Robots in machining

Helical milling is an alternative hole-making machining process which presents several advantages when compared to conventional drilling. In the helical milling process, the tool proceeds a helical path while rotates around its own axis. Due to its flexible kinematics, low cutting forces, tool wear, and improved borehole quality may be achieved. This paper presents a review of the helical milling process. As a first paper aiming to describe the current state of the art of helical milling process, the recent works about this process were summarized to point out the future trends in this field. Initially, the advantages of the helical milling were presented with regard to conventional drilling. Subsequently, the kinematics of the process was presented to standardize the nomenclature and to provide knowledge about the movements and parameters of helical milling. It was demonstrated the feed velocity decomposition in frontal and peripheral directions. Undeformed chip and cutting volumes of frontal and peripheral cut were described, and the ratio between the cutting volumes removed by frontal and peripheral cut was demonstrated to be dependent only of the borehole and tool diameters. Cutting forces and temperature studies were also summarized, corroborating that the helical milling is a smooth hole-making process. Afterward, tool life and wear studies in helical milling were summarized, testifying that the tool wear evolution can be monitored in frontal and peripheral cutting edges, with frontal cutting edges, in most cases, defining the tool life. Some statistical and soft computing applications on helical milling were also mentioned. To provide initial guidelines for applying helical milling, a screening of the current literature was performed summarizing equipment and cooling techniques used, and the levels of cutting conditions of helical milling applied for hole-making different materials. The quality of boreholes obtained by helical milling was assessed in terms of dimensional, geometrical, and microgeometrical deviations, besides burr and delamination levels, assuring that it can be obtained finished boreholes with helical milling. In the conclusions, future possibilities on research about helical milling were pointed out. This general review of helical milling may be referenced as a summary of the current results obtained in experimental and theoretical studies and to provide future research needs and opportunities.

A review of helical milling process

Off-line programming systems are essential tools for the effective use of robots in the manufacturing environment. This paper presents a dedicated off-line programming system for robotic drilling in aerospace manufacturing. Following a brief introduction of the system architecture, the paper discusses two major problems of off-line programming for robotic drilling, i.e., redundancy resolution and position correction. A new performance index is proposed for the combined requirements of singularity and joint-limit avoidance, followed by a discussion of the redundancy resolution scheme by using numerical optimization at the joint displacement level. A position correction method using measurement data of reference holes is developed for the enhancement of robotic drilling accuracy. Robot programs generated by using the developed system have been tested on a robotic drilling system, and the experimental results are provided.

An off-line programming system for robotic drilling in aerospace manufacturing

This paper presents for the first time the concept of measurement assisted assembly (MAA) and outlines the research priorities of the realisation of this concept in the industry. MAA denotes a paradigm shift in assembly for high value and complex products and encompasses the development and use of novel metrology processes for the holistic integration and capability enhancement of key assembly and ancillary processes. A complete framework for MAA is detailed showing how this can facilitate a step change in assembly process capability and efficiency for large and complex products, such as airframes, where traditional assembly processes exhibit the requirement for rectification and rework, use inflexible tooling and are largely manual, resulting in cost and cycle time pressures. The concept of MAA encompasses a range of innovativemeasurement- assisted processes which enable rapid partto- part assembly, increased use of flexible automation, traceable quality assurance and control, reduced structure weight and improved levels of precision across the dimensional scales. A full scale industrial trial of MAA technologies has been carried out on an experimental aircraft wing demonstrating the viability of the approach while studies within 140 smaller companies have highlighted the need for better adoption of existing process capability and quality control standards. The identified research priorities for MAA include the development of both frameless and tooling embedded automated metrology networks. Other research priorities relate to the development of integrated dimensional variation management, thermal compensation algorithms as well as measurement planning and inspection of algorithms linking design to measurement and process planning. © Springer-Verlag London 2013.

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A new paradigm in large-scale assembly-research priorities in measurement assisted assembly

Discrepancies of materials, tools, and factory environments, as well as human intervention, make variation an integral part of the manufacturing process of any component. In particular, the assembly of large volume, aerospace parts is an area where significant levels of form and dimensional variation are encountered. Corrective actions can usually be taken to reduce the defects, when the sources and levels of variation are known. For the unknown dimensional and form variations, a tolerancing strategy is typically put in place in order to minimize the effects of production inconsistencies related to geometric dimensions. This generates a challenging problem for the automation of the corresponding manufacturing and assembly processes. Metrology is becoming a major contributor to being able to predict, in real time, the automated assembly problems related to the dimensional variation of parts and assemblies. This is done by continuously measuring dimensions and coordinate points, focusing on the product's key characteristics. In this paper, a number of metrology focused activities for large-volume aerospace products, including their implementation and application in the automation of manufacturing and assembly processes, are reviewed. This is done by using a case study approach within the assembly of large-volume aircraft wing structures.

