28

Create a Wooden Maze with a CNC Mill Machine

ERIK CARLSON / LIBRARIAN I

White Plains Public Library

Type of Library Best Suited for: Any

Cost Estimate: CNC: about $2,000; Materials: about $30 for 8 projects

Makerspace Necessary? Yes (this could get messy)

PROJECT DESCRIPTION

Creating a wooden maze is a simple way to get people interested in computer numerical control (CNC) milling. It gives them an opportunity to design their own project and use basic computer-aided manufacturing (CAM) software to create toolpaths and operate the CNC machine. Although this is a basic project, participants in the program need to be able to control the mouse and have intermediate-level computer skills.

One of the greatest difficulties I had when I started developing programs around a CNC machine was how to interest people in the machines. Using acronyms like “CNC” and “CAM” mean nothing to the library users, and the machine itself is not very attractive. Everyone wants 3D printing, but CNC milling can be just as great. My first projects were pretty basic and uninspired. I had people engrave their initials or a simple design into wood or cork. Then I decided to complement the 3D printing program with the CNC machine, which helped. I still needed to think of something that would challenge people, something they would be motivated to make and show to their friends. What better fits this criterion than a maze? These instructions are for creating a wooden maze using 6.75 × 6.75 × 0.5-inch plywood. You can modify the size depending on the size of maze you want to create.

FIGURE 28.1

Completed CNC maze

OVERVIEW

I run this program in two sessions with no more than five participants. The first session runs for 1.5 hours. This is enough time for everyone to design a maze and create toolpaths. I invite the participants to come in between sessions to learn how to run the machine. It takes around two hours to cut out the maze. The second session can take thirty minutes to an hour depending on whether or not you cut the Plexiglass or have the participants cut it. I work mostly with teenagers, so I cut the Plexiglass myself.

MATERIALS LIST

NECESSARY EQUIPMENT

NECESSARY SOFTWARE

STEP-BY-STEP INSTRUCTIONS

Create a new design with Inkscape, an open-source, vector graphic software. To start, I like to resize the document to the size of my maze. The work area is one inch less than the block of wood, leaving room to attach the Plexiglass at the end. Go to “File” in the main menu and then click on “Document Properties.” In the new window find “Custom Size.” Change the “Units” to inches, then change the “Width” and “Height” to 5.75 and hit enter. Then close out of the window. I also like to add the “Grid” to help guide my design. To do this, go to “View” in the main menu and then click on “Grid.” Now we are ready to plot out our mazes.

There are a variety of designs, shapes, and objectives that go into creating a maze. The simplest to design is a linear maze, starting at one point and ending at another. This is the type of maze that we are going to design. (If you would like to add curves, please see my instructions for the cardboard plane cutout. There I show how to curve and round out angles in Inkscape. Project #30, “Laser Cut a Cardboard Glider Plane.”)

To get started, click on the tool “Draw bezier curves and straight lines” on the left side of the screen and plot out the course of your maze.

Next we can start adding our dead ends to the maze, the more the merrier. Keep in mind that the actual maze lines will be much thicker, so try not to make the lines too close together. When our designs are complete, select all (Ctrl + A), then click on “Object” in the main menu and then choose “Group” (Ctrl + G).

Next widen the lines to 0.25 inch. Click on “Object,” then “Fill and Stroke.” This will add a Dialog Box on the right of your screen. Click on the “Stroke Style” tab and change “px” to “Inches,” and then change the width to “0.25.” If these options appear grey, make sure you select your drawing/maze, so that a dotted line appears around your design. Then try again.

FIGURE 28.2

Inkscape fill and stroke settings

Now our maze should be the thickness that will be produced, and we can see if we made any mistakes by drawing our lines too close. If any of the lines are overlapped, ungroup your maze and select the lines that need to be modified. Remember to regroup when you are finished editing. My personal rule is to keep a minimum of two grid squares between the lines as much as I can.

If you do not have a 0.25-inch mill bit and use 0.125-inch bits, do not despair. You will have to take an extra step in Inkscape and draw an outline (using “Draw bezier curves and straight lines”) of the entire maze, then delete the original maze (the thick 0.25-inch maze) so only the outline remains.

