Welding machine for continuous welding of two layers of plastic film material (2', 2") together in a welding pattern, the machine comprising a welding drum which is arranged to be rotated around its axis, welding means arranged on the peripheral surface of the welding drum and exhibiting the welding pattern, heating arrangement arranged to heat the welding means to a welding temperature, an endless welding band, a set of band guidance rollers (20, 21, 22, 23) comprising a first application roller and a second application roller arranged to apply the welding band to the welding means on the surface of the welding drum over a peripheral extend of at least 90°, preferably at least 180° of the welding drum with a force radial to the welding drum in a first operational mode of the welding machine, the set of band guidance rollers comprising at least one displaceable tensioning roller for maintaining a tension of the welding band, a web guidance arrangement (30, 31) for guiding the two layers of plastic film material (2', 2") in between the welding drum and the welding band, and control means for controlling the operation of the welding machine, characterized in that the machine comprises one or more separation rollers (41, 42), and is arranged in a second operational mode of the welding machine to displace the one or more separation rollers (41, 42) by means of separation roller displacement means controlled by the control means, from a first position thereof and in between the welding means on the peripheral surface of the welding drum and the two layers of plastic film material (2', 2") to a second position of the one or more separation rollers (41, 42) where the two layers of plastic film material (2', 2") and the welding band are separated from the periphery of the welding drum by means of the separation rollers (41, 42). a welding drum which is arranged to be rotated around its axis, welding means arranged on the peripheral surface of the welding drum and exhibiting the welding pattern, heating arrangement arranged to heat the welding means to a welding temperature, an endless welding band, a set of band guidance rollers (20, 21, 22, 23) comprising a first application roller and a second application roller arranged to apply the welding band to the welding means on the surface of the welding drum over a peripheral extend of at least 90°, preferably at least 180° of the welding drum with a force radial to the welding drum in a first operational mode of the welding machine, the set of band guidance rollers comprising at least one displaceable tensioning roller for maintaining a tension of the welding band, a web guidance arrangement (30, 31) for guiding the two layers of plastic film material (2', 2") in between the welding drum and the welding band, and control means for controlling the operation of the welding machine, characterized in that the machine comprises one or more separation rollers (41, 42), and is arranged in a second operational mode of the welding machine to displace the one or more separation rollers (41, 42) by means of separation roller displacement means controlled by the control means, from a first position thereof and in between the welding means on the peripheral surface of the welding drum and the two layers of plastic film material (2', 2") to a second position of the one or more separation rollers (41, 42) where the two layers of plastic film material (2', 2") and the welding band are separated from the periphery of the welding drum by means of the separation rollers (41, 42).