Process Cycle Time Research Articles

An Adaptive Geometry Transformation and Repair Method for Hybrid Manufacturing

Hybrid manufacturing has become particularly attractive for refurbishing of high-value freeform components. Components may experience unique geometric distortions and/or wear-driven material loss in service, which require the use of part-specific, adaptive repair strategies. The current work presents an integrated adaptive geometry transformation method for additive/subtractive hybrid manufacturing based on rigid and nonrigid registrations of parent region material and geometric interpolation of the repair region material. In this approach, rigid registration of nominal part geometry to actual part geometry is accomplished using iterative alignment of profiles in the parent material. Nonrigid registration is used to morph nominal part geometry to actual part geometry by transformation of the profile mean line. Adaptive additive and subtractive tool paths are then used to add material based on constant stock margin requirements, as well as to produce blend repairs with smooth transition between parent and repair regions. A range of part deformation conditions due to profile twist and length changes are evaluated for the case of a compressor blade/airfoil geometry. Accuracy of the resulting adaptive geometry transformation method were quantified by (1) surface comparisons of actual and transformed nominal geometry and (2) blend region surface accuracy. Performance of the adaptive repair strategy relative to a naïve strategy is evaluated by the consideration of material efficiency and process cycle time. It is shown that the adaptive repair strategy resulted in an increase in material efficiency by 42.2% and a decrease in process time by 17.8%, depending on the initial deformation imposed on the part geometry.

Simulation of non-isothermal resin transfer molding process cycle and optimization of temperature system

The filling and curing stage of resin transfer molding is non-isothermal. The temperature plays an important role in both filling and curing stage and these two stages are strongly interrelated. The unreasonable temperature system will lead to excessive temperature difference and seriously affect the quality of the product. Therefore, it is necessary to analyze the non-isothermal filling and curing stage to find the best temperature system. In this paper, the FLUENT software has been secondarily developed to perform a full three-dimensional simulation of the non-isothermal resin transfer molding process cycle. The results have been compared with the known data to verify the accuracy of the simulation. The influence of temperature on the process cycle has been analyzed and the optimization of temperature system can reduce process cycle time and increase the uniformity of temperature distribution.

Measuring performance

Most organizations today have a set of key performance indicators (KPIs) that are used for decision-making. Because a balanced scorecard approach has been widely adopted, typically KPIs have moved beyond the basic financial metrics. However, developing the right set of KPIs is an important step in promoting continuous improvement and overall business success. Organization that implement six sigma or lean six sigma have a built-in set of KPIs, such as defects, ppm defective, process yields, process cycle times, and a variety of inventory statistics, such as WIP inventory. But I don't think this goes far enough in most situations. KPIs should be traceable to customer satisfaction, both for external customers and internal ones. Organizations should formalize customer requirements and then evaluate how they are doing with respect to this list when they conduct strategic planning sessions. This is a good way to develop the right KPIs. However, overemphasis on short-term financial results can skew this process. Too much focus on quarterly growth in sales or revenue and deflect attention from the issues that contribute to long-term business growth and success. Organizations often gravitate towards collecting data that is easy to obtain, but may not be necessarily useful. An example is information about customer satisfaction data. Surveys can be useful, but may not tell the complete story. One organization that I am familiar with has a customer service line. They reported very few serious complaints from that source. Analysis revealed that the average waiting time for customers that used this line was in excess of 30 minutes. Furthermore, the ability of the system to place calls on hold was limited, so a significant number of calls were “blocked”; that is, they were not answered at all. So the volume of customer issues that this service was designed to serve was dramatically underestimated. Some KPIs are lagging indicators of business performance. Examples include sales volumes and maintenance expenses. These are usually easy to generate, but may not provide much indication of future success. Reliable forecasts of future demand (demand isn't necessarily the same as sales) is usually a better business indicator. Leading indicators are harder to devise, almost always depend on the specific nature of the individual organization, and may be difficult to generate. For example, cycle time for new product introduction is often a critical measure of future business success in many industries. If this KPI is unsatisfactory or is getting longer for unexplained reasons it may indicate an area for lean six sigma intervention. Performance measurement is an important management tool for evaluating and improving organizational success. Leading KPIs can be an effective “canary in the coal mine” warning of impending trouble. The investment required to develop and maintain the correct set of KPIs will pay many dividends.

