Car Body Production Research Articles

Analysis of Work Posture in the Car Body Assembly Process Using the Rapid Entire Body Assessment Method

CV. Faisyal Putra Mandiri located at Kandangan Rejo Lebar street No.11 Surabaya City, is one of the manufacturing industry companies engaged in car body production. In their work activities there are still workers who do not apply ergonomic work postures while working. Unergonomic work positions can cause some parts of the body to not be in their normal position so that they are very vulnerable to musculoskeletal disorders. To overcome these problems, work posture improvement is carried out. Based on the results of the study, it was found that after simulating the use of tools in the metal cutting process, namely the Hydraulic Scissor Lift Table, it can reduce the risk of worker injury through a final REBA value of 7 with a moderate risk level to a final REBA value of 2 with a low risk level. Then in the welding process can reduce the risk of worker injury through the final REBA value of 9 with a high risk level to the final REBA value of 3 with a low risk level. In addition, it is recommended to use a chair as a tool, which is proven through work simulation to reduce the risk of injury. In metal cutting, the REBA value drops from 7 with a moderate risk level to 3 with a low risk level, and in welding, from 9 with a high risk level to 3 with a low risk level.

Numerical Simulation of Mechanical Joining of Three DP600 and DC06 Steel Sheets

There are many reasons to utilize various grades of steel in car body production. Automotive producers tend to choose steels with great formability and the capacity to absorb impact energy. The dominant method used for joining car body sheets has for many years been resistance spot welding, but the use of various steel sheets leads to research into alternative joining methods. Mechanical joining - clinching, is the innovative method to join these materials. Numerical simulation tools are used to optimize the joining of materials. Simufact Forming software was used to analyse the clinching joining of three sheets of material DP600 and DC06. According to the axisymmetric character of the mechanical joining process, the simulation was stream-lined to a 2D representation. The results of the simulation of the mechanical joining process were compared with the real samples prepared for metallographic observation.

Identifying cause-and-effect relationships of manufacturing errors using sequence-to-sequence learning

In car-body production the pre-formed sheet metal parts of the body are assembled on fully-automated production lines. The body passes through multiple stations in succession, and is processed according to the order requirements. The timely completion of orders depends on the individual station-based operations concluding within their scheduled cycle times. If an error occurs in one station, it can have a knock-on effect, resulting in delays on the downstream stations. To the best of our knowledge, there exist no methods for automatically distinguishing between source and knock-on errors in this setting, as well as establishing a causal relation between them. Utilizing real-time information about conditions collected by a production data acquisition system, we propose a novel vehicle manufacturing analysis system, which uses deep learning to establish a link between source and knock-on errors. We benchmark three sequence-to-sequence models, and introduce a novel composite time-weighted action metric for evaluating models in this context. We evaluate our framework on a real-world car production dataset recorded by Volkswagen Commercial Vehicles. Surprisingly we find that 71.68% of sequences contain either a source or knock-on error. With respect to seq2seq model training, we find that the Transformer demonstrates a better performance compared to LSTM and GRU in this domain, in particular when the prediction range with respect to the durations of future actions is increased.

Solving a multi-dimensional matching problem for grouping clamping points on car body parts

Modern car body production is faced by an increasing number of car models as well as individualizing options, which leads to the need for more adaptable assembly equipment, e.g. grippers and fixtures that can switch between models in a matter of seconds. Based on known clamping positions, automated jigs consisting of several clamps can already adapt to different part geometries.To enable an efficient flexible jig, exactly one clamp must be assigned to each clamping point of each model taking into account different optimization criteria. Therefore, clamping points need to be grouped across all different models in the planning phase. Grouping of clamping points e.g. in order to minimize adaptation time or tooling costs is usually performed manually.In this paper, the grouping optimization problem is formalized, and a mathematical algorithm is introduced to solve this multi-dimensional matching. The envisaged approach uses a greedy algorithm to get an initial solution, which is optimised to a technically feasible solution considering economical aspects. To conclude, a short evaluation of the achieved results - especially in comparison with expert based grouping - is given.

