Method for welding a first profile bar made of plastic with a second profiled bar made of plastic, the method comprising the following steps: ▪ Provide the first profile bar and the second profile bar; Machining of at least one profiled bar (1, 2), in particular in its mitre region (11, 21), with a parting-off knife, wherein the profiled edge (19, 29), which delimits the outer side of the profile, in particular the upper side (13, 23), lower side (14, 24), the inner fold or the outer corner, and the mitre surface of the profiled bar (1, 2), is machined by the parting-off knife, wherein a knife holder (6, 6a, 6b) is provided, which receives the parting-off knife is machined by the parting-off blade, wherein a blade holder (6, 6a, 6b) is provided which receives the parting-off blade, wherein a holder is provided which carries the parting-off blade, wherein the blade holder (6, 6a, 6b) is movably mounted on the holder and can be brought into at least two different positions by a drive; ▪ Heating of the profiled bars (1, 2) at least on their mitre surfaces, wherein the profiled bar (1, 2) is additionally machined by a milling cutter (5, 5a, 5b) before heating and the chips produced by the cutting-off blade or milling cutter (5, 5a, 5b) are extracted; ▪ Bringing together the mitre surface of the first profiled bar with the mitre surface of the second profiled bar in such a way that the heated areas of the mitre surfaces produce a material-locking connection between the first and second profiled bars (1, 2). with a second profiled bar made of plastic, the method comprising the following steps: ▪ Provide the first profile bar and the second profile bar; Machining of at least one profiled bar (1, 2), in particular in its mitre region (11, 21), with a parting-off knife, wherein the profiled edge (19, 29), which delimits the outer side of the profile, in particular the upper side (13, 23), lower side (14, 24), the inner fold or the outer corner, and the mitre surface of the profiled bar (1, 2), is machined by the parting-off knife, wherein a knife holder (6, 6a, 6b) is provided, which receives the parting-off knife is machined by the parting-off blade, wherein a blade holder (6, 6a, 6b) is provided which receives the parting-off blade, wherein a holder is provided which carries the parting-off blade, wherein the blade holder (6, 6a, 6b) is movably mounted on the holder and can be brought into at least two different positions by a drive; ▪ Heating of the profiled bars (1, 2) at least on their mitre surfaces, wherein the profiled bar (1, 2) is additionally machined by a milling cutter (5, 5a, 5b) before heating and the chips produced by the cutting-off blade or milling cutter (5, 5a, 5b) are extracted; ▪ Bringing together the mitre surface of the first profiled bar with the mitre surface of the second profiled bar in such a way that the heated areas of the mitre surfaces produce a material-locking connection between the first and second profiled bars (1, 2). ▪ Provide the first profile bar and the second profile bar; Machining of at least one profiled bar (1, 2), in particular in its mitre region (11, 21), with a parting-off knife, wherein the profiled edge (19, 29), which delimits the outer side of the profile, in particular the upper side (13, 23), lower side (14, 24), the inner fold or the outer corner, and the mitre surface of the profiled bar (1, 2), is machined by the parting-off knife, wherein a knife holder (6, 6a, 6b) is provided, which receives the parting-off knife is machined by the parting-off blade, wherein a blade holder (6, 6a, 6b) is provided which receives the parting-off blade, wherein a holder is provided which carries the parting-off blade, wherein the blade holder (6, 6a, 6b) is movably mounted on the holder and can be brought into at least two different positions by a drive; ▪ Heating of the profiled bars (1, 2) at least on their mitre surfaces, wherein the profiled bar (1, 2) is additionally machined by a milling cutter (5, 5a, 5b) before heating and the chips produced by the cutting-off blade or milling cutter (5, 5a, 5b) are extracted; ▪ Bringing together the mitre surface of the first profiled bar with the mitre surface of the second profiled bar in such a way that the heated areas of the mitre surfaces produce a material-locking connection between the first and second profiled bars (1, 2).