Monitoring method for a movement of movable elements (1 to 3, 6 to 8, 10) of a machine, wherein the movable elements (1 to 3, 6 to 8, 10) are moved by a control device of the machine by controlling drives of the machine, - wherein a first monitoring device -- checks whether there is a risk of a collision between a movable element (1 to 3, 6 to 8, 10) of the machine and another movable element (1 to 3, 6 to 8, 10) of the machine or with a stationary element, and -- depending on whether or not it detects the danger of a collision, it intervenes or does not intervene in a corrective manner in the control of the drives or outputs or does not output an alarm message to an operator of the first monitoring device - wherein a second monitoring device -- likewise checks whether there is a risk of a collision of a movable element (1 to 3, 6 to 8, 10) of the machine with another movable element (1 to 3, 6 to 8, 10) of the machine or with a stationary element, and -- depending on whether or not it detects the danger of a collision, likewise intervenes independently of the first monitoring device in a corrective manner in the control of the drives or outputs or does not output an alarm message to an operator of the second monitoring device, - wherein the first monitoring device carries out its said functions on the basis of executing a first computer program and the second monitoring device carries out its said functions on the basis of executing a second computer program, - wherein the first and the second computer programs (11, 14) are embodied in a diverse manner, - wherein the first monitoring device and the second monitoring device are devices that differ from one another characterised in that the first monitoring device and the second monitoring device are embodied in a diverse manner and the first or the second monitoring device (17, 18) are identical to the control device of the machine, wherein the monitoring device (17, 18) that differs from the control device of the machine is embodied as an industrial PC with a data link to the control device of the machine. - wherein a first monitoring device -- checks whether there is a risk of a collision between a movable element (1 to 3, 6 to 8, 10) of the machine and another movable element (1 to 3, 6 to 8, 10) of the machine or with a stationary element, and -- depending on whether or not it detects the danger of a collision, it intervenes or does not intervene in a corrective manner in the control of the drives or outputs or does not output an alarm message to an operator of the first monitoring device -- checks whether there is a risk of a collision between a movable element (1 to 3, 6 to 8, 10) of the machine and another movable element (1 to 3, 6 to 8, 10) of the machine or with a stationary element, and -- depending on whether or not it detects the danger of a collision, it intervenes or does not intervene in a corrective manner in the control of the drives or outputs or does not output an alarm message to an operator of the first monitoring device - wherein a second monitoring device -- likewise checks whether there is a risk of a collision of a movable element (1 to 3, 6 to 8, 10) of the machine with another movable element (1 to 3, 6 to 8, 10) of the machine or with a stationary element, and -- depending on whether or not it detects the danger of a collision, likewise intervenes independently of the first monitoring device in a corrective manner in the control of the drives or outputs or does not output an alarm message to an operator of the second monitoring device, -- likewise checks whether there is a risk of a collision of a movable element (1 to 3, 6 to 8, 10) of the machine with another movable element (1 to 3, 6 to 8, 10) of the machine or with a stationary element, and -- depending on whether or not it detects the danger of a collision, likewise intervenes independently of the first monitoring device in a corrective manner in the control of the drives or outputs or does not output an alarm message to an operator of the second monitoring device, - wherein the first monitoring device carries out its said functions on the basis of executing a first computer program and the second monitoring device carries out its said functions on the basis of executing a second computer program, - wherein the first and the second computer programs (11, 14) are embodied in a diverse manner, - wherein the first monitoring device and the second monitoring device are devices that differ from one another