The object of the invention is a method for decoring sand cores from various castings either of non-ferrous metals and their alloys or ferrous alloys.

The invention allows decoring from hot castings immediately after casting or after process of hardening is completed. The currently known technology does not allow it. The technology allows decoring of all types of sand cores: Cold box, Hot box, Croning, and cores with inorganic binders. Major advantages of the process are:

- Simple device for decoring is needed.

- Less expensive device for decoring is needed.

- No additional labour force is needed. Decoring can be performed at the same working place as casting.

- No sand blasting of castings is needed. Castings are devoid of remains of the core.

- A smaller amount of castings in the intermediate storage area between the casting phase and the decoring phase.

- Improved supervision and quality control of the process due to a rapid result and consequently less scrap. The castings are subject to serial control and finalization as early as half an hour after the casting procedure.

- The method is ecologically friendlier. Decoring is performed immediately after casting and dissimilation of binders is finished within a relatively short period of time. Owing to air blowing the sand gets cold rapidly.

- After decoring the sand is completely crushed. No additional crushing or preparation for further operation is needed.

- The inner surface of a casting is clean and no remaining sand is bonded. Additional sand blasting due to core remains is not needed.

The currently known technological solutions to decoring are based on two principles:

1. Vibration: a casting is clamped in a dedicated clamping device, and then it is hammered with pneumatic hammers to achieve cracks on the core. Then follows vibration of castings. The solution is protected by several patents: FR2850890, US2006272792, FR2901161, EP0326138, EP0325928, WO2004067209, WO2007132101, FR2711931, US4718473, FR2730436, EP0111461, FR2699840, US4722386, DE2947795, DE3219390, EP0304683, WQ9721523, FR2655895, W09213663, US5213150, JP63235063, GB2067938, DE3319312 and is rather problematic because of the following:

- Castings must be completely cooled down before decoring. This requires additional intermediate storage area and a delay of further production phases for at least 8 to 16 hours.

- Danger of cracks.

- Danger of damages on castings due to clamping.

- High maintenance costs of the device because the device is self-destructive due to high forces at vibration.

- Particles of sand remain on the surface of a casting which need to be removed by sand blasting.

2. Thermal decomposition: castings are heated in a furnace at 400 °C for 4 to 6 hours which causes thermal decomposition of the binder (phenol resins). After the thermal decomposition procedure the sand must be emptied from the castings. The solution is protected by several patents US3989227, WO9730805 and is rather problematic because of the following :

- Before being thermally decomposed, castings are collected into batches - palettes due to optimal costs of operation. This requires an additional intermediate storage area and a delay of further production phases for at least 16 to 24 hours.

- Particles of sand remain on the surface of a casting that need to be removed by sand blasting.

- Energy and financially wasteful procedure.

Description of the method for boring sand cores from castings

A dedicated hollow tool (2) is used in boring of sand cores, which tool crushes the centre of a sand core (3) by rotation and translation into the inside of a casting (1); air flows under the pressure from inlet holes (4) on the tool and flows through the holes towards a ceramic plate (5) directly to the place of sand crushing; the blown air removes the sand in direction outside a casting (7), and on the way out the mixture of air and sand removes the remaining core and .cleans the surface.