Sand moulding machine and method of producing sand mould parts

A method of producing sand mould parts, whereby a moulding chamber during a filling operation is filled with sand, and whereby the sand is subsequently compacted, the moulding chamber being formed by a chamber top wall, a chamber bottom wall, two opposed chamber side walls and two opposed chamber end walls, whereby the moulding chamber is filled with sand through at least one sand filling opening provided in one of said chamber walls, whereby a mould or mould part is provided with a pattern by means of at least one of the chamber end walls being provided with a pattern plate having a pattern, and whereby sand is compacted inside the moulding chamber by displacing at least one of the chamber end walls in a longitudinal direction of the moulding chamber, whereby a reference pattern is formed in an external face of a sand mould part by means of at least one reference pattern block associated with and positioned in fixed relationship to a said pattern plate, and whereby a position of a pattern face of the reference patterns of the sand mould parts is detected by means of a non-contact detector arranged adjacent a path of travel of the compacted sand mould parts, wherein the at least one reference pattern block forms a corresponding reference pattern including a pattern face having a tangent varying in a longitudinal direction of the sand mould part corresponding to the longitudinal direction of the moulding chamber, by that the non-contact detector detects the position of a number of different points distributed over the pattern face of the reference pattern in the longitudinal direction of the sand mould part, and by that the tangent in the longitudinal direction of the sand mould part is different between at least two of said points.