Defect-free Products Research Articles

Process Design and Thermal Performance in Deep Drawing of SiCp/2024Al Composite Sheet Using Pulse Current Heating

The deep drawing of SiC/2024Al composites using pulse current heating were designed and established in this works. The whole process system mainly include pulse current heating system, electrode lifting system, temperature control system and deep drawing forming system. In addition, the feasibility of thermal deep drawing using pulse current heating was experimentally investigated and the optimal process parameters were explored to ensure defect-free products. The temperature of specimen is up to around 673K at a rate of 13.5K/s under the current density of 21.7A/mm2. The stainless steel inserts make temperature difference reducing by 73.3%. Moreover, the workpiece was successfully deep drawn and exhibited good surface quality. The dimensional accuracy achieved within ±0.2mm.

Theoretical and Experimental Analysis of Deep Drawing Cylindrical Cup

There are mainly two methods of deep drawing analysis: experimental and analytical/numerical. Experimental analysis can be useful in analyzing the process to determine the process parameters that produce a defect free product, and the analytical/numerical modeling can be used to model and analyze the process through all stages of deformation. This approach is less time consuming and more economical. Sheet metal forming often includes biaxial in-plane deformation with non-proportional strain paths. In deep drawing of cylindrical cup, the deformation in the flange is dominated by pure shear deformation, while it changes to plane strain when the material is drawn into the die. This paper deals with the analysis of deep drawing of circular blanks into axi-symmetric cylindrical cup using numerical modeling. The blank drawability has been related both theoretically and experimentally with the initial diameter of the blank and deep drawing parameters. The strains in the radial and circumferential directions have been measured. A correlation on the flange thickness variation by taking into account the work hardening with the analytical and experimental values also has been searched.

Analysis of Hot Working Characteristics of Aluminium Based Composites Using Response Surface Methodology

During deformation process, it is essential to control the formability parameters viz., stress, strain, temperature, aspect ratio, volume fraction etc., to obtain sound and defect free products. Moreover, in deformation process in general, upsetting in particular, conducting too many trail experiments results in increased experimental time and cost. Hence modeling of process parameter attracts attention of researchers. The objective of modeling the process parameters is to determine which variables are most influential during metal forming operations. In the present investigation, by connecting the influential process parameters during metal forming in general upsetting in particular, a mathematical model have been developed using Design of Experiments (D.O.E) which could be applied to estimate the flow stress. Aluminium MMCs with silicon carbide (SiCp) and aluminium oxide (Al2O3) as reinforcement have been chosen in this current study as it has significant advantage over conventional materials.

Application of Statistical Process Control Tools to Improve Product Quality in Manufacturing Processes

Quality control and improvement at the process level is a vital activity for the achievement of defect-free products in various manufacturing processes. This study employs statistical process control (SPC) tools such as control charts and process capability ratio for quality control and improvement. The control charts employed are , R and the cumulative-sum (CUSUM). The process capability ratio used is the so called process capability index (PCI). These tools have been implemented with the aid of Minitab® statistical software. In this study, the manufacturing process of gelatin capsules is investigated in terms of quality of the capsules, which are produced and shipped for use by various drug companies. As a result of implementation of SPC tools, an expected reduction in the number of defective capsules by 29% relative to the stage before implementation was achieved.

Numerical analysis of damage for prediction of fracture initiation in deep drawing

The sheet metal may have inherent voids/imperfections present because of preprocessing. These voids/imperfections grow under the applied load resulting into final fracture. The occurrence of ductile fracture is often a limiting factor in metal forming processes. Prediction of the initiation of ductile fracture allows a prior modification of the process which can result in a defect-free final product with financial savings. The intensity of voids is often represented by introducing a variable called damage. This paper deals with the prediction of fracture initiation in deep drawn cup using Lemaitre's continuum damage mechanics model. The damage is incorporated in the constitutive equation through the principle of strain equivalence. The damage is evaluated using the damage growth law proposed by Lemaitre. An in-house 3D finite element formulation is employed for the analysis. The maximum cup height at which the fracture initiates is determined using the critical damage criterion. A parametric study of the maximum cup height is carried out to investigate the influence of material, geometric and other process parameters.

