CNC milling technology is a wonderful tool for making objects big to small, from simple to complex. The technical improvement of its implementation currently allows to create high quality furniture from it.
As with most machines the key to a successful job is in the person operating - in our case the maker. In guiding and running the machine, the maker has an essential role in the final value/look of the product. Yet, no longer is it just experienced makers that can get involved with CNC manufacturing. Since its processes have been simplified, it is now an accessible device that can be employed by a larger audience, which in turn is contributing to the expansion of the maker movement.
The majority of CNC machines are set up to cut standard wood based sheet material such as Chipboard, MDF, OSB or Valchromat. However, Birch Plywood stays our favourite material for its worldwide availability, durability and great aesthetic qualities. Most suppliers provide it in 1220x2440mm sheets with a standard thickness of 18mm, although oversized sheets up to 3000mm in length are available and other thicknesses such as 12mm or 24mm are commonly used.
To perform the cutting job, the sheet is screwed down onto a sacrificial board below it, stopping any movement whilst cutting. The material is usually fixed around its outside edges, it is therefore advised to keep all components at least 20mm away from the border when nesting them on the sheet.
In order to create and craft interesting and appealing products, most designs require the use of different cuttings preferences with distinction in depth as well as holes and chamfers. A cut through the total thickness of the material (i.e. 18mm) is called a ‘profile cut’, whereas a specific depth of material removal is called a ‘pocket’. Pockets can be of different depths from 1mm to 16mm.
There are a variety of woodworking cutters that can be run in order to carry out these functions. The most commonly used are the down-cutter (i.e.cutout and pockets), the V-cutter (i.e.chamfers) and the drill (i.e. holes).
The size of the cutter is also an important aspect to consider when drawing for CNC milling. Typically, a larger diameter tool will cut material faster, therefore designing with tooling in mind can help increase efficiency for cutting and keep the cost low. A 8mm diameter drill bit will help you to achieve this result whilst being one of the makers’ standard tools.
The machine can complete a 18mm deep perimeter cut in one pass but on visible components such as tops, the maker will operate two passes (i.e. 14mm followed by 18mm depths) to achieve cleaner edges. Accordingly, the router works from one end of the sheet; habitually cutting pockets first, followed by inside profile cuts and then perimeter profile cuts.
Toolpathing, which is the journey followed by the drill bit onto the sheet can vary a lot in time with each sheet and design, but is on average around 30mins (i.e. rising to one hour and a half for complex products). In order to save the plywood from harm, the maker controls the acceleration and deceleration of the cutter as it moves around curves in the toolpath.