Splitting Large Terrain Prints

Split on a grid with vertical cuts

Most models are split where a seam can hide in a crease. Terrain has no natural crease that runs straight, and a map is read as a whole, so the usual approach is a regular grid: every tile a rectangle, every cut vertical, every tile sharing the same flat bottom height. Tiles made this way sit flat on the bed, butt together side to side, and can be reprinted one at a time if one fails.

For the general method, connectors and tolerances on any model, see splitting oversized models and large prints and multi-part assemblies. This lesson covers what is different for terrain.

How many tiles

"Usable tile width" is less than the bed size. Leave room for a brim on FDM, for the slicer's margins, and for any parts of the bed your printer does not print well. Measure it If one area of your bed gives poor first layers, size tiles to stay out of it.

Split the grid evenly rather than filling the bed and leaving a thin sliver at one edge. A narrow strip of terrain is fragile and warps differently from its neighbors.

Where to put the cut lines

• Avoid cutting along a valley floor or river. That is where the base is thinnest, so the edge of the tile would be thin and weak. Shift the grid a little so cuts cross valleys rather than run down them.
• Avoid cutting through a summit or a feature people will look at closely. A seam across a peak is hard to hide.
• Cut through the whole model, base included. Each tile is then a complete solid with its own walls and bottom.
• Keep frames and text out of the tile cuts. Add a frame or lettering as separate parts, or after splitting, so every tile keeps the same base thickness and bottom height.
• Consider a crease where the map has one. Formlabs notes that cuts following creases in a model can hide seams. A straight grid is easier to plan and reprint; a cut along a sharp ridge or cliff line can be less visible. Choose per map.

Cutting in the slicer

You can split in the terrain or modeling software, or in a slicer. PrusaSlicer's cut tool, as Prusa documents it, cuts along a plane you place and can set by exact position, and offers a dovetail mode that makes a trapezoidal pin and tail on the cut face. It can add connectors:

• Plug: adds a plug to one side and subtracts the matching space from the other.
• Dowel: subtracts a hole from both sides and generates a separate pin to print.
• Snap: adds a snap-fit connector on one side and the space for it on the other.

When cutting into parts it can also place each part cut side down on the bed. For terrain tiles you usually want the opposite: keep every tile base down, so the cut faces become the vertical sides. Check each tile's orientation in the slicer after cutting.

Registration: pins, dowels or plain butt joints

Formlabs lists the options for aligning split parts (slots, pins, grooves, recesses, lips, dovetails and crease-following cuts) and gives two warnings that apply directly to terrain:

• Use aligners only if your printer makes dimensionally accurate parts; aligners that come out even slightly off may not line up.
• Straight cuts without aligners take longer to position during assembly but are more forgiving when prints come out slightly warped.

For terrain, dowels in the base below the landscape surface keep tiles level with each other without showing on top. Plain butt joints glued to a flat backing board are the forgiving choice if your tiles are not perfectly flat. Measure it Fit is printer- and material-specific: print two test edges with your connector before printing every tile.

Labeling and consistency

• Label every tile. Formlabs recommends a unique identifier for each part. For a grid, use row and column (A1, A2, B1...). Put the label on the bottom face, or in the file name if the bottom must stay clean.
• Use the same settings for every tile: layer height, top layers, material and color from the same batch where you can. Changing settings partway through a set shows as a change in surface texture at the seams.
• Print one tile first. Check flatness, edge quality and base thickness, and fix the profile before committing to the rest.

Assembly, gluing and hiding the seams are covered in assembling and finishing terrain models.