Page 1245 - Foton Workshop Manual - Auman EST-M

Body - Body assembly BW - 7

Repair of plastic parts IN

1. Correction of thermoplastic parts (slight elastic deformation)
a. The elastic position of bumper is usually deformed, showing depressions and bends. Most deformations in DI
the elastic area can be repaired by heating with a heat gun. The damaged area can be heated evenly to about
200 ℃ with a hot air gun. If possible, Its inside and outside should be heated at the same time.
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b. In addition, the damaged area can be corrected with wooden hammer, plastic wedge and other mechanical
tools.
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2. Welding of thermoplastic parts
Caution
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The welding is the most effective method to repair thermoplastic parts, such as, angular section, square
section, narrow circular sections in the reinforcement area.
a. Cut the cracking area into a V-shaped section for welding preparation. FR

● Cut a V-shaped weld with a scraper, with a weld opening angle of 60° ~ 70°.
● Use a 3mm drilling bit at the end of crack to prevent the extension of crack. If the weld edge is not smooth, ST
fix the cracking initiation position with a clamp and then drill the hole at the crack end before welding.
b. Determine the welding temperature based on the welding temperature (200℃ ~ 700℃) specified by the
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manufacture, and the thickness of the plastic materials and welding rod.
● Preheat the welding equipment for 3 ~ 4min, to allow it to reach the preselected welding temperature.
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● Cut the front end of the welding rod into a bevel, for gradual filling from the beginning of the crack weld.
c. Welding.
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● Push the front beveled welding rod into the heated quick welding nozzle preheat chamber until the tip of
the welding rod is exposed from the lower part.

When the welding rod and parts to be welded are in plastic status, start the welding operation. During
the welding of plastic parts, ensure a stable welding speed and stable operating pressure; during welding
pressure, only apply a pressure onto the welding rod.

● The lower end of the quick welding nozzle must be moved parallel to the repair surface. The parallel
movement in the greater length is achieved by appropriate tilting of the welding equipment.
● While moving the plastic welding gun, keep the welding rod perpendicular to the weld.
d. Inspect the welded joints.
● When welding, only a small or smooth protrution formed along the weld edge indicates a good weld
effect, which is critical for beveled weld welding. Inspect the weld for any of the following defects from the
back; re-weld it if necessary.
e. Rework the weld.
● After cooling, the protrution part of the weld can be ground with an angle grinding machine and P80 coarse
sandpaper, and then ground with the the track grinding machine and P120 ~ P220 fine sandpaper.
● Clean the repair surface with a plastic cleaning brush.
● Apply the plastic primer on the repair surface.
3. Plastic bonding

Caution
It applies to thermoplastic and thermoset parts, all thermoplastic parts must be bonded with
polyurethane-based adhesives. A reinforced belt can be used on weld and broken cracks to ensure the
initial ductility.

BW-007