Quality flow model in automotive paint shops

Improving paint quality is of significant importance for vehicle manufacturing. In this paper, a quality flow model is presented to analyse and improve quality in automotive paint shops. Specifically, we study the vehicle-painting process with multiple inspection stations. After each inspection, vehicles failed to achieve quality requirement will be repaired before moving to the next operation. In such systems, the quality variations may propagate along the painting process. To address this, a three-state quality flow model has been developed, and analytical formulas to evaluate product quality have been derived. In addition, to improve quality performance, a bottleneck analysis method has been introduced to identify the most critical stage that impedes product quality in the strongest manner. Two case studies at automotive paint shops are introduced to illustrate the applicability of the method.     

Sustainable manufacturing: a case study of the forklift painting process

Life cycle assessment (LCA) and design for environment (DFE) methods were applied to assess opportunities for reducing the environmental impacts of forklift manufacturing unit processes and to redesign those unit processes to increase overall sustainability. The unit processes of forklift manufacture generating the most environmental emissions were identified by applying LCA methodology. The results show that eco-toxicity and human toxicity were the most significant impacts of the forklift manufacturing process overall. Also, within the manufacturing unit processes, cutting, welding and painting had the highest impact values. In order to minimise environmental impacts, a new paint was created with increased solid content over the existing solvent paint used in the painting process. In addition, by applying DFE methodology and the high solid paint, overcoat and drying steps were eliminated from the forklift painting process. As a result, the environmental index of a follow-up LCA showed that environmental impacts could be reduced by 20%, while volatile organic compound (VOC) and paint usage could be decreased by 30% and 20%, respectively.     

A colour-batching problem using selectivity banks in automobile paint shops

This paper studies the colour-batching problem frequently raised in automobile paint shops, where selectivity banks are used as storage and retrieval systems to execute practices of resequencing car bodies before painting operations are performed. The purpose of resequencing is to obtain colour-oriented batches of cars in order to reduce setup costs incurred in paint shops. In this paper, two heuristic procedures, arraying and shuffling heuristics, are developed aimed at quickly and effectively achieving good colour-batching results. The arraying heuristic can be applied in the car placing stage, while the shuffling heuristic can be utilised in the car releasing stage. Computational experiments are carried out to evaluate the performance of the proposed heuristics. It is shown that the shuffling heuristic can generate comparable car retrieval sequences with an exact branch &; bound approach, and the proposed arraying and shuffling heuristics can be jointly applied to achieve good colour batching in a very short time duration of less than 0.4?s in comparison with two existing batching methods. These research findings can provide good insights into the practice of colour batching in automobile manufacturing.     

A materials selection procedure for sandwiched beams via parametric optimization with applications in automotive industry

The future of automotive industry faces many challenges in meeting increasingly strict restrictions on emissions, energy usage and recyclability of components alongside the need to maintain cost competiveness. Weight reduction through innovative design of components and proper material selection can have profound impact towards attaining such goals since most of the lifecycle energy usage occurs during the operation phase of a vehicle. In electric and hybrid vehicles, weight reduction has another important effect of extending the electric mode driving range between stops or gasoline mode. This paper adopts parametric models for design optimization and material selection of sandwich panels with the objective of weight and cost minimization subject to structural integrity constraints such as strength, stiffness and buckling resistance. The proposed design procedure employs a pre-compiled library of candidate sandwich panel material combinations, for which optimization of the layered thicknesses is conducted and the best one is reported. Example demonstration studies from the automotive industry are presented for the replacement of Aluminum and Steel panels with polypropylene-filled sandwich panel alternatives.     