Weld-Quality Prediction Algorithm Based on Multiple Models Using Process Signals in Resistance Spot Welding

An efficient nondestructive testing method of resistance spot weld quality is essential in evaluating the weld quality of all welded joints in the automotive components of a car body production line. This study proposes a quality prediction algorithm for resistance spot welding that can predict the geometrical and physical properties of a spot-welded joint and evaluate weld quality based on quality acceptance criteria. To this end, four statistical models that predict the main geometrical and physical properties of a spot-welded joint, including tensile shear strength, indentation depth, expulsion occurrence, and failure mode, were estimated based on material information, dynamic resistance, and electrode displacement signals. The significance of the estimated models was then verified through an analysis of variance. The prediction accuracies of the models were 94.3%, 93.4%, 97.5%, and 85.0% for the tensile shear strength, indentation depth, expulsion occurrence, and failure modes, respectively. A weld quality evaluation methodology that can predict the properties of a spot-welded joint and evaluate the overall quality requirements based on authorized welding standards was proposed using the four statistical models.

Synchrotron X-ray Analysis of the Influence of the Magnesium Content on the Absorptance during Full-Penetration Laser Welding of Aluminum

Full-penetration laser beam welding is characterized by a weld seam whose depth equals the material thickness. It is associated with a stable capillary and is therefore widely used for welding of sheet metal components. The realization of lightweight concepts in car body production requires the application of high-strength aluminum alloys that contain magnesium as an alloying element, which significantly influences the evaporation temperature and pressure. This change of the evaporation processes influences the geometry of the capillary and therefore its absorptance. In order to quantify the influence of magnesium on the capillary, their geometries were captured by means of high-speed synchrotron X-ray imaging during the welding process of the aluminum alloys AA1050A (Al99.5), AA5754 (AlMg3) and AA6016 (AlSi1.2Mg0.4). The 3D-geometries of the capillaries were reconstructed from the intensity distribution in the recorded X-ray images and their absorptance of the incident laser beam was determined by the analysis of the reconstructed 3D-geometry with a raytracing algorithm. The results presented in this paper capture for the first time the influence of the magnesium content in high-strength aluminum alloys on the aspect ratio of the capillary, which explains the reduced absorptance in case of full-penetration laser beam welding of aluminum alloys with a high content of volatile elements. In order to improve the absorptance in full-penetration welding, these findings provide the information required for the deduction of new optimization approaches.

Joining the High-Strength Steel Sheets Used in Car Body Production

Joining the High-Strength Steel Sheets Used in Car Body Production

Vacuum gripper without central compressed air supply

Compressed air operated industrial equipment has been always an important part of car body production. Advantages of compressed air powered tools are their robust construction, low-cost manufacturing as well as high performances especially forces at a minimum of construction size. Disadvantages are high operating costs, due to pressure losses in case of leakage, high installation costs and intricate cabling especially at highly flexible manufacturing systems. As a result, many automobile manufacturers aiming for a reduction of air powered production tools or even air free automobile manufacturing systems.Against this background a new concept of a vacuum grippers will be presented, which does not need central compressed air supply. Results of the development of suction cups will be shown, which are based on mechanical air displacement inspired by artificial muscles. Furthermore, a control of clusters of new suction cups with artificial intelligence is given.

