A code bigger than your print bed

By Tiehl Roberto Matías · 7 min read · Updated 27 October 2026

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A sign with the wifi code on the wall of a bar, the menu one on the door, the website one in the shop window. As soon as the piece passes twenty centimetres it stops fitting on the bed, and the usual answer is to break it into chunks. Before that, two sums are worth doing: one says you probably do not need to, and the other, if you do, says where you cannot cut.

First: does it really not fit?

This table uses a short link — this site's, 22 characters, which gives a code of 29 × 29 modules — at correction level H and with the four-module quiet zone. It takes a centimetre of margin off each edge of the bed, which is the prudent thing to do.

Printer	Bed	Code side	Module	Reads up to
Ender 3, Prusa Mini	180 mm	160 mm	4.32 mm	1.3 m
Prusa MK4, Bambu A1	250 mm	230 mm	6.22 mm	1.8 m
Bambu P1S and X1C	256 mm	236 mm	6.38 mm	1.8 m
300 mm bed	300 mm	280 mm	7.57 mm	2.2 m
350 mm bed	350 mm	330 mm	8.92 mm	2.6 m

The last column comes from the signage rule already used in the size guide: a code reads comfortably up to a distance of about ten times its side.

And if your link is longer than the example, the code will have more modules and each one will come out smaller. Before making the piece bigger, look at how much you can shorten the link: the calculator tells you how many characters you have spare before the next version jump, and the link guide explains how to set up a short redirect.

The cheap way out: move it further away

The ten-times rule can be read backwards, and then it turns into the cheapest solution of them all: if the code cannot grow, move it away.

A 230 mm code hung two metres up scans from below without trouble, because whoever is looking at it is that far away anyway. The typical mistake is putting it at eye level, where people come within half a metre and the code turns out to be enormous for what is needed.

Put another way: before multiplying the plastic by four, try raising the piece half a metre.

What error correction forgives and what it does not

If it does have to be split, the first question is what the joint line does to a code. And the answer has two very different halves.

The line itself is not the problem. A straight cut across this code touches 29 modules out of the 841 it has: 3.4 %. Level H tolerates up to 30 % damage, so a joint, even showing slightly, is absorbed without blinking. This is exactly what error correction exists for.

The problem is the three corner squares. Those carry no data: they are the finder patterns, and the reader uses them to locate the code in the image, work out how it is rotated and deduce where each module falls. It does that work before reading a single bit, so error correction does not protect them. A cut going through one of them is not recovered: the reader never even gets as far as trying.

From that comes the only rule that matters when splitting a code.

Where it can be cut

The strip at the top marks, edge by edge, where you can cut. For this code, 37 modules a side counting the quiet zone, the squares occupy columns 4 to 10 and 26 to 32, which leaves three free stretches:

• Edges 1 to 4 and 33 to 36: inside the quiet zone. Useful for trimming margins, not for splitting the code.
• Edges 11 to 26: sixteen positions in the middle. This is the useful stretch, the one that lets you split the piece into two similar halves.

Two more things, both following from the same fact:

• Cut at the edge of a module, not through the middle. Not because the code would stop reading — we have already seen it absorbs that — but because a module split into two halves with a groove down the middle looks bad and gets dirty when glued.
• A horizontal cut has exactly the same positions as a vertical one. The code is symmetrical in that respect: there are squares top left, top right and bottom left.

How many pieces each sign comes out in

With a 250 mm bed, that is 230 usable:

Sign	Module	Pieces	Columns	Cuts
300 mm	8.1 mm	2 × 2 = 4	19 + 18 modules	edge 19
400 mm	10.8 mm	2 × 2 = 4	19 + 18 modules	edge 19
500 mm	13.5 mm	3 × 3 = 9	13 + 12 + 12	edges 13 and 25
600 mm	16.2 mm	3 × 3 = 9	13 + 12 + 12	edges 13 and 25

All four splits fall inside the safe stretch, so they work out on their own. Notice there is nothing exotic to look for: splitting down the middle works, and splitting into thirds works too.

The one-metre sign

Here things change, and this is the case that justifies the whole guide.

A 1000 mm sign with this code gives 27 mm modules, so eight modules per piece fit on a 250 mm bed. Eight by five is forty, and the code is 37 across: it looks as though five columns and that is that. The even split would be 8 + 8 + 7 + 7 + 7, with the cuts at edges 8, 16, 23 and 30.

The way out is to give up on equal pieces and use six columns, with unequal widths chosen so that every cut lands in free ground:

4 + 7 + 6 + 8 + 8 + 4 modules, with the cuts at edges 4, 11, 17, 25 and 33

That is 36 pieces instead of 25. More assembly work, but it is the difference between a sign that reads and one that does not.

The general lesson: when the number of columns goes up, the pretty split stops being available, and the cuts have to be chosen by looking at where the squares are rather than by dividing the side into equal parts.

How to join the pieces

Three things that matter more than the glue:

• Print every piece with the same profile and, if you can, the same spool. A difference in flow between pieces moves the walls by a few hundredths, and once joined the module grid stops being regular. The reader expects a regular grid: it is one of the first things it deduces from the corner squares.
• Do not scale any piece. Not even so it «fits better». Each piece has to come out with exactly the module it is due.
• Align against a board, not against each other. Glue the pieces onto a flat base using a square, instead of fitting one to the next: alignment errors add up and the last piece ends up crooked.

If the base is light and the joint shows, run a little filler or base-coloured paint over it. It does not have to be invisible: what there cannot be is a dark line crossing the code, because the camera does read that as part of the pattern.

What it costs

Only the dark part, which is the one carrying the relief. The base is separate and depends on the thickness you choose:

Sign	Relief	Filament for the code
300 mm	1.2 mm	33 g
500 mm	1.6 mm	123 g
1000 mm	2.4 mm	741 g

That last number is the one to look at before starting: three quarters of a kilo of the dark colour alone, not counting the base, which on a one-metre sign easily runs to several kilos. Past a certain size, printing stops being the sensible option and a cut vinyl comes out cheaper. What is interesting about printing it is the relief, which you can feel and which stands up to the weather better than a sticker, as the outdoor guide explains.