Designing Multilayer CNC Projects

Flat images spring to life when you build them up in layers. Here’s how.

- By Randy Johnson

Get more CNC plans and video. woodmagazi­ne.com/ cnc

With CNC, you can duplicate parts with a couple of clicks and make as many as you want. So, customize this project to suit your favorite holiday—or make a set for every occasion. Change colors to red and green with a pine tree in the back to welcome Christmas guests. Paint the truck orange and brown with pumpkins in the bed for Halloween and Thanksgivi­ng. Or make it resemble one of your favorite old vehicles. Creating the design in Vectric VCarve software goes quickly using a few of the program’s basic drawing tools. The simple toolpaths require only three router bits to complete the cutting and carving. Because it paints so well, make the project from standard MDF for display in sheltered areas, or use an exterior grade MDF if the sign will be exposed to the weather.

1 Start with a photo or drawing of your favorite old pickup truck, car, or other vehicle. A straight-on side view, as shown here, works best.

2 After setting up your job dimensions, import the image into the VCarve software. Use the tracing and drawing tools (described at right) to create vector lines around the major parts of the image. For this truck, that includes the main body, the fenders and running board, the tires and wheels, and the side window. (I left off the sideboards on the bed.) Keep the parts bold and basic—think of them as simple puzzle pieces. Note that even though the tires tuck behind the fenders, I made them fully round because they’ll be visible when glued in place. Add the text and stars, or customize the design to fit your décor or holiday.

3 Separate the parts in the drawing and arrange them in the layout. Leave enough space around the parts so the waste area remains together as one piece. This waste material serves as a clamping jig for the parts in a later step.

Add the cutout toolpaths around the parts including tabs to hold the parts in place while cutting. I use a 1⁄4" upcut spiral bit for the outlines, and added a .25"-deep bevel that gets cut with a 60° V-bit around the fenders, tires, and the top half of the truck body. The bevel softens the edges and adds contour to the parts.

4 After cutting the parts, separate them from the waste, but leave the waste attached to your CNC spoilboard. If you need to take the waste part off your machine, drill some registrati­on dowel holes through the waste and into the spoilboard so you can accurately place the waste back on your machine for the V-carving step later. Drill the hole in the truck side for the flagpole [opening photo], if desired, using your drill press or a handheld drill.

5 Ease the sharp corners and sand smooth the machined edges of the MDF. Seal the parts with a couple coats of thin shellac and sand smooth with 180-grit paper. Then, spray on the paint. For this truck, I used a gloss metallic red and blue, and semi-gloss black. Let the parts sit for a couple days so the paint cures fully.

6 To create the details, put the parts back on the CNC, wedging them in place with 1⁄4" dowels in the kerfs. To get a snug fit, enlarge the dowels, if needed, by applying masking tape or reduce them by sanding. Then,

V-carve full-depth the stars, text, and tires with a 60° V-bit. Make a pocket cut using the downcut spiral bit to clear the middle area of the window to 1⁄8" depth, followed by the 60° V-bit around the window’s edge at 1⁄8" depth.

7 Carefully brush white latex paint into the newly carved details and wipe off any excess paint from surroundin­g areas with a damp cloth. Let dry and apply additional coats as needed.

8 Assemble the parts using an all-purpose gap-filling glue that sticks to painted surfaces. I used Loctite Go2 glue with good results. Add a picture hanger or garden stake to the back and display where guests can enjoy your handiwork.

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Screw location for securing to spoilboard.
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¼" dowels

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