Cutting the Parts I - Printing in Plastic: Build Your Own 3D Printer - page 36

Can you use a material other than plywood, such as Medium Density Overlay (MDO), High Density
Overlay (HDO), or Medium Density Fiber (MDF)? MDO is perfectly acceptable; it does cost a little more,
but it lacks a grain so parts can be laid out in any direction, which is a good thing. The surface of a MDO
sheet is covered with a thin MDF resin that has been applied with pressure and heat (like hardboard) to
provide an extremely smooth surface that doesn't require sanding. MDO is used for very smooth
concrete forming and has great structural properties. HDO is much more expensive than MDO and has a
thicker top surface. For purposes of the 3D printer, HDO is probably not worth the extra price in
material; MDO will suffice.
MDF is slightly more expensive than plywood; it's heavier and the dust produced when it is cut can
be harmful to breathe if the board contains Urea Formaldehyde (ask your retailer/home improvement
center if their stock of MDF contains this chemical). The best advice we can give if you choose to use
MDF is to always use a respirator and vacuum the area well after you cut a piece.

■ Note One final warning about MDF: as MDF is subject to humidity or direct penetration of water, the material

can thicken an additional 70% on top of its initial thickness. However, the material is incredibly stable if coated
with a chemical that blocks water permeation (i.e. polyurethane).

The 3D printer parts you see in this topic as examples are cut from Sandiply plywood. However, one
of the authors (Patrick) used a CNC machine to cut out parts for the 3D printer using MDO. Both
materials will work fine. Choose the one that fits your budget.
Once you've got your wood, a ruler, a pencil, and a tool for cutting, it's time to select the first part
to cut.

Lower Structural Sides - Parts A and B
You can consult the building plans and start marking and cutting whichever part you like, but we'd like
to offer up an order in which to cut the parts. The reason for this is that certain parts are large and others
are small, so cutting the large parts first will leave waste material behind that can be used to cut a smaller
part. If you cut the smaller parts first, you may find blocks of waste wood left behind that are just an inch
or two shorter than you need for cutting a larger part at a later time.
For this reason, we're going to suggest that the first parts you cut are the two pieces that will be used
to make the Lower Structural Sides. Figure 4-1 shows the building plan sheet for the parts that will
eventually be cut and drilled from these two first pieces.