Improving the Filterability of Particles by Healing the Seed Particles

A shift in particle size distribution toward smaller particle sizes has been observed in batches of Compound A Triethanolate, an isolated intermediate of a commercially available active pharmaceutical ingredient, leading to poor deliquoring of the filter cake and longer filtration times, which compromised the overall process cycle time. In the most extreme case, product breakthrough during filtration was observed, leading to significant yield loss. Compound A Triethanolate is crystallized through antisolvent addition/distillation/cooling crystallization in ethyl acetate/water/ethanol. Laboratory experiments were carried out using representative product streams in order to identify the cause for the shift in particle size distribution, which could be attributed to excessive secondary nucleation at an early stage of the process caused by the use of seed particles that have been previously dried under agitation. While statically dried particles exhibit a smooth surface, the surface of particles dried under a...

Establishment of maintenance inspection intervals: an application of process mining techniques in manufacturing

Reducing costs and increasing equipment availability (uptime) are among the main goals of industrial ventures. Well defined interval durations between maintenance inspections provide major support in achieving these targets. However, in order to establish the best interval length, process behavior, cycle times and related costs must be clearly known, and future estimates for these parameters must be established. This paper applies process mining techniques in developing a probabilistic model in Bayesian Networks integrated to predictive models. The probability of a given activity occurring in the probabilistic model output establishes the forecast boundaries for predictive models, responsible for estimating process cycle times. Availability (uptime) and cost functions are mathematically defined and an iterative process is performed in the length of intervals between maintenance inspections until the time and costs wasted are minimized and the best interval duration is found. The probabilistic model enables simulating changes in the event occurrence probability, allowing a number of different scenarios to be visualized and providing better support to managers in scheduling maintenance activities. The results show that production losses can be further reduced through optimally defined intervals between maintenance inspections.

Understanding Bottlenecks: An Operations Management Experiential Learning Exercise

ABSTRACTUnderstanding bottlenecks is an in‐class experiential learning exercise designed to improve students’ understanding of production system capacity issues. After an introductory teaching session on capacity and constraint management, students are formed into groups of six to assume the roles of one raw material handler, four production workers, and one finished goods receiver and are asked to produce 20 units of product beta. Prior to the start of the exercise, the students are asked to predict the completion time of the 1st, 10th, and 20th units of product beta. When all 20 betas are completed, students compare their predicted completion times to the actual completion times. The results of the game show that while students can easily identify the system's bottleneck, they often have difficulties distinguishing the practical implications of the process time of the system versus the process cycle time; thus, their predicted completion times of the 10th and 20th units are typically overinflated compared to actual completion times. A debrief session is then used to solidify students’ understanding of the relationship between bottlenecks and capacity. The exercise is well‐received and highly rated by students; furthermore, it is not resource‐intensive, requiring 40‐45 minutes of classroom time, 20‐25 strips of paper per group, and a visible stopwatch.

Work-in-Progress Inventory Control Case Study in Lean Management

Increasing the rate of converting raw material into finished product and delivering it on time is a main driver for each manufacturing industry to achieve continuous improvement in its business operation. This case study demonstrates the improvement of the work-in-progress inventory in a non-lean company seeking to adopt lean management. Introducing the value stream mapping (VSM) lean technique to identify the waste in the current production operation. A selection of lean tools such as Kanban card, supermarket racking and one-piece flow are applied to control and monitor the WIP inventory after justification of the factors (process cycle time, production facilities layout and facilities capacity allocation) that influence the change from the current production operation situation.The construction of the current VSM had identified the major waste in WIP inventory handling in the final fabrication process. The fluctuation of WIP inventory has been resolved by the implementation of supermarket racking; therefore, an improvement base for WIP inventory control has been established. Throughout this study, the lean management concept had been fostered into the production floor team and will continue developing to the organization.