Criterion for predicting expulsion in resistance spot welding of steel sheets

Resistance spot welding (RSW) is frequently accompanied by expulsion, an undesirable event taking place in manufacturing processes, including car body production. Many variables are involved in RSW, all of which can affect expulsion. This investigation aimed at developing an analytical model for predicting expulsion in RSW. Accordingly, based on force and moment balances, a criterion was established. It was proposed that expulsion took place when the molten metal ejected as a result of the pressure inside nugget. The model presented here considered that the pressure inside the nugget was mainly due to melting transformation and liquid thermal expansion. Hence, the model took into account the effects of nugget diameter, electrode force, base material yield stress, sheet thickness, and joint fit-up to predict the occurrence of expulsion. To assess the model, a number of experiments were done, where the effects of welding current, electrode force, sheet thickness, and galvanization coating of the steel were studied. Regarding the effects of electrode force and welding current, the prediction made by the analytical model was consistent with the results obtained from the experiments. However, it was observed that expulsion in the galvanized steel sheets occurred at larger nugget diameters. The macroscopic examination of the welded samples showed that, with galvanization the ability for a better electrode fit-up was increased, and according to the model this could result in thereby increasing the critical nugget size.

Experimental study on the magnetic pulse welding process of large aluminum tubes on steel rods

Solid state welding technologies enable dissimilar metal welding without critical intermetallic phase formation. Magnetic Pulse Welding (MPW) is a promising joining method for hybrid sheet connections in car body production or for manufacturing of dissimilar tube connections. Given a suitable MPW process design, the shear testing of MPW joints usually leads to failure in the weaker base material. This finding emphasizes the high strength level of the joining zone itself. Consequently, the transmission of higher forces or torques, respectively, requires stronger materials or adapted geometries. In the present experimental study, the diameter of an exemplary driveshaft was doubled to 80 mm at constant tube wall thickness to increase the load bearing capability. The characteristic impact flash was recorded at different positions around the tube’s circumference and it was used to adjust the most relevant process parameters, i.e. working length and acceleration gap, at the lower process boundary. In metallographic analysis, the final shapes of both joining partners were compared with the original driveshaft dummies on macroscopic and microscopic scale. The typical wavy interface between aluminum and steel was analyzed in detail. Doubling the tube diameter lead to four times higher torque levels of failure during quasistatic and cyclic torsion tests.

Experimental analysis of steel joints bonded with automotive grade hot setting structural adhesives

Recent trends in car body manufacturing indicate that the use of a consistent mix of lightweight materials in conjunction with adhesive bonding, not only allows substantial weight reduction, but can also drive down costs and potentially enables more intelligent designs. Yet, presently, it is highly desirable that the introduction of structural adhesives is made with minimum impact on the automotive body framing systems. Adhesives commonly deployed in car body production (i.e. body-in-white) are applied without any prior surface preparation and final curing is carried out during the baking process that follows the electrophoretic coating. Several structural adhesives have been tailored to the conditions dictated by the automotive production process. The aim of this work is to assess the mechanical properties of adhesive joints bonded with automotive grade hot setting epoxy adhesives employed for the assembly of frame and panels. Single-lap and T-joints were fabricated and adhesive hardening was carried out following the typical curing cycle employed in the process chain of automobile production. The resulting mechanical properties were assessed before and after exposure to a standard accelerated thermal cycling under controlled humidity. The evaluation of the mechanical behavior was done through a combination of testing and analysis, which included the assessment of fracture surfaces using optical microscopy to resolve the locus of failure.

Selected aspects of modular fixtures design for car body production

Nowadays, technical design is supported with a computer hardware and software. In order to ensure proper efficiency and comfort of the designer’s work, it is necessary to have hardware with good enough parameters and software able to transform concept into a virtual world. Firts of all, designing modular fixture for car body assembly it is obligate to obtain the necessary input data [2, 4]. It is connected with the close cooperation of designs engineers with the process designer and robotics. The sequence of manual or robotized operations and also the order of putting parts to the station must be clarified. Cooperating devices should be defined to avoid potential collisions. The correctness of this data is necessary for the designer to select the right tooling, and then to project the complete device. After receiving the input data, design engineer has to plan the method of picking up all degrees of freedom of every car’s body part. An important element of constructing the modular fixtures in the automotive industry is design methodology for manufacture and assembly (DFMA). Designing such types of fixtures is time-consuming. Therefore, to make work easier in case of structural changes (face-lifting) compliance with the DFMA principles is indispensable.

