Estimating manufacturing cycle time and throughput in flow shops with process drift and inspection

Process drift is a common occurrence in many manufacturing processes where machines become dirty (leading to more contamination) or processing parameters degrade, negatively affecting system performance. Statistical process control tracks process quality to determine when the process has gone out of control (has drifted beyond its specifications). This paper considers the case where parts examined at a downstream inspection station are used to determine when the upstream process is out of control. The manufacturing cycle time from the out of control process to the downstream inspection process influences the detection time that elapses until the out of control process is noticed and repaired. Because an out of control process produces more bad parts, the detection time affects the number of good parts produced and the throughput of the manufacturing system. This situation is common in many industries but no models of the phenomena exist. This paper presents a novel manufacturing system model based on queueing network approximations for estimating the manufacturing cycle time and throughput of such systems. These are important performance measures since they influence economic measures such as inventory costs and revenue. The model can be used for a variety of system design and analysis tasks. In particular, the model can be used to evaluate the placement of inspection stations in a process flow.     

Quantifying and reducing powder shear sensitivity when manufacturing capsules with lubricants

The purpose of this work was to develop a methodology that quantifies the extent of shear induced during an encapsulation process and show how formulation composition and manufacturing process designs can be changed to reduce the negative impact on drug product quality attributes. The powder feed system used in a dosing disc type pharmaceutical capsule filling machine induced additional shear of the powder prior to slug formation. The shear occurred both in the hopper portion, via the rotation of the feed auger and impeller, and in the powder bowl via the tamping pin agitation and/or shear against the stationary surfaces such as the powder level scraper. The extent of shear was quantified to assess the impact of further dispersing the hydrophobic lubricant, magnesium stearate, in both active and placebo formulations. Stratified samples over the course of the encapsulation run showed suppression in the drug dissolution profiles and decrease in the interparticulate tensile strength of the encapsulated product. The amount of shear (duration and rate) induced during the encapsulation unit operation can be much greater than that from typical bin blending operations and therefore requires consideration during product design and scale-up to ensure product robustness.     

Maintenance scheduling for a manufacturing system of machines with adjustable throughput

This paper considers the problem of analyzing and optimizing joint schedules of maintenance and throughput adjustment operations in manufacturing systems. The purpose of joint scheduling of maintenance and throughput changing operations is to maximize the cost benefits of maintenance operations in manufacturing systems in which some or all of the machines can execute their function under different process settings, resulting in different machine and system throughputs. Such a capability enables one to strategically slow down more degraded machines or accelerate freshly maintained machines so that production targets can be met and maintenance operations can be offset to times when they are less intrusive on the manufacturing process. A Monte-Carlo-simulation-based method is proposed for the evaluation of cost effectiveness of any schedule of maintenance and throughput changing operations, and a genetic-algorithm-based method is proposed to enable searching for schedules that would maximize the cost benefits of these operations. A matrix chromosome representation of the joint schedules of maintenance and throughput adjustment operations is introduced and several mechanisms of chromosome evolution and selection are proposed and analyzed in numerical simulations of such manufacturing systems. Results indicate a good ability for the newly proposed methods to achieve a tradeoff between cost benefits of production and losses due to maintenance operations through strategic allocation of maintenance and throughput changing actions.     

Transformation and thickening of chip during high throughput drilling

One of the major difference in drilling process when related to other conventional metal removal processes like turning and milling is that the drill tool has to work beneath harsh environment as the metal cutting region is situated deep inside the work material. Also, the chip flow is restricted only through the flutes, and hence there occurs transformation of chip shape, chip thickening, and changes in force and torque. In the present investigation, high throughput drilling has been performed under a dry and wet environment in an intermetallic titanium aluminide which is an exceptional class of material with superior properties. It is found that the chip shape transformed from spiral to folded ribbon as the depth of hole increased. Also, a substantial increase in chip thickness, thrust, and torque was observed, and toward the end of drilling, chip clogging occurred. An analytical model was established by applying the mechanics of oblique cutting to find the torque and thrust by measuring the thickness of chip, and this model was validated experimentally.     

