For the most part, successful gluing requires both mating surfaces to be flat and clean—free of grease, dust, and dirt. It helps to think of glue as creating a very thin film that bonds the two parts together; it is not meant to fill gaps or compensate for a poor fit.
Laser char itself is not the main issue. The bigger problem is that laser cutting often leaves a slightly zigzag edge, making the surface uneven. In addition, the laser beam cuts at a slight angle, so when parts are glued together, this can leave small gaps between the parts and weaken the joint.
Because of this, surface preparation is key. Light sanding or scraping of laser-cut edges greatly improves contact and joint strength.
Here are my Glue recommendations
- PVA / wood glue should be the primary adhesive for structural joints. It provides working time, allows minor adjustment, and forms a strong bond when surfaces fit properly.
- CA (cyanoacrylate) works best as a positioning or tacking aid to hold parts in place while the PVA cures. Used sparingly, it can be very effective, but it should not be relied upon to compensate for poor fit or gaps.
- Thick or gel CA can be useful in non-structural areas, but excessive use often leads to brittle joints and alignment issues.
In short, good fit first, glue second. The better the surface contact, the stronger and more reliable the joint, regardless of the adhesive used. Always use adhesives designated for the given jobs!
