Manufacturing Process Capability Research Articles

An integrated fuzzy strategic supplier selection approach for considering the supplier integration spectrum

The majority of the published supplier/vender selection (VS) literature obtained optimal solutions based on the operational metrics. The evaluation criteria of VS must be in alignment with a firm's strategy. This work considers strategic and operational factors with the consideration of supplier integration spectrum (SIS) to secure the efficacy of VS on the initial product stage. This study adopts supplier's manufacturing process capability indices (PCIs) and process yields as operational (hygiene) factors to estimate their quality capabilities while the business process-oriented criteria related with the performance of business process improvement (BPI) are suggested as the strategic (motivation) criteria for a supplier assessment visit. A fuzzy approach then aggregates the total scores of individual suppliers with the considerations of the strategic factors’ extra effect on the operational metrics and the supplier integration levels objectively. An empirical case study is performed to demonstrate the efficacy of the proposed system and to identify the best potential supplier(s). The conclusions and conducting processes of the case study also provide interesting managerial implications.

Ramp-up of hybrid manufacturing technologies

Hybrid manufacturing technologies provide a high potential in enhancing manufacturing process capabilities in terms of new product properties and sustainable production. Combining two or more technologies in one process or machine result in a larger range of options for the creation and optimization of technology chains. Sustainability is an important objective when using hybrid processes but also economic targets can be achieved. The aim of this paper is to present a method for detecting and evaluating hybrid manufacturing technologies and implementing them at the right moment into an existing production environment. A decision has to be made, whether a certain hybrid technology is suitable or not. To make this decision a risk-and-potential analysis of manufacturing technologies was developed. In the first part this article will provide an introduction to hybrid manufacturing processes. Further a design approach for hybrid technologies is shown. The second part concentrates on the possible implementation of manufacturing technologies during the ramp-up phase into the production environment.

Evaluating measurement and process capabilities by GR&R with four quality measures

This paper proposes a procedure for assessing a measurement system and manufacturing process capabilities using Gage Repeatability and Reproducibility (GR&R) designed experiments with four quality measures. In this procedure, a GR&R study is conducted to obtain replicate measurements on units by several different operators. The gage and part variance components are then estimated by conducting analysis of variance (ANOVA) on the GR&R measurement observations. Finally, the acceptance and rejection criteria of the precision-to-tolerance ratio ( PTR), signal-to-noise ratio ( SNR), discrimination ratio ( DR), and process capability index ( C p or C pk ), are employed to assess the measurement and process capabilities. Three previously studied case studies are provided for illustration; in all of which the procedure provided efficient capability assessments at minimal computational and statistical efforts. In conclusion, the procedure proposed in this research using GR&R designed experiments provides valuable procedure and helpful guidelines to quality and production managers in assessing the capabilities of a measurement system and manufacturing process, and deciding the needed actions for improving performance.

Measurement of Diode to Diode Spacing

Laser printers with multiple laser diodes in a single diode package may have diode to diode spacing requirements critical to print quality. Standard off-the-shelf equipment is seldom designed to measure to the nanometer resolutions and linearity desired, especially if the measurements are time constrained. Therefore characterizing the linearity of the measurement system is important to the understanding of the measurement system limitations.Diode to diode spacing is a comparison of the centroids of multiple adjacent laser spots in one or more axes. It is physically possible to measure the centroid location of the spots using various methods including scanning aperture, CCD/CMOS cameras or position sensing devices. The accuracies and precisions desired for good measurements as well as for good manufacturing process capabilities are often smaller than what are easily available with these products, often by an order of magnitude.A procedure has been developed to estimate the measurement system error over a wide range of scales. It can be applied to several of the common laser spot centroid measurement devices enabling estimation of measurement resolution of the relative centroid. This method is based on an innovative technique involving controllable movement on a much larger scale.

Manufacturing Process Capability and Specification Limits

In modern electronics, specifications for products have constantly been tightened due to performance competi- tion. The processes for product development and manufacturing have been developed to meet the tighter specifications and quality requirements. The development of test methods and measurement devices have not been as fast, and as a con- sequence, the relative impact of measurement errors has increased. Traditionally, the measurement inaccuracies have been compensated by tightening the acceptance limits. This study concentrates on analysing, through simulation, how compa- nies should minimise the failure costs by adjusting acceptance limits. The study shows, in contrast to the conventional thinking, that widening the acceptance limits makes business sense in some cases.

