Video: Accelerated Blisk Milling

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CAM developer Delcam and cutting tool supplier Technicut produced this brief video illustrating the highlights of a machining cycle that generated a blisk from an 804-mm diameter disk of titanium 6-4 in 35 hours. The two companies say that cycle time is less than half of what would be required to machine this same part with conventional methods. In the cycle shown, several factors contributed to that productivity:

• Roughing is performed in stages throughout the process. Lower sections of blades are left in their rough state to maintain stiffness while the upper portion is being machined.
• Tool paths specific to blisk machining programmed in Delcam’s PowerMill use barrel cutters from Technicut for semi-finishing and finishing. Offering a larger radius at the cutting surface than ballnose cutters, barrel cutters achieve the same cusp height between passes as a ballnose tool with a stepdown that can be three to four times as large.
• Initial rough machining operations between the blades use Technicut’s Titan X-Treme Ripper end mill not only to remove material quickly but also to relieve stresses in the material introduced by forging.

Blisks—one-piece bladed disks—are increasingly used in turbine engines in place of individual blades machined separately and fixed into a hub. The completed blisk in this video has 31 blades, each 84 mm long with a root radius of 4 mm and scallop height of 10 microns.