CIRP Annals

This paper introduces an effective new design-for-quality tool called AREM that visualizes assembly fault potential. Its evaluation formula is constructed on a fault occurrence model and enables quantitative evaluation of the fault generation potential of both product and assembly shop. The distinctive features of AREM are:(1) visualization of parts and operations having a high fault probability detection capability; (2) easy input by symbol selection as well as simultaneous assemblability evaluation; and (3) shop reliability, as well as product reliability, can be evaluated quantitatively. The method can be integrated with other DFX tools such as the assemblability evaluation method (AEM), and the recyclability/disassemblability evaluation method (REM/DEM) to realize a comprehensive production design evaluation system

The ‘Human factor’ is a major issue when optimizing manufacturing systems. The development in recommendations on how to handle this factor in the management of production reflects the change in dominating challenges faced by production in society. Presently, industrial societies are meeting new challenges. Qualitative interviews with Danish stakeholders in the education of engineers (BA & MA) confirm the picture given in international literature. Therefore, the didactics concerning the ‘human factor’ in the curriculum on production management has to reflect these changes. This paper concludes with a proposal on essential issues to be addressed in the curriculum qualifying university candidates to production management.

This paper deals with turning of hardened alloy steels (up to HV800). First, the research focuses on the evaluation of flow stress in machining of 100Cr6 (AISI 52100) bearing steel. A material constitutive law including work hardening, thermal softening, and strain-rate sensitivity has been looked for. The work hardening effect has been determined with the help of quasi-static compression tests performed on standard test specimens. The dynamic compression tests performed at “high strain-rates” using the Hopkinson bars, have shown no tendency to viscosity effects. Hot compression tests show that thermal softening plays a significant role in the the process feasibility. Cutting tests performed under various cutting conditions have highlighted the conflicting work hardening-thermal softening processes. This balance is discussed with a shear instability criterion, presenting the work hardening to thermal softening ratio through a revised material behavior law.

Semi-solid forging of the steel grades 100Cr6 and X210CrW12 reveals advantages compared to conventional manufacturing process technologies like casting and forging. These advantages result from the thixotropic flow behaviour prevailing when the material condition is varied. Two different strategies to generate a semi-solid precursor material are investigated. With the first strategy conventional rod material is inductively heated into the desired state and subsequently forged. For this purpose a fully automated semi-solid forging plant has been developed. The second strategy consists of producing the semi-solid precursor material directly from a slightly overheated melt with subsequent forced nucleation by means of a cooling slope. The results of the experimental work are presented and an outlook to both process variants is given.

A custom thermal microscope was constructed using a high-bandwidth thermal imaging system (40 megapixels/sec). The microscope was attached to a high-speed machining centre (20 thousand RPM/18.5 kW spindle) that was operated as a high-speed lathe to measure temperature distributions during orthogonal cutting of AISI 1045 steel at surface speeds of up to 605 m/min. Measurements were made for a wide range of cutting parameters and compared with finite element analysis. While the ultimate goal is to produce improved tool design, the results emphasize the need for predictive rather than interpretive simulation of the temperature fields in machining.

Nowadays in the automobile industry more and more high strength steels find their application. For their processing innovative forming technologies, like the non-isothermal hot stamping process, are required. With regard to a reliable numerical process design the knowledge of the thermal and thermo-mechanical properties is essential. Within this paper an experimental setup will be introduced, which enables the determination of the material's flow behaviour according to the hot stamping time-temperature-characteristics. Further results of investigations on the thermo-mechanical flow properties of the quenchenable, ultra high strength steel 22MnB5 in dependency of the temperature, the strain and the cooling rate etc. will be represented.

This paper describes a stereophotogrammetry method that reconstructs 3D microstructure surfaces from Scanning Electron Microscope (SEM) images. The microstructure surfaces are represented as 3D meshes with texture. The method's algorithm is based on the following stages: a) computing 3D points from 2D matched points; b) triangulating the 3D points into a 3D mesh; and c) mapping a 2D image as a texture on the surface. The textured 3D surface exhibits very realistic 3D microstructure surfaces for 3D visualization and engineering analysis. The performance of the proposed method has been analyzed and demonstrated on a variety of materials and complex geometries.

Research and development of laser based sintering technology has occurred at a rapid pace since its invention in the 1980s'. A wide range of materials have been developed including polymers, metals and ceramics. The ultimate goal for this technology is to provide manufacturing industries with fast and flexible means of producing parts that are truly functional. Step by step this active research area is leading towards rapid manufacturing solutions which will be significantly different from the rather limited rapid prototyping solutions of today. In processing metallic materials, porosity is still a major problem although a number of notable solutions such as infiltration with low melting point alloys or direct fusing with binary powder mixtures have been proposed. Neither of these solutions allows one to build components without compromising part strength and functionality. A process route is required that will allow solid parts to be built from a single powder component without requiring time consuming downstream processes. The surface quality must be consistent with those attainable by modern machining techniques. To this end, the present work examines the feasibility of using low energy high peak power laser pulses from a Q-switched Nd:YAG laser to melt stainless steel powder fractions whilst examining the melt displacement and the effects of rapid vaporisation of the powder layer.

