Mask shapes

The shell mold casting , shell mold casting or Croning process called, is a casting technique with lost form (i. E. Once usable). It was patented in 1944 by Johannes Croning in Hamburg. The model is a metal plate a few millimeters thick that can be heated and reused several times.

Procedure

The dry coated quartz sand with a thin layer of phenolic resin (approx. 8%), hardener and calcium stearate is poured onto a model plate heated to 250 to 350 ° C. The heat softens the phenolic resin ( melting temperature 90 to 115 ° C) and thereby binds the quartz sand in a layer thickness, depending on the effect of the heat. Then the molding material that has not melted together is poured back into the storage vessel. The preformed mask half is then lifted off with the help of ejectors mounted on the push-off plate. One half of the mask is now placed on a frame with the division facing up, and cores are inserted if necessary. Then the upper half of the mask is placed on the lower half of the mask with the help of hot glue and placed on a bed of sand for pouring. The resulting shape is called a mask shape.

advantages

• High productivity with little space requirement, suitability for all materials, good mold filling capacity , good gas permeability, lower wage costs, low molding sand consumption, high dimensional accuracy due to curing on the hot model plate, smooth surfaces, low wall thicknesses possible, molded masks can be stored, sand can be recycled.

disadvantage

• expensive model production (only suitable for series production)