Clinching of Dual-Phase Steels as an Alternative to Resistance Spot Welding

Resistance spot welding is the dominant method for joining the materials in the car body production. Progressive materials are being developed to improve the car’s fuel consumption and the safety of passengers as well. Advanced high strength dual-phase steels are such materials. Despite of the dominancy of resistance spot welding in car body production, innovative methods are being developed to reduce the joining time, process costs and improve the load-bearing capacity of a particular joint. Mechanical clinching is such process. The research focused on the evaluation of the possibility of clinching as an alternative method to the resistance spot welding. Experimental samples were prepared from dual-phase steel sheets DP600. The samples were tested by uniaxial tensile test, microhardness test and metallographic observations. Both joining methods have advantages and disadvantages which could destine them for specific utilization. Clinching joining is a progressive, fast and low-cost technique, but the joint’s load-bearing capacity is lower when compared to resistance spot weld.

Effect of crack opening velocity on fracture behavior of hyperelastic semi-structural adhesive joints subjected to mode I loading

Rubber-like adhesive joints provide substantial advantages compared to epoxy-based adhesive joints regarding their damping properties, fatigue resistance and energy consumption under impact. Polyurethane-based adhesives with high modulus are even used in structural applications like car body production. The work to be presented describes the dependency of mechanical mode I failure of a hyperelastic semi-structural adhesive on loading rate. Double cantilever beam (DCB) specimens were manufactured with an adhesive layer thickness of 3 mm. In a first test setup, driving velocity of the testing machine was controlled on optically measured crack opening velocity, varying over several orders of magnitude within external setpoint generation. The tests were driven until crack propagation took place and the position of optical measurement was not valid anymore. The J-integral according to Rice (1968) was calculated directly from measured force acting on the DCB specimen and rotation angle of force introduction points, using an analytical approach of Anthony and Paris (1988). In a second test setup, driving velocity of the testing machine was varied over several orders and tests were driven until complete failure of the adhesive joint. Pictures recorded from specimen's edge were used to analyze the rate dependency of crack propagation and fracture behavior.The observed correlation between J and current crack opening velocity showed that fracture energy was significantly and cohesive strength slightly increasing under higher crack opening velocities, while cohesive stiffness remained constant. In a certain range of loading rates, discontinuous crack growth with stick-slip crack propagation was observed. Below and above this range, crack propagation rate was tending to be more stable.

Product Flexible Car Body Fixtures with Position-dependent Load Balancing Based on Finite Element Method in Combination with Methods of Artificial Intelligence

In car-body production, the fixtures used for fixing the car-body panels during the joining processes predominantly consist of rigid constructions that are precise and specific for one car-model. In addition to the already presented automatic adaptation of such fixtures, and specific for the production of many different car-models using same fixture, different clamping robots have been developed. In order to meet the high quality requirements, the positional deviations of these clamping robots are adjusted due to different external loads. This control loop is carried out using a combination of finite element method, mathematical algorithms and modern methods of artificial intelligence.

Contribution to predefinition of the geometric features and their processing sequences in order to create a CAPP model

In order to create a Computer Aided Process Planning (CAPP) model for a family of parts, it is necessary to establish a database containing the geometric features specific to that family. In the car body production line industry, several families of parts can be determined each having specific geometric features. The parts that are part of a family of parts must be designed in such a way that at the end, they contain those specific features. The next step in the implementation of the CAPP model, is to create a database for processing sequences associated with geometric features. Combining these two databases, the database of geometric features and the processing sequences, the result is the NC program of the designed part. This study presents the creation of these two databases and the link between them.

