About filtration

For a casting foundry to be successful in today’s intensely competitive environment requires the
production of high quality castings, low dross levels, and higher productivity.
Non-metallic inclusions and slag are some of the
most common reasons for the formation of metal casting dross. They have undesirable effects on
the cast’s surface, its
mechanical properties, and its machinability.
The most effective way of eliminating slag and non-metal inclusions is through the use of ceramic filters.

Why use filters?

  • Filters capture metallic and non-metallic inclusions
  • Theychange the flow of metal from turbulent to laminar, thereby preventing secondary oxidation and deterioration of the moulds
  • They enhance the surface of castings and their machinability
  • By decreasing the dross content, they increase the productivity and efficiency of casting production


How does a filter work?        Animation of the filtration process

There are three filtration mechanisms when using pressed ceramic filters:

  • Filtration by "decanting", which captures particles larger than the holes on the inlet filter
  • Filtration by creating a "filter cake", which is formed by progressive capturing of particles at the inlet filter, while the filter cake also capturing inclusions that are smaller than the size of original filter holes
  • Deep filtration, which occurs in the perforations and channels throughout the filter, whose basic principle lies in the adhesion of particles on the walls of perforations and channels of the ceramic filter.  

Which type of filter should be selected?

A pressed filter is characterized by a balanced ratio of properties, which are important for achieving superior filtration results: high filtration effect, steady flow area, dimensional accuracy, and affordable pricing. The specific dimensions of pressed filters make it possible to calculate the required flow area and to select its appropriate size. A precisely defined and constant flow rate in pressed filters helps stabilize the technological process of casting, and in particular, increases the productivity of automatic casting production lines. Due to their full lateral sides, pressed filters are suitable for the introduction of automatic moulding using robots.

An important aspect to consider when selecting a suitable filter is the type of filtered metal and the casting temperature. The material, as well as number and diameter of holes, must be adjusted accordingly to ensure the enhanced filter characteristics described above. We will gladly help you select the most suitable type of filter and its appropriate placement in the inlet system.


Economics of filtration

The primary goal of using a filter is unquestionably to improve the quality of the casting, but it is also important to consider - especially in today's highly competitive environment - its impact on the cost of casting. At first glance, it may appear that the use of a filter increases the cost of casting, but in reality it is, or rather should be, the opposite. The use of filters must necessarily decrease the percentage of irregularities, which provide a positive economic impact on the price of the product. A simple calculation of the economic benefits of filtration.

 

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