This article presents a brief state of the art in the Swedish metal working industry regarding the production preparation process for the machine centre. The article is based on a relationship model from which a questionnaire was developed. The model incorporates the perceived preparation process efficiency, the amount of systematic preparation work, in relation to the companies’ premises as possible causes. The investigation is based on a general hypothesis that a more systematic approach in the preparation process leads to higher preparation process efficiency. This hypothesis was supplemented by two more hypotheses and additional analyses to create an understanding of the situation. The main finding in this investigation is that there appear to be no relationship between increased  ystematic preparation work and perception of higher preparation efficiency. The investigation also indicates that many metal working companies have little knowledge about the performance of their preparation process and that there is an efficiency improvement potential of nearly 30%.

The objective of this study was to analyze the impact of plasma-sprayed Ni5%Al particles on polished and grit-blasted Ti6Al4V samples under oxidized and nonoxidized conditions. For this purpose, measurements of thermal radiation and velocity of individual plasma-sprayed particles were carried out. From the thermal radiation at impact, splat diameter during flattening and temperature evolution during cooling were evaluated. Characteristic parameters related to the quality of contact between the splat and the substrate were retrieved. The flattening speed was introduced to characterize wetting, while the cooling rate was used to characterize solidification. The idea was to get a signature of particle impact for a given surface roughness and oxidation state by identifying parameters which strongly affect the splat behavior. Sieved Ni5%Al powder in a narrow range (+65 −75 μm) was sprayed on four sets of titanium alloy surfaces, consisting of polished and grit-blasted samples, one set had a nonoxidized surface and the other one was oxidized in an oven at 600 °C for two hours. Resulting splats after impact were characterized by scanning electron microscopy, the splats on oxidized surface showed pores in their core and detached fingers at the periphery. The cooling rate and flattening degree significantly increased on the oxidized smooth surface compared to the nonoxidized one. This trend was not found in grit-blasted surfaces, which implies that impact phenomena are different on grit-blasted surfaces than on smooth surfaces thus further work is needed.

The objective of this study was to analyze the impact of plasma-sprayed Ni5%Al particles on polished and grit-blasted Ti6Al4V samples under oxidized and nonoxidized conditions. For this purpose, measurements of thermal radiation and velocity of individual plasma-sprayed particles were carried out. From the thermal radiation at impact, splat diameter during flattening and temperature evolution during cooling were evaluated. Characteristic parameters related to the quality of contact between the splat and the substrate were retrieved. The flattening speed was introduced to characterize wetting, while the cooling rate was used to characterize solidification. The idea was to get a signature of particle impact for a given surface roughness and oxidation state by identifying parameters which strongly affect the splat behavior. Sieved Ni5%Al powder in a narrow range (+65 −75 μm) was sprayed on four sets of titanium alloy surfaces, consisting of polished and grit-blasted samples, one set had a nonoxidized surface and the other one was oxidized in an oven at 600 °C for two hours. Resulting splats after impact were characterized by scanning electron microscopy, the splats on oxidized surface showed pores in their core and detached fingers at the periphery. The cooling rate and flattening degree significantly increased on the oxidized smooth surface compared to the nonoxidized one. This trend was not found in grit-blasted surfaces, which implies that impact phenomena are different on grit-blasted surfaces than on smooth surfaces thus further work is needed.

To achieve sufficient adhesion strength within thermal spraying, the surface to be coated has to be modified. Grit blasting is the most common way to generate a clean and roughened surface. The bonding mechanism between the grit-blasted substrate and the coating is assumed to be due to mechanical anchoring, why an optimal surface roughness is essential. The surface roughness is usually evaluated using Ra which cannot fully characterize the complex nature of the chaotic substrate topography. This study was performed in order to evaluate if Ra can be replaced by other surface characteristic parameters such us R.q, Rpk, Rpv, Rk…with higher correlation to adhesion strength. Average roughness was measured by a perthometer and with white light interferometry to get 3D images of the surface topography. Disc shaped substrate samples of Ti6Al4V (AMS 4928) were grit blasted with aluminium oxide grit and plasma sprayed with a Ni5%Al coating. Adhesion strength was determined according to the ASTM C633 standard. The correlation between a number of different surface-parameters and adhesion strength were evaluated and compared with Ra.

