Demolding behavior

Describes the capability of clay-bonded molding materials to withstand the static and dynamic stresses occurring during separation of pattern and mold without any resulting damage to the mold. For implementation of modern compaction technology (higher compaction intensity, larger lateral pressure, low degree of humidity in the molding material) the demolding behavior is a critical factor. This is due to significant stresses occurring as a result of higher degrees of molding material compaction and accompanying increase in elastic properties of the molding material (elastic recovery). The respective demolding properties are closely dependent on the deformation capacity of the compacted molding material.

Demolding properties are mainly affected by composition of the molding material and by intensity of compaction. Moreover, ease of separation of pattern and mold may be specifically influenced by the following  measures:

  • Implementation of sufficiently large inclinations in the mold and/or the model
  • Facilitating the pattern-drawing process by vibration; this measure causes reduction of clamping and adhesion forces between the pattern and the mold
  • Application of adhesion-reducing coats on the pattern (separating agents, such as molding powder, parting oil, emulsions)
  • Reduction of adhesive friction between pattern and mold material by usage of pattern materials with high surface quality
  • Application of various machine-based technical solutions for demolding

Demolding properties cannot be rated using conventional strength test methods. The reason is that in pattern drawing, the mold is subjected to dynamic stresses in connection with deformation of the mold walls and tensile stresses. Conventional strength test methods (resistance to pressure and shearing) generally characterize the molding material behavior under static stresses.