CFD-based design and analysis of air-bearing-supported paint spray spindle

In this paper, an analytical scientific approach is presented for the design and analysis of an air-turbine-driven paint spray spindle, and it is used to improve further the design concept of the existing spindle applied in automotive coating and paint spraying applications. The current spindle on the market can operate at a maximum speed of 100,000 rpm and features a maximum bell size of 70 mm diameter. Given the increasing demands for high automotive coating/painting quality and productivity in assembly, the design and development of a paint spray spindle with a speed of 145,000 rpm or higher is needed. Computational fluid dynamics(CFD)-based simulation is applied in the approach. Accordingly, CFD simulation-based design and analysis are undertaken, covering the characteristic factors of velocity, pressure of the air supply, rotational speed of the air-turbine, and torque and force reaction on the turbine blades. Furthermore, the turbine blade geometric shape is investigated through the simulations. Three geometrical concepts have been investigated against the original model. The results on Concept_03 verified the higher angular velocity speeds against the theoretical model. The pressure and velocity effects in the blades have been investigated. The results show that the pressure and velocity of the air supply driving the turbine are critical factors influencing the stability of turbine spinning. The results also demonstrate that the force acting on the blades is at the highest level when the adjacent face changes from a straight surface into a curve. Finally, changing the geometrical shape in the turbine likely increases the tangential air pressure at the blades surface and relatively increases the magnitude of the lateral torque and force in the spindle. Notwithstanding this condition, the analytical values surpass the theoretical target values.     

基于设计思考和 TRIZ 的画架便携一体式画箱设计

目的画箱是绘画爱好者的必备器具,它可装载大量绘画工具,但其携带较为不便。方法提出分析和解决流程,挖掘作画人员的真实需求,采用TRIZ的最终理想解(IFR)和技术矛盾工具,分析现有作画工具使用过程中存在的技术矛盾。并应用矛盾矩阵,结合情境类比等相关方法,提出解决技术矛盾的初步概念方案。在综合各个初步概念方案的基础上,开发设计一款集画架、画箱、行李箱为一体的便携式画箱。该一体式画箱即可满足作画人员对于绘画工具多样性的需要,又可轻松携带和移动,具有良好的应用前景。     

Mould and phototroph growth on masonry façades after repainting

The appearance and durability of paint films are affected by microbial growth and fungi and phototrophs are considered to be especially important, degrading the films mechanically, by the production of metabolites, chiefly acids, and by enzymatic activity. In this study, fungi and phototrophs were identified before and throughout one year after painting two building façades in São Paulo. Disinfection with hypochlorite and high-pressure water jet cleaning of the façades caused reduction of at least 85% in the microbial population. Paint was applied with or without a biocide formulation (0.25% w/w)-carbendazin, N-octyl-2H-isothiazolin-3-one and N-(3,4-dichlorophenyl)N,N-dimethyl ure. The biocide reduced fungal colonization up to 10 months after painting on one building. However after 12 months biocide made no statistically significant difference. The major fungal contaminant was the genusCladosporium. After 10 monthsAureobasidium was also associated with black discoloration. On both the re-painted. façades, fungi were detected before phototrophs, contrary to the citations from the literature. SEM showed that fungal contamination was present not only on the surface, but between the old and new paint films and between old paint and rendering mortar. Under these conditions building façade details and micro-environment seem to be more important than biocide in controlling fungal growth.     

Revolution statt Evolution – Innovative Folientechnik für die Kfz‐Außenhaut

Revolution in Place of Evolution – Innovative Foil Technique for Automotive Body Shell Foil techniques represent an innovative option compared to traditional automotive painting. Cost reduction demands and light weight construction has brought forth the requirement to apply polymers at automotive body shells. Particularly, thermoplastic polymers enable a large freedom for the design of modern cars at moderate costs. The foil technique is also a promising approach for an introduction of long glass fibre reinforced thermoplastics into the outer body skin and to reach a Class A finish. One technology is the colormatchable foil technique (CFT). In cooperation with BASF Coatings AG, Münster INPRO developed this new technology to the stage of fundamental feasibility. This new technology stands short before its introduction in practice.     

