Method for producing components from polyurethane in a shot method

A method for the production of polyurethane components by the shot method, in which at least two reaction components are conveyed into a groove-controlled mixing head by means of metering pumps, in particular at metering pressures of at least 50 bar,

• wherein the reaction components are first conveyed in circulation through a respective component nozzle via a recirculation groove in a control slide in circulation back into a storage container,
• wherein the shot start is initiated by an electrical signal emitted by a machine control, as a result of which a hydraulic valve is switched and the control slide then moves from the circulation position into the shot position, so that the reaction components are entered into the mixing chamber, where they are mixed together and then discharged,
• wherein the shot end is then initiated by removing the electrical signal issued by the machine control, as a result of which the hydraulic valve is switched again and the control slide then moves from the shot position back into the circulation position, so that the reaction components are conveyed back again into the container via the recirculation groove in the control slide in circulation,
• wherein the media flows are briefly interrupted by the mixing head while the metering pumps are running when the control slide is moved from the circulation position to the shot position and vice versa,
• wherein the conveyed volume flows between the metering pump and the mixing head are each conveyed through a volume flow meter, which consists of at least one housing with an inlet opening and an outlet opening and at least two rotatably mounted bodies, in particular gear wheels, co-operating in this housing, wherein these rotatably mounted bodies are set in rotation in response to a volume flow conveyed by the volume flow meter,
• wherein the method comprises the steps of:
• a) Determining the actual shot start by analyzing the course of the respective pressure of the reaction component after the electrical signal for the shot start has been generated and determining the time point at which the reaction component enters the mixing chamber of the mixing head and storing the time point of the actual shot start,
• b) Determining the actual shot end by analyzing the course of the respective pressure of the reaction component after the electrical signal for the shot end has been generated and determining the time point at which the reaction component no longer enters the mixing chamber of the mixing head and storing the time point of the actual shot end,
• c) Determining of the delivered volume of the reaction components by means of the volume flow meter of the respective reaction components, which was delivered by the metering pumps in the period between the time point of the actual shot start and the time point of the actual shot end and outputting the respectively determined volumes.