Scrap materials, reworking

Returning to our discussion of benefits, we note that they fell into two principal areas the time-value of information and the improvement in laboratory productivity. As we saw, assessing the benefits from the time-value of information requires examination of the total process through which that information will be used. For example, using data such as the anticipated improvement in laboratory turn around time, the rate at which material Is produced and its value, and the current the financial losses attributable to scrap or rework, one can estimate the savings in dollars to be accrued (each hour of faulty production avoided through faster lab turnaround time yields as a gain to the firm, the revenue that otherwise would have been lost). 

Material produced during start-up and shutdown of the process may have to be either scrapped or reworked, since it is likely to have received less than the targeted levels of coating as a result of reduced exposure to the spray application process. 

Rework/Scrap Costs. Scrap and rework can consume significant amounts of labor in trying to recover the material. Scrap recovery savings are always less than the cost of the original material. This is a good candidate for continuous improvement, and I have seen a lot of low-hanging fruit to be picked in the area of scrap reduction. 

The European Alliance for SMC reports that since the introduction of the CCC project during 2001, scrap and rework rates have been substantially reduced and many process improvements have been implemented. The changes introduced range firom raw material analysis and tightening of tolerances to improvements in mold heating and materials handling practices. 

They will be less accepting of the current levels of waste in the supply chain. Their focus will be on scarcity of materials and improving human welfare. They will be pushing to redefine commonly accepted processes for returns, scrap, and rework. 

Machine cell justification is a trade-off between the benefits of manufacturing in a cellular layout versus the costs associated with under-utilization and movement of equipment. Under-utilization of equipment is created by the assumption that none of the operations required for a part family can be performed outside the cell (no inter-cell movement). This results in the purchase of additional equipment to satisfy the machine requirements of those parts not produced within a cell. The benefits used in the MAPFLO analysis are inventory reductions, scrap and rework reductions, and reductions in material handling. Reduced setup times due to design similarities in a part family are offset by an increase in the number of setups... 

The thermoplastic or thermoset nature of the resin in the colorant—resin matrix is also important. For thermoplastics, the polymerisation reaction is completed, the materials are processed at or close to their melting points, and scrap may be reground and remolded, eg, polyethylene, propjiene, poly(vinyl chloride), acetal resins (qv), acryhcs, ABS, nylons, ceUulosics, and polystyrene (see Olefin polymers Vinyl polymers Acrylic ester polymers Polyamides Cellulose ESTERS Styrene polymers). In the case of thermoset resins, the chemical reaction is only partially complete when the colorants are added and is concluded when the resin is molded. The result is a nonmeltable cross-linked resin that caimot be reworked, eg, epoxy resins (qv), urea—formaldehyde, melamine—formaldehyde, phenoHcs, and thermoset polyesters (qv) (see Amino resins and plastics Phenolic resins). 

LIMS will produce savings from expedited QC testing -- reduction of rework and scrap, improved claims processing on out of spec raw materials, and lower inventory maintenance and insurance — of 25,000 the first year 50,000 the second, and 100,000 thereafter. 

Figure 10 Rework (left) and Scrap (right) for Flow Diagrams. Rework and scrap often are more difficult to handle than good product. Even though rework is often concealed, most items have rework. Material-removal scrap occurs in machining and press operations scrap units occur everywhere. (From Work Design Industrial Ergonomics, 5th Ed., by S. Konz and S. Johnson. Copyright 2000 by Holcomb Hathaway, Pub., Scottsdale, AZ. Reprinted with permission)...

Pre-consumer, industrial scrap represents a possible exception to the product quality issue. As one example, the edge trim from multi-layer film cannot be reworked using existing technology. Approximately 25% of the purchased raw materials used for multi-layer films are now burned or buried. This scrap represents a known and controllable feedstock for the selective dissolution process. The component polymers can be recovered in pristine form. Many have values upwards of US 4.00 per kg. 

Preconsumer plastic Plastic material diverted from the waste stream following an industrial process, but excluding reutilization of material such as rework, regrind, or scrap generated in a process and capable of being reclaimed within the same process. ... 

Reduce molding costs such as mold start-up costs, part-molding costs, material costs, mold rework costs, and scrap and regrind costs. 

As established by the predecessor military standards, process indicators are not intended to be reworked or even dispositioned, and they can be included in product delivery without correction of the product. They are, however, not desirable and indicate the relative success of the process and materials if the process or materials could lead to defect conditions, the process may need to be adjusted or corrected for future production. Process indicators should be monitored as part of the process control system. Should the number of process indicators indicate abnormal variation in the process or identify an undesirable trend, the process should be analyzed. This analysis may result in action to reduce the variation and improve yields before there is a defect trend that may require rework or scrap or, worst of all, result in customer dissatisfaction. 

The development of casein in the USA proceeded more slowly than in Europe. It was not until 1919 that the first casein plastic that was up to European quality standards was made in the USA. Even then, the industry in the USA did not take off for several reasons climatic differences meant the European processes could not be copied in a straightforward manner in the USA, the long and costly process did not yield easily to faster processing in automatic machines, and the scrap could not be reworked, so 50% waste was not uncommon. All this made competition with established materials more difficult. ... 

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