Online buffer management for transmitting packets with processing cycles

We study an online buffer management problem under the model introduced by Azar and Gilon (2015) [5] recently. Unit-sized packets arrive and are kept in a First-In-First-Out buffer of size B in an online fashion at a network server. Each packet is associated with an arrival time, a value and a processing cycle time in the buffer. The density of a packet is defined to be the ratio of its value to processing time. It is assumed that every packet can be transmitted only after its processing cycle is completed and only the packet at the head of the buffer can be processed. A packet is allowed to be preempted and then discarded from the buffer. But, the value of a packet is attained only if it is successfully transmitted. Under the model, the objective of online buffer management is to maximize the total value of transmitted packets. This model finds applications to packet scheduling in communication networks.In this study, we consider the model with constant density from a theoretical perspective. We first propose some lower bounds for the problem. Azar and Gilon obtained a 4-competitive algorithm for the online buffer management problem for packets with constant density. Here, we present a (2+1B−1)-competitive algorithm for the case B>1 as well as its generalization to the multi-buffer model. Moreover, we prove that the competitive ratio of a deterministic online algorithm is at least four when the buffer size is one. We also conduct experiments to demonstrate the superior performance of the proposed online algorithm against the previous approach.

Ultra-high-speed processing of nanomaterial-reinforced woven carbon fiber/polyamide 6 composites using reactive thermoplastic resin transfer molding

High-speed molding of continuous carbon fiber-reinforced composites was carried out by thermoplastic resin transfer molding using a very-low-viscosity thermoplastic monomer. After dispersing 0.1 wt.% of various nanomaterials in ε-caprolactam, a monomer of anionic polymerized polyamide 6 (A-PA6), the processing temperature and catalyst-activator contents were optimized based on the polymerization induction time required for resin injection in the mold. Additionally, the dispersion stability, solidification time, monomer conversion, crystallinity and mechanical properties of the composites were evaluated. Higher dispersion stability of the nanomaterials in A-PA6 resulted in a significantly shortened process cycle time – on the order of seconds –and higher crystallinity in the composite. In addition, carbon fibers treated with atmospheric plasma were used to increase the rate of resin impregnation into fibers. These factors not only increased composite fabrication productivity but also enhanced its mechanical properties.

Characterization of the tool influence function in a dual-axis wheel polishing process to achieve high material removal rates

Various computer controlled optical surfacing (CCOS) processes have been proposed and developed in previous researches for producing ultra-precision optical surfaces, based on the fundamental CCOS principles, i.e., predictable material removal and dwell-time based process control. The main limitation for using the CCOS processes in real industrial applications, however, is the low material removal rates related with most of the CCOS processes, due to the ‘gentle’ tool-workpiece contact feature, resulting in very slow material removal and long process cycle time. This paper presents a novel dual-axis wheel polishing (DAWP) technology using a semi-rigid polishing wheel, designed to achieve high material removal rates and high convergence rates of surface roughness. Modeling for the tool influence function (TIF) was carried out based on the finite element analysis (FEA) and the results of the material property tests, for predicting and characterizing the material removal behavior of the DAWP. Fixed spot polishing experiments on BK7 glass and fused silica were carried out using the DAWP tool, to verify the validity of TIF models and to acquire the variation of TIF and material removal rate under different processing parameters. The experimental results show that the measured and theoretical TIFs match rather well, and the DAWP tool can realize much higher material removal rates on both materials. A BK7 ground flat surface was polished to validate the actual polishing performance of the DAWP tool. After one pass polishing, excellent surface quality was obtained. The preliminary study in this paper shows that, the DAWP tool has a good potential to be used for making large size optical components, significantly increasing the polishing efficiency and reducing the process cycle time.

Equations to estimate processing and forwarding costs, while considering log size: clear-cutting operations in Nasunogahara, Tochigi prefecture, Japan