Interparticle photo-cross-linkable Pickering emulsions for rapid manufacturing of complex-structured porous ceramic materials

A new series of Pickering emulsions that can be photo-cured by interparticle photo-cross-linking reactions using small amounts of multifunctional acrylate (MA) monomers is proposed to rapidly manufacture complex-structured porous ceramic materials. In our new process, water in oil (w/o) Pickering emulsion was designed by vigorous mixing of water and polyethyleneimine partially complexed with oleic acid (PEI–OA)-stabilized SiO₂/toluene suspension containing small amounts of MA and a photo-radical initiator. Ultraviolet light irradiation to this w/o Pickering emulsion induced the formation of interparticle photo-crosslinks, which resulted in successful photocuring by photo-radical polymerization of MA and the Michael addition reaction between the polymerized MA and PEI–OA on the particles in the oil phase. We further applied the newly designed photo-curable Pickering emulsion and demonstrated that SiO₂ components with pores related to the dispersed aqueous phase and complexed outer structures could be shaped via silicone molding or a hybridized approach of photocuring and green machining. Because of the reduced amounts of MA used, the porous SiO₂ green components could be heat-treated using rapid heating profiles without any structural collapse for dewaxing and partial sintering.     

Analysis on high throughput layout of container yards

The operational efficiency of handling resources plays an important role in promoting container flows at a container terminal. As these handling resources operate on specific yard layouts, a well-designed layout will promote the performance of the handling activities. This study aims to discuss a design process to maximise the throughput capacity, as well as minimise the resource configuration when designing the yard layout. Various experiments were conducted and analysed to demonstrate the effects on the layout structure and the resource configuration for the two types of parallel yard layouts: the double-lane yard layout where vehicles can access the block at both side and the single-lane yard layout where two adjacent blocks in a row are grouped together and vehicles can access each block at only one side. According to the findings, the container flows by vehicles exert greater influence on the design of a container yard compared to the time taken for container processing by quay cranes and yard cranes. It is also found that the single-lane yard layout is preferable when high throughput capacity is required, whereas the double-lane yard layout is superior in favour of high efficiency of vehicle flows.     

Biopharmaceutics classification by high throughput solubility assay and PAMPA

The purpose of the present study was to examine the relevancy of the high throughput solubility assay and permeability assay to the biopharmaceutics classification system (BCS). Solubility and permeability were measured by high throughput solubility assay (HTSA) and parallel artificial membrane permeation assay (PAMPA), respectively. High throughput solubility assay was performed using simulated gastric fluid (SGF, pH 1.2) and simulated intestinal fluid without bile acid (SIF, pH 6.8). We categorize 18 drugs based on the BCS using HTSA and PAMPA. Fourteen out of 18 drugs were correctly classified (78% success rate). The result of the present study showed that HTSA could predict BCS class with a high success rate, and PAMPA could also be useful to predict the permeation of drugs.     

Impact of scheduling free goods on the throughput performance of a manufacturing operation

Theory of Constraints philosophy operates under the assumption that the goal of a for-profit business is to ‘Make money now and in the future’. Consequently, it is a manager's job continuously to search for ways to increase their operation's throughput. Increasing the amount of free goods the operation accepts is one way a manager can do this. Free goods are items that do not use the capacity of the operation's primary constraint. Because of this, it is possible to increase their output. However, increasing the number of free goods processed decreases the amount of protective capacity within the operation. Protective capacity plays a key role in the ability of an operation to deliver orders on time. Increasing the amount of free goods the operation processes is an action that could jeopardize the system's future throughput because it will impact on the operation's ability to ship orders on time. In order for managers to fulfil the goal of making money now and in the future, they must maximize total throughput while minimizing late orders. This paper provides some initial insights about how managers can intelligently manage free goods to balance these competing goals.     

Edge electrospinning for high throughput production of quality nanofibers

A novel, simple geometry for high throughput electrospinning from a bowl edge is presented that utilizes a vessel filled with a polymer solution and a concentric cylindrical collector. Successful fiber formation is presented for two different polymer systems with differing solution viscosity and solvent volatility. The process of jet initiation, resultant fiber morphology and fiber production rate are discussed for this unconfined feed approach. Under high voltage initiation, the jets spontaneously form directly on the fluid surface and rearrange along the circumference of the bowl to provide approximately equal spacing between spinning sites. Nanofibers currently produced from bowl electrospinning are identical in quality to those fabricated by traditional needle electrospinning (TNE) with a demonstrated ～ 40 times increase in the production rate for a single batch of solution due primarily to the presence of many simultaneous jets. In the bowl electrospinning geometry, the electric field pattern and subsequent effective feed rate are very similar to those parameters found under optimized TNE experiments. Consequently, the electrospinning process per jet is directly analogous to that in TNE and thereby results in the same quality of nanofibers.     