The new generation of 3D digitalisation provides us with additional possibilities for obtaining more complete information regarding physical environments faster (a shop or part of a factory, a mechanical system, etc…). Based on a general overview of a given environment, it is possible to extract some repository data from this basic information to structure the numerical model. Next some complementary scans can be taken, depending on the level of detail and the final valorisation objective for the numerical model. This approach can be applied to the redesigning or the reconstitution of an old mechanism and its simulation in virtual reality.

A new measurement technique is proposed for the assessment of thermally induced errors of machine tools. The basic idea is to measure changes of length by a telescopic double ball bar (TDEB) at multiple locations in the machine's workspace while the machine is thermally excited. In addition thermal machine error models are verified and optimised by comparing measured and predicted TDEB length deviations. Validation measurements reveal that more than 60 % of the thermally induced errors can be described by the thermal machine error model proposed at any time and at any position in the machine's workspace.

This paper deals with an innovative technique concerning CO2 laser machining in order to create 3D cavities to be used as moulds for the casting of polymer resins, vaporizing PMMA layer by layer.The removal of a single layer is achieved using multiple overlapping straight grooves. The groove profile (depth and width) has been predicted by theoretical models which investigate the influence of cutting sequence, number of passes, laser beam scanning speed and radiant flux.The removal depth varies proportionally with the number of layers, while the surface roughness, influenced by the grooves spacing and the orientation of the scanning direction between successive layers, cannot be decreased under a minimum value.

In today's industrial production men and robots usually work separately from each other in order to avoid accidents. By this, the advantages of an interoperable automated and manual assembly can not be used for a flexible and efficient production. If it would be possible to overcome the separation of man and robot, the accuracy and speed of robots could be combined with the flexibility and reliability of human workers. Especially for complex assembly and handling tasks, this combination is useful. A system based on digital 3D image analysis has been developed, which supervises the common working area of robot and man.

This paper presents a 3D coupled thermo-mechanical finite element model for the simulation of segmented chip formation in metal cutting. For modelling, a commercial finite element code is used. The generation of segmentation is achieved either by element erase with respect to damage or by modification of material flow stress data; both being coupled with continuous adaptive remeshing. A normalized Cockroft-Latham model is utilized as the damage criterion for element erase. Flow stress modification is achieved by using Rhim's material model. Fundamental observations from the simulations are concluded and a guideline for further research is proposed.

In engineering applications such as interactive design and simulation, some of the main object manipulations include feature interaction. Today's CAD systems provide object-oriented structures which can explicitly represent functional and geometrical interactions among features. However, conventional interaction algorithms for manipulating these structures cannot cope with non-geometrical information such as feature functionality. Interaction among features plays an essential role in defining functionality. In this paper, a new method is described which focuses on implementation of an interaction mechanism for design and simulation. Two interaction categories are handled: (1) neighboring interaction, which is primarily geometrical (blending and trimming) and (2) functional interaction (machining). Since most interactions are performed in a sub-domain rather than in the entire domain, the advantage of the locality property is considered in both cases.

Simple analytical models of three dimensional (3D) elliptical vibration cutting are developed in order to simulate the cutting process quickly and to understand the basic mechanics. The elliptical vibration cutting has recently been applied in industry mainly to ultraprecision machining of dies and molds, where the vibration locus is not generally perpendicular to the cutting edge and thus all directions of shear, chip flow and cutting force have the 3D components. Therefore, the 3D elliptical vibration cutting models are developed, and the basic cutting mechanics are discussed in the present research.

Micro electrochemical machining (ECM) using ultra short pulses with tens of nanosecond duration is presented. 0.1 M sulfuric acid was used as electrolyte and 3D micro structures were machined on stainless steel. To prevent taper, a disk-type electrode was introduced. Using the disk-type electrode, taper could be eliminated. To improve productivity, multiple electrodes were applied and multiple structures were machined simultaneously. Since the wear of tool electrode is negligible in ECM, micro wire can be used as tool electrode. Using a platinum wire electrode with 10 urn diameter, various 3D features were machined on stainless steel plate.

