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Home  Filtration technology  Gating system designing

Gating system designing

When designing the gating system with filters, it is necessary to consider more criteria, preceding correct filter choice and its layout in the gating system. When designing the gating system, we usually find the starting point for solution of a certain problem. In practice we face two main requirements of the foundries concerning putting the filters into production:

1. Requirements for reduction of the manufacturing costs of the foundry

  • Reduction of scrap level (cost savings for nonconforming products, increase of manufacturing productivity)
  • Minimizing of occurrence of the foundry defects (cost savings in the cleaning shop and shortening of terms of product delivery)
  • Simplification of the gating system (higher yield of the molten metal and foundry flask)

2. Requirements for increase of quality of the castings

  • Manufacturability of the casting (complex, thin-wall castings, special alloys, high temperatures and  casting speed)
  • Increase of external purity of the castings (e.g. better surfaces, reduction of allowances for machining and improved machinability)
  • Increase of internal purity of the castings (e.g. elimination of leaks, improvement of mechanical features of the casting)

Specific conditions, under which we want to reach the requested result, is another criterion for filter choice:

  • Foundry technology (gravity casting, pressure casting; sand casting, die casting, ceramic shell casting …)
  • Moulding technology (green sand mix, furan mix; degree of automation, ...)
  • Casting (cast alloy, casting temperature, gross and raw weight)
  • Pouring technology (method of pouring from ladles or from the casting unit, metal treatment, quality of batch, ...
  • Layout in the mould, possibility of gating system modification for filter placing

Based on definition of the initial conditions, it is possible to select the correct filter, its layout in the gating system and to design the gating system cross section:

I. Filter material – determines resistance to the casting temperature, mechanical and chemical load and character of the melt:

Selection of the filter type depends on the parameters identified above and a suitable filter type can be chosen from the LANIK company production

II. Filter shape and dimensions

Filter size is designed mainly by the metal quantities to be filtered within a certain time period, in particular by the filter capacity and casting speed. It must also correspond to the mechanical load during casting and to the shape of the chamber in the gating system of the mould.

III. Filter porosity

The ppi unit is used for identification of foam filter porosity. From the point of filtering efficiency we always try to apply the filter with the highest porosity (small pores). But sometimes its necessary to use the filter with the porosity lower than could be used normally, in particular if higher casting speed is requested.

IV. Filter layout in the gating system

 In particular three general principles are applied; it is advisable to keep them:

  • to place the filter in the gating system as close to the casting as possible
  • to select the shortest possible (preferably straight) gating system
  • mould cavity has to be filled by metal smoothly, without and impacts or shocks

V. Filter position in the gating system

Chosen by the method of moulding and filter insertion into the mould gating system. There is a number of methods of filter positioning, each of them having its specific features.

Further details about filter position and layout in the gating system can be found in the section Filter placing in gating system

created by Omega Design