Bellows drain pipe connected to heat shrink sleeve.

Baking: Apply a red flame (or use a dedicated annular baking tool) starting from one end, moving uniformly along the circumference of the heat-shrink tube (it is strictly forbidden to move the flame along the long axis or to let it stay in one place). Once one full circumference has shrunk properly, gradually extend the heating (note: heat uniformly one circumference at a time, rather than moving straight along the axis, otherwise it may cause surface wrinkling or cracking). During the baking process, promptly apply gentle pressure to the already shrunk areas using a smooth roller (a roller or rod matching the shape and size of the corrugation) or while wearing heat-resistant gloves, ensuring it fits snugly against the waveform and removing any residual air (be careful not to scorch the bellows). When the heating shrinkage reaches about 5cm from the end, turn the flame to heat the hot melt adhesive on the inner wall of the heat-shrink tube, then switch to the outer wall. After the heat-shrink tube is fully shrunk, use a low flame to evenly heat the entire area (to fully melt the hot melt adhesive) until the hot melt adhesive begins to seep out from the ends.

It is important to emphasize that the flame heating temperature must be properly controlled: neither too high, which could burn the outer wall of the PE tube and cause the end of the heat-shrink tube to crack, nor too low, which would prevent the hot melt adhesive from fully melting and bonding firmly, failing to meet the required peel strength.