Mechanical Joining of the Combination of Steel Sheets and Aluminium Alloy Sheets

Constructions of steel sheets and sheets from aluminium alloys are widely used in car body production to reduce the total car weight. The reduction in car weight is needed to improve fuel efficiency. Aluminium alloys play a more important role in future car body generations. Properties of this material give some advantages and open the way for new applications in the automotive industry. It is not possible to join the multiply material combination by conventional joining methods such as resistance spot welding. Therefore, alternative joining methods are being developed. One of the alternatives is mechanical joining - clinching. Clinching is suitable for joining the thin sheets from ferrous and non-ferrous metals. Mechanical clinching is also well known as a speed and efficient cold joining process, mainly for joining the thin-sheet applications. In this process, the local plastic deformation of the sheets is created by the clinching tool. The paper focuses on the evaluation of the properties of mechanically clinched joints, realized on the combination of the zinc-coated steel sheets DC06 and H220PD and sheets from aluminium alloys EN AW 5754 with various hardness H11, H22 and H24 and EN AW 6082. The tensile test and a metallographic observation were used to evaluate the clinched joint properties. Mechanical clinching proved to be suitable technique for joining the observed combination of steel sheets and aluminium alloy sheets. It is necessary to consider the orientation of the sheets relative to punch and die.

Jigless Laser Welding in the Car Body Production

Jigless Laser Welding in the Car Body Production

Automatic Adjustment of Car Body Fixtures Using Artificial Intelligence

In car-body production, the fixtures used for fixing the car-body panels during the joining pro-cesses predominantly consist of rigid constructions that require a time-consuming manual set-up process. To automate the adjustment process and reduce ramp up times, different adjustment modules have been developed at the Fraunhofer IWU in order to meet specific requirements. Because of high quality requirements, produced components will be checked against an adjustment database. The exactly positioning for each clamping point will be derived, with the aid of mathematical algorithms and modern methods of artificial intelligence, based on measured values and the knowledge of the template technicians.

打磨粒度对A7N01P-T4铝合金焊接接头组织及力学性能的影响

铝合金具有密度低、强度高、挤压性能好、焊接性优良及加工性能好等特点，已经成为高速列车车体生产的主导材料。在铝合金车体生产过程中，焊接技术是使用最为广泛的生产加工方式。高速列车铝合金车体焊接完成后，焊缝部位会形成一定的余高。余高不但影响高速列车整体结构尺寸精度，还会影响高速列车的安全可靠性，因此为了满足实际使用要求，大部分焊接接头均要求打磨余高。因而焊缝余高打磨工艺的研究是相当必要的。本文研究了不同打磨粒度对A7N01P-T4铝合金对接接头疲劳性能的影响。结果表明不同打磨粒度铝合金对接接头抗拉强度，延伸率差别不大。不同打磨粒度对铝合金对接接头疲劳性能的影响多变的。疲劳裂纹源均萌生于焊缝缺陷，多见于气孔，夹渣与硬质相，因而焊接接头的质量对疲劳性能的影响占主要原因。 Aluminum has a low density, high strength, good extrusion performance, good weldability and ex- cellent processing performance and other characteristics, which has become the dominant vehicle production materials of high-speed trains. In the aluminum car body production process, welding technology is the most widely used production and processing method. After the completion of high-speed train’s aluminum body welding, Weld will be a certain reinforcement. Weld reinforcement will not only affect the overall structure of the dimensional accuracy, but also affect the safety and reliability of high-speed trains, so in order to meet the actual requirements, most of the welded joints require more than a high polish. Thus, research on weld reinforcement grinding process is very necessary. This article studied on the effect of different polished size on the fatigue properties of A7N01P-T4 aluminum butt joints. The results showed that different size polished aluminum butt joints tensile strength has little difference on elongation. Effects of different grinding size on the polished aluminum butt joints fatigue properties change greatly. Fatigue crack initiation in weld defects was more common in the pores, slag and hard phase. Thus the main reason that affecting the fatigue performance of welded joints is the welding quality.