On the uniform vorticity in a high Reynolds number flow

A method is proposed for determining the value of the uniform vorticity (₀) in the inviscid region of a high Reynolds number (Re) flow with closed streamlines. An asymptotic treatment of the area integral of the Navier-Stokes equations over the enclosed region leads to a constraint involving the core vorticity; this requires the solution of the momentum equations at O(1) and O(Re ^{–% MathType!MTEF!2!1!+-% feaafeart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaaGymaiaac+% cacaaIYaaaaa!3816!\[1/2\]}) both in the core and in the surrounding boundary layers, although we are subsequently able to show that, under the assumption that the core vorticity at O() is also constant, the value of ₀ depends only on the flow at O(1). The analysis is verified numerically for the case where the boundary is an ellipse, and is also shown to be in agreement with the only case for which an analytic solution is available, namely when the enclosing boundary is circular. The validity of the above-mentioned assumption is also discussed.     

高均匀度直下式LED平板灯设计

目的:设计兼顾照明均匀度和厚度的直下式平板灯光学配光系统。方法:基于矢量折射反射定律和曲面微分几何原理,推导自由曲面的偏微分方程,并基于几何构型法的多自由曲面的数值构建方法,设计用于直下式LED平板灯的双自由曲面透镜。结果:将该透镜用于阵列照明,LED芯片间距为60 mm,数量降低9倍,在距高比为3∶1时实现大面积均匀照明平板灯的薄型化设计,照明均匀度达到93.4%。结论:平板灯的厚度下降为传统灯具的1/3,有效提高了直下式平板灯的性价比。     

高熵合金增材制造研究进展

基于不同的高熵合金(high-entropy alloys,HEAs)体系,综述了增材制造高熵合金的最新研究进展,阐述了不同成分高熵合金增材制造的快速凝固微观组织、偏析和析出行为,着重分析了增材制造高熵合金的力学性能、变形及强化机理.指出不同的高熵合金体系应选择适合的增材制造工艺,并且成型质量的影响因素还有待进一步研究,最后提出利用增材制造技术可以研发和制备出具有优异强度-塑性组合的高熵合金.     

Performance obstacles for direct and indirect labour in high technology manufacturing

Performance obstacles are factors in the work environment that restrict productivity by inhibiting employees in the execution of task responsibilities. In spite of their apparent importance, little research has been done to describe, categorize, or assess these obstacles. A research project carried out in 12 United States electronics firms demonstrates that employees in two groups (circuit board assemblers and manufacturing engineers) view performance obstacles as having a significant influence on their performance. Materials and information obstacles emerged as being the most important to the circuit board assemblers. For the engineers, information and control/authority were the most important obstacle categories. Managers tended to agree with circuit board assemblers about the importance of obstacles for that employee group. However, managers tended to disagree with the engineers, giving lower ratings of importance than the engineers did in several categories. The research provides a step toward a typology of performance obstacles, demonstrating similarities and differences between employee groups and it suggests that at least in some areas managers may not be as accurate as they could be in assessing the influence of performance obstacles on their employees. The findings indicate that the themes that have prevailed in the research on operations management (i.e. materials, quality, scheduling) are viewed by employees as being predominant factors in the productivity equation.     

Block-copolymer-assisted synthesis of hydroxyapatite nanoparticles with high surface area and uniform size

Abstract

We report the synthesis of hydroxyapatite nanoparticles (HANPs) by the coprecipitation method using calcium D-gluconate and potassium hydrogen phosphate as the sources of calcium and phosphate ions, respectively, and the triblock copolymer F127 as a stabilizer. The HANPs were characterized using scanning electron microscopy, x-ray diffraction, and nitrogen adsorption/desorption isotherms. Removal of F127 by solvent extraction or calcination alters the structure of HANPs. The solvent-extracted HANPs were single crystals with their 〈001〉 axis oriented along the rod axis of the HANP, whereas the calcined HANPs contained two crystal phases that resulted in a spherical morphology. The calcined HANPs had much higher surface area (127 m² g^?1) than the solvent-extracted HANPs (44 m² g^?1).     

一种适合潜热输送的高温相变石蜡乳状液的热性能

针对太阳能利用、余热利用、集中供暖等应用背景,采用差示扫描量热法(DSC)遴选了一种相变温度合适(相变峰值87℃)、相变潜热值较大(203.9J/g)的工业石蜡,并以此为相变材料,采用非离子型乳化剂及助乳剂复配的方法研制了3种浓度的石蜡乳状液高温潜热输送材料。测定了石蜡乳状液高温潜热输送材料的相变点、相变潜热等热物性,并研究了其蓄热特性。结果表明,该材料是一种在80～90℃之间存在相变的储、传热工质,在相变区间内的储、载热密度远大于水,是一种良好的潜热输送材料。