Three nested stages and a cone-tipped core, printed in place. Flip the tower and the stages spiral down their helical grooves; flip it back and they wind home.
Validated: watertight ×4 · zero clash across full travel · straight-pull jam confirmed (the groove constraint is real)
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The one rule:slice the STL exactly as it loads. The nested body positions ARE the assembly — auto-arrange or “split to objects” turns a working toy into four separate cups.
All four bodies — three nested stages and the cone-tipped core — come in ONE file, positioned as the print-in-place assembly. Never auto-arrange, never split to objects.
PLA, 0.2mm layers, 2–3 perimeters, no supports. The 0.8mm radial gaps between stages are tuned so FDM printers bridge nothing and fuse nothing.
Fresh off the bed, twist each stage back and forth a few times to crack any micro-strings in the grooves. If stages bind hard, regenerate with gap at 1.0mm — printer calibration varies.
Hold it upside down and the stages spin down their two-start helical grooves to full extension, then spiral back when flipped again. The grooves end above the base, so nothing falls apart.
The parts are printed already assembled, with engineered air gaps (0.8mm here) between every moving surface. FDM printers can't print into thin air without supports — which is exactly the point: the gaps stay empty, so the parts come off the bed nested and free to move.
Each stage carries two small rider bumps that run in two-start helical grooves cut into the stage around it. Straight pulling jams — the validation scan confirms 189 contact points blocking a straight pull — but rotation follows the helix freely. That constraint is the toy: motion is only available as a spiral.
Equal-taper cones geometrically cannot keep bump-and-groove engagement constant — engagement decays as taper × travel, so coned designs loosen as they extend. Cylindrical mating surfaces keep the engagement identical over the full travel. That's a real kinematics decision baked into the generator, not a style choice.
One parameter: gap. Stuck stages → regenerate at 1.0mm; sloppy stages → 0.6mm. It's the same clearance-calibration idea as every print-in-place model: find your printer's number once and reuse it.
Yes — no login, no watermark. The geometry is generated by a pre-validated parametric script (watertight ×4 bodies, zero rest interpenetration, zero clash across the full helical travel). If you want a different toy entirely, describe it in the PrintMakerAI editor.
Gear trains, hinges, latches, articulated figures — the PrintMakerAI editor designs working mechanisms from a plain-English description, with the same print-in-place clearance thinking this toy uses.
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