Impress molding process


The cycle starts by dosing of prepared green sand first into the weighing hopper and then into the moulding machine. At that time the pressing frame is in upper position. The table is lifted with pattern carrier and flask. The shutter opens and feeds the sand into the flask. The multiple squeeze heaf shuttles over the flask and levels the sand.

Now the table with pattern plate and flask starts lifting to the upper positions and pre-squeezes the sand from below. For final compactation of the mould active squeezing follows from top and applies up to 1,5 N/mm2.

After active squeezing the table is lowered again and mould and pattern are separated by lifting the pressing frame. Finally the table is completely lowered while the flask is set onto the rollers of the mould conveyor and the pattern plate carrier is centred in the internal pattern change device. The cycle ends with the transport of the unmoulded flask into and the moulded flask out of the moulding station. This sequence follows the idea of the “old foundry men” of using the pattern in order to compress the sand which has the benefit of an extremely simple process using only inexpensive equipment without many valves, nozzles and ventings. The originated forces for squeezing are opposed by counter force. Overall moulds with excellent quality can be produced which are reflected in the following advantages:

  • an ideal resistance of the mould, with higher hardness values on the pattern side;
  •  excellent gas permeability;
  • perfect reproduction of the pattern details;
  •  fettling is nearly non-existent;
  • low-noise mould production;
  • energy saving of 20-30 %

After moulding about 8 positions are provided for core setting before the flask is closed. The closed flask is transferred to the pouring-side, where about 10 positions are provided for pouring. After pouring the flasks are cooling for about 2 hours. The flasks are taken with the left transfer car into cooling #2 and with right transfer car back via line #3 and line #4. At the left end of line #3 and #4 the flask are taken again by transfer car and are given to the push-out station.

Flask and sand fall on the shake-out and are separated. The sand is collected and separated from iron waste before it is lifted with a bucket elevator to the rotary screen and hot sand silo. The sand is discharged to a fluid bed cooler and discharged at <45°C. The cold sand is stored in the used sand silos. Used sand, bentonite and graphite are given with water to a turbine mixer. The prepared moulding sand is discharged and transported back to the moulding line hopper.