Abstract: A setting-up plate is mounted on an X-Y table of a component placement machine. The plate has an array of fiducial marks thereon whose positions are accurately known. A control system drives the table by an amount which should bring each mark in turn to a reference point of a detecting device. The detecting device detects the actual position of the mark relative to the reference point. Errors in the table drive are thereby detected and can be allowed for.

Abstract: A component placement machine comprising an X-Y table, at least two pick-up tools movable between an up-position and a down position is set up to allow for movement of each tool in a horizontal plane in moving between its down position and its up position. A test piece is removably mounted in a pocket on the X-Y table so that it is accurately reproducibly mounted. The test piece is picked-up by a pick-up tool in its down position and a detection device detects the actual position of the piece on the tool in its up position. This is repeated for all the tools so that, when the X-Y table drive is used to compensate for variations in component position on a tool, as detected by the detection device, account can be taken of said movement in a horizontal plane.