Automation of Chamfering by an Industrial Robot; For the Case of Hole on a Free Curved Surface

Abstract

Abstract:The study deals with the automatic chamfering for the case of hole on a free curved surface on the basis of CAD data, using an industrial robot. As a chamfering tool, a rotary-bar driven by an electric motor is mounted to the arm of the robot having six degrees of freedom in order to give an arbitrary position and attitude to the tool. The robot control command converted from the chamfering path is transmitted directly to the robot. From the experimental results, the system is found effective to remove a burr along the edge of a hole on a workpiece with free curved surface.

Precision Robotic Machining: Modelling and Control Innovations for Improved Performance

“…Before a part can be machined, it needs to be localized within the robot's workspace such that an appropriate path can be planned. Various methods have been examined for part registration, including jigging [61], laser scanning [11,47,48,[62][63][64][65], robot touch-off localization [44,61,66,67], and vision systems [68][69][70][71][72]; however, each of these has its challenges. Jigging is a costly solution that necessitates custom fixtures for each workpiece and is not appropriate for a wide range of situations due to workpiece variability, space constraints, and other factors.…”

“…The contouring path consists of a time-series of 3D tool centre target points p p , unit-length normal direction vectors u n , and commanded forces f d . The planning of such a path has been extensively covered in works such as [66][67][68]193] and can be accomplished in CAD/CAM software packages such as Solidworks CAM [194] or Siemens NX CAM [195]. As the robot contours the part, an admittance controller corrects for path errors by modifying the tool centre from p p a distance a along u n to the corrected tool position p t , as…”

“…Moreover, the reflective surface of many metal workpieces can lead to incorrect data, in particular near workpiece imperfections. Touch-off localization [44,61,66,67] can give accurate results but is exceedingly slow since robot speed is limited near an unknown object, and as the number of touch-offs is small, localization data is sparse and sensitive to outliers caused by imperfections such as burrs, flashing or scallops.…”

“…Prior research has been done to increase the accuracy of robotic machining operations through improved workpiece registration. Part registration has been investigated using jigging [61], laser scanner [11,47,48,[62][63][64][65], robot touch-off localization [44,61,66,67], and vision systems [68][69][70][71][72]. However, each of these solutions has its drawbacks.…”

“…Laser systems can also be affected by workpiece reflectivity or skewed by the presence of large burrs or flashing [62]. Touch-off testing can be used to localize parts [44,61,66,67,212] but is also prohibitively slow since robot speed is limited near unknown geometries. Moreover, the part can only be sampled sparsely, making touchoff testing vulnerable to outliers from burrs.…”