Fuzzy inference to assess manufacturing process capability with imprecise data

Process capability indices provide numerical measures on whether a process conforms to the defined manufacturing capability prerequisite. These have been successfully applied by companies to compete with and to lead high-profit markets by evaluating the quality and productivity performance. The loss-based process capability index C pm , sometimes called the Taguchi index, was proposed to measure process capability, wherein the output process measurements are precise. In the present study, we develop a realistic approach that allows the consideration of imprecise output data resulting from the measurements of the products quality. A general method combining the vector of fuzzy numbers to produce the membership function of fuzzy estimator of Taguchi index is introduced for further testing process capability. With the sampling distribution for the precise estimation of C pm , two useful fuzzy inference criteria, the critical value and the fuzzy P- value, are proposed to assess the manufacturing process capability based on C pm . The presented methodology takes into the consideration of a certain degree of imprecision on the sample data and leads to the three-decision rule with the four quadrants decision-making plot. The fuzzy inference procedure presented to assess process capability is a natural generalization of the traditional test, when the data are precise the proposed test is reduced to a classical test with a binary decision.

An inverse method of teaching specialised manufacturing subjects: decomposing a focal representative product to sustain analysis and interaction of details

The paper presents an ‘inverse’ method to teach specialist manufacturing processes by identifying a focal representative product (RP) from which, key specialist manufacturing (KSM) processes are analysed and interrelated to assess the capability of integrated manufacturing routes. In this approach, RP should: comprise KSM processes; involve innovative designs; be a daily used and/or market successful product; appeal to the profile of the course. The ‘inverse’ teaching method was implemented to a new third year specialist manufacturing module, manufacturing process capability through two stages as follows. Knowledge transfer that involved detailed teaching/analysis of technical capabilities of KSM processes through the decomposition of a focal RP, i.e. vacuum cleaner. Then, analysis of how entities (parts of RP) interact/couple to enable the generation of complex entities (assemblies of RP) was brought to students’ consideration. Knowledge exercise consisted of group/individual coursework assignments that were designed to stimulate students to use the RP approach for acquiring specialist manufacturing knowledge not discussed during the knowledge transfer stage. Furthermore, the KSM processes were exercised/coupled to generate new families of RPs. The evaluation and analysis of coursework assessments and the formal/informal feedback showed that this module helped students develop abilities to select and optimise capabilities of new manufacturing processes and then couple them to generate new RPs. However, it was found that students are less confident in dealing with inter-process/disciplinary topics that enable them to propose industrial viable manufacturing routes. Apart from individual circumstances, this might be due to previous engineering knowledge convened using by classical descriptive teaching approach. Additionally, the use of RP exercise offers an efficient method for ‘probing’ students’ abilities to interrelate key manufacturing processes for the generation of successful products are proposed.

Robust, Producible Design Process Evolution

ABSTRACT Until about 10 years ago, design engineering and manufacturing at our company were separate organizations. Design engineers produced part designs for an integrated engine system and expected manufacturing to make and assemble the parts. Tolerance decisions were influenced by the arguing ability of each discipline along with historic precedent. Most form-fit-function characteristics were about 95% producible or two-sigma designs. Nonconformance control by a Material Review Board (MRB) was used by design engineering to monitor manufacturing quality. Although this process demonstrated the ability to produce excellent engines, it depended on inspecting in quality, multiple rework loops and resulting high cost. This article will discuss the evolving process used to design engines that are producible and error proofed. Discussion will include the organizational structure supporting the needed culture change, the six-sigma impact of common terminology and data driven decisions, the structured approach using manufacturing process capability data to facilitate producibility, use of assembly defect and customer escape data to drive error-proofing early during the design process, and the focus on standardized notes and automated characteristic accountability for error prevention. Discussion will include examples demonstrating the significant improvements in quality and producibility accomplished by the new process.

Leveraging Six Sigma disciplines to drive improvement

Six Sigma provides the opportunity and discipline to eliminate mistakes, improve morale, and save money. Doing things right and keeping them consistent are the ideas behind Six-Sigma. A fundamental objective of Six Sigma is to achieve customer satisfaction with continuous improvement in quality. Process control and manufacturing variation reduction are important but companies often discover that the majority of their quality problems were actually created during the design process. An example of improving manufacturing process capability to give bottom line cost savings and customer satisfaction is presented in this paper. The methodology to increase system robustness through Design for Six Sigma (DFSS) is presented and demonstrated through the extension of the case study of crankshaft journal lobing design robustness improvements.

