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Innovation breakthrough in surface friction technology

A new surface friction technology for greensand and inorganic process has been developed by FATA Aluminum.

In the 1990s FATA Aluminum began proposing the use of proprietary surface friction technology for the mechanical recovery and re-use of spent sand at its customers’ foundries. At that time the R&D goal was to integrate initial mechanical greensand treatment with subsequent thermal regeneration of surplus sand coming from cast iron foundries. This allowed the cost to be minimised and facilitated the maximum efficiency of equipment then currently on the market. This process was designed to eliminate bentonite and mineral coal from spent sand so that the foundry might produce cores without having to mix regenerated sand with new sand.

The surface friction process developed by FATA Aluminum basically uses a full-pipe pneumatic system to collect and move sand.

Using a suitably powerful blower to overcome circuit resistance and drag, the sand is blown into a wear-resistant cast iron chamber, creating a suspended fluidised bed with variable density (essentially a sort of sand cushion) maintained by the same blower air used for fluidisation.

The grains of sand from the transporter pipe are blown into the fluidised bed, where surface friction with suspended sand grains cleans them while gradually reducing their forward movement. This process does not depend on direct impact with the metal bell or suspended sand grains, but is the result of mutual surface friction between the grains suspended in this air cushion.

The need for mechanical treatment of cores coming from inorganic sand processes forced the company to discuss its conviction of trying to discover new solutions. The final results from benchmarking the FATA solution against more commonly used mechanical technologies indicate that the company’s surface friction option outperforms other mechanical treatments available today, and has convinced the company to continue this technology by developing a new generation of high performance equipment.

Improving treatment efficiencies

The company’s research and subsequent development activities have concentrated on optimising output while maintaining or even improving treatment efficiencies and have gone through two successive design stages:

  1. Fabricating a small-scale version of the equipment that allows FATA to evaluate small batches for output/quality ratios at different equipment settings.
  2. A subsequent and targeted test series undertaken on prototype equipment at the FATA Aluminum plant.

During this R&D period, FATA succeeded in improving the dense full-pipe system by creating a continuous even sand transfer flow between full-tube and fluidised bed; transport pipe sand density is now exactly the same as the initial fluidised bed sand density. Consequently, surface friction is more gradual with immediate effect while reducing any abrupt speed variations to zero. This simple modification to machine geometry gave surprising results – with a thicker cushion of fluidised sand, the sand grains became more energetically active over a longer treatment time while not being subjected to dangerous mechanical shock. 

These tests verify that this equipment can be calibrated to achieve a 95 to 96 per cent sand yield.

Several such surface friction cells can be mounted in parallel or in series, depending on customer requested productivity or treatment type.

The standard FATA Aluminum surface friction treatment is efficient, acting only on sand grain surfaces and not subjecting the physical integrity of the grains themselves to any risk from mechanical shock. In instances of angular or sub-angular shapes, the sand grain edges are polished smooth, increasing geometric grain quality and giving a superior final product compared to original sand.

This evolution in surface friction technology enables mechanical treatment equipment to satisfy even extremely elevated sand quality standards such as those required by sands bound with inorganic resins.  

Contact: FATA Aluminum srl, Tel: +39 (0) 11966 3380, email: info@fataaluminum.com web: www.fataaluminum.com