Intro: CNC Maze Cube
This guide overviews how I made a cube with four mazes machined into four consecutive sides using a Haas super mini mill CNC machine. It walks through each part of the process, from design to finish, but assumes the reader already has some basic CAD, CAM (computer aided manufacturing) and CNC mill operating skills.
I decided to make my maze out of machinable wax, (here's an instructable to make your own wax: https://www.instructables.com/id/Machinable-Wax/), but this process could very easily be adapted for steel, or aluminum.
Step 1: Design in CAD
I modeled my part in Siemens NX 9.0, though you could use a different program if you prefer. There overall dimensions of my cube were 3.5'' cubed. Each distance from the outside of the cube to the top of the walls of each maze was .125'', to accommodate an acrylic cover of 1/8'' thickness later. Each maze path is an additional .15'' deep.
It's important to note that I know I would have to actually remove the material to form the maze paths. For this reason, I made sure the maze paths were at least 3/16'' wide everywhere, so that I could use a 3/16'' tool to machine out the paths.
To start, I made a 3.5'' cube in CAD. For each face, I found a mazes I liked on google images and imported a JPG image file into my CAD program. I then sketched out the maze and made extruded it to make a solid body of all the maze paths on the face. Finally I subtracted the maze path body from the large 3.5'' cube, thus removing the material to form the maze paths. I subtracted basic extruded rectangles from the large body to get the thickness of the acrylic.
I put a hole in the center of each maze that was .136'' in diameter, so that I could later hand tap the hole with a 8-32 tap and put in a 8-32 screw which I used to attach the acrylic plates. The holes were 3/4'' deep.
Step 2: CAM (Computer Aided Machining)
I used NX again for my CAM.
I imported my part file of the maze cube, and a 3.5'' cube with not features to represent my blank (the starting product).
As the Haas mini mill is a 3 axis machine, I could only mill one face at a time, so I created one program for each different maze I had.
As this is not a CAM tutorial, I'm not going to go through each step of my CAM. If you're unfamiliar with the process, there are tutorials online. Here's a youtube video that shows what the process is like:
Here's an basic overview of my CAM program:
3/4'' Endmill to quickly rough out material for acrylic cover. (feed 15ipm, 2400rpm)*
3/16'' Endmill to remove material for maze paths. (feed 8ipm, 7000rpm)*
Drill in drill chuck for the center holes
*These feeds and speeds are approximations for if I were using aluminum, on the actual machine, I then overrode the feed rates manually to about 160% as I actually was using wax)
I didn't use a center drill because machining wax is so forgiving and didn't cause the drill bit to walk off center.
Step 3: Prepare Blank for Machining!
First, I and to cut my cube off from a larger stock piece of wax. I had a 3.5"x3.5"x8" piece of wax, which I cut down to about 3.6" long with a horizontal band saw. Included in this step is a picture of a piece of 4x4 wood in the saw, as the blue wax did not show up very well in the picture.
Since the band saw is an inherently imprecise too, i intentionally oversized my cut to be about 3.6" long. I then went on a manual mill and removed the last 100 thousandths of an inch to get a prefect 3.5" cube (the second picture). I also took a (very shallow) pass at each side with a flycutter to get a great surface finish.
Step 4: CNC!
The fun step! Here I actually ran my CAM program in the Haas mini mill. The first picture is my actual maze in the mill, and the second one is a farther away shot of the machining setup for a different part (that I found online) for those who are unfamiliar.
This step is actually pretty easy. Most important is to load your tools into the machine, load the part into the vice, and setup the XYZ coordinate system for the part. After that I just pressed go, jacked up the feed rate as it was set for aluminum but I was using wax, and watched. I also did not use any coolant, as I was machining wax, didn't need it, and wanted to avoid the mess.
I then flipped the part 90 degrees, re did my XYZ coordinate system, and ran the next program for the next maze, until I had four mazes engraved into the part. It's worth noting I could have made six programs and had a maze on each side, but I wanted to have two clean empty faces for resting the final product on a table.
The last picture is the part after I pulled it out of the mill. One hole for tapping is missing as I forgot to load the drill bit and just stopped that part of the program. I ended up manually drilling the one hole.
The last thing to do to the wax part is manually tap the wax holes to get a thread in them. Good quality machining wax is tap-able. I used an 8-32 tap. Here's an instructable on tapping holes: https://www.instructables.com/id/Tapping-screw-threads/step3/Twist/. I did pretty much exactly this, though I used a smaller tap and tap handle.
Step 5: Lasercut Acrylic
I used a laser cutter to cut out the acrylic plates. They measured out to be 3.5'' by 3.3'' (I intentionally oversized the 3.3" dimension because I knew the laser would melt away a bit more material than it should have).
I also put a hole in the center of each rectangle that was .17" to comfortably let the threads of the screw through, but not the head. The acrylic is held in place by the wax ridges and pressure from the screw, it's not tapped.
Step 6: Screw in Acrylic, Add Balls, Done!
Before you carefully screw in the acrylic with the 8-32 screws (it's easy to strip the internal threading in the wax, be careful) put a small 1/8'' diameter steel ball in each maze. They're very cheap and available online, search "1/8'' diameter steel ball" (or glass, plastic, or aluminum if you prefer).
That's it! Pass it around to your friends and see who can solve all the mazes quickest!