The Protal process combines surface preparation using a laser and thermal spraying in one production step. The laser preparation is based on a photomechanical reaction induced by the interaction between a laser of high instantaneous power and a polluted surface. The mechanism of bonding and the coating-substrate interface are then changed in comparison with grit blasting resulting in a significantly reduced substrate roughness. This study is aimed at finding the optimal Protal process parameters for the coating adhesion of a Ni5%Al sprayed on Ti6Al4V and IN718 alloys. The parameters investigated are laser beam intensity, the time delay between the laser impact and the spray impact, powder feed rate, substrate roughness and temperature. A test plan including these parameters is analysed by means of a fractional factorial design of experiment method. The adhesions of the coatings are measured using the ASTM C633 standard test. Data are analysed by a multiple linear regression model using a least squares fit. In addition, the coating/substrate interface is examined by optical and electron scanning microscopy (SEM) techniques as well as by Auger electron spectroscopy. Substrate roughness, substrate temperature and laser intensity are all shown to have a negative correlation with adhesion strength within the investigated range. Areas of diffusion are noticed at the coating/substrate interface.

Abstract A detailed study of a swirling flow in a tube is presented in the first part of the paper. A simplified analytical solution of the governing equations indicates specific modes of the tangential velocity and that the decay of the swirl effect is exponential. The problem is then solved in three dimensions using computational fluid dynamics (CFD) and a comparison with analytical expressions shows that the CFD code is reliable in terms of accuracy. The CFD results confirm that a fundamental swirling mode is reached within a short distance from the inlet. The torque swirl number is introduced to physically estimate the intensity of the swirl. A companion value is given: it is the average deviation.

In this report, we present a photogrammetric system that can be used during welding operation with a robot. It should be able to give the position and the orientation of the Tool Center Point with a high accuracy (less than 0.5 mm). After a view on the historic of PosEye®, we describe its two different ways of working: using active or passive markers. We then explain one way to improve the accuracy of the sensor by taking in account the distortion of the image due to the projection. This part is followed by investigations on a so-called “flash collar” which permits to fix diodes when we use passive markers. We finish by some tests to have a better idea of the accuracy of the sensor. This accuracy is only available for the position, as it has been realized on a Coordinate Measuring Machine which is only able to give information on its position.

Partially ionized plasmas corresponding to different ionization degrees are derived and connected one with each other by the diffusion approximation methodology. These plasmas are the following electrical discharges:a thermal arc discharge, glow discharges in local thermodynamic equilibrium -LTE- and in non-LTE, and a non-LTE glow discharge interacting with an electron beam (or flow)

Most simulation studies done to deeper understand high-intensity welding arcs address axi-symmetric configurations and use the electric potential formulation. This formulation involves the assumption of a one-dimensional magnetic field. The assumption is justified in its original frame: rather long arcs (about 10 mm), and when the electrode tip is excluded from the computational domain. However, arcs applied to welding are shorter, and the electrode geometry is important to take into account. The present work questions the assumption of a one-dimensional magnetic field for simulating short welding arcs. We have compared three different approaches for modeling the magnetic field: three-dimensional, two-dimensional axi-symmetric, and the electric potential formulation. These models have been applied to water cooled anode Gas Tungsten Arc Welding (GTAW) test cases with truncated conical electrode tip (tip radius of 0.5 and 0.2 mm) and various arc lengths (2, 3 and 5 mm). For the axi-symmetric cases studied in the present work, the three- and two-dimensional models give exactly the same results. The one-dimensional simplification of the magnetic field turns out to have a significant unfavorable effect on the simulation results. For axi-symmetric welding applications, it is argued that the two-dimensional axi-symmetric formulation should be used. Copyright © 2013 ASM International® All rights reserved.

