter diam; the feed rate is a function of rpm and flute density. This makes cutting tool design vital, because more flutes at a higher surface feet/minute (SFM) means higher feed rates.

Describing MAG's new carbide tooling, which runs at 390 fpm "With a 1" [25.4-mm] cutter and maximum number of flutes, we may only be running at 1500 rpm and 100 ipm [2.5 m/min], but that is very high-speed machining in titanium," says Cooper.

Others are looking ahead to the newer, harder materials like titanium as well, seeing that the technique has proven itself for aluminum.

"High-speed machining aluminum is becoming almost standard today," says Rudy Canchola, application manager for Mazak Corp.'s Western Regional Headquarters and Aerospace Technology Center located in Gardena, CA. For him, the greater machining challenge today is in the hightemperature alloys, like stainless 15-5 or titanium 5553 or 6A14V. These are materials finding more and more use in aerospace. His recent projects using a variety of tools on Mazak equipment included titanium tests on the Mazak VCN-510 C VMC. "We have demonstrated machining titanium with solid carbide end mills up to 500-600 fpm. We think that is impressive," says Canchola.

They also tested 15-5 stainless steel using the Mazak Vortex 815-II five-axis machining center. Tools from seco, Ingersoll, Kennametal, and Sandvik were tested on the stainless material. Using a climb cut method; he reports speeds of 400-600 fpm.

"Most of our machines have the ability to perform at these high surface feed rates. If the customer is going to be cutting this type of material, we provide them with the information we developed in these tests," says Canchola.

For machining higher-temperature alloys, the look-ahead feature of the controller is not as important as in aluminum, since the speeds simply are not as high. A feature of control that is important is the ability to measure the loads on the spindles and axes and adjust accordingly. Mazak equipment senses electrical feedback from the servomotor and adjusts speed to match machining conditions-even stopping the machine and changing the tool if needed.

Brace Morey

Contributing Editor