The paper deals with the problem of testing, measuring, or copying 3D shapes from a physical object using a digital elaboration based on a telecamera image. Utilising the shadow-moiré method, light and dark interference fringes are created on the image of the object and each fringe relates to a well defined depth; this information, together with the image plane measurement, can be used to obtain a complete 3D shape model reconstruction.Descriptions of the principal problems encountered and the solutions adopted are discussed. Problems include: a need to improve poor resolution and precision resulting from off-the-shelf instrumentation, as well as difficulties related to the automatic fringe analysis and to the creation of a mathematical model to be imported in a CAD system.However, considering that only commercially available and low cost instrumentation has been used, the method, though not feasible for all applications, produces a satisfactory overall performance.

The recent advancements achieved in 3D analysis of surface micro-topography have raised a great interest of researchers and industrial users for the possibilities of the new techniques, in spite of their major complexity. In this paper the state-of-the-art in measurement methods, reference surfaces, visualisation techniques, definition and use of parameters is reviewed, considering advantages and limits of the 3D characterisation. The need to develop further studies on the functional meaning of parameters is highlighted. Finally, comments on traceability and standardisation are given.

The paper describes a three dimensional vision-based modeling system, which can efficiently and accurately construct solid models of a machining environment including the workpiece setup with jigs and fixtures on the machine table. The unique methods of the object recognition with various key technologies have been developed based on the simultaneous real and virtual stereo image processing. Since the constructed model accurately matches with the real setup, real time NC program verifications can be performed for 100% collision-free machining simulation. The prototyped system has been successfully verified by implementation on several real machining systems.

The integration of mechanical and electronic functions into three dimensional circuit boards leads to innovative areas of application and possiblities. This obviously is a topical challenge for development of adapted assembly and soldering processes. To solve these problems, analytical and experimental research work is going on with emphasis on mounting SMD's on inclined planes and solderability on thermoplastic devices. Therefore the alternatives of using industrial robots and enlarged SMD-machines are investigated, with the objective to develop new problem orientated Assembly Systems.

For the assembly of hybrid microsystems a high accuracy in the range of a few micrometers is required. The combination of a parallel robot with an integrated 3D vision sensor uses positioning marks on the objects for object recognition. Within the assembly process, relative positioning accuracies in the submicrometer range have been obtained. Therefore, it is necessary to use a calibration strategy for matching the coordinate system of the 3D vision sensor with the coordinate system of the robot. The construction of the system, the calibration applied and the positioning accuracy achieved by the robot will be discussed.

In Precision Engineering components are getting smaller and tolerances become tighter, so demands for accuracy are increasing. To improve the precision of Coordinate Measuring Machines (CMMs) we designed an alternative high precision 3D-CMM with measuring uncertainty beneath 0.1 μm in a measuring volume of 1 dm3. The machine design is based on the Abbe and Bryan principle, thus smaller measuring errors are feasible with less effort on software compensation. Application of a light and stiff construction, compensated air bearings and well-positioned linear motors result in high stiffness and favourable dynamic behaviour. A statically determined design, extensive use of aluminium and mechanical thermal length compensation make the machine less sensitive to temperature changes. To prevent mechanical disturbances an active vibration isolation system was designed. This paper focuses on machine design aspects showing analytical- and experimental results and design synthesis.

Fast and high-quality machining operations require high dynamic path accuracy of the machine tool in use. Complementary to the work done on NC path planning and mechatronic simulation, in this paper a device is introduced for direct 3D measurements of dynamic path deviations at the tool center point (TCP). With it, linear as well as rotary axes can be tested in one setup, thus dynamic parameters such as jerk and acceleration limits can be set homogeneously for obtaining the required dynamic path accuracy. Relevant Eigenfrequencies of the machine can be identified. Measurement method, uncertainty estimation and result evaluation are explained in this paper.

A novel artefact for calibration of the height in 3D microscopy is presented. The artefact comprises three steps having a common vertical axis, which allows z-coordinate calibration at different magnifications without requiring repositioning. The artefact is suitable for transferring traceability to 3D techniques at the micrometer and nanometer scale, e.g. 3D SEM, confocal microscopes etc. Two different series of samples were fabricated using EDM with three steps of 2–5–7 μm, and 20–50–70 μm, respectively, from a 3 mm diameter carbide wire. The artefact steps were calibrated on a stylus instrument according to ISO 5436 and measured on 3D microscopes.

The micro-scale temperature fields in the cutting of two AISI 4140 steels with different machinability ratings were measured. A custom infrared microscope was constructed; each pixel was calibrated separately to reduce measurement uncertainty. Orthogonal cutting experiments were performed on a high speed machining center with surface speeds up to 500 m min−1 and uncut chip thicknesses ranging from 0.1 mm to 0.3 mm. The results indicate that in certain critical regions of the thermal field, improved machinability correlates with significant reductions in temperature that exceed measurement uncertainties. Such micro-scale temperature measurements will help to design materials with further improved machinability.