Abstract: A system is provided for filling and sealing bags and is especially useful with woven polybags formed of thermoplastic material. The system includes a plastic welder having a folding device for folding over a portion of the filled bag which is sealed by a welding tip and pinch rollers. The welding tip may be moved between welding and non-welding positions based on a bag sensor or timer. A contact prevention member prevents the welding tip from contacting and damaging a coating on a portion of the bag. The system is configured to form a substantial seam without using hot melt adhesive.