Selecting a CNC Router
Selecting a CNC router for the home, or small workshop, depends very much
on knowing what your expectations are. CNC machines vary greatly in
size and price. Here we are are mainly concerned with the hobbyist
end of the market rather than the professional end. For the
hobbyist, however, there is still a range of options that need to be
- The size of the items you wish to make.
- For the CNC machine it will be the overall size of the
components to be machined, not simply the dimensions of the cuts or
carvings. The whole piece of stock must be able to be mounted on
the machine bed. For most machines there are fixed limits on the X
(width) and Z (height) dimensions but there may be the possibility for
the length (Y axis) to be longer than the machine bed. Remember
that the length of machining is limited to the Y-axis travel, though it
may be possible to make longer cuts by re-positioning the stock
(carefully and accurately).
- Given the the stock must be held down to the machine bed you need to
allow space for the clamps so that they are clear of the cutter
paths. See section on holding down options for more details here.
- Most of the small-sized CNC machines are suitable for cutting wood (of
all sorts, including MDF and plywood) and plastics (acrylics,
polycarbonates, etc). Cutting aluminium is possible but particular
care is required to select the correct cutters, speeds and feeds, as
well as providing lubrication/cooling. to the cutter.
- At the small-sized end of the market the robustness and stiffness of
the machines vary considerably.
- Many small machines, and most kit-based options, tend to be made from
lightweight aluminiun extrusions that are bolted together. These
machines may perform well for occasional use but their limitations will
become obvious if they are pushed too hard.
- For more intensive work applications, a solid welded frame (steel or
aluminium) is required, together with large linear running rails and
- In addition to the basic hardware, a controller box is also
required. This will contain all the electronics, and micro
processor capabilities, to drive the axis motors (to move the cutting
head to nominated X, Y and Z positions). It also is used to turn on and
off the spindle and to set its speed, and to interpret the
machining instructions (generally known as G-Codes) that are created by
the CAM software.
- In some cases these machining files are passed to the machine on a USB
stick and the controller has the necessary micro-computer built in to
interpret these to provide the required machine operations.
- In many cases, however, this machine control function is performed on
a stand-alone computer where the G-Code instructions are sent to the CNC
machine controller by a directly connected cable. Historically
this was a "parallel printer" type cable, but now it is more likely to
be a USB cable or an Ethernet cable.
At the hobbyist end of the market machines are commonly designated by
- A 4030 machine has a usable bed size of 300 mm in the X direction and
400 mm in the Y direction.
- A 6040 machine has a usable bed size of 400 mm in the X direction and
600 mm in the Y direction
- A 6090 machine has a usable bed size of 600 mm in the X direction and
900 mm in the Y direction
Some larger machines might be designated similarly (e.g. 1212 might mean
1200 x 1200 mm), but more typically there actual bed dimensions are
The available movement in the Z direction is also important, Mostly
this will be in the 100 - 150 mm range, and this is quite suitable for
many applications. This height limits the:
- Maximum depth of cuts
- The maximum length of cutters
- The thickness of stock
If you have special needs then the available Z travel may be more
significant. Mostly there is also some adjustments that can be made
on the machine by moving the spindle up and down in its holder. This
provides some additional flexibility but, of course, not while the machine
Once the required size is decided then the next decision will be where to
get your machine. For fully assembled machines there are options
that that come from the USA and Europe, but only a few from
Australia. Most machines, and most usually those at the less
expensive end of the market come from China. There are some local
suppliers that import Chinese made machines and they may provide some
local support. Alternatively you may choose to import directly,
potentially saving considerable sums on the cost. Care is required
however as there are considerable variations in quality and reliability,
and you need to be confident that you can get support and spare parts.
If you decide to import directly be mindful of:
- The shipping costs.
- The assembly quality of the chosen machine, this can vary
considerably. Get a local recommendation if possible.
- The availability of support and spare parts - when things go wrong.
- There are many horror stories in the web, and many successes also.