Modeling and testing of energy absorbing lightweight materials and structures for automotive applications

As a consequence of the increasing demands in automotive industry concerning crashworthiness and passive safety, the concern for energy management and safety demands also increases. The goal of energy management is to reduce the forces and stresses on an occupant or a pedestrian during a crash event; in some cases it may be possible to reduce the forces by a factor of two. This requires usage of new advanced materials in automotive components. Energy absorbing foams and other lightweight materials like plastics and polymer composites are increasingly used in automotive industry. Hence, extensive study of energy absorbing behavior of these materials as well as the automotive components is needed for further improvements in numerical modeling and crash simulations. The paper enlightens recent advances in investigation of mechanical properties and energy absorption ability of the mentioned lightweight materials as well as modeling with finite element codes for crash simulations.     

镜面彩电用新型水星银白漆喷涂机理及质量控制

从水星银白漆喷涂机理着手探讨涂膜质量控制措施,以便快速、准确地分析处理生产过程中出现的喷涂质量问题。     

Visualization of a lost painting by Vincent van Gogh using synchrotron radiation based X-ray fluorescence elemental mapping

Vincent van Gogh (1853-1890), one of the founding fathers of modern painting, is best known for his vivid colors, his vibrant painting style, and his short but highly productive career. His productivity is even higher than generally realized, as many of his known paintings cover a previous composition. This is thought to be the case in one-third of his early period paintings. Van Gogh would often reuse the canvas of an abandoned painting and paint a new or modified composition on top. These hidden paintings offer a unique and intimate insight into the genesis of his works. Yet, current museum-based imaging tools are unable to properly visualize many of these hidden images. We present the first-time use of synchrotron radiation based X-ray fluorescence mapping, applied to visualize a woman's head hidden under the work Patch of Grass by Van Gogh. We recorded decimeter-scale, X-ray fluorescence intensity maps, reflecting the distribution of specific elements in the paint layers. In doing so we succeeded in visualizing the hidden face with unprecedented detail. In particular, the distribution of Hg and Sb in the red and light tones, respectively, enabled an approximate color reconstruction of the flesh tones. This reconstruction proved to be the missing link for the comparison of the hidden face with Van Gogh's known paintings. Our approach literally opens up new vistas in the nondestructive study of hidden paint layers, which applies to the oeuvre of Van Gogh in particular and to old master paintings in general.     

Requirements management: an enabler for concurrent engineering in the automotive industry

Defining and agreeing the product requirements is especially important when the design and manufacture of a system is part of an Extended Enterprise. To realize an all-inclusive concurrent engineering process, tools for the upstream design activities are needed. In practice, it is often difficult for the companies to have a shared understanding of what needs to be developed, and so specifications contain ambiguities in describing the product requirements. This paper clarifies the problem domain in the context of a complex product, designed and manufactured in a pan-national Extended Enterprise and serving a highly competitive market. The authors show how the challenge can be addressed through the application of ontology. A model of a requirements-management tool is proposed that will allow the various systems and associated levels of a product to be described and then shared through the supply chain. A prototype system is presented and illustrated through a case study from the automotive industry.     

Production system design for quality robustness

In automotive assembly plants, vehicles with defects are either repaired (e.g., components are exchanged, scratches are polished, etc.) or reworked (e.g., the whole vehicle is repainted) to maintain high product quality. The performance of vehicle quality is typically characterized in terms of the first time quality and also the quality buy rate. First time quality is defined as the good job ratio of all first time processing jobs, while the quality buy rate is the good job ratio of all processed jobs, including the first time jobs and reworked jobs.

In this paper, we study a repair and rework system at an automotive paint shop with random first time quality. Specifically, we show that paint quality, in terms of quality buy rate, can be described by a function of repair capacity and first time quality. Increasing the repair capacity can improve the quality buy rate and reduce unnecessary repaints. Variations in first time quality may lead to a reduction in the quality buy rate and an increase in unnecessary repaints, and consequently, a substantial waste of production capacity and materials. In addition, we observe that the average quality buy rate depends primarily on the mean and coefficient of variation of the first time quality rather than its complete distribution. Based on these results, we introduce the notion of quality robustness and show that the design of a production system should accommodate randomness in first time quality to achieve a robust quality buy rate. Finally, a case study on a repair and rework system redesign to improve paint quality is presented.     

