Short Throughput Times Research Articles

A study on throughput time of multi-technology platforms

This paper discusses the impact on throughput time of substituting several stand-alone machines by a multi-technology platform. A characteristic threshold in terms of lot size and number of processes to machine the workpiece is derived mathematically. This threshold identifies regions in which either multiple stand-alone machines or a multi-technology platform will lead to shorter throughput times. The model shows that a reduction of interoperation and reconfiguration time is in particular desirable for small lots and simple parts, whereas a reduction of processing time is important for large lots and complex workpieces. Furthermore, the threshold is compared to part cost and productivity thresholds. It is concluded that a reduction of throughput time is easier to achieve than an increase of productivity through multi-technology platforms.

Aflatoxin determination using in-line immunoaffinity chromatography in foods

Short throughput times with high precision and sensitivity are of interest of any laboratory. An in-line immunoaffinity chromatographic cleanup procedure coupled to High Performance Liquid Chromatography (HPLC) and fluorescence detection was developed for the purpose of quantification of the aflatoxin content in food (peanuts, dried figs, and paprika powder). The analysis of the aflatoxin content was performed by HPLC equipped with an in-line immunoaffinity column and a Kobra cell for enhanced detection. Detection limits ranging from 0.14 to 0.32 ng/mL and quantification limits from 0.29 to 0.64 ng/mL were obtained. The trueness was evaluated by analyzing certified reference material and through spiking of aflatoxin reference solutions to food products. The recovery ranged from 75.7 to 92.9% for AFB1, 72.1 to 103.0 % for AFB2, 76.0 to 107.9 % for AFG1 and 82.1 to 103.3% for AFG2. The intra-day (RSDr) repeatability and inter-day (RSDR) reproducibility of measurements were calculated. Both were within the maximum values obtained from the Horwitz equation. The interference experiment showed no interference from other mycotoxins.

A multiple-logistic-objective-optimized manufacturing planning and control system

A multiple-logistic-objective-optimized (MLOO) manufacturing planning and control approach is developed in an attempt to optimize the logistics objectives of a short throughput time, a low work in process, and high schedule reliability. The proposed approach also needs to effectively cope with disturbances including internal disturbances (equipment failure, rework, etc.) and external disturbances (variations in demand patterns, unsatisfied raw material delivery, etc.). This paper focuses on make-to-order manufacturing systems with routing flexibility. Simulation experiments are conducted using industrial data in order to compare the MLOO approach with several existing methods. The simulation results indicate that MLOO is able to optimize the target logistics objectives and effectively cope with disturbances.

Perceived efficiency in the emergency department—Short throughput times or rather having a lot to DO?

Perceived efficiency in the emergency department—Short throughput times or rather having a lot to DO?

Order release in synchronous manufacturing

Synchronous manufacturing aims at achieving the benefits of intermittent production lines in production situations that operate without lines. Benefits such as short and constant throughput times and predictable capacity loading can be acquired through an appropriate design of the synchronous manufacturing system and its control system. The order release mechanism is an essential part of this control system. It determines the sequence in which orders are released to the shop floor. As orders may differ in the amount and distribution of their capacity requirements over subsequent production stages, total capacity load may vary overtime. If the available capacity per period is not flexible, capacity balancing becomes an issue in the order release decision. Human employees that work in such a system should be safeguarded from frequent unbalances in their working pattern. They are empowered and trained to contribute to several stages of production, but their motivation decreases rapidly if their working schedules do not give attention to stability issues. In practice, employees in the cells use heuristics to solve this problem, but the effectiveness of these heuristics is questioned. This article designs heuristics based on insights from assembly system design and workload control. These heuristics can be used by the employees within the synchronous manufacturing system. As an alternative, we design a solution approach that provides the employees with an optimal release sequence. The differences in the design approaches are discussed.

Design of POLCA material control systems

POLCA is a material control system designed for make-to-order or engineer-to-order companies. These firms have to cope with a high variety of customised products, and strong pressure to provide short throughput times. POLCA constrains the amount of work in progress on the shop floor in order to achieve a short average shop floor throughput time. Earlier work has shown that the POLCA system has the capability to reduce both the average shop floor throughput time and the average total throughput time, but it is only effective if the POLCA system has been appropriately designed. The design of the POLCA system is therefore being investigated and discussed in this paper. We give an extensive literature review and give attention to the authorisation mechanisms of POLCA, the design of control loops, the route-specific capacity signals (POLCA cards), and specific facilities needed to use the POLCA system in practice. Finally, we report on the design of a POLCA system in practice, the first complete implementation of POLCA in The Netherlands, and present the quick scan that was used in the design of the POLCA system for this SME.

