One of my first constructions with the Handibot was a simple box. A box is a very important shape to be able to make, since it is a good challenge in a traditional woodworking shop. A box will tell you if your table saw is “square” and your measurements are “true”. It will tell you if your box joints are “strong”. Not sure why I put quotes around strong, other than a weak joint will result in scrap wood on the floor.
A box is also the first of many geometric primitives, or polyhedra. Think about Dungeons & Dragons die. Now think about making a set of Dice (Die).
I used makercase.com, which is a perfect app for creating laser cut templates. I just adapted it to my dimensions and tolerances for the CNC Handibot.
This meant fitting my template within a 6″ x 8″ cutting area. I could have cut each side as large as 6″ x 6″ but I prefer 3″ dice, about the same size as fuzzy dice that I could hang from my rear view mirror…
So, a singe pass of the router will result in 6 sides. Each side has finger joints, or box joints to create an interlocking assembly.
With CNC milling, you select the “Kerf” or cutting tool width, when finalizing your tool path design.
For example a laser will burn away approximately .02 of material (in wood) so you have to adjust your design tolerances accordingly.
A typical router bit for doing a straight cut into wood is 1/8″ so I set my cutting path to cut “outside” of the line. Now, to ensure a tight fit and not have to rely on hand-sanding, I offset the cutting blade by .01, which means my exact digital dimensions now have a slight undercut, so everything “just fits”.
One other learning (the hard way) is that every production run of plywood is a bit different. If the tag says 1/8″ plywood, take out a caliper and measure it. On some days, it is actually .175″. On another purchase, it is .2 or 1/5″ This will dramatically impact your finger joints, since they are measured based on the thickness of the wood for a tight fitting joint. Or the box will fall apart and land on the floor. Glue is messy and ruins your paint/stain unless you have excellent edge control of the glue. (I don’t). So I like to rely on my Japanese Woodcutting ethics and use no glue. Unless of course I am using “Captive Bolts” and T-Slots on my joints. Then I rely on my Victorian Steampunk woodworking ethics. And maybe some glue for my American Woodworking ingenuity. Whatever works, make it YOUR style….
I have broken 1/8″bits before, so be careful what material you use as your underlay surface (MDF is much harder than plywood). Now, I cut straight through the 1/5″ plywood in two passes which is easier on the tools.
I take the makercase.com template into Adobe Illustrator just because I am most familiar with the vector editing tools there, but you can use Inkscape (free) or V-Carve (comes with Handibot) to achieve your design intent.
My design intent for the box, was to add the Dots (or as they are called,”Pips”). I just referred to an actual set of dice for placement, to prevent humiliation from the dice rolling community. All corresponding sides must equal 7 and there are 6 ways to make a 7 or 6:1 Odds. But that’s for another post.
Before cutting the parts, I coated the wood with water-based color stain, and coated with a clear water based polyurethane. This gives a nice contrast between the coated surface and uncoated edges of the pieces.
I exported the tool paths, uploaded to my Handibot, cut and assembled the parts, and immediately put them into good use: