Mechanical / physical

The cardboard joints keep falling apart

Slots need a snug cut. Glue needs time. A servo horn screwed into flimsy flute will tear.

The problem

An arm, claw, or bridge collapses at a fold, or the servo horn rips out of the cardboard when it moves.

Horn: The plastic arm that screws onto the servo output. You attach your cardboard lever to the horn, not to the servo body.

1
Cut slots slightly undersized and ease them with the knife. A floppy slot will never clamp. Recut a new piece rather than taping a slot that is already too wide.
2
Use two layers of cardboard at the servo mount, grain crossed. Single-layer mounts tore in QA when the arm picked anything heavier than a ping pong ball.
3
Let glue set before you run the sweep. Hot glue skins over fast but the joint is weak for a few minutes. Driving a servo into wet glue shears the horn.
4
If the package skipped which way the flute should run, run the corrugation along the long beam, like a ruler, not across it.

If you walked the steps and the mechanism still does not move, write to us. This is the fallback, not the first stop.