# Micromouse maze building¶

## Introduction¶

According to the international micromouse competition rules:

• The maze is composed of 18 x 18 cm unit squares.
• The maze is 16 x 16 unit squares.
• Walls are 5 cm high and 1.2 cm thick.
• The outside wall encloses the entire maze.
• The sides of the maze walls are white, the tops of the walls are red, and the floor is black. The maze is made of wood, finished with non-gloss paint.

Warning

Do not assume the walls are consistently white, or that the tops of the walls are consistently red, or that the floor is consistently black. Fading may occur; parts from different mazes may be used. Do not assume the floor provides a given amount of friction. It is simply painted plywood and may be quite slick. The maze floor may be constructed using multiple sheets of plywood. Therefore there may be a seam between the two sheets on which any low-hanging parts of a mouse may snag A tolerance of 5% is assumed for sizes.

A 16 x 16 maze is probably too big to build one at home for training, so we probably want to build a reduced version instead.

## Requirements¶

Worst case scenario is when there is only one way to get from one point to another in the maze (i.e.: no loops) and the maze ending is just a 1x1 square (while training we may not need to always have a 2x2 ending).

An example of a dense 8x8 micromouse maze.

Note that:

• All squares in the maze have 2 walls around except for two of them (i.e.: starting and ending points), which have 3.
• All internal walls are actually shared between two squares.

Supposing our maze width is $$w$$ and height is $$h$$, the maximum required number of walls would be:

$n_{walls} = w h + w + h + 1$

Taking this into account, and of course, our available space, we can decide on our training maze size.

Note

We may want to reduce the total number of walls by using long single-pieced walls for the external walls. We will not need to make 2 * (w + h) extra small walls, but we will not really save that much material and will make those walls not interchangeable.

Of course, we must also take into account that, for a $$w$$ by $$h$$ maze, we will need to make pillars for the walls:

$n_{pillars} = w h + w + h + 1$

Note the number of pillars is exactly the same number as the maximum number of walls required, although this number is always fixed, no matter the maze configuration.

We also need to take into account the space required for the base to make sure it fits somewhere at home!

\begin{align}\begin{aligned}x_{mm} = w * 180 + 12\\y_{mm} = h * 180 + 12\end{aligned}\end{align}

As an example, here is a table with different maze sizes and their associated requirements:

Maze build requirements
Size Maximum walls Pillars Width (mm) Height (mm)
3x5 24 24 552 912
4x4 25 25 732 732
4x6 35 35 732 1092
6x6 49 49 1092 1092
8x8 81 81 1452 1452
16x16 289 289 2892 2892

## Walls¶

There are different ways to make the walls. It depends very much on which tools we have available and our budget as well. The method described here only requires to have acces to a saw and white glue. Walls will be made with 4 mm MDF wood, which is cheap (found a 2.44 x 1.22 m sheet at a nearby warehouse for about 5€).

To make the walls we will glue three parts together, like in a sandwitch:

• Two 167 x 50 mm pieces outside, represented in blue.
• One 172 x 30 mm piece inside (with optionally rounded corners), represented in green.

Maze wall design.

We will be making a 4x6 maze, so we will cut the 2.44 x 1.22 m sheet this way:

• Ten 1220 x 50 mm rectangles.
• Five 1220 x 30 mm rectangles.

Then:

• We cut the 50 mm rectangles in 7 pieces of 167 x 50 mm. Take into account the saw width before making the cut. We use 167 instead of 168 to have a small marging when placing the walls in the maze.
• We cut the 30 mm rectangles in 7 pieces of 172 x 30 mm. Here again, take into account the saw width to try to make the cuts are fine as possible.

## Base¶

The base can be a single-pieced 12 mm wood, in which we need to make through-holes for the pillars’ wooden dowels. Dimensions are according to our maze size, of course.

For our 4 x 6 maze we will cut a 860 x 1220 mm rectangle.

Note

MDF wood is ideal for the base too (cheap and nice surface finish).

## Pillars¶

For the pillars we will use 3D-printed plastic. The 3D design can be defined using CadQuery:

"""
This script defines a micromouse maze pillar.
"""
from Helpers import show

HEIGHT = 50.
WIDTH = 12.
HOLE_DIAMETER = 6.
HOLE_DEPTH = 21.
GROOVE_WIDTH = 4.3
GROOVE_DEPTH = 2.5
GROOVE_LENGTH = 26.

# Pillar body
.box(WIDTH, WIDTH, HEIGHT)\
.faces('<Z').workplane()\
.hole(diameter=HOLE_DIAMETER, depth=HOLE_DEPTH)

# Grooves
aux = WIDTH / 2. - GROOVE_DEPTH / 2.
pillar = pillar.faces('>Z').workplane()\
.pushPoints([(aux, 0), (-aux, 0)]).rect(GROOVE_DEPTH, GROOVE_WIDTH)\
.cutBlind(-GROOVE_LENGTH)
pillar = pillar.faces('>Z').workplane()\
.pushPoints([(0, aux), (0, -aux)]).rect(GROOVE_WIDTH, GROOVE_DEPTH)\
.cutBlind(-GROOVE_LENGTH)

show(pillar)


Maze pillar design.

We will also require 6 x 30 mm wooden dowels for each pillar. The dowels can be inserted in the pillar with a hammer.

Note

Instead of making 30 mm grooves we may want to make them complete along the pillar (i.e.: 50 mm). In that case the pillar would simply become a bit weaker on the base and could more easily break.