Integrated Product and Process Control for Sustainable Semiconductor Manufacturing

Semiconductor fabrication is a manufacturing sequence with hundreds of sophisticated unit operations and it is always challenged by strategy development for ensuring the yield of defect-free products. In this paper, an advanced control strategy through integrating product and process control is established. The proposed multiscale scheme contains three layers for coordinated equipment control, process control and product quality control. In the upper layer, online control performance assessment is applied to reduce the quality variation and maximize the overall product performance (OPP). It serves as supervisory control to update the recipe of the process controller in the middle layer. The process controller is designed as an exponentially weighted moving average (EWMA) run-to-run controller to reject disturbances, such as process shift, drift and tool worn out, that are exerted to the operation. The equipment in the process is individually controlled to maintain its optimal operational status and maximize the overall equipment effectiveness (OEE), based on the set point given by the process controller. The efficacy of the proposed integrated control scheme is demonstrated through case studies, where both the OPP (for product) and the OEE (for equipment) are enhanced.

Concurrent design of electroplating system for X-abilities: a graph theoretic approach

The electroplating process has been widely accepted for plating automobile parts, aircraft parts and spacecraft components with high strength and stiffness to weight ratios, high quality and reliability, dimensional accuracy and surface finish of the product. This process is widely acceptable in various industries. Designing the electroplating products requires a lot of skill with multidisciplinary knowledge. The present approach offers a ‘virtual design’, which optimises the concurrent design approach and ultimately leads to the achievement of the six sigma limits, i.e. almost defect-free products from the plating technology. The new design utilises the advantages of the graph theoretic approach to consider all the design aspects together in a single methodology with the help of matrix algebra and permanents. It is essentially a virtual methodology which decides the process, the product strength and the weakness with the help of a multinomial defined by using matrix algebra. The design index, developed u...

Development of Laser Direct Ablation Process on Solder Resist in Printed Circuit Boards

In recent, the laser direct ablation process (LDA) for opening solder resist (SR) is getting the spotlight because this process favors small size opening and process shortening. However, it is concomitant with a desmear process which causes SR whitening defect. The SR whitening, in general, is known to be caused by the diffused reflection of the SR surface reformed and coarsened by the chemical reaction between the permanganate and SR polymer components. The process comprising the surface treatment on the SR prior to conducting LDA is proposed to resolve the problem. Therefore, the whitening defect-free products can be obtained even after the wet chemical desmear or plasma desmear. As an application, selective surface finish products, which are treated by gold surface finish and organic surface finish at different areas in the same substrate, can be fabricated using the LDA process.

On-Line Monitoring of Run-to-Run Control Performance in a Discrete Microelectronics Manufacturing

Semiconductor manufacturing is challenged by strategy development for ensuring the yield of defect-free products. In this paper, an on-line performance assessment strategy is proposed to evaluate the EWMA-based run-to-run (RtR) controllers in a discrete microelectronics fabrication. Expressions of minimum variance performance (MVP) and best achievable performance (BAP) are derived in a rigorous way. Technologies such as close loop identification and numerical optimization are employed in order to carry out on-line monitoring. Case studies of the chemical mechanical polishing (CMP) unit operation show the efficacy and the attractiveness the strategy.

Analysis of Edge Crack of Thin Strip during Cold Rolling

Cracks in metal product significantly decrease quality and productivity of the rolled thin strip. In this paper the stress intensity factor (SIF) solution of edge crack defect of thin strip during cold rolling was investigated, and a globe analysis was applied to the problem of free edge of thin strip. The effective stress intensity factor range is important because it represents the major physical cause of crack growth. The present study provides insights of the mechanics of edge crack growth that has been frequently observed during thin strip rolling. The efficiency and reliability of the SIF analytical modelling has been demonstrated. The proposed method for predicting edge crack is useful for producing defect-free products in rolling, and provides insights of the mechanism of edge crack growth.

Numerical simulation of fracture in cup drawing

Prediction of the initiation of ductile fracture in deep drawing allows a prior modification of the process which can result in a defect-free final product. This paper deals with the prediction of fracture initiation in deep drawn cup using Lemaitre’s continuum damage mechanics model. The damage is incorporated in the constitutive equation through the principle of strain equivalence. The damage is evaluated using the damage growth law proposed by Lemaitre. An in-house 3D finite element formulation is employed for the analysis. Finite element formulation is based on updated Lagrangian approach. Logarithmic strain measure is used. The incremental stress is made objective by evaluating it in a frame rotating with the material particle. The material is assumed to be elasto-plastic with isotropic strain hardening using von Mises yield criterion. Modified Newton-Raphson iterative technique is used to solve the nonlinear incremental equations. The fracture location predicted by the present formulation is in agreement with the results reported in the literature.