Once we are happy with our designs, we are ready to save and export them into a CAM program. I use MakerCAM.com because it is free and easy to use. Save your design by clicking on “File,” then “Save-as.” Change the file to “Plain SVG.”

Open MakerCAM and import your design by clicking on “File” in the main menu, and then choose “Open SVG File.” Add a 6.75-inch square by clicking on “Insert” in the main menu and then choose “Rectangle.” Make the width and height 6.75 and click “Ok.” Move the square to the intersection of the X-Y axis. Then center your maze in the square. You may have to resize your design after importing it to the CAM program. To do this, highlight your maze in red, click on “Edit” in the main menu, and then choose “Scale Selected.” Go little by little when scaling (down or up), subtract by increments of “5”. This will give us a better visual of what our finished projects will look like.

FIGURE 28.3

Maze design in MakerCAM

Next we can create our toolpath. In MakerCAM, be sure that only your maze is highlighted in red by drawing a selection box around the maze. When highlighted, click on “CAM” in the main menu and then choose “Follow Path Operation.” This will open a new window to input our toolpath parameters.

I use a 0.25-inch mill bit. I set the “Target Depth” to -0.3125 so that there is room for the ball to move without touching the Plexiglass. I generally use a very small “Step Down Rate,” so I set it to 0.015625. I find that there are fewer mistakes made this way. I set the “Feedrate” to 30 and the “Plunge Rate” to 10.

Next click on the check box to “View Cuts,” then go back to “CAM” and click on “Calculate All.” This will show the path that the machine will take to cut out your maze. Now we can export the g-code by clicking on “CAM” again and selecting “Export Gcode.”

After it is saved you can open GRBL, a motion-control software, and import your project. Clamp your piece of plywood and set up your CNC machine to run the program.

When the machine is finished, sand any rough areas and remove any burr. Remember to sand the edges and corners as well to make them smooth. For some strange reason my machine decided to add a hole towards the bottom.

Now we are ready to fit our Plexiglass over the top. The cleanest way to cut Plexiglass is to score it with a utility knife (I score it about 25 times just in case). I put the Plexiglass between two boards, lining up the scored line in the Plexiglass between the edges of the two boards. Depending on the size of the Plexiglass, I will use a ruler to help distribute the pressure. With a smaller piece I hold the Plexiglass wearing a glove. I give the Plexiglass a strong push to break it along the score. If you have a table saw and don’t mind the dust, then you can cut that way. Remember to sand only the edges of the Plexiglass and remove any burr left over from the cuts. Also try to sand the corners down a bit so they are not sharp either.

I cut the Plexiglass about 0.25 inch smaller than the piece of wood and check it by lining it up with my maze. Alternately, you can measure the Plexiglass so that it is flush to the sides of your wood. Drill four holes in the corners to attach it to your piece of wood. Be sure to use a backer to drill into; it is easy to accidentally break off a corner of Plexiglass. Also be sure to check that your holes will not interfere with the maze. With the design I used for this I was not very careful to keep the corners clear, so my screws were not evenly placed in the corners. If you want the object of the maze to be to get the ball out, drill holes to put the ball in at the start and/or end.

Next you can add your ball. I found a small bead that fit in my maze perfectly. You can 3D print a ball, but ball bearings are the best way to go. Once the ball is moving smoothly, you can screw the Plexiglass onto the top. You can also paint or stain the wood to make it look nicer, or engrave your name on the back. Now you should have a nice maze to challenge your friends or give as a gift.

LEARNING OUTCOMES

Through this project participants will . . .

RECOMMENDED NEXT PROJECTS

Once you feel comfortable creating and teaching how to create this maze, you can try more difficult designs, like a more circular maze or taking a design like a logo and turning it into a maze. You can also make a larger maze, depending on the size of your CNC machine. Also, see my project in this section on how to “Build a Six-Piece Interlocking Burr Puzzle” as well as others in this section on milling and cutting.