About this project
A drink coaster with a spirograph pattern inside a round rim - the same curves the classic toy draws with a toothed wheel rolling inside a ring. Change the teeth counts and the pen hole and a new pattern appears; the pattern always fills the coaster and stays joined to the rim. A small loop on top lets it hang on a hook between uses, or as a wall or window decoration. Prints flat in one piece.
How it's built
- Spirograph - a hypotrochoid: a wheel with rolling teeth turns inside a ring with fixed teeth, and a pen at a set fraction of the wheel radius traces the curve until it closes. The pattern has fixed / gcd(fixed, rolling) lobes.
- Scale - the curve is scaled so its outermost point lands just inside the rim, whatever the settings.
- Strokes - the curve is stroked to width and blended with the rim where they meet and where strokes cross.
- Hanging loop - a disc filleted onto the top of the rim, with a hole that always clears the rim. Switch it off for a plain coaster.
- Body - extruded to thickness with rounded edges.
Parameters
| Group | Slider | What it does |
|---|---|---|
| Coaster | Diameter | 50-140 mm |
| Coaster | Thickness, stroke width, blend | Body thickness, line weight, fillets at crossings |
| Spirograph | Fixed teeth, rolling teeth | Pick the pattern; the readout shows the lobe count |
| Spirograph | Pen | Pen hole as a fraction of the wheel radius - above 1 draws loops |
| Hanging loop | On/off, loop radius, hole radius | Size the hole for your hook or cord; the loop always keeps 1.5 mm of material around it |
Printing
Print flat, no supports. PETG or ASA handle hot mugs better than PLA. A stroke half-width of 1.2 mm or more gives sturdy lines; a silk or two-tone filament shows the pattern off.
UpdatedOct 29, 2026
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