4.3 What the checks missed

AI workstation · 11 Oct 2026

The joints were never designed

The renders of B2 showed z-fighting where the parts met: two surfaces flickering in the same place. That was the clue. The check script fused the parts into one solid before it tested them, and the parts overlapped. The tray sat 6 mm inside the band. The band's round end was buried 4 mm in the VESA plate.

In a fused solid, an overlap looks exactly like a joint. So the checks proved that the parts fit in space, not that anyone could screw them together. Nobody had chosen a screw, a hole or a lap.

Lesson: a fused check solid shows fit, not assembly. Design every joint before trusting a split.

Second opinions

I wrote a dense technical brief of B2 and gave it to two other models for review. I treated their answers as reviews, not as authority. They agreed on two points:

1. Print B2 as one piece on its side. A side print repeats the profile in every layer. A tray or pad as wide as the band is then a T-junction inside every layer, as strong as the plastic, with no joint at all. A narrower feature starts above the bed and overhangs.
2. Stiffness and creep, not strength, are the risk. The stresses are tiny. The problem is the lever.

The creep problem

PLA creeps under a constant load at room temperature. B2 holds the screen on a curve that reaches round the PC, so the screen's weight acts on a long lever of thin plastic all day, every day.

I integrated the bending along the band's centreline (solid section, $E$ = 3.3 GPa):

$$\theta = \int \frac{M}{EI} \, \mathrm{d}s$$

Those are short-term values for a solid section. A print with 2 walls is softer (two 0.42 mm walls on each face give about half the solid stiffness of an 8 mm band), and creep multiplies the lean change over months. The screen would slowly nod forward.

The fix is not a thicker band. It is a different layout that puts the support under the load. That became stand v2.