Critical Step In Production Research Articles

APPLICATION OF THE MULTICRITERIA DECISION-MAKING FOR SELECTING OPTIMAL MAINTENANCE STRATEGY

Assessing the best set of maintenance guidelines for various types of failures is often a challenging and complex task. It requires understanding various factors such as safety aspects, environmental issues, energy savings, costs, budget constraints, system reliability, resource utilization, and more. Implementing the correct maintenance process is a critical step in production to increase reliability and improve the effectiveness and quality of the production system. Despite the significant importance of this issue, there are not many studies that analyse and develop procedures for selecting the optimal maintenance strategy. This paper presents the selection of the optimal maintenance strategy using multicriteria decision-making, specifically the Analytic Hierarchy Process (AHP), for a case study involving a company in the automotive industry. The defined alternatives are the four most commonly used machine maintenance strategies in the industry: corrective, preventive, condition- based maintenance, and total productive maintenance. The decision criteria considered in the analysis are: production quality, reliability, costs, and safety, along with their respective sub-criteria.

Investigation of passive acoustic emissions during powder mixing in a V-blender

Powder mixing is a complex process and a critical step in production across various industries. Passive acoustic emissions provide a promising potential for inline powder mixing monitoring. Vibrations from these emissions were measured during rotations of a V-blender using glass beads as a model solid as well as starch granules. Vibration profiles were correlated to specific phases of particle motion within the revolving V-shells. The phase, labeled Feature #1b, associated with particle collisions of the V-shell lid with attached accelerometer provided the largest measured vibration amplitudes and most reliable and relevant information on particle movement. After wavelet filtering to remove large-scale vibrations of the V-shell, the optimal information extraction method was identified as the average of the 50 highest amplitudes within the Feature #1b phase. An example illustrating the mixing of two size ranges of granules shows the potential of this monitoring method for pharmaceutical powder mixing in V-blenders. • Passive acoustic emissions are measured by a sensor on the lid of a V-blender. • Passive acoustic emissions from collisions reflect particle size and flow. • The largest emission amplitudes occur from collisions with the V-blender lids. • The 50 largest emissions amplitudes allow a mixing profile to be estimated.

Archeochemistry reveals the first steps into modern industrial brewing

A historical beer, dated to the German Empire era, was recently found in northern Germany. Its chemical composition represents a unique source of insights into brewing culture of the late nineteenth century when pioneer innovations laid the foundations for industrial brewing. Complementary analytics including metabolomics, microbiological, sensory, and beer attribute analysis revealed its molecular profile and certify the unprecedented good storage condition even after 130 years in the bottle. Comparing its chemical signature to that of four hundred modern brews allowed to describe molecular fingerprints teaching us about technological aspects of historical beer brewing. Several critical production steps such as malting and germ treatment, wort preparation and fermentation, filtration and storage, and compliance with the Bavarian Purity Law left detectable molecular imprints. In addition, the aging process of the drinkable brew could be analyzed on a chemical level and resulted in an unseen diversity of hops- and Maillard-derived compounds. Using this archeochemical forensic approach, the historical production process of a culturally significant beverage could be traced and the ravages of time made visible.

Sensitivity analysis of the expansion process for alloy UNS N08028

Due to the good mechanical properties of forged parts, the forging process plays a decisive role in the manufacturing of seamless stainless steel pipes for oil country tubular goods (OCTG) lines. Tough competition between manufacturers gives them plenty of incentive to make their processes in raw material and energy usage more and more efficient. In this context the expansion process is one of the critical production steps in the manufacturing of seamless stainless steel pipes. This work presents a sensitivity analysis of a finite element method (FEM) for the simulation of the expansion of the alloy UNS N08028. The input parameters ram speed, tool angle, initial ID and final ID of the billet as well as temperature were used to describe responses like tool wear and material loss. With the aim to minimize the tool wear and to reduce the material waste, a study of influence of the input parameters on the mentioned responses were performed. This development is supported by experimental work in order to validate the simulation model. The sector demand for new materials with specific properties and the cost-intensive experimental trials justifies the use of such simulation tools and opens great opportunities for the industry.

