3D Printable LED Sign File

I have a flat PNG of my design and need it converted into a clean, print-ready 3D model for an illuminated sign. The finished size is roughly 600 mm × 600 mm. PETG will be the printing material, so please keep wall thicknesses, overhangs and tolerances appropriate to that filament.

Sign specifics
• A continuous channel must run along the artwork lines to seat the flexible LED strip and silicone diffuser: 8.2–8.3 mm wide, 5–6 mm deep, with about a 1° outward draft so the diffuser sits snugly but can still be pressed in.
• Add a 10 mm backing border behind the outer perimeter, plus any internal ribs you judge necessary for strength. Inside those ribs create concealed wiring passageways so I can thread power leads through the sign without visible cables.
• Because a single piece that large won’t fit on most beds, break the model into logical, jigsaw-style sections I can print on a 220 × 220 mm plate and friction-fit or glue together afterward. Pegs, tongues or alignment keys are welcome.
• I’d like the visible face to be smooth so post-processing is minimal.

Deliverables
• Native CAD file (Fusion 360, SolidWorks, or similar)
• Assembled STL plus individual STLs for each printable part
• Simple PDF assembly guide showing order of pieces and wire routing

I’ll supply the PNG as soon as we start; you can trace or vectorise it before extruding the neon channel. Looking forward to a sturdy, well-thought-out model I can drop straight into my slicer.