Economic batch quantity

For made-in items, the equivalent is economic batch quantity (EBQ). However, lack of communication with other parts of the chain, and negligible effort to understand changing conditions, constitute fundamental weaknesses. 

Forecast at generic level Economic batch quantities Maximise efficiencies... 

By progressively reducing the Kanban quantity (i.e. the amount demanded from the supplying work station) bottlenecks will become apparent. Management will then focus attention on the bottleneck to remove it by the most cost-effective means possible. Again the Kanban quantity will be reduced until a further bottleneck is revealed. Hence the Kanban philosophy essentially seeks to achieve a balanced supply chain with minimal inventory at every stage and where the process and transit quantities of materials and stock are reduced to the lowest possible amount. The ultimate aim, say the Japanese, should be the economic batch quantity of 1 ... 

The operations research field has given us the means of calculating an optimal batch size. It relies on minimizing the total cost of procuring and carrying a product in inventory. An efficient order (batch) size, or economic order quantity (EOQ), is computed as follows ... 

At present 60% of traded chemicals have production volumes ofless than 101 p.a. This shows a dear need for an effective way to produce these small quantities. Up to now, small quantities in chemical synthesis can only beproduced inbatch onamuM-purpose basis. The first question to answer is which production mode is the more economic batch or continuous This question is new, since there was hardly any adequate equipment to carry out small applications in a continuous mode. Microchemical engineering offers several new possibilities to improve this situation. There are some strong arguments to produce these small quantities in a continuous mode ... 

The batch model, illustrated in Figure 26.5, holds that products and services are delivered in "economic" batch sizes. The picture illustrates the pattern of production and movement along the supply chain. There s an "efficient" batch size for every operation. For products, this includes production steps as well as reordering for warehouses down the distribution chain. The batch size quantity is reduced to an equation taught in most courses on production and inventory management. 

In fact this logic does not necessarily conflict with the traditional view of how the economic batch (or order) quantity is determined. All that is different is that the Japanese are seeking to minimise the batch quantity by shifting the curve that represents the cost of ordering or the cost of set-ups to the left (see Figure 5.12). In other words, they focus on finding ways to reduce set-up costs and ordering costs. 

The effect of moving the curve to the left on the economic batch/order quantity is seen in Figure 5.13. 

Figure 5.13 Reducing the economic batch/order quantity...

Customer sales orders for products are tracked against corresponding purchase orders made to suppliers as well as existing inventory holdings, while optimal inventory holding calculations are made through a combination of sales forecast, lead time, and economic replacement quantities (ERQ). In Bossard s case, ERQ is based on similar calculation to economic order quantity, but with an adjustment for real-world constraints in batch order quantities. 

Nylon-6 can be easily polymerized at atmospheric pressure. A continuous process was developed in 1940, called the VK process, which in German stands for vereinfacht kontinuierlich or simplified continuous (73). The VK process is widely used in industry in the 1990s, whereas batch processes, being less economical, are gradually phased out of use. Procedures are also available for making gram quantities of nylon-6 and nylon-6,6 in the laboratory (74). 

Batch reactors are widely used in the chemical industry for producing materials that are needed in limited quantity, particularly in those cases where the processing cost represents only a small fraction of the total value of the product. Since modern industry stresses the use of continuous processes because they lend themselves most readily to mass production, chemical engineers may, in some instances, tend to overlook the economic superiority of batch operations. One should not become so fascinated with the continuous process, or the more complex and interesting design analysis associated therewith, as to lose sight of the economic penalty exacted by this degree of technical sophistication. 

All experiments up to this time employed only minute quantities of seed crystals. In investigating the variables affecting the growth of the dextrose crystals, Newkirk found that the operation could be controlled by using much greater proportions of seed crystals than had hitherto been employed.8 The excessive formation of crystal nuclei too small and numerous to be able to grow to satisfactory size could be avoided by this means. The operation was most economically carried out by leaving in the crystallizer 25 to 30% of a finished batch to act as seed for the... 

Batch crystallizers are often used in situations in which production quantities are small or special handling of the chemicals is required. In the manufacture of speciality chemicals, for example, it is economically beneficial to perform the crystallization stage in some optimal manner. In order to design an optimal control strategy to maximize crystallizer performance, a dynamic model that can accurately simulate crystallizer behavior is required. Unfortunately, the precise details of crystallization growth and nucleation rates are unknown. This lack of fundamental knowledge suggests that a reliable method of model identification is needed. 

The large number of herbs that are available for customers, combined with the relatively low volumes required, means that it may not be economically viable for an extract manufacturer to cany production volumes of large number s of extracts on the off-chance that someone will want one or two of them before then shelf-live has expired. The usual practice is for extract manufacturers to carry a fairly wide range of dried herbs in sample quantities so that when a customer asks for a sample it can be produced within a reasonably short time. Once a new herbal drink has been developed using samples and perhaps a pilot batch, a production-size batch of extract will be made for the product launch. After that, if the product sells and there is a demonstrable demand pattern, it is possible that the extract manufacturer will agr ee to make a batch for stock to be called off by the drink manufacturer. 

When production volume is sufficient, it is economical to build one plant for one product. Batch production in a single unit may be limited by maximum reactor size. Holdups of greater than 20,000 gal are handled in separate parallel reactors. To use common upstream and downstream facilities, the reactors may not be operated simultaneously but on overlapping schedules. When long reaction times cannot be avoided, the reaction sections operate batch wise however, feeding reactants and recovering products may be continuous for economic reasons. This practice is typical of many processes, such as the saponification of natural fats in intermediate quantities. In the production of ethanol by fermentation, two reactions (saccharification and fermentation) are operated on a batch basis, while hydrolysis (conversion of starch to dextrin) and product recovery by distillation are continuous. 

Soil sorption coefficients are most often determined using a batch technique (Organization for Economic Cooperation and Development, 1983 American Society for Testing and Materials, 1993 2001), whereby a small quantity of the soil is agitated for a period of time (e.g., 18 hours) with an aqueous solution of the chemical under investigation the phases are then separated and the concentration of chemical measured in one or both of the phases. While in principle the method is simple, problems can arise due to, for example, incomplete phase separation, lack of time for equilibration, volatilization loss, and chemical instability. 

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