The Adhesive Library

Repair guide

How to repair a cracked ABS plastic housing

ABS welds to itself with solvent cement, which softens both faces and fuses them into one piece. Done properly the repair is as strong as the original plastic, which no surface adhesive can match.

The short answer

Use ABS solvent cement, not superglue. Solvent cement dissolves the surface of both sides of the crack and lets the plastic re-fuse, so the joint becomes part of the moulding rather than a layer stuck on top. Open the crack slightly, run the cement into it, press the halves together and hold for two minutes. On a crack in a visible or stressed panel, reinforce the inside face with a patch of scrap ABS bedded in the same cement.

Difficulty
Difficult
Time needed
20 minutes work, 24 hours before load
What you need
ABS solvent cement with brush applicator, isopropyl alcohol, 180 grit abrasive paper, a scrap of ABS sheet for a patch, masking tape or a clamp, gloves

A cracked housing almost always fails again at the same line, because the crack is where the moulding is thinnest or where a fixing boss concentrates the load. A surface adhesive bridges the gap but leaves the weak section weak. Solvent cement is different: it is not a glue at all, it is a solvent that turns the top fraction of a millimetre of each face back into soft ABS. Clamp them together and the two faces become one.

That is also why preparation matters more than product choice. The solvent has to reach clean plastic. Grease, silicone polish and release agent all stop it working, and mould release is still present on a lot of injection-moulded housings years later.

If the part carries load, add material. A strip of scrap ABS bonded across the back of the crack roughly triples the section at the weakest point, and costs nothing.

Step by step

  1. Work somewhere ventilated. ABS solvent cement gives off strong fumes and should not be used in a closed room.
  2. Clean both sides of the crack with isopropyl alcohol and let it flash off. Do not use household sprays, they leave silicone behind.
  3. Key the inside face either side of the crack with 180 grit abrasive, about 15mm each side, then wipe the dust away.
  4. Flex the housing gently to open the crack a fraction and run solvent cement into it with the applicator brush.
  5. Release the flex so the crack closes, press the faces together and hold for two minutes without moving them.
  6. For a load-bearing crack, cut a patch of scrap ABS to cover the crack plus 20mm each side, brush cement on both patch and housing, and press it onto the inside face.
  7. Leave the repair 24 hours before putting any load on it. The solvent has to leave the joint before it reaches full strength.

What to avoid

Do not use cyanoacrylate. It grabs in seconds and feels like a repair, but it sits on the surface as a hard brittle film and the housing cracks straight through it the next time the panel flexes.

Do not fill the crack with cement and leave a bead standing proud. Excess solvent stays trapped, keeps softening the plastic and leaves a permanently weak, slightly sunken line.

Do not test it early. A solvent weld feels solid long before it is strong.

ABS solvent cement is flammable and the vapour is harmful to breathe. Use it outdoors or with a window open and a fan, keep it away from any flame, and wear nitrile gloves. Check the plastic really is ABS before you start. Solvent cement will craze polycarbonate and will not touch polypropylene or polyethylene at all.

The full bonding guide

Everything about gluing ABS to ABS

Last reviewed 13 September 2026.