CNC Routers
About Routers
Routers and mills both operate in a very similar fashion and share many G-codes, but routers are lighter, faster, and used for cutting soft materials like wood or plastic. Mills are heavier, more rigid, and designed for precise machining of hard materials such as steel. The main difference lies in their construction, cutting power, and the types of materials they’re built to handle.
Routers typically use a gantry setup to move the cutting tool around the part, rather than the part moving around the tool. This allows for much faster travel speeds since the spindle and motor typically weigh less than the table. They also generally operate in the range of 10 000-15 000 RPM, and can get as high as 30 000 RPM, but with very low torque. For this reason, routers are ideal for soft materials like MDF, polycarbonate, or delrin since they require little effort to cut but have very high surface speeds.
Routers also come in many different sizes, from desktop routers as small as a printer to table routers big enough to lie down on. This, and the fact that most are gantry-style, make routers potentially much more affordable than mills as well as being able to be built by hand from a kit or from scratch.
What Changes?
While it is completely possible to make the same part out of the same material on a mill and a router, the path to do it will differ. The first thing to consider is machine limitations; some mills can't run the spindle beyond 5000 RPM and some routers can ONLY run above 5000 RPM. Routers are also limited in power output while mills are limited in feedrate. All of these factors will necessarily affect how the part is programmed for one machine versus another.
Something else to consider which often gets overlooked is work holding (see Mill page for more info). Most mills have a sturdy, usually cast iron or similar, table with T-slots and typically a vise as well. Routers are much more diverse in their work holding options; some tables have T-slots like a mills, while others have grids of threaded holes, magnets, or vacuum systems. It is important to understand the tools at your disposal in order to create a rigid fixture. This is very commonly the longest step of any manufacturing process besides designing the part, so it's worth it to be careful and mindful and not to rush.
However, keep in mind that the machine itself is only so rigid as well. Since routers are not usually as rigid as mills, it is recommended to take cuts with a smaller depth and width to not stress the machine. With a smaller depth of cut, it is now also possible to run the machine faster, which works to the router's advantage.