When designing your CNC project there are many
variables to take into account. From the thickness &
properties of a given material through to the way in
which you design part intersections and approaches
to fastening. There are lots of things to plan for.
Don't worry if you aren't familiar with all the
intricacies of CNC based design- we are and we are
here to help you.
This section of our site is designed to give you
a basic understanding of some of the principle
techniques involved in producing your projects using
Layout of parts
When planning the layout of your CNC project
please remember that the arrangement of the parts to
be cut needs to allow for retaining sections. If we
look at the diagrams below we can see that one of
the layouts has a uniformly spaced approach and the
other has components which are positioned butting
together. The first approach is acceptable the
second will not process correctly. Without retaining
sections the parts will move during cutting- this
results in inaccurate results.
When cutting with a CNC tool we need
to take into account the diameter of the cutting
bit. For example. If we are cutting parts with an
6.35mm diameter bit we need to remember that the
tool will leave a hole in the substrate 6.35mm
larger all the way around.
When planning the layout of parts it
important to allow for the additional space that
each toolpath will occupy.
Processing thicker materials
Cutting bits are the key to any CNC system. Use
the right bit for the right material and you will
get excellent results.
From our experience a lot of signage and display
work requires the use of a fairly fine bit. The
general rule of thumb for cutting bits is that they
will cut to a maximum depth which is no greater than
200% of the bit diameter.
The obvious approach for thicker material would
be to use a larger diameter cutting bit. The problem
with this is that tight shapes such as lettering
won't cut accurately with a larger cutting bit as
there will not be room for the bit to move through
the material without it destroying areas we want to
So how do we cut thick materials with a fine
The process we employ to get around this problem
is referred to as "passing". We tell the machine how
deep we want the cutting bit to penetrate- for
example if we are cutting 18mm thick material with a
3.95mm bit we might say cut only 6mm deep in any one
action or "pass". The software will then interpret
this data and instruct the CNC machinery
So, in this example the CNC will cut round the
perimeter of our part three times in negative 6mm
increments- the final "pass" cutting through the
last 6mm deep section of our 18mm sheet.
Area clearing/ Pocket machining
Area clearing or pocket machining as it's
sometimes referred to is the process whereby an area
is cut to a specified shape and depth in one
operation. Again, this is an automated feature of
our CNC systems and is a vital tool for creating
many CNC projects.
How the process works
Area clearing/ pocket machining employs both
perimeter toolpathing and elements of passing. As an
example lets say we want to machine a recess into an
12mm sheet of MDF. We are going to form a basic
trenched joint. For this we need to assign an area
clearing strategy to a rectangle which is 12mm wide
by the length of the panels we are going to join.
This rectangle is assigned a clearance tool path
which will cut around the inside of our 12mm
rectangle using a 3.95mm bit- if we were to ask the
machine to go to the outside of the rectangle it
would area clear an area 12mm +3.95mm +3.95mm- the
two extra dimensions represent the diameter or the
tool as it travels along the outside of the
perimeter- this refers directly to the toolpath
strategies we covered earlier.
Using this area clear method we can ensure that
we get recesses which are precisely the shape &
dimension we want and which also have a specific,