Introduction: Bent-Wood Box With CNC Carved Lid
This is cool little project I do with my Grade 8 Woodwork students. It's a great project that incorporates a very traditional craft - the art of bent-wood boxes, with a very high-tech application - a CNC carved lid. The finished product is not only functional, it's aesthetically pleasing.
Step 1: First Nations Artwork
The lid of the bent wood box starts out as a digital image, either produced freehand or copied from an existing source. I use ArtCAM Express to create the toolpaths neccessary to carve the vectors. I use a combination of V-Carved elements and Profile cuts to produce the finished image. I have found that carving the lid in a piece of 5/8' MDF allows for a really crisp line once the carving has been painted.
Step 2: Simple Hold Down Jig
Since we make quite a few of these boxes in my middle school shop, I created a simple hold-down jig that allows us to quickly register each piece to the same spot every time we machine a new lid. The pieces are held in place with a couple of wedges. These small lids only take a few minutes to carve. Once they're finished, students quickly sand away "the fuzzies" and then paint the carved recesses with black acrylic paint. Once the paint has dried overnight, students go back and sand the faces of the lids with 120 grit sandpaper and a sanding block.
Step 3: Eye-Popping Graphics
This simple CNC engraving process produces really nice results that students are really proud of. And even if they can't paint within the lines, it's not a big deal because once the paint has dried, they can simply sand away any paint outside of their engraving.
Step 4: Making the Bent Wood Box
We make the box out of Western Red Cedar, which is a traditional material of choice used by West Coast First Nations. I prepare the box blank, mitre the ends to 45 degrees, and then I carefully router the three remaining v-cuts. The v-cuts are critical to the success of the finished box. They need to be routered so that each of the four segments of the box will be the same length. And the depth of these v-cuts is also critical. I try to leave about 1/16" of material remaining so that when it comes time to bend the corners, the fibers of the wood bend easily without cracking. We soak the box blank in a hot water bath for 15 minutes (or you could use a steam box if you have one). Once the blank has been soaked, the wood fibers (and particularly, the lignin) is warm enough to be stretched - but patience and a soft touch is required here! Bend the corners too quickly, and they will likely crack. Once the blank has been formed into a box, we wrap a small elastic band around it and set it aside to dry overnight. After all of the water has evaporated out of the wood, the one open joint can be glued. Again, an elastic is used to keep the box together while the glue dries. It's then time to add a bottom and a lid insert and the box is almost complete.
Step 5: A Unique Box
The end product is truly unique. Not only is the lid of this small box visually appealing, looking closely at the box reveals wood grain that is continuous and wraps around corners! My students think that's pretty cool!