Fast electromigration wafer mapping for wafer fab process monitoring and improvement

In this work, a set up for fast wafer level electromigration (WL-EM) is developed with the use of a standard electrical analyser, a semi-auto probe station with a hot chuck, and a PC. EM tests on multiple test structures are carried out simultaneously and tests are done at multiple locations (EM mapping) across the wafer. Measured data are imported into MS EXCEL and analysed with a macro automatically. Good correlations are demonstrated between the fast WL-EM test and classical package level EM at 0.1% failure rate. For several years reliable EM monitoring charts are created with the fast WL-EM set up. The fast EM mapping test does not only exploit the advantages of fast WL-EM test in terms of short throughput time and low cost (without packaging) for process monitoring, the additional information on EM performance across the wafer makes the test extremely valuable for process improvement.

Semi-interchangeable machines: implications for workload control

Workload control (WLC) is developed as a production planning and control concept for make-to-order job shops. Effective WLC requires a profound decision regarding order release to allow balancing the workload across capacity groups. WLC design has to reflect the company characteristics, especially machine characteristics. In practice, machines that perform the same type of operations are generally not completely identical but semi-interchangeable. The importance of the load balancing function requires careful consideration of semi-interchangeability within WLC. This paper develops different control alternatives to deal with semi-interchangeability and tests them in a simulation study. The results of the study indicate that the most intuitive control option—grouping semi-interchangeable machines into a single capacity group and making the routeing decision at dispatching—does not give the best performance, despite the advantages of pooling synergy. For a low degree of interchangeability it is more attractive to place semi-interchangeable machines in separate capacity groups and to make a routeing decision at order release. This enables more detailed load balancing resulting in shorter throughput times. More generally, it is shown to be advantageous to postpone the final routeing decision until dispatching, though considering separate capacity groups for a preliminary routeing decision at the time of release.

Autonomous control of production networks using a pheromone approach

The flow of parts through a production network is usually pre-planned by a central control system. Such central control fails in presence of highly fluctuating demand and/or unforeseen disturbances. To manage such dynamic networks according to low work-in-progress and short throughput times, an autonomous control approach is proposed. Autonomous control means a decentralized routing of the autonomous parts themselves. The parts’ decisions base on backward propagated information about the throughput times of finished parts for different routes. So, routes with shorter throughput times attract parts to use this route again. This process can be compared to ants leaving pheromones on their way to communicate with following ants. The paper focuses on a mathematical description of such autonomously controlled production networks. A fluid model with limited service rates in a general network topology is derived and compared to a discrete-event simulation model. Whereas the discrete-event simulation of production networks is straightforward, the formulation of the addressed scenario in terms of a fluid model is challenging. Here it is shown, how several problems in a fluid model formulation (e.g. discontinuities) can be handled mathematically. Finally, some simulation results for the pheromone-based control with both the discrete-event simulation model and the fluid model are presented for a time-dependent influx.

CAD/CAM Software for Extremely Low Repetitive Machining Center Work of Block Like Components Using Automatic Setup Free Block Machining Technology

Setup-Free Block-Machining Technology has been studied in the interest of manufacturing extremely low repetitive and high variability products, in shorter throughput time and for reduced cost than using conventional machining methods. By specially designed setup-free attachment mounted on the table of a horizontal machining center, block like components, falling into a small size range, can be automatically machined from all of the six orientations in only one process without using other fixtures. To establish procedures and technologies for automatic operation of the single process block machining equipment, the Personal Computer (PC) Based CAD/CAM software, of which CAM phase generates NC program automatically, is structured. Machining Feature-based CAD concept, that is a subset of the parametric feature-based design principle but limiting the user's choice to features machinable by machining centers, is the principal methodology that makes the CAD output possible to be automatically processed in the CAM phase for generating the NC program.

An investigation into the rapid prototyping of moulds for expanded polystyrene foam

Expanded polystyrene foam, a packaging material, is traditionally injection-moulded by classical moulding techniques. However, the design and fabrication of these moulds is both intricate and time-consuming. In today's manufacturing environment of short time-to-market, the luxury of producing a mould for, often, a first-off article for client approval, is virtually untenable. Rapid prototyping technologies appear to offer an alternative method of fabrication which promises to drastically reduce the time for mould fabrication. When rapid prototyping of the mould is combined with microwave curing of the polystyrene, as an alternative source of energy to traditional steam heating, the benefit of considerably short throughput times can be expected. This paper describes the computer-integrated design and fabrication of both the mould and foam product, and discusses the main issues associated with rapid prototyping the mould, viz. accuracy of the prototype mould and the suitability of acrylic resin used in stereolithography apparatus for fabricating the mould, as well as the parameters for moulding expanded polystyrene using microwave energy. Initial results suggest that both the stereolithography process, and the acrylic resin used to build the stereolithographic model, can be used for rapid prototyping expanded foam products and their associated mould.

