Phone

A calculator-shaped phone case styled after the TI-30Xa, with the top shell hinged along the right long edge so it folds open like a book and lies back behind the bottom shell, exposing the whole phone. Lay the phone screen-up in the bottom shell, close the top, and it clicks shut on the other three sides; the screen sits behind an oversized 66 × 42 mm window where the LCD would be. The keypad is 40 recessed divots in a 5 × 8 grid, with the buttons printed as a separate set 0.5 mm smaller on each side so they drop in and sit slightly proud. A camera opening sits in the back of the bottom shell, "TI-30Xa SOLAR" is engraved above the window, and a separate hinge pin runs the full length of the hinge. It prints as four separate parts: bottom shell, top shell, buttons and hinge pin.

Remix hooks

• Shells: each about 96 × 176 mm on the plate; the top shell is 11.5 mm thick and the bottom shell 10.5 mm. The 176 mm length is the real constraint — shorten it and the 5 × 8 button grid has to lose rows, and the hinge spacing follows the same length.
• Hinge: a full-length piano hinge set into a notch along the right edge, so nothing protrudes past the outline. Five knuckles about 7 mm across, three on one half and two on the other, with 0.5 mm gaps and round clearance cutouts where the opposite knuckles pass. The body is a little wider overall to swallow it. This is the part worth redesigning first: move the notch to the left edge for a left-handed fold, or lengthen the knuckles for more stiffness.
• Hinge pin: 3 mm thick with a 5.5 mm head, 174.5 mm long, running in 3.5 mm holes and stopped by a closed end so it cannot slide through. Print it lying flat. A 3 mm metal rod is a direct drop-in substitute if you want it tougher.
• Phone cavity: 80 × 165 mm and 10 mm deep, closed at both ends when shut. That clears an iPhone 17 (about 71.5 mm wide) and the Pro Max sizes (about 77.6 mm). This is the first number to touch for fit; narrowing toward 76 mm tightens things up for standard phones, and going past about 82 mm starts to thin the side walls.
• Screen window: 66 × 42 mm, deliberately oversized so the cutout does not fight the phone's own bezels. Shrink it to hide more of the display, grow it for more live screen.
• Camera opening: 48 × 42 mm in the back of the bottom shell, sized around a large camera bump — a smaller phone just gets extra opening, so this is a safe one to trim down to your own lens.
• Button divots: 12.5 × 9.5 mm, 1.2 mm deep, in a 5 × 8 grid; the separate button set lays out on a 73.5 × 99.5 mm plate at 11.5 × 8.5 mm each — 0.5 mm clearance per side — so they drop in without binding and sit slightly proud. Deepen the divots to 1.6 mm if you want them flush.

Obvious directions to take it: swap the uniform 5 × 8 grid for a true TI-30Xa layout, engrave the legends onto the buttons instead of leaving them blank, add a raised lip around the rear camera opening, add a lanyard loop, or print the shells in contrasting colours. The snap closure is the easiest thing to tune — deepen or shave the rim bumps if the lid is too tight or too loose. It pairs well with a second-colour button set and with any phone that fits the slot dimensions above.