Jean-Yves Hascoët

Tool path programming optimization for incremental sheet forming applications

Incremental sheet forming is an emerging process to manufacture sheet metal parts that is well adapted for small batch production or prototypes. The adjustment time is short, as it is sufficient to modify the tool motions to optimize the manufacturing process. Tool path generation therefore becomes a key topic linked to incremental sheet forming, and process characteristics ask for dedicated tool paths. Hence, this paper first discusses the impact of tool path types and other programming parameters on process implementation through an experimental campaign performed on a parallel kinematics machine tool. Then, a new approach to generate and control Intelligent CAM programmed tool paths is proposed. The major purpose of this innovative concept is to use process constraints for programming and controlling the tool path, which are adapted during the running of the CNC program according to real-time process data evaluation. Validation studies and an industrial implementation are finally presented to assess the efficiency of the proposed approach.

A new DFM approach to combine machining and additive manufacturing

Design for manufacturing (DFM) approaches aim to integrate manufacturability aspects during the design stage. Most of DFM approaches usually consider only one manufacturing process, but product competitiveness may be improved by designing hybrid modular products, in which products are seen as 3-D puzzles with modules realized individually by the best manufacturing process and further gathered. A new DFM system is created in order to give quantitative information during the product design stage of which modules will benefit in being machined and which ones will advantageously be realized by an additive process (such as Selective Laser Sintering or laser deposition). A methodology for a manufacturability evaluation in case of a subtractive or an additive manufacturing process is developed and implemented in a CAD software. Tests are carried out on industrial products from automotive industry.

A new global approach to design for additive manufacturing

Nowadays, due to rapid prototyping processes improvements, a functional part can be built directly through additive manufacturing. It is now accepted that these new processes can increase productivity while enabling a mass and cost reduction and an increase of the parts functionality. However, in order to achieve this, new design methods have to be developed to take into account the specificities of these processes, with the Design For Additive Manufacturing (DFAM) concept. In this context, a methodology to obtain a suitable design of parts built through additive manufacturing is proposed; both design requirements and manufacturing constraints are taken into account.

A new versatile in-process monitoring system for milling

Tool condition monitoring (TCM) systems can improve productivity and ensure workpiece quality, yet, there is a lack of reliable TCM solutions for small-batch or one-off manufacturing of industrial parts. TCM methods which include the characteristics of the cut seem to be particularly suitable for these demanding applications. In the first section of this paper, three process-based indicators have been retrieved from literature dealing with TCM. They are analysed using a cutting force model and experiments are carried out in industrial conditions. Specific transient cuttings encountered during the machining of the test part reveal the indicators to be unreliable. Consequently, in the second section, a versatile in-process monitoring method is suggested. Based on experiments carried out under a range of different cutting conditions, an adequate indicator is proposed: the relative radial eccentricity of the cutters is estimated at each instant and characterizes the tool state. It is then compared with the previous tool state in order to detect cutter breakage or chipping. Lastly, the new approach is shown to be reliable when implemented during the machining of the test part.

Laser polishing of additive laser manufacturing surfaces

The additive laser manufacturing (ALM) technique is an additive manufacturing process which enables the rapid manufacturing of complex metallic parts and the creation of thin parts so as, for example, to decrease parts weight for biomechanical or aeronautic applications. Furthermore, compared with selective laser sintering technology, the ALM process allows creating more huge parts and material gradient. However, for aesthetic or tribological functions, the ALM surfaces need an additional finishing operation, such as the polishing operation. Polishing processes are usually based on abrasive or chemical techniques. These conventional processes are composed by many drawbacks such as accessibility of complex shape, environmental impact, high time consumption and cost, and health risks for operators. In order to solve these problems and to improve surface quality, the laser polishing (LP) process is investigated. Based on melting material by laser, laser polishing process enables the smoothing of initial topography. However, the ALM process and the laser polishing processes are based on laser technology. In this context, the laser ALM process is used directly on the same machine for the polishing operation. Moreover, an alternation between both processes can be established during the manufacturing operation in order to treat nonaccessible surfaces. Currently, few studies focus on laser polishing of additive laser manufacturing surfaces, and it tends to limit the industrial use of additive manufacturing technology. The proposed study describes an experimental investigation of laser polishing surfaces obtained by additive laser manufacturing process. The investigation results in the improvement of complete final surface quality, according to laser polishing parameters. This experimental study introduces the laser polishing of thin section parts, in order to develop laser polishing applications. According to a manufacturing chain context, the final objective is to create a multiprocess mastery in order to optimize the final topography and productivity time.