ABSTRACTThis study develops equations by which one can estimate processing and forwarding costs for clear-cutting operations, while considering log size and assuming moderately and gently sloping sites. Processing cycle times were estimated by using the average delimbing and bucking times related to average log volume and piling time related to the number of logs extracted from the stem. Forwarding cycle times were estimated by using the forwarding distance, the out-hauling and in-hauling travel velocities, and the loading and unloading time related to the number of loaded logs. The forwarding volume was estimated by using the relationship between the average log volume and the number of logs loaded on the forwarder. Differences in processing costs between 0.02 and 0.20 m3/log worked out to around USD 10.00/m3, whereas differences in forwarding costs between 0.02 and 0.20 m3/log worked out to around USD 4.00 and USD 7.00/m3 for thinning and clear-cutting operations, respectively. Finally, operational system costs were estimated: differences in operational system costs with the extraction of small-sized logs (and while not considering log size) between maximizing revenues and profits were USD 9.08, USD 9.05, and USD 9.36/m3 at Site A, Site B, and thinning operations, respectively. However, those costs ranged from USD 36.65 to USD 87.65/m3 for Site A, from USD 28.75 to USD 70.21/m3 for Site B, and from USD 27.71 to USD 70.81/m3 for thinning operations. Thus, costs should be estimated while duly considering log size.

Multivariate process capability analysis applied to AISI 52100 hardened steel turning

Hard turning operations have been extensively investigated owing to their ability to reduce process cycle time, increase process flexibility, ensure high-dimensional accuracy, and enable machining without a cutting fluid. These processes are rather common for dealing with multiple quality characteristics. To evaluate the process ability and meet customer needs, multivariate statistical techniques are recommended for estimating the capability indices. Principal component analysis can be applied to reducing the problem dimension and estimate process capability indices. The aim of this study was to assess the capability of AISI 52100 hardened steel turning operations and achieve process specifications. Multivariate process capability indices were calculated to assess five roughness parameters of surface finishing. By using a weighted approach of principal component analysis, a new method is proposed for estimating the process capability indices. The results highlight not only the relevance of conducting a multivariate capability analysis in the case of actual machining but also how successfully the proposed method was performed.

Reverse Engineering on Process Cycle Time in a Medium Scale Industry – Data Anthology

Reverse Engineering on Process Cycle Time in a Medium Scale Industry – Data Anthology

Manufacturing Enhancement through Reduction of Cycle Time using Different Lean Techniques

In recent manufacturing system the most important parameters in production line are work in process, TAKT time and line balancing. In this article lean tools and techniques were implemented to reduce the cycle time. The aim is to enhance the productivity of the water pump pipe by identifying the bottleneck stations and non value added activities. From the initial time study the bottleneck processes were identified and then necessary expanding processes were also identified for the bottleneck process. Subsequently the improvement actions have been established and implemented using different lean tools like value stream mapping, 5S and line balancing. The current state value stream mapping was developed to describe the existing status and to identify various problem areas. 5S was used to implement the steps to reduce the process cycle time and unnecessary movements of man and material. The improvement activities were implemented with required suggested and the future state value stream mapping was developed. From the results it was concluded that the total cycle time was reduced about 290.41 seconds and the customer demand has been increased about 760 units.

Optimizing MRI Logistics: Prospective Analysis of Performance, Efficiency, and Patient Throughput.

The objective of this study is to optimize MRI logistics through evaluation of MRI workflow and analysis of performance, efficiency, and patient throughput in a tertiary care academic center. For 2 weeks, workflow data from two outpatient MRI scanners were prospectively collected and stratified by value added to the process (i.e., value-added time, business value-added time, or non-value-added time). Two separate time cycles were measured: the actual MRI process cycle as well as the complete length of patient stay in the department. In addition, the impact and frequency of delays across all observations were measured. A total of 305 MRI examinations were evaluated, including body (34.1%), neurologic (28.9%), musculoskeletal (21.0%), and breast examinations (16.1%). The MRI process cycle lasted a mean of 50.97 ± 24.4 (SD) minutes per examination; the mean non-value-added time was 13.21 ± 18.77 minutes (25.87% of the total process cycle time). The mean length-of-stay cycle was 83.51 ± 33.63 minutes; the mean non-value-added time was 24.33 ± 24.84 minutes (29.14% of the total patient stay). The delay with the highest frequency (5.57%) was IV or port placement, which had a mean delay of 22.82 minutes. The delay with the greatest impact on time was MRI arthrography for which joint injection of contrast medium was necessary but was not accounted for in the schedule (mean delay, 42.2 minutes; frequency, 1.64%). Of 305 patients, 34 (11.15%) did not arrive at or before their scheduled time. Non-value-added time represents approximately one-third of the total MRI process cycle and patient length of stay. Identifying specific delays may expedite the application of targeted improvement strategies, potentially increasing revenue, efficiency, and overall patient satisfaction.

