Accurate Robot Technology

Serial link articulated robots applied in aerospace assembly have largely been limited in scope by deficiencies in positional accuracy. The majority of aerospace applications require tolerances of +/-0.25mm or less which have historically been beyond reach of the conventional off-the-shelf robot. The recent development of Electroimpact's Accurate Robot technology represents a paradigm shift for the use of articulated robotics in airframe assembly.

With the addition of secondary feedback, high-order kinematic model, and a fully integrated conventional CNC control, robotic technology can now compete on a performance level with customized high precision motion platforms. As a result, the articulated arm can be applied to a much broader range of assembly applications that were once limited to custom machines, including one-up assembly, two-sided drilling and fastening, material removal, and automated fiber placement.

Manufacturers require the ability to program systems offline, whereby teaching methods become obsolete as they are inherently time-consuming and unique. Guiding robots real-time via metrology has proven to improve positional accuracy, however requiring expensive, sensitive equipment. External systems tend to restrict the working range and suffer from line of sight issues. It is desirable to have an inherently accurate standalone automation system wherever possible which is the premise of the Accurate Robot.

The Accurate Robot system is controlled via industry standard Siemens 840Dsl CNC which handles all controls requirements and offers a familiar interface to programmers and operators. Drawing from common axis configuration in machine tool design, the robot arm is integrated by Electroimpact with patented secondary position sensors at the output of each axis. Though not married to a specific articulated arm, Electroimpact has had great success implementing the technology on KUKA Robotics products and is our preferred supplier.

Repeatability is significantly improved enabling the system to be calibrated to accuracies below +/-0.25mm over a large global volume. This patented solution has broadened the range of applications for unguided industrial robots in the aerospace industry to include high-precision single and dual-sided drilling and fastening, accurate material removal (trimming, milling), and accurate robotic fiber placement. The positioning system can be packaged in a number of ways including rigid floor mounting, horizontal linear axis mounting, vertical axis mobile platform, etc.

All process functions are carried out by a single multi-function end effector. Processes can include one-sided pressure to the work piece, auto-normalization, Boelube and/or flood coolant delivery, thru-tool coolant delivery, vacuum swarf extraction, automated vision, automated touch probing, precision drilling and countersinking, hole inspection, sealant application, fastener insertion, and milling. The MFEE is controlled with the Siemens 840Dsl CNC that is also used to control the robot. All process tools (spindle, probe, and camera) are mounted to a single plate (shuttle table) which is servo indexed to present the current process tool to the TCP. The tools, shuttle table, pressure foot, and supporting frame are mounted to a servo-controlled "clamp" axis which provides the necessary pressure to the work piece. Drill thrust loads are monitored real-time for tool breakage and wear detection.