Manufacturability analysis to combine additive and subtractive processes

Purpose – The purpose of this paper is to propose a methodology to estimate manufacturing complexity for both machining and layered manufacturing. The goal is to take into account manufacturing constraints at design stage in order to realize tools (dies and molds) by a combination of a subtractive process (high‐speed machining) and an additive process (selective laser sintering).Design/methodology/approach – Manufacturability indexes are defined and calculated from the tool computer‐aided design (CAD) model, according to geometric, material and specification information. The indexes are divided into two categories: global and local. For local indexes, a decomposition of the tool CAD model is used, based on an octree decomposition algorithm and a map of manufacturing complexity is obtained.Findings – The manufacturability indexes values provide a well‐detailed view of which areas of the tool may advantageously be machined or manufactured by an additive process.Originality/value – Nowadays, layered manufact...

An eXtended Manufacturing Integrated System for feature-based manufacturing with STEP-NC

Computer Numerical Control (CNC) feature-based programming with STandard for the Exchange of Product data model-compliant Numerical Control extends the collaborative model of manufacturing data exchange all along the numerical data chain. This study considers the mutations related to this approach from the manufacturing system level to the industrial enterprise as a whole. The eXtended Manufacturing Integrated System concept is introduced to fill in the gap of the current manufacturing data exchange bottleneck. It is composed of eXtended Computer Aided Design (CAD) and eXtended CNC systems to link the CAD model to the real machined part through the Manufacturing Information Pipeline. The contributions associated with these concepts are demonstrated through a validation platform implemented on industrial CNC manufacturing equipments.

An enhanced machining simulator with tool deflection error analysis

This paper presents a machining simulator for an NC machining application that is being developed in the IRCCyN laboratory. Compared with current machining simulators, the most distinguished feature of the machining simulator is its ability to analyze errors caused by tool deflections. The errors are reflected on a 3-D solid simulation model during the simulation process so that errors generated by the previous tool passage can be considered in the error calculation for the next tool passage. After simulation, the errors can be quantified in various ways by comparing the simulation model with the original geometry model. The analyzed errors can be used as input data in developing optimization algorithms for removing or reducing errors.

A new digital chain for additive manufacturing processes

Additive manufacturing is, nowadays, a higher process than most traditional processes (machining, etc.). But there still remains a domain where this process is not very competitive: that being its digital chain. Indeed, it is too poor in information to allow for the development of advanced additive manufacturing operations and therefore to compete with the traditional processes. This paper proposes to use the STEP-NC concept, which contains high-level information, in order to integrate the additive manufacturing processes in a complete STEP-NC digital chain in accordance with the norm work group committee ISO TC 184/SC 1. This paper proposes to develop this digital chain with a classical CNC controller, which is also present in machining equipment, and to hence benefit from their development possibilities.

Toolpaths for additive manufacturing of functionally graded materials (FGM) parts

Purpose – The purpose of this paper is to propose an evaluation of toolpaths for additive manufacturing of functionally graded materials (FGM) parts to ensure the manufacturing of parts in compliance with the desired material distribution. The selection of an appropriate path strategy is critical when manufacturing FGM parts. Design/methodology/approach – The selection of a path strategy is based on a process modeling and an additive laser melting (ALM) system control. To do that, some path strategies are selected, simulated and compared. Findings – The comparison of some paths strategies was applied on a study case from the biomedical field. Test-parts were manufactured and analyzed. Results show a good correlation between the simulated and the deposited material distributions. The evaluation of toolpaths based on the process modeling and the system control was validated. Originality/value – Nowadays, FGM parts manufactured with ALM processes are not functional. To move from these samples to functional p...