Achievable tolerances in robotic feature machining operations using a low-cost hexapod

Abstract

Portable robotic machine tools potentially allow feature machining processes to be brought to large parts in various industries, creating an opportunity for capital expenditure and operating cost reduction. However, robots lack the machining capability of conventional equipment, which ultimately results in dimensional errors in parts. This work showcases a low-cost hexapod-based robotic machine tool and presents experimental research conducted to investigate how the widely researched robotic machining challenges, e.g. structural dynamics and kinematics, translate to achievable tolerance ranges in real-world production to highlight currently feasible applications and provide a context for considering technology improvements. Machining trials assess the total dimensional errors in the final part over multiple geometries. A key finding is error variation which is in the sub-millimetre range, although, in some cases, upper tolerance limits < 100 μm are achieved. Practical challenges are also noted. Most significantly, it is demonstrated that dimensional machining error is mainly systematic in nature and therefore that the total error can be dramatically reduced with in situ measurement and compensation. Potential is therefore found to achieve a flexible, highperformance robotic machining capability despite complex and diverse underlying scientific challenges. Overall, the work presented highlights achievable tolerances in lowcost robotic machining and opportunities for improvement, also providing a practical benchmark useful for process selection.

Light automation for aircraft fuselage assembly

“…The main contribution of the work presented herein is the analysis of the preselected solutions for the alignment stage, and as result reference values for the performance of alignment systems based on the combination of industrial manipulators and metrology systems. Contrary to J D Barnfather et al (7) , which deals with similar problem but uses hexapod robots, this work attains to anthropomorphic, commercial off-the -shelf (COTS) industrial robots.…”

Roboti̇k İşleme Yöntemi̇ Üzeri̇ne Bi̇r Derleme

“…Barnfather vd. [26] ise bir hexapod robotun üç farklı mastar kalıp kullanarak elde edebileceği tolerans değerlerini tespit etmişlerdir. Deneylerde takım tezgahı test mastarı, silindirik cep açma ve nozzle test mastarları kullanılmıştır.…”

“…vd [26]. ise bir hexapod robotun üç farklı mastar kalıp kullanarak elde edebileceği tolerans değerlerini tespit etmişlerdir.…”

New Indices for Evaluating Vibration Characteristics of Flexible-Joint Robots

“…The challenges for these robotic processes result from inherent disadvantages of industrial robots compared with machine tools, such as low positioning accuracy and being prone to vibrations [5]. Modern metrology techniques such as laser tracking [6,7] and photogrammetry based measurement [8,9] can be adopted to improve the accuracy of industrial robots through kinematic calibration [10,11] and positioning error compensation [12][13][14]. However, the influence of robot vibration on the processes is difficult to mitigate by these metrology techniques.…”