Abstract: Partially assembled spacer frames formed by a plurality of joined spacer frame segments are advanced past a sealant applying station defined by first and second sealant extrusion nozzles positioned for applying sealant to opposite spacer frame segment sides and a third sealant extrusion nozzle positioned for applying sealant to the exterior spacer frame side. Extrusion nozzle controllers render the nozzles operative to apply sealant to the spacer frame segments in response to control signals. A spacer frame detection system produces signals indicating the presence of the spacer frame at the sealant application station. A signal processor coupled to the detection system and to the nozzle controller produces control signals for intermittently operating the third extrusion nozzle in response to the presence of the leading end of the spacer frame segments at said station, and the approach of the junctures of subsequent spacer frame segment ends and the trailing frame end.