Feeder
Speiser or Steiger is a term from foundry technology and describes geometric sprue bodies on cast parts, in the form of which the void volume deficit is to be placed during the cast part solidification and which are removed again during the cleaning process of the cast parts. Feeders on cast steel parts are removed with oxy-fuel cutting by burning and removing the material in the so-called kerf using the heat of oxidation from the supplied oxygen.
A feeder should therefore avoid the formation of cavities in a casting and has different tasks in a casting mold:
- Control of the solidification direction of the poured melt (if possible directed towards the feeder)
- Compensation for the reduction in the specific volume of the poured melt during the liquid / solid phase transition
- Ventilation of the mold during the casting process (exception: dummy feeder )
The shape of feeders is usually cylindrical and led out of the mold, more rarely spherical and as a dummy feeder (the feeder is completely hidden by the molding material ).
The cylindrical or spherical shape is chosen on the basis of the good to very good volume / surface ratio (module as a geometric parameter for solidification rate).
"Feeder variants": natural feeder, insulating feeder, exothermic feeder: By insulating or additionally heating the feeder after the casting process, the feeder dimensions can be kept smaller, which leads to material savings (better casting yield).
literature
- Rabinovic, BR , Mai, R. , Drossel, G .: Basics of casting and feeding technology for sand mold casting, VEB Deutscher Verlag für Grundstoffindindustrie, 2nd edition Leipzig 1989