Materials selection for hot stamped automotive body parts: An application of the Ashby approach based on the strain hardening exponent and stacking fault energy of materials

Complex stamping operations are becoming widespread in the automotive industry to produce vehicle body parts with adequate mechanical strength and reduced wall thickness. The need for weight reduction drives the development of new metallic materials capable of achieving a good balance between formability and mechanical properties. Advanced high strength steels play a major role in this scenario. The aim of this work was to develop a materials selection strategy for hot stamped automotive body parts using the Ashby approach. The selection process was based on the formability of metallic alloys derived from two fundamentals materials properties, the strain hardening exponent and the stacking fault energy.     

Local scheduling problems submitted to global FIFO processing constraints

This paper deals with local scheduling problems as part of a global process management policy. The industrial context is an automotive assembly plant. An automobile manufacturing process creates a list that schedules orders so as to optimize production costs. Such a list must respect the vast majority of shop-related constraints, notably those of the assembly shop, which are the hardest to schedule. This list also allows one to provide information to suppliers regarding the parts they are required to deliver to the assembly plant. PSA Peugeot-Citroën has set the ambitious objective of ensuring compliance with all list entries upon arrival at the assembly plant. This objective is equivalent to instituting a global first-in, first-out (FIFO) management policy for all operations upstream of the assembly line (i.e. body shop, paint shop) and in particular it enables one to make significant reductions in component inventories.

However, FIFO-based flows are difficult to achieve. They first require setting up local production scheduling in the plant in order to satisfy constraints specific to each shop (body shop, paint shop, assembly line); this step will be referred to as ‘local scheduling’. Moreover, a number of disturbances intervene to change the initial order.

The aim of our work is to lay out a new policy for managing flows (called ‘reorderable scheduling’). The premise is to define the maximum scheduling level allowed upon input into each shop so as to guarantee restoration of the initial list order (i.e. reordering) at the assembly entrance.

We will start by studying, from a theoretical perspective, a very general base case and then we will characterize the maximum authorized local scheduling disturbance that enables us to fulfil the global management objective (i.e. FIFO). We will also show the implementation of this method in our industrial case within the context of an automotive assembly plant and finally perform the validation step by means of simulation.     

The potential for composites in structural automotive applications

The primary use of fiber-reinforced composites in automobiles, with the exception of a few specialized low volume vehicles, has been in semi-structural or decorative parts. Use of composites in primary structural areas of the vehicle, such as body structures, has been very limited to date. Such applications offer a tremendous opportunity for future expansion of composites in the automotive industry. In addition to materials cost, there are two over-riding criteria for significant application of FRP materials in automotive structures: (1) proof of structural functionality/durability; and (2) development of rapid, reproducible fabrication procedures to optimize manufacturing economics.

From a structural viewpoint, there are two major categories of material response which are critical to the application of composites to automobiles: fatigue (durability) and energy absorption. An abundance of evidence is accumulating relating the functional properties of these materials in simple structures. It is clear that the fundamental requirements of energy absorption and fatigue resistance are satisfied by composites and the main challenge is to translate these capabilities into complex structures with less well-defined load inputs. The less quantifiable, but equally important, functional requirement of ride quality (usually defined in terms of noise, vibration and ride harsness, NVH) also appears to be attainable through the utilization of composites. Even though this factor has been historically related to vehicle stiffness, and composite materials are less stiff than steel, all the indications are that the effective stiffness of composite structures meet NVH requirements—the elimination of joints through part integration plays a critical role in achieving such synergistic effects.