Better defect detection and prevention through improved inspection and testing approach in small and medium scale software industry

One of the challenging issues in software industry is to deliver high quality software through effective defect management. Inspection and testing are two important approaches that address defects. An empirical study of existing inspection technique in leading small and medium scale software industries in India shows the capability in delivering maximum of 96% defect-free product. The paper aims to improve effectiveness of inspection and testing approaches for achieving 99% defect-free product. It analyses defect patterns and gives concrete ranges for inspection and testing. It introduces 'depth of inspection (DI)' metric to indicate productivity and quality levels for software process. This approach emphasises that an optimal level of 10%-15% of inspection time and 15%-25% of testing time out of whole effort with DI value in the range of 0.4 to 0.7 at each phase of software development eliminates 99% defects in small and medium scale industries.

New approaches for online visual inspection of products with multiple-characteristics and known tolerances

The increasing customer requirements regarding better quality products and lower costs are challenges that should be resolved. Also, lean manufacturing, as an effective approach to increase efficiency of production systems, that is based on eliminating wastes and reaching excellence, makes it necessary to find and apply non-traditional approaches in manufacturing and quality control. Costs of product quality control are among those costs that do not add value to the product and should be maintained within limited ranges in order not to affect the final product cost. Either classical inspection methods (measuring methods) or even traditional quality control approaches are costly; and, unfortunately, do not guarantee defect-free products especially for products with multiple quality characteristics. In this work, an efficient online 100% visual inspection approaches are introduced. Those approaches are based on digital imaging of products and analysing their data using advanced mathematical approaches to extract the product features. Statistical tools are then applied to compare the extracted features with a master feature for the product. The developed approaches give a good performance in inspecting multi-dimension products at low costs and very little inspection errors.

Finite element simulation of earing defect in deep drawing

Deep drawing is an extensively used press working process since it eliminates expensive machining and welding operations and enables the production of components at a very high rate. The workpiece material used in a deep drawing process is anisotropic in nature, due to a prior thermomechanical treatment. Earing is one of the major defects observed in a deep drawing process due to the anisotropic nature of the sheet material. Knowledge about the ear formation in deep drawing allows a prior modification of the process, which can result in a defect-free final product with financial savings. In this paper, a recently proposed anisotropic yield criteria by Barlat et al. for rolled sheets is used to model the anisotropy for simulating the earing defect in square and circular cup drawing processes. The effect of the tooling geometry and process parameters on the ear formation is studied. It is shown that, in the square cup, the uneven metal flow rate, rather than the material anisotropy, is mainly responsible for the flange earing. Finite element formulation, based on the updated Lagrangian approach, is employed for the analysis. The stresses are updated in a material frame and the logarithmic strain measure is used, which allows the use of a large increment size. Isotropic hardening is assumed, and it follows a power law. Inertia forces are neglected due to small accelerations. The modified Newton–Raphson iterative technique is used to solve the nonlinear incremental equations.

Pressing Velocity Control Considering Liquid Temperature Change in Press Casting

Abstract To newly create the sand casting method to drastically improve productivity and casting quality, author's group has actively developed advanced control technology in foundry. In high-speed filling of the press casting process using greensand mold, some defects are caused by increased pressure of molten metal, such as metal penetration which the solidified molten metal flows into between the sand particles. Hence, we will propose controlling the pressing velocity in order to suppress increasing pressure. Considering pressure constraint for a defect-free product, control velocity pattern is then derived by using proposed mathematical model of molten metal's pressure in the mold. The simple pressure model is derived by considering the wall shearing stress depended on molten metal's temperature to accurately represent actual pressure behavior during pressing. Analytical results for the liquid temperature decrease during filling and its consideration for the pressing control are mentioned in this paper. The effectiveness of control result using the model is checked by CFD: Computational Fluid Dynamics simulations. In near future, experimental examinations will be carried out by practically using water and molten metal.

