Thermal transfer printing machine for printing images on articles by means of a heated pad, particularly for printing images in cavities or recesses

A printing machine for thermal transfer printing of images (I) on articles (A), comprising

• a frame structure, stationary in operation,
• one or more support elements fixed to the frame structure and arranged to support the article (A) on which at least one image (I) is to be printed,
• a thermal transfer assembly with a transfer pad having an active surface which is heated in operation, the thermal transfer assembly being placed above said support elements and being movable vertically relative to the frame structure between a raised rest position and a lowered working position,
• an actuator arranged to cause a vertical translational movement of the thermal transfer assembly relative to the frame structure between said raised rest position and lowered working position, and
• supply and guide elements arranged to advance, along a predetermined path extending in part between the active surface of the transfer pad and said support elements, a flexible printing ribbon (N) which on a side thereof facing said support elements carries, at predetermined intervals, images (I) formed of a thermally transferable ink,
• wherein the printing machine further comprises a position sensor arranged to provide electric signals indicative of a vertical position of the transfer pad, and a control unit arranged to carry out
• a learning phase wherein said control unit causes a subsequent descent run of the thermal transfer assembly until the transfer pad is brought into engagement with a first article (A) of a predetermined type positioned on said support elements, and through said position sensor detect and store reference data characterizing said descent run, and
• a subsequent printing phase, wherein said control unit causes a subsequent descent run of the thermal transfer assembly, towards and up to a second article (A), of the same type as said first article (A), positioned on the support elements, detecting and comparing with said reference data corresponding data which characterize the current descent run, and stopping said printing phase when the comparison of said data is indicative of an anomaly in the current descent run.