Halloween Graveyard Automaton - Skeleton Hand Rises From Coffin

Old Ezra Thorne was buried in 1831, and his headstone says it plainly: STILL HERE. This is a little graveyard automaton for your desk or mantel. Turn the bone crank on the side and the coffin lid slowly creaks open while a skeletal hand rises out and claws at the air. At the end of each turn the lid suddenly slams shut with a satisfying clack, and the cycle starts again.

The scene: an old stone retaining wall holds up a lumpy mound of fresh grave soil full of clods, pebbles, exposed roots and tufts of grass. A six-sided coffin is half buried in the mound at a slight angle, with a raised gothic cross, iron nail heads and wood grain on its lid. Behind it leans a cracked gothic headstone with a pointed arch, a deep crack, an engraved R.I.P., name, dates and epitaph. A bare dead tree, a crooked wooden grave marker and a carved crank stone with an engraved turning arrow complete the story.

HOW IT WORKS

A horizontal shaft runs through the base and carries a snail (drop) cam. Over one turn the cam lifts a knife-edge follower slowly by 11 mm, then the follower falls off the cam step. The follower is the bottom of a vertical slider that runs in a guide channel. On top of the slider sit the skeletal hand (fingers 2 mm thick or more) and a bone-shaped pusher. The pusher lifts the coffin lid, which is hinged at the foot end on a print-in-place pin hinge, to about 24 degrees, so the hand rises up to 11 mm out of the coffin. When the cam drops, gravity brings the slider and the lid down together and the lid hits the coffin rim with a clack.

Operate it by turning the crank CLOCKWISE when you look at the crank side (the arrow on the crank stone shows the direction). A snail cam only works one way; turning backwards pushes the follower against the drop step.

FILES (2)

Unburied_PrintInPlace.step - print-in-place: graveyard frame (base, wall, mound, coffin, headstone, tree, hinge pin), cam shaft, hand slider and coffin lid, four separate bodies already in printing position with clearances.

Unburied_CrankHandle.step - the bone crank with a tiny skull knob and a D-shaped press-fit peg.

PRINTER AND SETTINGS

Bed size: the main part is 111 x 80 x 108 mm (fits any 180 x 180 x 180 printer and most smaller ones). The crank is 26 x 13 x 37 mm.

Nozzle 0.4 mm, layer height 0.2 mm, 3 walls, 4 top and 4 bottom layers, 15 percent infill (gyroid or grid), supports OFF, no brim needed (use a brim only if your bed adhesion is weak). Material PLA (PETG also works). Print speed: normal; slow the outer walls down if your printer rings on tall parts.

Estimated print time and filament (typical 0.4 mm printer at standard speed, faster on CoreXY machines): main part about 12 hours and 150 g, crank about 20 minutes and 3 g.

PRINT ORIENTATION

Both files are already oriented. Keep them exactly as they import: the graveyard upright with the coffin lid printed open at 50 degrees (it falls closed after printing), and the crank standing on its skull with the peg pointing up.

COLORS

One color is enough: the deep textures, lettering and reliefs read well in a single grey, stone or bone color. For the full look, paint or use a multi-color printer: earth brown soil, grey stone for the wall, headstone and crank stone, dark wood for the coffin and lid, bone white for the hand and crank, moss green for the grass. No filament swaps by layer height are needed.

AFTER PRINTING (FREEING THE PARTS)

1. Gently rotate the lid down until it rests on the coffin, then lift it a few times so the hinge moves freely.

2. Push the hand up and down a few times with a fingertip so the slider breaks free in its channel.

3. Fit the crank (see below) and turn it clockwise slowly for the first few turns. A little resistance at first is normal; it frees itself after a few turns.

ASSEMBLY (ONE STEP)

Press the crank's D-shaped peg into the D-shaped socket in the end of the shaft on the crank stone, flat side to flat side, until the hub touches the shaft end. The three small crush ribs hold it firmly. Add a tiny drop of glue only if your printer prints holes oversize.

TIPS AND TROUBLESHOOTING

- If the hand does not fall back down, check that nothing (a string or a blob) sits in the slot under the coffin floor; a thin blade or a fingernail clears it.

- If the crank feels stiff, turn it back and forth a quarter turn a few times, then continue clockwise. Never force it counterclockwise.

- If the crank is loose on the shaft, add a strip of tape around the peg or a drop of glue.

- The lid slam is driven by gravity, so keep the model on a level surface.

CHANGES FROM THE ORIGINAL BRIEF (FOR PRINTABILITY)

- The shaft end is a D-shaped socket and the crank carries the D-shaped peg. A D-shaft sticking out sideways would be an unsupported horizontal stub, so the male and female parts were swapped. It still press-fits and works the same way.

- The coffin lid is printed standing open at 50 degrees so that its underside and relief print cleanly without supports; it simply falls closed after printing.

- The coffin is rotated 8 degrees in the scene instead of tilted, so the vertical slider stays perfectly vertical.

- The cam lift is 11 mm (the base would have to be much taller for more). The bone pusher opens the lid wider than the hand rises, so the hand clearly emerges.

- The earth mound sits on a stone retaining wall: it gives a flat, stable, support-free base and a place for the crank stone. The optional crow and lantern were left out; a dead tree and a wooden grave marker were added instead.