a programmed painter robot the spraying device actuated by the robot is to be initially switched on and subsequently switched off by a switching command fn produced by a robot control program at time t 0 the switching command fn causes a separate control unit e g one containing a microprocessor to deliver after a preadjusted waiting period ending at time t 1 an actual switching on signal fn 39 for a paint needle valve in the spraying device because of the unavoidable signal response delay times resulting from the control elements e g valves in the spraying device the paint needle valve will actually open after a certain paint needle opening time t8 which is monitored and measured following the paint needle valve opening time t8 a report back signal is produced by the paint needle valve at time t 2 in a manner to be described subsequently after a paint flight time t6 the paint contacts the body to be coated at time t 3 the total time between t 0 and t 3 is the switching on time or lead time t0 of the paint needle valve recorded in the robot program as a process parameter a paint needle valve switching off time t1 also recorded as a process parameter is determined in a manner similar to the determination of the switching on time t0 the paint needle valve switching off time t1 comprises the time beginning from the.