Yield Losses
These are volume losses stemming from weight differences between raw materials and products or between all raw materials input and the products.
The former are material losses caused by increasing wall thickness to more than the necessary level, in order to prevent casting defects (sand inclusion, surface flaws) in the raw materials or to cover the insufficient precision of shaping molds. these losses sometimes cause the extension of machining time or the reduction of the service life of cutting blades.
The latter represents the difference between slag weight/gate weight / burr volume and product weight-material losses causing yield decline due to increased burr occurrence resulting from insufficient mold precision. In aluminum casting, the weight of the runner and burr is applicable instead of the above weights.
In the cylinder block process of automobile engines, for instance, burrs are produced because of partial weakness of sand molds and misalignment of sand molds and core molds. In many cases, a fairly large number of workers is required to remove the burrs. Reducing such burrs is a major problem related to yield, energy, and worker-hour losses.
Energy Losses
These are losses of such energy as electric power, fuel, steam, air, and water (including wastewater).
Because electricity, fuel, and utility costs represent a high percentage of the total cost, all companies are striving to reduce them. improvement has been achieved with regard to major energy losses, but a considerable number of minor losses are left unrectified, so there is much room for improvement. In the case of hydraulic equipment, various problems must be detected by studying the following points.
- Is the pressure-setting appropriate?
- Is the holding time appropriate?
-Is the hydraulic pump type suitable?
Detected problems should be solved one by one. Finding and improving many minor energy losses adds up to great results.
(including sub-material losses)
These are monetary losses resulting from the manufacturing and repair of dies,jigs, and tools necessary for the production products.
Die, jig, and fixture losses represent expenses arising as a result of manufacturing of new molds,replacement due to the end of service life or breakdown, repair following wear, manufacturing or repair of mold parts, and manufacturing or repair of jigs and tools. if the repair frequency is high, expenses naturally grow.
Losses of sub-materials necessary for production include expenses of cutting oil, consumables and replacement parts, and pharmaceuticals and gas, etc. these losses have to be managed after they are converted into basic units.
A general problem concerning these losses is that the degree of their occurrence in not clear. To reduce manufacturing cost, it is absolutely necessary to extend MTBF of mold repair. to prevent product breakage and to extend the service life of replacement parts.
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