Sensitivity analysis of the Expansion Process for Alloy UNS N08028

Due to the good mechanical properties of forged parts, the forging process plays a decisive role in the manufacturing of seamless stainless steel pipes for oil country tubular goods (OCTG) lines. Tough competition between manufacturers gives them plenty of incentive to make their processes in raw material and energy usage more and more efficient. In this context the expansion process is one of the critical production steps in the manufacturing of seamless stainless steel pipes. This work presents a sensitivity analysis of a finite element method (FEM) for the simulation of the expansion of the alloy UNS N08028. The input parameters ram speed, tool angle, initial ID and final ID of the billet as well as temperature were used to describe responses like tool wear and material loss. With the aim to minimize the tool wear and to reduce the material waste, a study of influence of the input parameters on the mentioned responses were performed. This development is supported by experimental work in order to validate the simulation model. The sector demand for new materials with specific properties and the cost-intensive experimental trials justifies the use of such simulation tools and opens great opportunities for the industry.

EF-based strategies for productivity improvements at wet-etch stations

In complex manufacturing environments, Cycle Time (CT) reductions obtained at critical production steps could generate considerable productivity improvements and lead to capacity increases at no investment costs. A wet-etch station operating in a real semiconductor manufacturing plant has been modelled to investigate the impact of different assignment strategies on CT performance. Assignment strategies based on the “Earliest Finish” (EF) concept have been developed and their productivity efficiency compared with a workload balance-based strategy. The EF-based strategies differ from each other for both computational complexity and amount of real-time information required. Encouraging results obtained for a high detail level EF strategy have inspired the development of conceptually similar strategies characterised by reduced implementation efforts. Fundamental implementation constraints, suggested by the manufacturing engineers familiar with the wet-etch station, have been taken into account throughout the different stages of this study. CT reductions ranging between 11% and 28% could be achieved at the modelled wet-etch station.

Flavour quality critical production steps from fruit to extra-virgin olive oil at consumption

The production of olive oil comprises a number of production steps where the quality of the oil may be controlled through an understanding of how the production step influences key compounds such as volatiles and biophenols. In this study, critical production steps and significant inter-relationships between isolated production steps from fruit to oil-at-consumption were identified with the application of multivariate statistics. Having identified the key steps and relationships, sensory attributes associated with volatile and compounds may be enhanced and maintained during production and through to consumption. Our study showed that flavour compounds (e.g. oleuropein and derivates) could be controlled through olive fruit properties whereas transfer of the best sensory attributes from the fruit (e.g. arising from C5 and C6 volatiles) was critically controlled during oil extraction. Once olive oil was produced, maintenance of quality was critically controlled through storage conditions. Consequently, quality attributes from phenolic and volatile compounds could be targeted for maximum transfer from the olive fruit to oil while taking into account the impact on aroma, bitterness, and pungency of fresh oils and the subsequent loss in flavour quality during storage and consumption.

A Uniform Residence Time Flow Cell for the Microreactor-Assisted Solution Deposition of CdS on an FTO-Glass Substrate

Photovoltaic cells have long been a desirable alternative to the consumption of fossil fuels, but current manufacturing practices suffer from poor energy efficiency, large carbon footprints, low material utilization, and high processing temperatures. A critical step in production of thin film CdTe and CuInSe2 solar cells is the chemical bath deposition of a CdS thin film to serve as a “buffer layer” between the optically absorbent layer and the transparent conducting oxide. In prior work, functional CdS films were demonstrated at low temperature using a continuous flow, microreactor-assisted deposition process showing good selectivity of heterogeneous surface reactions over homogeneous bulk precipitation. In this paper, we develop a flow cell for implementing a uniform CdS film over a 152 mm substrate. Analytical models are coupled with computational fluid dynamic simulations to design a flow cell with more uniform flow fields. Experimental results demonstrate a 12% coefficient of variance for a 21.5 nm t...

