The moulding machine includes a moulding chamber having at least one chamber end wall provided with a pattern plate adapted to form a pattern in a mould part and associated with a reference pattern block positioned in fixed relationship to a pattern of said pattern plate and adapted to form a reference pattern in an external face of a mould part. The reference pattern block includes a face having a tangent varying in a longitudinal direction of the moulding chamber and being adapted to form a corresponding reference pattern in the sand mould part. A non-contact detection system (87) detects the position of a number of different points (P1, P2) distributed over the pattern face of the reference pattern in the longitudinal direction of the sand mould part, and the tangent (T1, T2) in the longitudinal direction of the sand mould part is different between at least two of said points.