CNC milling of solid wood and plywood: what is possible

The machine follows a file, so its strengths are accuracy and repetition. The hundredth part comes out like the first, internal cut-outs sit where the drawing puts them, and holes for fittings line up. Typical work:

• Contours: furniture sides, shelves, brackets, curved panels, letters and templates.
• Pockets, grooves and holes: recesses for hinges and fittings, housings for joints, cable channels.
• Engraving: lettering, patterns, markings and decorative surfaces.
• Nesting: many parts laid out on one sheet so the offcuts stay small.
• 3D relief: curved faces and shapes milled from a solid blank.

Solid wood has a direction. Along the grain the cutter leaves a clean edge; across it, especially at end grain and on curves where the direction changes, fibres can lift and tear out. Sharp tools, the right feed and a light finishing pass reduce this, but some edges still need sanding by hand.

Wood also holds internal stresses. When a deep pocket is cut or one face is milled away, a board can bow, so thick parts are often roughed out, left to settle and then finished, or milled from both sides. Wide parts are made from glued solid wood panels rather than single boards, because they stay flatter. And a solid part keeps moving with the humidity after milling, so tight fits across the grain need a small allowance.

Plywood is built from cross-laid veneers, which makes it stable and strong for its weight. It suits furniture carcasses, shelves, structural parts and anything with long, narrow sections. The difficult part is the edge: the face veneer can splinter on the top or bottom surface, so the cutter type and the order of cuts matter. Plywood edges show their layers, and many people use them as a visible detail, especially in birch plywood.

MDF has no grain at all. It mills to a crisp profile and a smooth pocket in any direction, which makes it the usual base for painted parts and relief panels. Its cut edges are porous and need sealing or priming before paint, the board is heavy, and ordinary MDF must be kept away from water.

The cleaner the input, the faster the quote and the fewer surprises. The best start is a vector drawing at full scale in millimetres with closed contours, for example in DXF format, or a 3D model for relief work. A dimensioned sketch, a drawing or a photo of a sample also works: the file is then prepared from it, which takes extra time. Add these details:

• Material, thickness and quantity.
• Which face is visible and which way the grain should run.
• The dimensions and fits that really matter, and where tolerances can be looser.
• Holes and fittings, with sizes and depths.
• Whether finishing is needed: sanding, rounded edges, lacquer, oil or paint.

The router What Else uses has a 1500 × 3000 mm working field, 300 mm of Z travel and positioning accuracy of up to 0.1 mm, and a vacuum table holds sheets flat. In practice, the fit of a part depends more on the material than on the machine: a sheet thicker or thinner than its nominal size, or wood moving with the humidity, changes the result more than the router does. Name the fits that matter and test them on a first article before a series.

A round cutter cannot make a perfectly sharp inside corner; it leaves a radius equal to its own. Where a square part has to fit into a pocket, the drawing gets small relief cuts in the corners, or the corner is finished by hand. Parts cut right through are held by small tabs, which are trimmed and sanded afterwards. Milled edges usually get a light sanding before any lacquer or paint.

What Else mills solid wood, plywood, MDF and other sheet materials in its own workshop, for its own projects and for outside clients.