Drying system groups feature a dust-free PTC heating system for stable temperature control and a contamination-free interior drying process. This ensures an excellent drying effect and high production efficiency. groups of drying systems feature a PTC heating mode, offering an outstanding drying effect, high production efficiency, and no contamination. A positioning device is equipped between the heating rod and tubes to prevent the heating rod from damaging the tubes. The drying system can be switched on or off according to production requirements.