Experiences from design and production of Wendelstein 7-X magnets

The Max-Planck-Institut für Plasmaphysik in Greifswald is building the stellarator fusion experiment Wendelstein 7-X (W7-X). The manufacturing of the W7-X superconducting magnet system, which consists of 50 non-planar and 20 planar coils, was finished in March 2008. The production was a technical challenge for the W7-X design crew as well for the manufacturer due to the complex 3 D shape of the non-planar coils and the stringent requirements for geometrical tolerances. The manufacturers had to solve several technical problems and to consider major design changes even at advanced stages of manufacture. Finally the coils are passing the acceptance tests at cryogenic temperatures at CEA Saclay with a very good performance. Results of the W7-X coil production will be given and critical production steps will be identified. Lessons will be taken from the experiences gained from design, manufacturing and test methods. The reasons for the considerable time delays will be explained.

Yet Another Method for Marking Incisal Edges of Teeth for Bitemark Analysis

Over the years many methods have been proposed and presented for marking or "highlighting" the incisal edges of anterior teeth on a dental stone model -- one of the critical steps in production of transparent overlays for bitemark analysis. A method is presented here that is an extension and refinement of the "paint the edges" method shown at least as early as 1966 by Gustafson. This method uses "invisible ink" and ultraviolet illumination to produce a very high contrast image of the incisal edges of the teeth on the model. The advantages of this new method are that it is nondestructive, it does not leave visible marks on the models, operator subjectivity in selecting the portions of anterior teeth to be highlighted is reduced, and the author submits that this technique lends itself to easy construction of overlays using computer image-processing software such as Adobe Photoshop and ImageJ.

Pulsed thermography inspection of the target elements for the W7-X divertor

The need for non-destructive inspection of the interface between carbon fibre composites (CFC) and copper is met by different thermographic inspection procedures. The most established one is transient thermography where the component is heated via the cooling system by introducing hot water. This method is applied on finished components containing a cooling system. A promising set-up is pulsed thermography where the component is heated externally by a single powerful flash of light. This method can be applied in any stage of production which enables the recognition of critical production steps. Results obtained from test bodies containing artificial defects demonstrate the defect resolution and the good reproducibility of this method. Since no reference element is needed the efficiency of inspection is raised to a level which is appropriate for industrial application. Finally, the rating of the first test series of W7-X divertor components shows excellent coincidence with the results obtained from high heat flux tests.

Diffusion of methanol–liquid CO 2 and methanol–supercritical CO 2 in silica aerogels

Drying of alcogel is the most critical step in production of transparent and monolithic silica aerogel. If alcohol extraction with liquid or supercritical carbon dioxide is used, diffusion of alcohol through the alcogel to the CO 2 plays an important role. Dependent on the diffusion times, the quality and shape of aerogel samples vary from cracked (short diffusion times) to transparent crack-free aerogels (long diffusion times). At medium diffusion times, the non-transparent area was observed inside the aerogel samples. Diffusion coefficients of methanol in the liquid CO 2 at two different temperatures and the diffusion coefficient of methanol in supercritical CO 2 inside the silica aerogel were determined from the dependence of the width of the non-transparent damage area on diffusion times.

Influence of Timing and Method of Harvest on Rapeseed Yield

A critical step in production of winter rapeseed (Brassica napus L.) in humid environments is seed harvest. This 3-yr study (1986 to 1989) evaluated the effect of harvesting method, harvester type, and seed color stage on seed yield of three rapeseed cultivars (‘Westar’, ‘Cascade’, and ‘Bridger’) near Tifton, GA. No consistent trends were exhibited by swathing or direct combining rapeseed. Seed yield was influenced by weather conditions and crop stage rather than harvesting methods. Both harvesting methods seem potentially acceptable for rapeseed production in the Southeastern USA; however, the added input requirements for swathing may reduce the economic potential for this practice. A draper table-type combine significantly reduced seed yield losses when compared with an auger-type combine. Auger-type combines may need modification to reduce potential seed losses. Mechanical losses reduced total seed yields from 21 to 66%. The best machine-harvested rapeseed yields were obtained in 1988–1989 with a draper table-type harvester, either directly combining at 70 to 90% of dark seed (average yield for all cultivars of 1427 lb/acre) or swathing at 50 to 70% of dark seed (average yield of 1294 lb/acre).