Rail bed cleaning machine, comprising - a first excavator device for excavating the ballast of the existing ballast layer, - a second excavator device for excavating an existing formation protection layer underneath the existing ballast layer, - a first FPL processing unit with i. a first screening unit for separating coarse elements and fine elements from the excavated formation protection layer, ii. a crusher for crushing the coarse elements screened out of the excavated formation protection layer into chippings, iii. a coarse element conveyor device for conveying the coarse elements screened out of the excavated formation protection layer from the first screening unit to the crusher, and - a first old FPL conveyor device for conveying the excavated formation protection layer from the second excavator device to the first FPL processing unit, - a second FPL processing unit for processing the excavated formation protection layer, which comprises a mixing device for mixing the excavated formation protection layer with a processing aggregate material, - a fine element conveyor device for conveying fine elements from the first FPL processing unit to the second FPL processing unit, characterised in that the first FPL processing unit further comprises: - a second screening unit for separating coarse elements and fine elements, - a chipping conveyor device for conveying the chippings from the crusher to the second screening unit, and - a return conveyor device for returning the coarse elements screened out in the second screening unit into the crusher. - a first excavator device for excavating the ballast of the existing ballast layer, - a second excavator device for excavating an existing formation protection layer underneath the existing ballast layer, - a first FPL processing unit with i. a first screening unit for separating coarse elements and fine elements from the excavated formation protection layer, ii. a crusher for crushing the coarse elements screened out of the excavated formation protection layer into chippings, iii. a coarse element conveyor device for conveying the coarse elements screened out of the excavated formation protection layer from the first screening unit to the crusher, and i. a first screening unit for separating coarse elements and fine elements from the excavated formation protection layer, ii. a crusher for crushing the coarse elements screened out of the excavated formation protection layer into chippings, iii. a coarse element conveyor device for conveying the coarse elements screened out of the excavated formation protection layer from the first screening unit to the crusher, and - a first old FPL conveyor device for conveying the excavated formation protection layer from the second excavator device to the first FPL processing unit, - a second FPL processing unit for processing the excavated formation protection layer, which comprises a mixing device for mixing the excavated formation protection layer with a processing aggregate material, - a fine element conveyor device for conveying fine elements from the first FPL processing unit to the second FPL processing unit, - a second screening unit for separating coarse elements and fine elements, - a chipping conveyor device for conveying the chippings from the crusher to the second screening unit, and - a return conveyor device for returning the coarse elements screened out in the second screening unit into the crusher.