Squeezing

High quality cast repressing

Metal casting processes may cause shrinkage cavitation and/or porous microstructures in the workpiece, depending on the shape of the cast component. These weaken the mechanical integrity of the workpiece and are not acceptable for downstream drilling in the affected workpiece area. Repressing specific locations of the metal cast during the cooling phase of the workpiece following the introduction of molten metal is a common used method for reducing the quantity and size of flaws in a workpiece.

How it works

This happens at a time when the injected metallic cast material is no longer entirely liquid but semi-crystalline and still has a viscosity allowing local redistribution of the metallic cast material by applying pressure. Repressing is a process where a squeeze pin is pressed into a non-critical area of the semi-crystalline cast material of the workpiece in order to apply localized pressure to the workpiece. The pressure then propagates through the cast material, thus reducing the size of shrinkage cavities and closing pores in the defect areas. This entire process is referred to as 'squeezing'.

Our squeezing solutions

Squeezing is usually implemented using cylinders with piston diameters of 25 to 63 mm. Strokes usually do not exceed 20 mm and the cylinders are installed deep inside the mold. These are perfect parameters for the AHP Merkle block cylinder.

  • Since this application always involves high temperatures, at least one Viton sealing kit should be used. Some applications even require cylinder cooling. There is no standard for this yet – we will design this upon customer request.
  • Another proven technique has emerged in the meantime. Here, a designed bypass is integrated into the cylinder piston to effect frequent oil exchanges. This has now become a standard of its own at AHP Merkle. However, since bypasses should not be implemented without prior consultation, this standard option is not found in the catalog.
  • We will be pleased to advise you on our operation modes 251 and 261.
  • Now there is also an increasing demand for squeeze pin position monitoring. There are various solution approaches here, too, all of which require special consultation. However, the first patent registered by AHP Merkle should be mentioned at this point. It is about position monitoring via a temperature-resistant fiber optic cable.