Computational Screening of Nanoporous Materials for Hexane and Heptane Isomer Separation

Computational high-throughput screening was carried out to assess a large number of experimentally reported metal–organic frameworks (MOFs) and zeolites for their utility in hexane isomer separation. Through the work, we identified many MOFs and zeolites with high selectivity (SL+M > 10) for the group of n-hexane, 2-methylpentane, and 3-methylpentane (linear and monobranched isomers) versus 2,2-dimethylbutane and 2,3-dimethylbutane (dibranched isomers). This group of selective sorbents includes VICDOC (Fe2(BDP)3), a MOF with triangular pores that is known to exhibit high isomer selectivity and capacity. For three of these structures, the adsorption isotherms for a 10-component mixture of hexane and heptane isomers were calculated. Subsequent simulations of column breakthrough curves showed that the DEYVUA MOF exhibits a longer process cycle time than VICDOC MOF or MRE zeolite, which are previously reported, high-performing materials, illustrating the importance of capacity in designing MOFs for practical ...

Design for manufacture: Cost-estimating model for randomly oriented strand advanced composite aerospace parts

This work aimed at developing a parametric cost-estimating model based on physical laws for making three categories of thermoplastic composites structural aerospace parts from discontinuous prepreg randomly oriented strands. The proposed cost model will use Microsoft Excel spreadsheet developed in house which imputes all industrial and academic data for calculating costs elements such as material, labour, energy, machinery, building costs and costs of working capital, overheads and then the total cost per part. This research study focused, on one hand, at estimating the heating costs for experimental and virtual parts by changing the volume and keeping the same process cycle times. The heating power was determined by simulating the process thermal diagram numerically using finite elements COMSOL software and validated by experimental data. On the other hand, the tooling costs were estimated by DFMA software for experimental and virtual moulds by changing the projected area. Then, the heating energy and tooling costs sizing scaling laws were established under linear equation forms limited to the size of platens areas. These linear equations were inputted in an Excel spreadsheet to calculate the cost of new parts, which have not been made yet. The variation of the total cost with the size and the complexity of the part were investigated. The results showed that the calculated heating energy costs of the three experimental randomly oriented strand parts were different due to different geometries of the heating platens and the moulds. For the mould cost, the more complex the form was the higher the cost. For total cost, it was also demonstrated that the manufacturing cost of L-bracket part was higher than that of flat plate and T-shape part due to higher process cycle time.

Study to Reduce Process Cycle Time and to Improve Surface Roughness of a Mobile Phone Unibody Case through Cutting Force Optimization

Study to Reduce Process Cycle Time and to Improve Surface Roughness of a Mobile Phone Unibody Case through Cutting Force Optimization

Diseconomies of Time Compression

This paper discusses the concept of time compression diseconomies and its importance to the sustainability of competitive advantage. It focuses on a key driver of time compression costs, the time-dependency of resource accumulation, and illustrates the effects of three characteristics of this accumulation process (productivity, cycle time and absorption constraints). The effects are illustrated using a stylized stocks-flows simulation with the iThink software.

An investigation on the effect of sintering mode on various properties of copper-graphene metal matrix composite

The present work investigates the effect of sintering mode and graphene addition on the microstructural, mechanical and electrical properties of copper–graphene metal matrix composites reinforced with varying amounts (0.9, 1.8, 2.7 and 3.6 vol%) of graphene particles fabricated through powder metallurgy route. Sintering was carried out at 900°C in 95%N2-5%H2 (forming gas) atmosphere with a heating rate of 5°/min for conventional and 20°C/min for microwave with a holding time of 60min in both cases. All the composites were found to couple well with microwave field and had resulted in 63% reduction in the processing cycle time as compared to the conventional process. Micro-structural analysis revealed the homogeneous distribution of graphene in copper matrix. Copper-graphene composites exhibited excellent wear resistance due to higher hardness and excellent lubricating nature of graphene. It was observed that porosity has a significant effect on the electrical conductivity values.