Process for producing polyurethane moldings

A process for producing a cellular or compact polyurethane molding comprising:

• a) conveying at least one isocyanate component and at least one polyol component by a metering machine into a mixing head via component lines;
• b) mixing the isocyanate and polyol components in a mixing chamber to form a polyurethane reaction mixture;
• c) discharging the polyurethane reaction mixture from the mixing chamber into a mold;
• d) registering pressure of the isocyanate and polyol components by means of a pressure transducer in each of the component lines;
• e) transmitting the pressures registered in d) to a monitoring device to form transmitted pressure profiles;
• f) comparing the transmitted pressures profiles with corresponding reference pressure profiles stored in the monitoring device;
• g) signalling a malfunction in the event that at least one of the transmitted pressure profiles deviates from the corresponding reference pressure profile beyond a predetermined tolerance threshold;
• h) metering of the isocyanate and ployol components into the mixing chamber is initiated and terminated by opening and closing of one or more slides associated with a nozzle of each of the component lines into the mixing chamber, the opening and closing of the slides effected hydraulically by opening and closing of associated hydraulic valves;
• i) transmitting opening and closing times of the hydraulic valves to the monitoring device;
• and
• j) assigning temporally the opening and closing times of the hydraulic valve to the transmitted pressure profiles in the monitoring device, so that the transmitted pressure profiles are temporally assigned to a start and a stop of a shot of polyurethane reaction mixture to the mold.