Manufacturing and assembly automation by integrated metrology systems for aircraft wing fabrication

The application of robotics to the assembly of large aero-structures has been limited by the large size and inherent compliance of the components involved. The compliance of the components is significant and simple 'pick and place' approaches cannot be used due to the inherent dimensional variability between mating parts. The research described in this paper aims to solve this problem by using a non-contact sensing system to measure part deformation and misalignment in real time. The acquired data can then be processed through a mathematical algorithm to calculate the relative component positions required for optimal assembly. The data can also be used to check gross distortion of components and to reject those outside the specification limits. Existing part-to-part holes were used to provide alignment for individual components within the structure. A series of experiments were performed to investigate the feasibility of the method. Results are presented along with a discussion of the problems that may be encountered during robotic assembly. The experimental results show that robots when combined with non-contact metrology can be used for the assembly of compliant aero-structure components within required tolerance limits.

Adaptive robotic assembly of compliant aero-structure components

Purpose – This paper aims to describe the development and testing of a system for the automated assembly of aircraft fuselage panels.Design/methodology/approach – The system described in this paper uses a low‐cost industrial robot and laser stripe sensor to assemble stringers on to a fuselage panel prior to riveting. The method uses a combination of measurement and best fit placement algorithms to optimally locate parts relative to existing features.Findings – The paper demonstrates that with a combination of metrology and mathematical processing standard industrial robots can be used to assemble aero‐structure subassemblies. The paper also demonstrates that the system can work within the tolerances required within the aerospace industry.Originality/value – The paper introduces techniques for compensating for the inherent distortion that occurs in airframe components during manufacture. This is an enabling technology that will significantly increase the number of possible applications for industrial robot...

Automated assembly of fuselage skin panels

Purpose – Describes the application of standard industrial robots to the assembly and riveting of aerostructure sub‐assemblies.Design/methodology/approach – Describes the design and operation of special purpose end‐effectors for assembly and solid riveting and their integration in an aerostructure sub‐assembly fabrication cell. The robots are controlled by a novel control system which allows the cell to compensate for distortion and misalignment of the components.Findings – Demonstrates that with advanced control standard industrial robots can be used to assemble aerostructure sub‐assemblies.Originality/value – Introduces techniques for compensating for the inherent distortion that occurs in airframe components during manufacture. This is an enabling technology that will significantly increase the number of possible applications for robots in the assembly of aerostructures.

Automated aerostructure assembly

Purpose – The purpose of this paper is to describe the measurement‐assisted assembly of aero‐engine fabricated components and evaluate its capability.Design/methodology/approach – The system described in this paper uses in‐process measurement sensors to determine the component's exact location prior to the assembly operation. The core of the system is a set of algorithms capable of best fitting measurement data to find optimal assembly of components.Findings – The paper demonstrates that with a combination of non‐contact metrology systems and mathematical processing, standard industrial robot can be used to assemble fabricated components. Scanning parts after it has been picked up was very effective as it compensates for possible components deformation during previous manufacturing processes and robot handling errors.Originality/value – The paper introduces techniques for compensating the deformation that occurs in aero‐engine fabricated components and potential component handling errors. The developed sy...

Measurement assisted robotic assembly of fabricated aero‐engine components

Modern aerospace structures tend to consist of large numbers of geometrically complex structural components which by their very nature tend to suffer from significant levels of physical distortion and are thus difficult to assemble. One solution to this problem is to use large complex jigs which physically control the shape of the parts. These jigs are usually loaded using either direct manual labour or manual labour assisted by cranes or lifting devices. The use of manual operations represents a significant health and safety risk and increased likelihood of damaging components during assembly. The application of automation in the processing of such structures has so far been confined to small product specific cells owing to difficulties in pre-defining and fixing the exact geometry and positioning of parts within the work volume. The use of specially designed jigs, fixtures and aids such as drilling templates can be adapted to support automation but are expensive, have long manufacturing lead times and cannot be economically modified for use on other aircraft types. The paper proposes a solution to the above problems using standard industrial robots and an advanced control and non-contact metrology systems. The developed methodology is generic and has been evaluated and demonstrated in a number of different applications. The application described in this paper is the assembly of regional jet fuselage panels. Results are presented along with an analysis of the accuracy and repeatability of the system and its elements.

https://www.tandfonline.com/doi/pdf/10.1080/09511920903529255

Nirosh Jayaweera

Papers

Adaptive robotic assembly of compliant aero-structure components

Automated assembly of fuselage skin panels

Automated aerostructure assembly

Measurement assisted robotic assembly of fabricated aero‐engine components

Metrology-assisted robotic processing of aerospace applications