A simulation comparison of process and cellular layouts in a dual resource constrained environment

Cellular manufacturing is an integral part of a comprehensive Group Technology program designed to improved the productivity of batch production systems. It has been suggested that shorter throughput times and accompanying reductions in work-in-process inventory are possible due to the inherent flexibility of cellular layouts with respect to worker scheduling. This research examines the impact of a dual resource (labor and equipment) constrained shop on the relative performance of cell layouts vis-a-vis process layouts. In addition, three operator scheduling rules are tested in the cellular layout. The first rule assigns operators on a first come-first served basis to jobs competing for an operator's services. The second rule requires operators in a cell to select a job from the machine queue with the longest queue of jobs. The third rule has operators remaining at a machine queue until it is empty. In the process layout, operators are assinged to waiting jobs on a first come-first served basis. In the initial experiment, the process layout outperformed the cellular layout on both work-in-process levels and throughout time. Additional experiments investigated the sensitivity of the initial results to changes in shop congestion. The process layout outperformed the cellular layout in all of the experiments. The results may be attributed to lower machine and labor utilization in the cellular layout from the dedication of equipment to limited part families.

The identification of geophagia by neutron activation analysis

Chemical markers for use as indicators of geophagia in Jamaica is reported. Five volunteers each ingested 10 g of each of three common soils of Jamaica to which carmine (an inert gastrointestinal dye) had been added. A pre-ingestion faecal sample and all post-ingestion faecal samples were collected until no more carmine was seen. The faecal and soil samples were analysed by instrumental neutron activation analysis. Of the 14 elements quantified, Dy, Eu, Ce, Hf, and Th were consistently detected in the post-ingestion but not in the pre-ingestion faecals. These elements should therefore be excellent markers of geophagia as they are present in insignificant levels in food compared to soils. Because of high sensitivity and short throughput times, Dy and Eu appear to be the most promising elements for the detection of the occurrence of geophagia.

A manufacturing planning and control system for a flexible manufacturing system

A flexible manufacturing system (FMS) can offer important advantages in terms of more efficient production, shorter throughput times, lower stocks and a higher quality of work. To realize these advantages, a well designed manufacturing planning and control system (MPCS) is a key condition. In practical cases, these planning and control systems are often based on a hierarchical structure. This paper discusses the most relevant characteristics of such a hierarchical MPCS and, by using a practical case, describes possible solutions to a variety of subproblems.

Gut architecture, digestive constraints and feeding ecology of deposit-feeding and carnivorous polychaetes.

We analyze gut architectures of 42 species of marine polychaetes in terms of their anatomically distinct compartments, and quantify differences among guts in terms of ratios of body volume to gut volume, relative compartmental volumes, total gut aspect ratios and compartmental aspect ratios. We use multivariate techniques to classify these polychaetes into 4 groups: carnivores with tubular guts; deposit feeders with tubular guts; deposit feeders with 3 gut compartments; and deposit feeders with 4 or 5 gut compartments. Tubular guts, morphological expressions of plug flow, are common among deposit feeders and may allow relatively rapid ingestion rates and short throughput times. Median gut volume per unit of body volume in deposit feeders (31%) is twice that of carnivores (15%) and ranges up to 83% in one deep-sea species. Deep-sea deposit feeders tend to have relatively larger and longer guts than closely-related nearshore and shelf species. Guts of a number of deep-sea deposit feeders and nearshore and shelf deposit feeders from muddy environments are relatively longer and narrower as body size increases, suggesting that digestive diffusion limitations may be important. Gut volume scales as (body volume)1 while ingestion rate scales as (body volume)0.7. If diet and the chemical kinetics of digestion do not change appreciably, throughput time and thus the extent of digestion of given dietary components therefore must increase as a deposit feeder grows. Digestive processing constrainst may be most important in juveniles of species (especially those species with plug-flow guts) that are deposit feeders as adults.

Technical difficulties associated with the formation of C-11 labeled carboxylic-acids

data. If the quality of the laboratory is poor then the decision may be made to ignore the laboratory result and proceed to care for the clinical condition of the patient. Alternately, the physician may decide to reorder the test a second time to see if a statistically different result is obtained. Most interferences in analytical methodologies can be eliminated by a chromatographic sample preparation step prior to analysis. However, chromatographic separations are not usually automated, are poorly mechanized, and add time and expense to the analysis. In a high volume service clinical chemistry laboratory, the extra step required by a chromatographic separation is very undesirable. Therefore, today many inaccuracies remain with the routine methods used rather than adapt a cure for the accuracy problem by adding a manual chromatographic sample preparation step. In conclusion, the development of highly accurate instrumental methods of chemical analysis for the clinical laboratory remains a very difficult task. When one includes the nonanalytical priorities in method development, then decreasing emphasis on accuracy is often accepted by members of this field. Decentralization of the service laboratory causes some additional reassessment of the criteria for test methods. A list of desired characteristics for test methodology can be created. That list of performance criteria in decreasing order of importance is: 24-hour availability of results, minimum sample pretreatment, wide selection of different types of tests, low operator skill, high precision, low total cost per analysis, short throughput time, and high accuracy. Analytical chemistry has much to contribute to the field of clinical chemistry analysis but ways must be found to produce highly accurate test results while lowering the cost and decreasing the difficulty of the analysis. We as analytical chemists have addressed the cost issue but have not contributed much to the improvement of accuracy while simplifying the technical difficulty of the clinical laboratory tests. This last task then remains as a challenge for the near future.