This chapter is concerned with the matter of mathematically modelling and computationally simulating the thermo and fluid dynamical phenomena occuring in the workpiece during a gas metal arc welding (GMAW) process, and does so by employing a continuum mechanical approach and a finite element formulation for approximating the solution of equations expressing the continuity of mass, the balance of linear momentum, the conservation of energy and the motion of the weld pool surface. GMAW is an electrode arc fusion welding process. The designation arc fusion signifies that an electric arc is struck between the welding electrode and the workpiece, and this causes the base material to melt on either side of the joint. During the subsequent solidification this will cause fusion between the workpiece parts. The electrode consist in a filler metal, and it is hence consumed during the process and molten droplets are, under the influence of electromagnetical and gravitational forces, transferred to the liquid weld pool. Mass is thus added to the workpiece and this causes a reinforcement of the joint.

In this paper a system is presented that combines a robot off-line programming software with a finite element model that predicts temperature-time histories and residual stress distributions. The objective is to develop a tool for the engineer where robot trajectories and welding process parameters can be optimized on parts with complex geometry. The system was evaluated on a stainless steel gas turbine component. Robot weld paths were defined off-line and automatically downloaded to the finite element program, where transient temperatures and residual stresses were predicted. Temperature dependent properties and phase change, were included in the analysis. Assumptions and principles behind the modeling techniques are presented together with predicted temperature histories, residual stresses, and fixture forces.

The application of commercial software (OLP) packages for robot simulation, and programming, use interactive computer graphics, provide powerful tools for creating welding paths off-line. By the use of such software, problems of robot reach, accessibility, collision and timing can be eliminated during the planning stage. This paper describes how such software can be integrated with a numerical model that predicts temperature-time histories in the solid material. The objective of this integration is to develop a tool for the engineer where robot trajectories and process parameters can be optimized on parts with complex geometry. Such a tool would decrease the number of weld trials, increase productivity and reduce costs. Assumptions and principles behind the modeling techniques are presented together with experimental evaluation of the correlation between modeled and measured temperatures.

The manufacturing industry constantly strive to develop the competencies of their expert production engineers in order to achieve and maintain a competitive advantage. Research shows that the absorptive capacity of a firm is central in order to reach such a goal. The absorptive capacity of a firm is their ability to recognize the value of new external information, assimilate it, and apply it to commercial ends, and thereby exploit the conditions for innovation. In this paper we explore the rationales of organizations in the manufacturing industry for taking part in technology-enhanced competence development projects in collaboration with universities. Through interviews with key informants in 15 manufacturing industries we study the capabilities that organizations’ need for participation in e-learning initiatives. We present a framework for technology enhanced learning readiness comprised of awareness, e-learning maturity, dynamic capability and co-creativity.

The manufacturing industry is continuously facing global competition and customer demands which impose the need to knowledge development to manage changes and long-term business goals. Continuous and lifelong learning is often seen as processes that support competence development and learning integrated within work. In this paper we focus on processes of learning within the manufacturing industry and how learning initiatives as technology mediated courses (TMC) can support learning from the workplace learning needs. Is learning initiatives integrated in work considered as means for strategic business goals? Can TMC be an important learning tool for support of knowledge creation? The study is performed through interviews with production managers and human resource managers with eight manufacturing industries in the western part of Sweden. Through the study we try to understand what knowledge the industry needs to evolve and achieve effective production. We also study the readiness for technology mediated learning. Early results show that the industries have interest in learning initiatives such as TMC and are willing to co-produce knowledge together with universities. We present a matrix model that interlinks business goals and the industries current use of technology mediated learning tools. However, the experience of using tools such as web conference systems and learning management systems for learning initiatives is diversified.

Comprehensive models of heat transfer require specification of the total amount of heat received by the workpiece. The objective of this work was to critically examine the use of a water-cooled stationary anode calorimeter to obtain both arc efficiency and total heat input into the workpiece. For simplicity and clarity, this last quantity is called the gross heat input. The effects of current, material type and water flow rate on the calorimeter performance were determined experimentally. Some measures for reducing errors in calorimetry were evaluated. Improvements were made to reduce heat losses from the top surface of the test coupon and boost heat removal from the opposite surface. A sensitivity test was conducted to estimate the effect of measurement inaccuracies. The results demonstrate the effectiveness of calorimetry for measuring gross heat input in arc welding.

