Split for printing

Cut a part that does not fit the bed into two halves that key back together.

The commonest problem in printing a model you did not design for your own printer is that it does not fit the bed. This cuts it at a plane and puts the two halves back where the part was, with a joint between them.

Both halves stay editable. Each one is the original part intersected with a half-space, so it is still a real solid with its own history — not a flattened mesh. Move them apart, round an edge, export them separately.

The joint is what makes it go back together. *Pins* are round dowels printed onto one half, dropping into sockets in the other: they locate the halves precisely and print with no overhang worth the name. *Keys* are rectangular instead, which is what you want when the halves could otherwise twist about a single pin. *Dowels* put a socket in both halves and print the pin as its own small part — so neither half has anything standing off its cut face, both lie flat on the bed, and when the fit is wrong you reprint a two-gram pin instead of a whole half. *Bolted* drills a clearance hole through the joint and traps a nut inside the far half, and it is the only one that comes apart again. *None* is a plain butt cut for gluing.

Shape and taper tune the key itself. A round key lets the halves spin about it, so a single one needs a partner; a Triangle, Square or Hex key stops rotation on its own. Tapered narrows the key away from the cut — easier to start, and a smaller flat bridge over a blind socket — while Straight is the tightest fit. Whatever you pick, the clearance is applied square to the key’s faces, so a hex fits its socket the same way a round one does.

Clearance is the whole game. A key cut to exactly its socket will not go in — printers are not that accurate. The Fit control is the same one every joint in OwlCAD uses: Tight, Normal or Loose, or Custom to type a number. If you do not know your printer’s number, print the fit test coupon once and you will.

One undo puts it back. The split is a single step, so if the position was wrong, undo and try again — nothing is baked.

1. Select the part in the viewport or the scene tree.
2. Press C, or pick Split for printing from the Modify menu above the model (it is in the right-click menu too).
3. Pick the axis to cut across — Z for something too tall, X or Y for something too long.
4. Set the position — type it, or drag the blue plane in the viewport by the part that sticks out past the model. It opens at the middle of the part, and the read-out shows the range it can sit in.
5. Choose a joint — Pins to locate the halves, Keys to stop them twisting, Dowels to keep both faces flat, Bolted to take it apart again — then Split.