A hybrid neural network-feature-based manufacturability analysis of mould reinforced plastic parts

The purpose of this research is to establish a method to perform manufacturability analysis of reinforced plastic components by using a hybrid system including automatic feature recognition and a feature-based assessment of manufacturability. Feature recognition plays a fundamental role and is usually the first step in downstream activities concerning the product development process, such as design for manufacturing, design for assembly and process planning. Critical features to successful reinforced plastic moulding are identified, and the relationship between geometric information of the model, expert geometric reasoning and knowledge of related manufacturing processes is clarified and predetermined in a useful and efficient manufacturability analysis system. A prototype system using solid modelling, object-oriented programming and a rule-based system, which is intended to consider the fuzziness of the expert reasoning about reinforced plastic component design, is under construction to test the proposed concepts. The major contribution from this work is a consistent and systematic methodology for analysing the geometry of models, allowing assessment of manufacturability. This methodology considers available manufacturing process capabilities, materials and tooling required. Some virtual parts have been used to test the system, showing promising results.

An object-oriented information model for manufacturability analysis of printed circuit board fabrication

Assessing the manufacturability of a design is important for lowering the printed circuit board (PCB) cost, increasing process yield, and reducing the time-to-market. Many have recognized the need for a neutral information model for sharing product information, however, the modeling and exchange of manufacturing information is equally important to the successful manufacturability evaluation. Modeling the manufacturing information for PCBs is fraught with difficulty. The reasons are that the PCB industry experiences frequent technical advances, design knowledge is separated from process knowledge, and a great variation exists among companies in processes and capabilities. To address these issues an EXPRESS object-oriented manufacturing model of the manufacturing equipment and manufacturing process capabilities is proposed. The model is developed by considering PCB design and fabrication separately and then identifying the couplings between design decisions and the realization of those features in manufacturing. The data model captures equipment imposed limitations on designs and the couplings between design parameters and their impact on the manufacturing system. The model forms the basis of a manufacturability evaluation system for PCB fabrication and is illustrated through an example.

Improving the manufacturing process quality and capability using experimental design: A case study

Experimental design is essentially a strategy of planning, designing, conducting and analysing experiments so that valid and reliable conclusions can be drawn in the most effective manner. Experimental design has proved to be very effective for improving the process performance, process capability and reducing rework and replacement costs due to excessive process variability. The paper highlights common problems and gaps in the state-of-the-art in experimental design. The paper also presents a case study performed in a UK firm on a laser welding process for optimizing the product life using experimental design methodology. A significant improvement in the product life was observed. The result of the case study reveals the stimulus for the wider application of experimental design techniques by engineers within the company to achieve process improvement at low costs. Computer softwares such as Minitab and Design-Ease were used for analysing the experimental results.

Quality technique transfer: Manufacturing and software

An argument for quality technique transfer between manufacturing and software is put forward in which it is recognised that the nature of the production process differs and that the emphasis accorded given stages in the respective life cycles may also differ. The relevant issues that contribute to successful transfer are discussed before a case is made for potential candidate techniques from manufacturing, electronics, and avionics. A common feature of the underlying analysis is identified as an increase in the emphasis placed on quantitative approaches. The paper then proceeds to explain the example techniques which are: the manufacturing process capability measures for Statistical Process Control (SPC); Taguchi Fractional Factorial Experiments; built in testing from VLSI technology; and Black Box recording, derived from avionics, in usage testing. Instances of the implementation of each are given and it is concluded that practical implementations of transferred techniques are related to: the product development phase; the maintenance phase; and the process improvement sphere. The strength of pressures to overcome existing product deficiencies are reasoned to mitigate implementation costs.

Towards pultrusion process optimisation using artificial neural networks

Abstract The pultrusion process involves resin impregnated fibres and mats passed through a heated die, which cures the resin and produces the final product. When the process is examined in detail the number of parameters affecting the final product quality and process efficiency is very large. Parameters can range from the basic such as process speed, to the more complex such as the crosslinking reaction of the resin in the die. More important than the individual parameters are the relationships between these different parameters. Due to the complexity of the problem, the more usual compact mathematical descriptions of the whole process are not feasible in commercial manufacturing environments. This paper describes the use of artificial neural networks (ANNs) for pultrusion process modelling of real process data and their potential for intelligent machine control. It details how the use of ANNs can offer insights into the importance of the connections between the individual process parameters without having any ‘knowledge’ of the process. Such insights could lead to a greater understanding of the process, reduced product development time and increased manufacturing process capability and efficiency.

