A coating preparation plant (CPP) and dip tank were installed and commissioned by local foundry consumables supplier Foseco – the foundry division of Vesuvius – in January, says Foseco South Africa sales and marketing manager Enno Krueger.
There is a continual demand for foundries to manufacture increasingly complex, high- performance castings, while driving down production costs, says Krueger.
Foseco South Africa saw the need for automotive castings producer Atlantis Foundries to take advantage of the available technology on offer from Foseco and thus entered into discussions with Atlantis management and engineers regarding the optimis-ation of its coatings application.
Foseco proposed the total coatings management concept, which would enable Atlantis Foundries to achieve the highest standards possible in coatings technology, he adds.
A significant portion of pro-duction costs can be attributed to rework, owing to surface defects, which can be eliminated or significantly reduced through the use of the correct refractory coating, he says.
The choice of coating is specific to the metal/mould interactions that are to be overcome, and the rheological properties can be modified to the application requirements.
However, Krueger says a coat-ing will only achieve improved performance when it is applied at the correct layer thickness. If the layer thickness is too thin, the coating will not provide adequate protection and, if it is too thick, there is the risk of scabbing defects, the formation of runs and drips and the cost penalty of using too much coating.
Variations in dilution, through poor process control and measurement, will lead to variations in applied layer thickness, resulting in variations in surface finish, defect levels and rework costs. Traditionally, coating dilution has been con-trolled through intermittent measurements of the diluted product using viscosity cups or Baume.
However, the intermittent nature of these tests and the dependence
on an operator to interpret results and ensure the coating
is homogenised after dilution inevitably lead to application
variations, highlights Krueger.
These variables can be reduced by the application of an automated CPP. The benefits of such a system are that coating density is continually monitored, and additions of either coating or dilutant are added and homogenised to ensure the product is always supplied for the defined application, he adds.
The CPP is designed to accommodate a wide range of application methods, includ-ing spray, dip and over-pour, and can be connected to all major packaging systems, from drums to bulk silos. The CPP can be configured to work automatically, manually or inter-mittently depending on the foundry process, he concludes.