Every printer has a limit and every good map idea is bigger than it. A 150 mm plate is a nice object; a 600 mm wall map of your county is a different thing entirely, and it is nine tiles, not one impossible print.
Two ways to split
By grid. "Three columns by two rows." Use this when you already know the arrangement you want on the wall — a 3×2 panel above a desk, say.
By tile size. "No piece bigger than 200 mm." Use this when you know your bed and want the software to work out the grid. This is usually the right one: set your printer from the list and every piece comes out inside the build volume without you doing arithmetic.
The second also survives you changing your mind about the overall size. Double the map width and you get more tiles rather than tiles that no longer fit.
Print one tile first
The most useful advice here, and the most ignored. A twelve-tile map is thirty hours of printing. Print one corner tile, look at it properly, and then commit.
What you are checking: whether the relief reads at that scale, whether the contour lines are thick enough, whether the colour changes land where you expected, and whether the tile actually fits your bed with a brim on. All four are cheap to fix on tile one and expensive on tile twelve.
Add a frame
A raised border around each tile does three jobs at once. It hides the seam where pieces meet, so small gaps stop being obvious. It gives each piece a defined edge instead of a ragged cliff of terrain. And it makes the finished wall look deliberate rather than broken.
Without a frame, a multi-tile map reads as one map that cracked. With a frame, it reads as a set of panels. The second is what you want.
Three things that save grief
- Number the undersides. Scratch or emboss a row and column on each tile as it comes off the bed. Twelve grey terrain tiles look identical in a box, and working out which corner is which from the contours is genuinely difficult.
- Print the edge tiles last. By then you have your settings right, and the edges are what people look at.
- Keep one filament batch. Grey PLA from two different spools is two different greys, and on a wall that shows. Buy enough at the start.
Mounting them
Do not glue tiles to each other. Thermal movement is real on a large panel, and a rigid glued grid will bow. Mount each tile to the wall or backing board individually with a small gap — a millimetre is plenty — and the frame edges will read as a deliberate grid.
For a backing board, 6 mm ply or MDF cut to the full map size works well, with tiles on double-sided foam tape. The foam absorbs the movement.
How big is too big
There is a real ceiling, and it is not the tile count. It is the area, because map data for a large region takes a long time to fetch and a lot of memory to mesh.
A practical guide: terrain and contour lines scale to very large areas without trouble. Buildings, roads and land cover do not — past roughly 100 km² you should be switching those off and letting the shape of the land carry the model. A county-sized wall map of terrain with contours is straightforward. The same county with every building on it is not a sensible request of anyone's browser.
Doing it
In the map maker, the Print tab has both splitting modes and a list of common printers — A1 mini, P1S and X1C, H2D, MK4, Prusa Mini, Ender 3, K1 Max and the Saturn. Pick yours, choose a total map width, and it shows you the grid and the size of each piece before you export anything.
Export once and you get every tile as a separate part, named by its position.