Tolerance Design: A Handbook for Developing Optimal Specifications

Tolerance Design: A Handbook for Developing Optimal Specifications

Manufacturable DUV lithography processes for 0.25μm technology contact and via layers

One of the critical applications of DUV (248nm) lithography for 0.25 μm technology is the imaging of contact and via holes. The goal of this work was to demonstrate and verify manufacturing process capability for imaging 0.25 μm design rule (300 nm) contacts and vias for integration into an existing process flow, including exposure on a first generation (NA-0.50, σ=0.51) production capable DUV stepper. Furthermore, a simulation study was carried out to estimate the optimised optical parameters for a next generation stepper with variable NA and Sigma. Finally, process latitudes for sub-300 nm contacts were measured and an estimate of minimum manufacturable contact sizes using conventional DUV lithography was made.

Reliability Assessment Based on Design and Manufacturing Tolerances for Control Burst Mechanism of Small Arms

Very often specified tolerance is made greater than process tolerance, depending upon (i) the manufacturing process capability, and (ii) the 'aspiration level' of the designer in effecting a specified tolerance. This applies to multiple components merging into an assembly. In assembly tolerance, errors due to mating are inherent. Common errors arise due to clearance, misalignment in planes and distortion that may cause side stack. Such errors affect the functional performance of the subsystem and consequently become the main cause of failure. Probability distribution of the assembly tolerance and probability distribution of stacked up tolerance of the Components in actual practice leave a common zone of interaction, based on which the in-built reliability changes. From the designer's tolerance, one may have an idea about the 'aspiration level' of assembly tolerance stacking error. Assuming both these parameters, viz., actual stacking error and designer's aspiration level of stacking error to follow the normal probability distribution, it is possible to get the reliability of the product assembly. The paper presents a real life case study for assessing the reliability of sub-assembly at the initial stages of development for control burst mechanism (CBM) of rifle.

Advanced materials mean advanced engines

In this, the third Finniston Lecture, the recent advances in aero engine technology made possible by interdisciplinary collaboration between materials scientists and design and manufacturing engineers are reviewed. Of crucial importance is the efficient and cost effective design of component geometries with due regard for material properties and manufacturing process capability. The three operating parameters that most directly define the thrust and fuel consumption of an aircraft gas turbine – fan airflow, or diameter, overall pressure ratio, or compressor delivery temperature, and turbine inlet temperature – are in turn largely dependent on these capabilities. As bypass ratios of commercial turbofans increase, the weight of the large diameter components becomes increasingly important. Titanium and composite materials, each with their own advanced manufacturing techniques, allow thrusts of 100000lb to be achieved at acceptable weight. Overall pressure ratio is a major influence in improving fuel consumption. The resulting temperature determines the choice of material – nickel alloy or advanced titanium, and detail design of components in this area is important to make full use of the material capability. High pressure turbine blades represent a most complex design challenge. Nickel alloys have developed to a third generation single crystal standard and ceramics offer a prospect of even higher temperature capability. It is concluded that planning from the start to have dual use application in civil and defence markets is the most cost effective route to further progress.

Critical Variables in Wood Manufacturing's Process Capability: Species, Structure, and Moisture Content

Critical Variables in Wood Manufacturing's Process Capability: Species, Structure, and Moisture Content

Advanced materials mean advanced engines

AbstractIn this, the third Finniston Lecture, the recent advances in aero engine technology made possible by interdisciplinary collaboration between materials scientists and design and manufacturing engineers are reviewed. Of crucial importance is the efficient and cost effective design of component geometries with due regard for material properties and manufacturing process capability. The three operating parameters that most directly define the thrust and fuel consumption of an aircraft gas turbine – fan airflow, or diameter, overall pressure ratio, or compressor delivery temperature, and turbine inlet temperature – are in turn largely dependent on these capabilities. As bypass ratios of commercial turbofans increase, the weight of the large diameter components becomes increasingly important. Titanium and composite materials, each with their own advanced manufacturing techniques, allow thrusts of 100 000 lb to be achieved at acceptable weight. Overall pressure ratio is a major influence in improving fue...