Kerfing is the use of parallel engraving lines that are cut deep enough to allow an otherwise too-thick piece of plywood to become curved. It has been used for a long time in making the curved wooden sides of acoustic guitars, but I thought it could be useful for some chairs I designed.
With the right dimensions, it is possible to design a plywood piece which can only be put into position by bending it. This can be useful in many ways for objects assembled with plywood pieces.
The traditional way you bend plywood is to glue several layers of thin plywood together in a mould. Using steam to soften the wood fibres, the piece is set and dries over time to produce a piece of plywood that has a fixed bent shape. I want to talk about bending of plywood in a much simpler way which fits the central concept of many CNC-related designs: ease of manufacture/assembly. The purpose I want to focus on here is not necessarily for aesthetics (although it can be a nice by-product) but for strength.
The most basic joint is the slot joint, and it’s a staple when designing for CNC cutting. It’s the joint that, in its simple form, just needs just the standard router bit, doesn’t need any other implements like screws or dowels and it’s very easy to assemble.
Being able to draw an object in CAD is one thing, but as I wanted to use plywood milled using CNC routing, I would need to go through a few more steps before I could give the CNC router operator CAD files he could use.
The decision to use plywood milled by CNC routing has implications at every stage of the design. The fact that plywood is a sheet material means that I’ll have to break it down into parts that assemble together. It feels like I have to put my IKEA thinking cap on and work out a flat-pack arrangement of parts and the order they should be assembled. I need to become the cartoon man in the IKEA instructions.
If you are familiar with routers and electric drills as woodworking tools, then you can imagine a Computer Numerical Control (CNC) router as one of these attached to a robot arm. You can program this arm to cut a material (like plywood) along the lines you want by preparing a CAD file formatted in a certain way. But first, I'll explain a bit more about CNC routers based on what I've learned so far with the CNC routing company I use, and how I found this company in the first place.
If you’re considering digital fabrication for solid objects then you’ll need to become familiar with Computer Aided Drafting (CAD) or be able to call on someone who is. It’s the language everyone in digital fabrication speaks, whether they are involved in 3D printing, water jet cutting, CNC routing, laser cutting or any other additive or subtractive digital fabrication technology.