Adaptive Machining Makes a Robot More Productive

The recent Paris Air Show not only showed examples of the latest aircraft, but also examples of the latest manufacturing processes for aircraft production. Among the exhibits was an automated system for machining and polishing jet engine turbine blades. This system consists of a Flexmill S Series platform in which an overhead ABB robot manipulates a turbine blade for probing, machining and polishing in one continuous process—fully automated, of course.

The Hardware Platform

Flexmill, an offshoot of Finland-based JOT Automation, is a supplier of modular robotic solutions for manufacturing companies, especially those in the electronics industry. The company's S Series platform is specially designed for robot-based milling, grinding, linishing (surface smoothing) and polishing processes. Depending on the application, various models of articulated (jointed-arm) robots from major robot developers can convey a part to processing stations within the machine or bring powered tools to a stationary part clamped in a workholding fixture.

The blade processing system shown at the air show is equipped with an ABB six-axis robot mounted to the overhead frame of the machine's structure. This configuration frees the space below for a variety of processing stations. In this case, two abrasive brush wheels rotating in separate, side-by-side spindles are located on the right of the workzone. On the left is a wall bracket that holds a touch-trigger probe on one level and a high-speed air spindle for a milling cutter on another level. All of the programmable axes required for processing the blades are part of the robot.

The space between these stations gives the robot plenty of room to maneuver the end-of-arm gripper holding a turbine blade. The blades used in this demonstration were roughly the size of a cake knife: about 6 or 7 inches long and about 3 to 5 inches wide. The system can also handle larger or smaller blades.

This Flexmill configuration takes up about 30 square feet of floor space, but larger systems can be configured to meet requirements.

Unlike the PowerMill and PowerInspect software, Delcam Automation is cloud-based process control software provided by Delcam Professional Services, a team of manufacturing software experts that creates a customized workflow for an application. For example, in this application, in-process inspection data is collected and used to reshape a nominal CAD model so that it represents the as-machined part. This new model is then used to automatically generate a unique set of tool paths for remachining. Once this workflow is established for the application, the adaptive machining feedback loop is coordinated by a computer connected to the machine control and linked to a cloud-based processing site, either on a shop's network or on the Internet. The Delcam Automation system manages all of the process control for the fully automated cell, as well as the complex computing tasks, and provides the cell with the control commands required to keep production flowing.

Typically, blades processed on the cell make one or two passes across the grinding and milling stations. The abrasive wheel removes approximately 20 microns in a polishing cycle that lasts 30 seconds per side. Milling the tip edge using a carbide side-cutting milling cutter that runs at 8,000 rpm removes about 0.25 mm from the tip.