Process variables and how they indicate mixer performance

For foundries that require greater sophistication, a range of fiilly automated mixer control systems are available. These systems use microprocessor technology to provide automatic corrective control of mixed sand production and need only limited operator involvement. The additional benefits achievable with automated control systems are mainly due to the much reduced dependence on the operator and the more rapid correction of variations in conditions. The latter is also performed without having to stop production. 

Optimisation of the binder and resin use results in a minimisation of the consumption of chemical additives. 

Volatile organic compounds make up to 50 - 60 % by weight of the binder components. The amount depends on fte binder system type. Most are emitted during sand mixing and metal pouring. A reduction in the use of binder results in a corresponding reduction of VOC emissions. 

In most cases, reductions of 5 % in binder levels and 1 % in scrap moulds are easily achieved using modem mixer control systems. Many foundries have realised savings that have been considerably higher. Reductions in binder addition of 5 to 25 % have been reported for various foundries, as well as almost eliminating scrap moulds production. 

The installation of an automated mixer control system in an iron foundry using cold-setting resins allowed the foundry to reduce the resin addition rate from 10 kg/minute (1.22 % resin to sand weight) to 8.89 kg/minute (1.09 %), which correspondingly resulted in a 10 % saving in the amount of catalyst used. The number of defective moulds fell by over 60 % and cost savings of over GBP 37000/year (1995 UK prices) were achieved. 

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Table 4.21 Process variables and how they indicate mixer performance [71, ETSU, 1998]...

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