ABS plastic is used in a variety of applications, from an alternative to PVC in tubing to the fairings of motorcycles. Sometimes a piece may crack from impact or other forces. Repairing a crack is a simple process that will result in a strong and durable patch. The piece will need to be repainted once it has been repaired, but using this method of initial repair will prevent having to buy a new piece.
Clean the plastic thoroughly. Sand off any paint that may be present down to the primer using the 200 grit sandpaper.
Secure the piece with clamps in its proper form with the side that will be least visible after the repair facing you. This means that in the case of a panel, the plastic on either side of the crack should be aligned perfectly, and the interior side of the panel should be facing you.
Drag the hot soldering iron along the crack from end to end while following its progress on the other side with a finger. If the plastic in contact with your finger becomes too hot to touch, the soldering iron is too hot and needs to be turned down or the speed of its progress along the crack needs to be increased.
Sand the fused plastic to a rough finish on both sides of the piece with 200 grit sandpaper.
Clean off the sanding residue and fill in the voids in the fused plastic with generous amounts of ABS cement. Repeat this process on both sides. Wait for the cement to dry.
Sand the ABS cement. Begin with 400 grit sandpaper and use progressively finer grits. Finish the cement to a smooth black finish with the 1100 grit wet/dry sandpaper.