Although each of the basic compaction methods described above can be used individually, it is common to combine them to produce a more uniform mould compaction degree on both, the horizontal and vertical planes. In such a case, the process of compaction is divided into two stages: pre-compaction of loose moulding aggregate, followed by the final compaction. Squeezing is frequently employed in Stage 2. In some moulding machines, more than two basic compaction methods are combined. However, disadvantage of the multi-stage compaction is extended cycle time of the moulding process.
The jolt-squeeze method described above is a typical example of a combined method of compaction. The process is commonly found in the jobbing-type foundries with frequent pattern changes. Another typical arrangement is a combination of blowing or shooting, used for mould filling and aggregate pre-compaction, with subsequent compaction by squeeze from a flat, contoured or multi-piston head. An example is Disamatic (Georg Fischer Disa Ltd.), an automatic moulding machine producing the vertically jointed box-less greensand moulds. It combines the moulding aggregate shooting into the moulding chamber, followed by high-pressure squeeze from both sides. The F. Hansberg Company uses an additional air flow for 0.8 s after the shooting of moulding aggregate, followed by squeezing from above. Vacuum shooting is usually combined with squeezing; a box-less moulding production line of Haflinger, the German Company, is a good example. Vacuum shooting followed by the compressed air (Air-Impact) pulse compaction utilizes the Bühler Company in its Vacuum-Formatic moulding machine. The combination of vibration and squeezing reduces energy consumption to overcome the internal friction of the particles of the moulding aggregate, thereby increasing the compaction degree and achieving a more even compaction throughout the mould volume.