By brushing with a swab or brush, the fine refractory fillers can easily be applied into the relatively large pores between the sand grains of the moulding material, which makes this type of application particularly suitable for pockets and other hard-to-reach areas. Nevertheless, the effiency of the application process depends enormously on the operator which often leads to varying wet film thicknesses. Coatings which are not optimised for this application can exacerbate this effect. In order to minimise the possibility of "human error", coating systems have been developed that are characterised by special properties with a uniform coating application.
As the coating usage can be accurately regulated, the application efficiency is particularly high.
Cores or core packages are normally coated in a dipping tank. This application method is particularly suitable for automated processes and is common in automative foundries where high throughput and transfer efficiency (99%) are required . Coatings whose rheological properties are optimised for dipping prevent the formation of drops and runs. It is therefore not necessary to "shake" the cores.
By particularly using the correct filler combination smooth casting surfaces with low penetration can be achieved.
Flow coating is a very quick and reliable application method with high reproducibility, used for small and large moulds and cores.
To achieve the best application efficiency, the mould to be flooded is hanged at an angle of 20 to 40° (relative to the vertical). The operator or manipulator applies the coating from top to bottom with lateral movement of the lance. Special flow coating nozzles with an adjustable discharge speed facilitate the application of the coating.
Flow coatings have very good flow-coating properties, so that an equal coating application can be achieved even when coating moulds with complex geometries or large core packages. Automated application using flow coating nozzles in conjunction with a conveyor belt is a good alternative to the dipping of cores coupled with significantly reduced drying times.
The spraying of coatings has been well-established for years, especially in the production of large castings. The high application speeds, fast drying times and reduced crane & handling capacities are just some of the many advantages. In addition, spraying represents a high-quality and economical variable of coating application due to the different spraying techniques such as low pressure (air atomised) airless (high pressure with minimal vapor) also for many mould and core areas, including green sand, 3D printing, dies and centrifugal casting + in the vacuum "V" process.