A flame cutting machine having motor means for traveling one or more gas operated cutting torches along one or more workpieces includes a flame height control for maintaining each torch at a predetermined precise spacing from the workpiece. The height control does not require any mechanical element extending between the torch and the workpiece to sense spacing and is insensitive to surface conditions of the workpiece. Torch to workpiece spacing is sensed at the point of contact of the flame with the workpiece rather than at an adjacent area. An electrical voltage is applied between each torch and the associated workpiece whereby the cutting flame constitutes an electrical resistor, the resistance of which is a function of torch to workpiece spacing. The voltage drop across each flame is continually compared with a predetermined selectable reference voltage indicative of desired torch to workpiece spacing and correction signals are generated when necessary to actuate a servomotor that restores the desired spacing of the torch and associated workpiece. Means are also provided for maintaining different torch to workpiece spacings for preheating and cutting stages of operation and for manually adjusting all torches jointly or any selected torch individually and further means disable the automatic flame height control system in response to a pronounced increase in the electrical resistance of any flame such as occurs if a torch passes off the edge of a workpiece.
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