A Test-oriented Embedded System Production Methodology

In the business world, the use of Agile methodologies has been demonstrated as providing a pro-active, rather than reactive, path for the developer to create defect-free products. Although similarities exist with business desktop and line-of-business systems, the closer connection of signal processing systems to the hardware side of a product, and associated physical constraints, makes the adaption of desktop Agile methodologies for the embedded world difficult; and the adoption of these methodologies by developers problematic. We focus on our experiences in developing test frameworks to support transforming a subset of extreme programming from the world of desktop applications into a suitable embedded domain production methodology. Details are provided of the issues surrounding an Embedded xUnit testing framework that will permit development of digital signal processing applications on a wide range of standalone and multi-processor systems in research, teaching and commercial development environments.

Deformation analysis of surface defect on hot rolling by 3-D FEM simulation

The major objective of this research is to develop a 3-D FEM simulation technique in order to analyze the deformation behavior of surface defects on hot rolling. The developed technique will be applied to quantify the relationship between rolling condition and the process parameters, and the rolling pattern will be tested to verify and validate the simulation technique. This technique will allow us to quantify the shrinkage of slab width at the head and tail, width spread after the horizontal rolling, dog-bone shape, position change of the slab corner as the slab is being rolled, strain distributions. And the shape change of surface defects in hot rolling was investigated using the 3-D rolling simulation technique. The proposed prediction method of surface defect can be utilized to make defect free products in rolling.

Poka - Yoke in Welding

Integral Coach Factory is the Premier Coach (ICF) building Industry in Indian Railways. This factory has so far produced more than 30000 coaches in about 170 designs. It was the first among the Indian Railway production units to get ISO 9001 certification. Quality of the coach is being ensured from the raw material to end product. In ICF. fabrication of coaches are being carried out by welding process. Though welding is a reliable metal joining process, the soundness of the weldment largely depends on Men, Machine, Material and Method. The quality of the weldment is ensured by implementation of various quality tools. Even then it is quite difficult to achieve 100% defect free product in manufacturing. Even if 100% inspection is resorted to at every stage of manufacturing defects are inevitable since the inspection is being carried out by human and human errors are inadvertent and inevitable. Poka-Yoke is a tool which achieves 100% defect free product at low cost with the aid of low cost equipments. These low cost equipments aids the employee to manufacture defect free product. The aim of this study is to develop Poka-Yoke methods in a welding application. Few parameters which affect the quality of the weld are identified, and various methods are developed to control these parameters and eliminate defects. The parameters identified are shielding gas flow rate, pre and post heat temperature, welding sequence and electricity. These parameters are recorded in a standard format. Poka-Yoke Techniques were applied to control the above said parameters and ensure error free welding in ICF.

An Improved Process Design for the Hot Backward Extrusion of Ti-6Al-4V Tubes Using a Finite Element Method and Continuum Instability Criterion

The hot backward extrusion process of Ti-6Al-4V tubes was designed by finite element (FE) simulation and experimental validations. In the hot backward extrusion of Ti-6Al-4V alloy, the main problems to emerge were surface cracks and sticking between the punch and the workpiece. The punch designs and back draft angles were investigated with a common hot backward extrusion condition. Then, based on a relatively good die design, the optimum process conditions were suggested. The design criteria were to achieve uniform distributions of strain and temperature and to produce a defect-free final product. As a model for predicting the forming defects, the continuum instability criterion developed by Ziegler was coupled to the internal variables generated from FEM simulation. Experimental observations were carried out on the extruded Ti-6Al-4V tubes to validate the model for predicting the forming defects. The die-chilling and friction greatly influenced the deformation mode of the tube and the formation of surface cracks. The formation of defects in the extruded tube was attributed to the non-uniform distribution of strain, strain rate, and temperature in the extruded tubes at the given experiment conditions.

Evaluation of performance of manufacturing processes and their improvement through employee training

Manufacturing of defect-free products has long been recognised, and important for any company aspiring to build its market share (Lim et al., 1999). It is appreciable to develop management policies for the effective use of available resources. The employee community is the influencing source available in any organisation, and has to be utilised properly to meet the organization's objectives. Employee training will improve the production performance by way of minimising the losses in production. In this paper, a case study, conducted on a particular production process of a radiator manufacturing company is presented, in which the findings of a survey conducted for assessing the proficiency of shop floor employees, levels of training provided and the encouraging effects of training on production are discussed.