Changeover time

Particularly ia the case of frequent product changes, great attention has to be paid to the reduction of changeover time, which may take up to 10 days (2). 

If only the dimensions of the profile are to be changed for subsequent production, then only the final die plate has to be replaced. For this purpose, the head is equipped with a double comb-wedge unit, which allows the changing of the final dies without the need to exchange the sphce bar. This is another decisive step towards minimal changeover times. 

An important step in the optimization of production processes is to assign the production capacity in a certain period to the several products that can be produced on a production line. For simplicity, we ignore changeover time here. In this situation, the optimal capacity assignment is defined as follows. 

We can then conclude that while the discrete time STN and RTN models are quite general and effective in monitoring the level of limited resources at the fixed times, their major weakness in terms of capability is the handling of relatively small processing and changeover times. Regarding the objective function, these models can easily handle profit maximization (cost minimization) for a fixed time horizon. Intermediate due dates can be easily modeled. Other objectives such as makespan minimization are more complex to implement since the time horizon and, in consequence, the number of time intervals, are unknown a priori (see [11]). 

Operation and maintenance (O M) costs for the hquid-phase system are based on 0.08/kWh hour power, 10/hr labor for 1 hr/day, 360 annual days of operation, influent contaminant concentrations of 1 mg/Uter, 5% absorption/weight, 1.00/lb carbon, and a 5-year system life at 8% interest. O M costs for the vapor-phase system are based on a >99% removal of aU VOCs from water with an influent concentration of 1 mg/liter, 75 1 water to air ratio (volume based), 5% absorbency, 10.00/hr operator, 40 hr/year changeover time, no power, no freight, 5-year system life at 8% interest, 5% capital for maintenance, and 1.00/lb regeneration or replacement carbon. 

Length of the production campaign—if it becomes shorter than about 10 working days, the changeover time for preparing the plant for the production of the next product becomes too long and overburdens the production costs. 

In the short term, more advanced companies meet the overall supply chain demand while simultaneously minimizing the overall costs of inventory, production, and missed sales opportunities. Further, with frozen production periods they avoid unnecessary changeovers, smoothen the whole production, purchasing, and maintenance process, and achieve superior adherence-to-plan and productivity performance. Nevertheless, if required, they can react promptly to unforeseen changes thanks to reduced changeover times, flexible suppliers, and powerful IT tools that adjust the plans quickly. 

ICP-OES limits of detection for many elements lie in the range 1-100 ng/ml (ppb) in solution. A few elements, notably Li, Be, Mg, Ca, Sc, Ti, Mn, Cu, Sr, Y and Ba, have limits less than 1 ng/ml. ICP-MS on the other hand generally is more sensitive (by 1-3 orders of magnitude) and gives isotope specific information ICP-OES to a first approximation only gives total element concentrations. The principal advantages of the technique is that it is multi-element and that data acquisition takes approximately 1 min with a changeover time between samples of a similar order. The technique has drawbacks ... 

Strip packaging machines are generally more flexible than blister packers changeover times are shorter and much lower in cost (except for the very widest machines). They are, therefore, more ideal for short runs. The largest machines with integral cartoning are similar in price to the fastest and largest blister units. 

Both systems described above have limitations. In the parallel mode either double pumps or dual valves (as shown in Figs. 4.7, 2.6 d) 9] have to be used to control the sequential elution of the columns. This is not necessary in the alternating mode. However, the. sample consumption is usually larger for the latter because the time for. sample changeover is determined by the sample loading time, and not by the normally shoner elution time. On the other hand, unless separate pumps are used for loading and elution, both systems lack the possibility of independent control over the sample changeover time. Therefore, if minimum sample consumption is required, a more complicated three-pump system will be necessary. ... 

Batch production is considered by the first seven approaches shown in Table 4.2. Timpe and Kallrath (2000) propose a time-discrete MILP for the IPPSP with multiple production sites/plants, multiple production modes, intermediate storages, sales points, and transports between sites, storages, and sales points. The model uses different time scales for production and sales planning which allows a more precise planning of production. In a production period, a site can produce in different modes whereby changeover times and costs are considered. To store intermediate and raw materials, one-product and multiproduct tanks are available and an assignment of products to tanks is implemented. The... 

The ability to process many different parts within FMS with minimum engineering effort and changeover time requires both physical and logical enablers (ElMaraghy 2006 and Wiendahl et al. 2007) Hard (physical) enablers ... 

Short changeover time as well as low costs for workpiece holders Comparatively low removal rates at high wastage of grain... 

Roll forming can also be used for low-volume production because setup or changeover time for new parts is not lengthy. 

---