Many of the properties of composite structures depend on the control of fiber location and part integration which in turn are a direct fucntion of the fabrication process. Current high production rate fabrication processes such as compression molding of sheet molding compound (SMC) type materials go only part way to optimizing the properties and economics. Optimum automotive composite structures will probably require a combination of processes, some of which will need significant development, to realize the enormous potential for composites in the automotive industry. Full-scale structures may involve SMC type molding, thermoplastic stamping and the developing preform molding (HSRTM) process which hasm perhaps, the greatest potential of all the processes of revolutionizing the use of composite structures. Technological breakthroughs in fabrication technology do not appear to be necessary, the main requirement is the development of existing assorted techniques combined with a concerted effort by all aspects of the composite and automotive industry.     

Terahertz paintmeter for noncontact monitoring of thickness and drying progress in paint film

We propose a paintmeter for noncontact and remote monitoring of the thickness and drying progress of a paint film based on the time-of-flight measurement of the echo signal of a terahertz (THz) electromagnetic pulse. The proposed method is effectively applied to two-dimensional mapping of the painting thickness distribution for single-layer and multilayer paint films. Furthermore, adequate parameters for the drying progress are extracted from the THz pulse-echo signal and effectively applied to monitor the wet-to-dry transformation. The THz paintmeter can be a powerful tool for quality control of the paint film on the in-process monitoring of car body painting.     

Energy consumption model of Binder-jetting additive manufacturing processes

Considering the potential for new product design possibilities and the reduction of environmental impacts, Additive Manufacturing (AM) processes are considered to possess significant advantages for automotive, aerospace and medical equipment industries. One of the commercial AM techniques is Binder-jetting (BJ). This technique can be used to process a variety of materials including stainless steel, ceramic, polymer and glass. However, there is very limited research about this AM technology on energy consumption aspect. This paper presents a method to build an energy consumption model for printing stage of BJ process. Mathematical analyses are performed to find out the correlation between the energy consumption and geometry of the manufactured part. Based on the analyses, total energy consumption is calculated as a function of part geometry and printing parameters. Finally, test printing is performed to check the accuracy of the model. This process model provides a tool to optimise part geometry design with respect to energy consumption.     

Liquid immiscible alloys

The microstructure formation, during casting, of alloys being immiscible in the liquid state such as copperlead or aluminium-lead has gained renewed scientific and technical interest during the last fifteen years. Especially, a new experimental tool, research under reduced gravity conditions, was able to cast new, unexpected results and theories into the discussion on the nature of the complex process of microstructure evolution in such alloys. Prior to the first experiments performed at reduced levels of gravity acceleration, it was generally agreed that the process of phase separation during cooling through the miscibility gap is dictated solely by gravity-induced effects such as natural convection and sedimentation. Fundamental and applied research in space and in earth laboratories could show that there are other mechanisms operating concurrently and under suitable conditions with equal strength. In addition applied research was able to utilize the often unexpected results from space experimentation to develop new casting processes which allow one to produce microstructures on earth suitable for bearings in automotive applications. Therefore this article describes the extensive progress that has been made during the last decade and also the fundamentals of immiscibles. In addition it will be shown that the combination of classical laboratory research, research under reduced gravity conditions and a newly developed computational modelling technique seems to be just becoming available to solve the problems of decomposition, spatial phase separation and microstructure evolution during cooling of an alloy through the liquid miscibility gap.     

一种新型空分流程的研讨

通过对一种新颖的高压氮膨胀液化液氧泵内压缩常温分子筛净化空分流程的组织构思和对换热、制冷、精馏系统全面的计算，为开拓化工企业高压用氧（９．５ＭＰａＡ）的新型空分流程探索出了一条可行的路。根据计算，新流程和原有的高压氮节流液化液氧泵内压缩切换式换热器冻结空分流程相比，氧提取率可提高９％，单位氧能耗可下降２％，流程组织大大简化，高压氧的生产安全可靠，显示了新流程的生机。