Examensarbetet inriktade sig på att utifrån ett antal definierade problemställningar som

framkommit under projektarbetet, finna lösningar och förslag på hur Saab skall lyckas med

att utföra sampassnings analys i processutrustningen. De problem som definierades under

projektarbetet var bland annat att finna mätutrustning som är bättre lämpad att utföra

mätningar i processutrustningen än en Faro arm och att titta på konstruktionsförbättringar

som kan underlätta och snabba upp mätningen av processutrustningen och att med det

förslag på mätutrustning och föreslagna konstruktionslösningar analysera om de

ergonomiska förutsättningarna blivit bättre. När det gäller mätutrustningen så är Leica

Absolute Tracker AT901 ett mätsystem som skulle fungera alldeles utmärkt, detta

mätsystem skulle lösa åtkomsten för mätning av stöd och styrningar på ett ergonomiskt

sätt. Mätsystemet klarar de uppsatta kraven i grundkravspecifikationen och har den

mätnoggrannhet som efterfrågas. klarar en tuff arbetsmiljö att mäta i, är portabel i det

avseendet att den är tillräckligt lätt att hantera och har en idrifttagnings tid som också är

enligt uppsatta krav i grundkravspecifikationen. Under examensarbete framkom det att

sidolineutrustningens leverantör ej följt Saabs TKS (standard), varken under konstruktion

eller tillverkningsfasen. Dåligt upp märkta och placerade utgångar var några av de problem

som upptäcktes under projektarbetet. Med dessa förslag på mätutrustning och

konstruktionsförbättringar och att säkerställa att de valda leverantörerna av utrustningar

följer Saabs krav så anser arbetsgruppen att sampassning i processutrustningen kan utföras

med önskat resultat. 

Material properties of welds are strongly influenced by the thermal history, including the thermo-fluid and electromagnetic phenomena in the weld pool and the arc heat source. A necessary condition for arc heat source models to be predictive is to include the plasma column, the cathode, and the cathode layer providing their thermal and electric coupling. Different cathode layer models based on significantly different physical assumptions are being used. This paper summarizes today’s state of the art of cathode layer modeling of refractory cathodes used in GTAW at atmospheric pressure. The fundamentals of the cathode layer and its physics are addressed. The main modeling approaches, namely (i) the diffusion approach, (ii) the partial LTE approach, and (iii) the hydrodynamic approach are discussed and compared. The most relevant publications are systematically categorized with regard to the respective physical phenomena addressed. Results and process understanding gained with these models are summarized. Finally, some open questions are underlined.

 Producing welds with properties matching those of the steel is a challenge at high strength levels. The present study investigated how cooling rates and dilution affects strength and toughness when welding steels with yield strengths of 777 MPa and 1193 MPa. Overmatching weld metal strength was achieved for the less strong steel and weld strengths >1000 MPa were recorded for the stronger steel. Fracture in transverse tensile testing was always located in base material or HAZ. Low dilution, rapid cooling and single pass welding contributed to higher strength. Impact toughness was higher for lower strength and low dilution.

Force control is introduced to robots to solve the problem in machining applications due to the fact that the robot compliance might cause deviation between actual and desired robot path. Also large tolerances in the casting process as well as positioning errors from the clamping create deviations for which the force control technology can adept. Force control has also shown successful in automatic learning of paths along non linear surfaces.

This study investigates the possibility of introducing robots equipped with force control at Volvo Aero Corporation in order to robotize polishing and deburring processes. These are today performed by manual labor. This study investigates more specifically the ABB Force Control machining application package. The polishing process has shown to be very complex and today’s version of the ABB force control package cannot give sufficiently robust results to be recommended for implementation. The major issue is the non-existing compliance of tool orientation needed to adapt to casting and positioning deviations due to varying work piece dimensions. The deburring process has however shown to be easier to handle, and a robot cell and methodology is proposed in this report.

In machining of nickel based superalloys, such as Inconel 718, tool wear is a major problem due to the high stresses and the high temperatures at the tool chip interface. Enhanced knowledge of the tool wear mechanism and capability to predict tool wear are therefore of great importance in machining of nickel based superalloys. The objective with this paper is to investigate if the finite element method (FEM) can be used to predict the flank and crater wear of uncoated cemented carbide tool in turning ofInconel 718. An empirical model has been implemented in a commercial FE-code and the tool geometry is continuously updated to capture the evolution of wear. Experiments have been conducted to obtain parameters for the empirical wear model and for validation of the simulations. The worn geometry at the flank and rake face as well as the cutting edge radius was measured with white light interferometry. Wear model parameters were calibrated by fitting a simulation against measured worn geometries at the flank and rake face. Then separate simulations at other cutting speeds were compared with corresponding experiments to validate the model performance.

