Things you need:
1) Access to a CNC router table, I made this one at TechShop on the ShopBot (techshop.ws)
2) Plywood, I bought mine for $50 at a home store
3) Files, you can make them yourself in CAD and CAM software or you can use mine
2) Tung Oil
Step 1: First We Need to Draw It
You can download the raw .AI file I made at the link below. I left this file unfinished so you can adjust the slots to accommodate whatever size plywood you buy. The plywood I used was .74 inch thick so I had to adjust the little slots for that tolerance. This .AI file is where you do that.
This is also the file where you can adjust any sizes and lengths. Want the coffee table a little shorter? This is the file. Want the top a bit longer? This is the file. Remember, if you monkey a lot of stuff around, you need to double check that it will all fit together when you assemble it.
Step 2: Cleaning Up the .AI File to Make One Clear Cutline
If you don't want to do that yourself, you can download my .AI file below that I've already cleaned up. However, if your plywood is any thickness other than .74 I can't guarantee that the slots and tabs will fit together. If you want to chance it, here's my .AI file.
Step 3: Running It Through the CAM Software
In VCarve we're setting two (one "inside cut" and one "outside cut") profile toolpaths, adding dogbone fillets, as well as saving endmill and plywood settings. If none of this rings a bell, you'll probably want to take TechShop's "CAD/CAM VCarve Pro and Cut 3D" class. After that you should recognize what we're talking about and again a DC can get you unstuck.
Tip!: The dogbone fillet tool in VCarve is a bit funky. If you're using a .25" endmill like I did in this project, use a .125" setting in the dogbone fillet tool. For some reason the .25" dogbones come out too big --the .125" is perfect.
Tip!: Always save your toolpaths in a file that your router table knows. In my case (TechShop Pittsburgh's ShopBot) I saved it as a "ShopBot Arc (inch) w/ Speed" (an .spb) file. If you save it as a Laguna or some other proprietary file type, the table's going to jump around like a backup dancer from "Thriller."
Tip!: Use plenty of tabs. If the parts break free from each other you could injure yourself or even worse you could ruin the cut and have to go get more plywood.
So here are my files. In the .ZIP you'll find:
1) VCarve file
2) .25" endmill setting for plywood
3) ShopBot Arc (inch) w/ Speed file
Step 4: Cutting It Out!
1) Set your plywood on the ShopBot table and nail it down using the plastic brads. (That's how we do it in TechShop Pittsburgh. Other TechShop's have vacuum tables or if you're using a different type of CNC router table you might use clamps or something.)
2) Put your endmill in and start your spindle.
3) Zero your axes (X, Y, and Z). Zero the Z high, couple inches off the top of your plywood at least .
4) Load your file into the ShopBot software.
5) Do an air cut (standard practice in TSPGH). Make sure nothing wild happens. Watch for any bizarre behavior now while the business end of the ShopBot is a few inches above your material.
6) Then, using the Z-zero aluminum bar, zero your Z axis TO THE TOP OF THE MATERIAL. If you're using my files as they are in this Instructable, you need to zero to the top of your ply. If you zero to the table under the plywood, the router's going to drop .25" inch into ShopBot table itself and dig a nice long trench you'll have to pay for. If you do another project on the ShopBot, you may want to zero off the table then set in your material. That's fine. But this time, using these files, zero off the top. (It's how I have it set in VCarve.)
Step 5: Bang It Together
Step 6: Step Back. Behold. Admire Your Own Cleverness.
Step 7: Finishing (Optional)
What you'll need:
1) Paint. Any color. You can see I used red
2) Walnut colored stain
3) Tung oil for preservation
I painted the edges red and let those dry. Sanded the flat surfaces with fine sand paper. Did two coats of walnut stain and let those dry. Then I did two coats of tung oil and used "00" steel wool between those. Let it dry and viola!