Robots in machining

Incremental sheet metal forming in general and Single Point Incremental Forming (SPIF) specifically have gone through a period of intensive development with growing attention from research institutes worldwide. The result of these efforts is significant progress in the understanding of the underlying forming mechanisms and opportunities as well as limitations associated with this category of flexible forming processes. Furthermore, creative process design efforts have enhanced the process capabilities and process planning methods. Also, simulation capabilities have evolved substantially. This review paper aims to provide an overview of the body of knowledge with respect to Single Point Incremental Forming. Without claiming to be exhaustive, each section aims for an up-to-date state-of-the-art review with corresponding conclusions on scientific progress and outlook on expected further developments.

Single point incremental forming: state-of-the-art and prospects

The present study proposes the use of an industrial serial robot to reduce the investment cost and to increase the process flexibility of Friction Stir Welding (FSW). The first part of the study characterizes the impact of pin axis position on FS Weld (FSWed) quality. The second part shows a method to compensate the lateral pin deviation in real-time during Robotic Friction Stir Welding (RFSW). This paper shows that a robot with an embedded real-time algorithm for the compensation of the lateral tool deviation can reproduce the same FSWed quality as a gantry-type CNC system. The elastostatic model of an industrial robot is carried out by the classical identification technique and this is embedded in the robot controller. Based on force measurements along the welding process, the corrected path is calculated in real-time. We use the compensation algorithm in order to do a lot of industrial project on real parts (confidential parts).The algorithm which is presented in the paper increase the precision of the robot.The algorithm which is presented could be used for other process like incremental sheet forming or deburring.

Impact & improvement of tool deviation in friction stir welding

Modern manufacturing systems are often composed of a variety of highly customized units and specifically designed manufacturing cells. Optimization of assembly and training of staff requires a series of demo installations and excessive use of costly operational resources. In some cases, components are located at different sites, making the orchestration of the whole system even more difficult.Virtual Reality (VR) collaboration environments offer a solution by enabling high fidelity testing and training of complex manufacturing systems. On the other hand, such platforms are difficult to implement in an engineering perspective, as they are required to provide reliable, standard interfaces towards both robotic components and human operators.The VirCA (Virtual Collaboration Arena) platform is a software framework that supports various means of collaboration through the use of 3D augmented/virtual reality as a communication medium. VirCA offers functions for the high-level interoperability of heterogeneous components in a wide range of domains, spanning from research & development, through remote education to orchestration and management of industrial processes in manufacturing applications. This paper provides an overview of the industrial requirements behind high-fidelity virtual collaboration and demonstrates how the VirCA platform meets these requirements. Use cases are provided to illustrate the usability of the platform. HighlightsThe paper identifies the synergies of recent advances in Future Internet and ICT.Surveys the need of high-fidelity virtual collaboration for industrial robotics.Introduces the VirCA platform as a remote collaboration and orchestration framework.Shows the integration of ontologies and CogInfoCom methods into industrial setups.Presents use case examples of knowledge-driven automation scenarios based on VirCA.

Design, programming and orchestration of heterogeneous manufacturing systems through VR-powered remote collaboration

https://hal.archives-ouvertes.fr/hal-00917604/document

Elasto-geometrical modeling and calibration of robot manipulators: Application to machining and forming applications

In this paper, a coupling methodology is involved and improved to correct the tool path deviations induced by the compliance of industrial robots during an incremental sheet forming task. For that purpose, a robust and systematic method is first proposed to derive the elastic model of their structure and an efficient FE simulation of the process is then used to predict accurately the forming forces. Their values are then defined as the inputs of the proposed elastic model to calculate the robot TCP pose errors induced by the elastic deformations. This avoids thus a first step of measurement of the forces required to form a test part with a stiff machine. An intensive experimental investigation is performed by forming a classical frustum cone and a non-symmetrical twisted pyramid. It validates the robustness of both the FE analysis and the proposed elastic modeling allowing the final geometry of the formed parts to converge towards their nominal specifications in a context of prototyping applications.

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Off-line compensation of the tool path deviations on robotic machining: Application to incremental sheet forming

https://hal.archives-ouvertes.fr/hal-00966854/document

A Process/Machine coupling approach: Application to Robotized Incremental Sheet Forming

In this work, an off-line compensation procedure, based on an elastic modelling of the machine structure coupled with a Finite Element Analysis (FEA) of the process is applied to Robotized Single Point Incremental Forming (RSPIF). Assuming an ideal stiff robot, the FEA evaluates the Tool Center Point (TCP) forces during the forming stage. These forces are then defined as an input data of the elastic robot model to predict and correct the tool path deviations. In order to make efficient the tool path correction, the weight of three numerical and material parameters of the FEA on the predicted forces is investigated. Finally, the efficiency of the proposed method is validated by the comparison between numerical and experimental geometries obtained with or without correction of the tool path.

https://hal.archives-ouvertes.fr/hal-00872570/document

Force Prediction for Correction of Robot Tool Path in Single Point Incremental Forming

Incremental sheet forming is an emerging process to manufacture sheet metal parts. This process is more flexible than conventional one and well suited for small batch production or prototyping. During the process, the sheet metal blank is clamped by a blank-holder and a small-size smooth-end hemispherical tool moves along a user-specified path to deform the sheet incrementally. Classical three-axis CNC milling machines, dedicated structure or serial robots can be used to perform the forming operation. Whatever the considered machine, large deviations between the theoretical shape and the real shape can be observed after the part unclamping. These deviations are due to both the lack of stiffness of the machine and residual stresses in the part at the end of the forming stage. In this paper, an optimization strategy of the tool path is proposed in order to minimize the elastic springback induced by residual stresses after unclamping. A finite element model of the SPIF process allowing the shape prediction of the formed part with a good accuracy is defined. This model, based on appropriated assumptions, leads to calculation times which remain compatible with an optimization procedure. The proposed optimization method is based on an iterative correction of the tool path. The efficiency of the method is shown by an improvement of the final shape.

Springback effects during single point incremental forming: Optimization of the tool path

The incremental sheet forming is an innovative process which allow the production of complex parts with simple tools. It consists to deform locally a sheet with a non cutting hemispherical punch tool. To validate the use of a machine it is important to evaluate the required e ffort level to deform the sheet. This step can be done with a numerical simulation tool. This process involves higher levels of deformation than traditional stamping. Due to the high level of deformation reached, it seems to be obvious that the choice of the hardening law plays an essential role in the estimation of the e ffort level. In this paper the numerical simulation of the incremental forming of a truncated cone is proposed. This simulation is based on a finite element modeling of the elastoplastic behaviour of the forming sheet. Two hardening laws are implemented and their influences on forming e fforts evaluation and final geometry are evaluated.

https://hal.archives-ouvertes.fr/hal-00873690/document

Jérémy Belchior

Papers

Off-line compensation of the tool path deviations on robotic machining: Application to incremental sheet forming

A Process/Machine coupling approach: Application to Robotized Incremental Sheet Forming

Force Prediction for Correction of Robot Tool Path in Single Point Incremental Forming

Springback effects during single point incremental forming: Optimization of the tool path

Approche couplée matériau/structure machine : application au formage incrémental