Repair guide
How to bond a resin 3D-printed part to a steel bracket
Two-part epoxy handles both halves well, but the print must be fully washed and post-cured first and the steel abraded to bright metal, or the joint fails at one surface or the other.
The short answer
Wash and post-cure the print, abrade the steel to bright metal, key the print with 180 grit, and bond with a two-part epoxy. The two failure modes are opposite: on the print side, leftover uncured resin acts as a release agent; on the steel side, the epoxy bonds to mill scale or oil rather than metal. Fix both and this is a strong, rigid joint.
- Difficulty
- Moderate
- Time needed
- 30 minutes work, 24 hours cure
- What you need
- Two-part epoxy, isopropyl alcohol, soft brush, UV cure lamp, 80 and 180 grit abrasive, clamps, gloves
A resin print is not ready to bond straight off the build plate. The surface carries a film of unpolymerised resin that a quick rinse does not remove, and anything glued to that film is attached to a layer that has almost no strength of its own. A proper isopropyl wash with a soft brush, a second wash in clean alcohol, and a full UV post-cure is the difference between a joint that holds and one that pops off in your hand.
Mild steel has the mirror-image problem. Straight from a supplier it carries mill scale and oil; from a workshop drawer it carries a light oxide film. Both are loosely attached to the metal underneath, so an epoxy bonded to them peels away carrying the layer with it. Abrade with 80 grit to bright metal, degrease, and bond the same day.
Think about the direction of the load too. Both materials are rigid, so the joint has no give at all, and a rigid joint is strong in shear and weak in peel. Increase the overlap rather than the glue thickness, and if the print has a flange or a boss, use it: a peg into a drilled hole in the print multiplies the strength far more than any adhesive choice.
Step by step
- Wash the print in isopropyl alcohol with a soft brush, then rinse in clean alcohol.
- Post-cure the print fully under UV. A tacky surface is not ready.
- Abrade the steel bonding face with 80 grit until it is bright, then degrease with isopropyl alcohol.
- Abrade the print's bonding face with 180 grit and wipe the dust off.
- Dry fit and check the faces meet across their whole area. Pack or sand until they do.
- Mix two-part epoxy to the ratio on the pack and spread a thin layer on both faces.
- Bring them together, slide slightly to expel air, and clamp lightly.
- Leave the clamp on for 24 hours, then a further day before full load.
What to avoid
Do not bond a print that is still slightly tacky. Uncured resin is a release agent.
Do not bond over paint, primer or rust on the steel. The joint is only as good as the layer underneath.
Do not design the joint so the load peels it. Rigid adhesive joints do not tolerate peel.
Uncured resin is an irritant and a sensitiser, so wear gloves when washing prints. Freshly abraded mild steel flash rusts within hours in a damp room, so prepare and bond in one session. Cured resin is brittle: if the bracket carries anything that could injure someone, do not rely on a printed part.
The full bonding guide
Everything about gluing Resin 3D print to Mild steel
Last reviewed 13 September 2026.