This article describes two studies conducted to compare assembly performance and learning rate between computer based training and traditional training of skilled assembly operators. The studies were performed with pre-series production parts from a car cockpit and they were integrated as part of the overall training activities during a new vehicle product launch. The computer based training tool used was a desktop based commercial VR tool with focus on cognitive interactive procedural learning. Both studies indicate that computer based training can replace instructor based training for this level of assembly complexity and that it has a positive effect in preparing skilled operators

The work done in this report is made within the metal deposition research project in the MIA-group (Mechatronics in Industrial Applications) at the University of Trollhättan/Uddevalla (HTU). Metal deposition is a method of building metal work pieces using weld material. The aim of the MIA-groups research is to develop a control system for automated robotised metal deposition. The research conducted is a continuation of the thesis “Development of Sensor System for Automated metal deposition” by Mr Jan-Erik. Henriksson, Ms Jessica Jansson and Mr Simon Cronholm. The aim of the work conducted in this report is to determine what effects changes of the weld speed and electrode angle do to the geometry of the weld seam. During the initial experiments it was noticed that differences in the weld process occurred due to the final rolling method of the plate used. To achieve similar results as in earlier experiments cold rolled plates had to be used. The electrode angle affects the weld such that the narrowest weld is performed with the electrode perpendicular to the plate. As the electrode is tilted the width of the weld is increased. The effect of increased weld speed is less oxides on the weld seam, more stable welding process and less deformation of the plate caused by shorter exposure of heat. While conducting the experiments more experience of improvements in equipment and important parameters for the metal deposition process. 

The work done in this report is made within the metal deposition research project in the MIA-group (Mechatronics in Industrial Applications) at the University of Trollhättan/Uddevalla (HTU). Metal deposition is a method of building metal work pieces using weld material. The aim of the MIA-groups research is to develop a control system for automated robotised metal deposition. The research conducted is a continuation of the thesis “Development of Sensor System for Automated metal deposition” by Mr Jan-Erik. Henriksson, Ms Jessica Jansson and Mr Simon Cronholm. The aim of the work conducted in this report is to determine what effects changes of the weld speed and electrode angle do to the geometry of the weld seam. During the initial experiments it was noticed that differences in the weld process occurred due to the final rolling method of the plate used. To achieve similar results as in earlier experiments cold rolled plates had to be used. The electrode angle affects the weld such that the narrowest weld is performed with the electrode perpendicular to the plate. As the electrode is tilted the width of the weld is increased. The effect of increased weld speed is less oxides on the weld seam, more stable welding process and less deformation of the plate caused by shorter exposure of heat. While conducting the experiments more experience of improvements in equipment and important parameters for the metal deposition process

During the winter 2003/2004 a new research group MIA (Mecatronics in Industrial Applications) was formed at HTU (University of Trollhättan/Uddevalla). One of the primary research areas of the group is to develop an automatic robotised metal deposition. Metal deposition is a method where a metal feature is built by adding welding material to create the wanted shape. A common way to build a part is to add material by powder or wire. The material is melted using a heat source, e.g. a tungsten electrode (TIG welding equipment) or laser. The idea of the method is to building up layers to create the wanted products or add metal features, like flanges, bosses and pads, to existing products. As one of the first steps of the research a patent search have been conducted which aimed at finding patents for metal deposition and sensor system used to control the metal deposition process. The search resulted in 17 patents where most of the patents can be classified into the more general type of patents and only two can be classified for control and sensor system. During the search of patents the search had to be narrowed using more search words. The reason was that a search with “wide” and few words generated such amount of patents so it was impossible to look into the information. From the patents found only a few covered the use of control and sensor system for metal deposition. One way of explaining this is that the research is just in the beginning and that the MIA group has found an area that still have much yet to develop.