An additive manufacturing apparatus (10, 10', 100), comprising: first and second spaced-apart side walls (28, 28', 128, 30, 30', 130) extending along a pre-defined path and defining a build chamber (14, 14', 114) therebetween, wherein the first and second spaced-apart side walls (28, 28', 128, 30, 30', 130) extend outwardly from a turntable (12, 12', 112) and wherein the turntable (12, 12', 112) defines a moveable build platform (16, 16'); one or more build units (20, 120, 184) mounted for movement along the pre-defined path, wherein the pre-defined path is a ring (31, 31'), wherein at least one build unit is a fusing unit disposed in a housing (18, 118), wherein the fusing unit (20, 120) comprises: a powder dispenser (44, 144) positioned above the build chamber (14, 14', 114); an applicator (42, 142) configured to scrape powder dispensed into the build chamber (14, 14',114); and a directed energy source (46, 146) configured to fuse the scraped powder, wherein the housing (18, 118) includes an opening (36, 136) configured to receive at least a portion of the build chamber (14, 14', 114) therein, wherein a seal (38, 138) is disposed around the opening (36, 136) to provide sealing engagement between the opening (36, 136) and the first and second spaced apart side walls (28, 28', 128, 30, 30', 130) of the build chamber (14, 14', 114). first and second spaced-apart side walls (28, 28', 128, 30, 30', 130) extending along a pre-defined path and defining a build chamber (14, 14', 114) therebetween, wherein the first and second spaced-apart side walls (28, 28', 128, 30, 30', 130) extend outwardly from a turntable (12, 12', 112) and wherein the turntable (12, 12', 112) defines a moveable build platform (16, 16'); one or more build units (20, 120, 184) mounted for movement along the pre-defined path, wherein the pre-defined path is a ring (31, 31'), wherein at least one build unit is a fusing unit disposed in a housing (18, 118), wherein the fusing unit (20, 120) comprises: a powder dispenser (44, 144) positioned above the build chamber (14, 14', 114); an applicator (42, 142) configured to scrape powder dispensed into the build chamber (14, 14',114); and a directed energy source (46, 146) configured to fuse the scraped powder, wherein the housing (18, 118) includes an opening (36, 136) configured to receive at least a portion of the build chamber (14, 14', 114) therein, wherein a seal (38, 138) is disposed around the opening (36, 136) to provide sealing engagement between the opening (36, 136) and the first and second spaced apart side walls (28, 28', 128, 30, 30', 130) of the build chamber (14, 14', 114). a powder dispenser (44, 144) positioned above the build chamber (14, 14', 114); an applicator (42, 142) configured to scrape powder dispensed into the build chamber (14, 14',114); and a directed energy source (46, 146) configured to fuse the scraped powder, wherein the housing (18, 118) includes an opening (36, 136) configured to receive at least a portion of the build chamber (14, 14', 114) therein, wherein a seal (38, 138) is disposed around the opening (36, 136) to provide sealing engagement between the opening (36, 136) and the first and second spaced apart side walls (28, 28', 128, 30, 30', 130) of the build chamber (14, 14', 114).