article will show you how-to build a CNC hot wire foam cutting
machine. Foam is a great building material that is lightweight
and inexpensive. With a CNC foam cutter you can quickly build
complex shapes including wings and fuselages.
machine works by moving a heated (hot) wire through foam.
The heat of the wire melts the foam leaving the desired shape
in the foam. When you are finished you have a "shuck"
(unused part) and a "core" (used part).
is the first in a two part series that will show you how to
build a CNC foam cutter. The second part will cover the hot
wire and hot-wire power supply as well as operating the machine
with the software and various cutting techniques.
This machine can be built using a drill press, band saw or
jig saw, a metal chop saw, hand drill and simple hand tools.
You will also need basic electrical tools such as a volt meter,
soldering iron, wire strippers, flush wire cutters, flux and
wanted to purchase materials locally, as a result much of
the CNC machine materials were purchased at the local big-box
home improvement store.
heart of the machine is a HobbyCNC FoamPro kit that include
a 4 axis stepper motor controller circuit board and four 130
oz-in stepper motors. The machine will be run by Giles Muller
Foam Cutting Software (GFMC Pro). The machine also has a few
purchased machined parts. They include 1/2-10" lead screws
that are machined on either end, bearing blocks and motor
130 oz-in Torque Stepper Motors
this machine can cut:
Expanded polystyrene "breadboard foam"
Blue or Green Extruded Polystyrene Foam Insulation
Drill Bits (3/16 is used most)
Wood Drill Bit
and 3/4" Metal Hole Saw
Fluid or Oil (for drilling)
saw or jig saw
Deep Well Socket
Wire Cutters (Side Cutters)
Solder (0.025 diameter)
the article I show you what I used to build this machine. Chances
are that other ways, different methods, materials and different
hardware will also work. With the exception of the Ultra High Molecular
Weight Polyethylene (UHMW) plastic, some electrical supplies and
the bearings, all other materials were purchased locally at the
"big-box" home improvement stores and the local auto parts
store. The bearings were purchased in the skate board section of
the local sports store.
x 1/16" Wall Steel Tube
(2) at 25" Long
Thick, 1.25" x 1.25" Aluminum L Stock
(2) at 24.75" Long
(4) at 6" Long
(electrical isle of home improvement stores)
(8) at 60" Long
(4) at 25" Long
(2) at 56.75" Long
Thick, 1.25" Wide Aluminum Flat Bar
(2) at 6" Long
(4) at 4" Long
Thick UHMW Plastic
(Ultra high molecular weight polyethylene)
(2) at 3.5" x 2.5"
ID Rubber Fuel Hose (from auto parts store)
(2) at 1.25" Long
(2) at 1.0" Long
Super Strut -Steel L Bracket
(electrical isle of home improvement stores)
Super Strut - Steel Flat Bracket
(electrical isle of home improvement stores)
1/16" x 4" x 4" Steel L Bracket
(decking isle of home improvement stores)
(16) Skateboard Bearings
(from sports store)
1-1/2" Long 5/16 Shoulder Bolts
3/8 Spring Clips
(4) 1/4" Spring Clips
(electrical isle of home improvement stores)
3/8" x 1" Screws
(4) 1/4" x 1" Screws
(4) 1/4" Washers
Plywood or Particle Board
(1) at 48" x 57"
(2) at 1" x 1.625" x 57"
1/4" Hose Clamps
(from auto parts store)
CNC offers a FoamPro kit that includes a stepper motor driver
board kit (unassembled), four 130 oz-in stepper motors, hook
up wire and a printer port cable. The stepper motor controller
board is connected to a printer port on a computer and controlled
by software designed to run a 4-axis CNC machine.
kit includes nearly everything that you will need, but you
will need to provide a case for the board, a cooling fan and
two power supplies. One power supply will power the stepper
board and the other will power the hot wire to cut the foam.
from HobbyCNC provides excellent tech support through a Yahoo!
group which you can join after you purchase a HobbyCNC kit.
HobbyCNC package comes well protected in lots of of bubble wrap.
The kit includes the board and a large bag of components.
Look at all those parts! Once you organize the parts it will
make it much easier to find the ones that you need when putting
the board together.
kit includes capacitors, voltage regulators and resistors.
HobbyCNC board is well marked and easy to read. The instructions
are detailed and complete. The stepper motor chips come in an
electrostatic safe bag.
Tech Machining First Look
fit and finish on motor mounts
machined parts make building the machine easy!
Tech Machining Introduction
Precision Tech Machining is a full service machine shop that
also offers products that help the hobby CNC machine builder.
The offer ACME lead screws, lead screw nuts, bearing blocks
and motor mounts. These products makes it easier to build
a CNC machine without having a mill and lathe in your garage.
screws come machined on both ends to accept the bearing blocks
and a drive coupling. Used in the review are two 24" and
two 48" lead screws. All lead screws are 1/2"-10 ACME
Bearing blocks and two motor mounts make this machine easy to
build without a mill and a lathe. The vertical axis bearing
blocks (center - four required) we specially designed for this
Dimensions are are shown in the review. If a dimension is not
shown, it's either a non-critical dimension or the part is match
drilled in place.
holes for 8/32 screws were drilled with a 3/16" drill bit.
of the "Super Strut" material is done with a metal chop
saw. This chop saw was purchased at a discount tool store for $50
and has worked well for many projects before this one. Use a tape
measure to measure the lengths. Use a T-Square to make sure that
the guide on the saw and all cuts are square. Measure to the outside
of the saw blade and leave about 1/32" between the mark and
the blade. You should cut all pieces to +/- 1/16" tolerance
"Super Strut" channels are bolted together using spring
nuts. These are inserted into the channel and are held in place
using the springs that are attached to them. The base machine builds
very quickly. When tightening the parts use a square to ensure that
the channels are at right angles.
aluminum was cut using a jig saw and a metal blade. The brackets
for the vertical axis start out as L stock and are trimmed as shown.
Use a file to clean the edges up. You will need to make four of
holes for the bearings are drilled in a few steps to make sure they
are in the right place. Using the multi-step process will help prevent
the drill bit from "walking" and drilling off from where
you intended it. First, measure and mark where you want the hole.
Then use a punch to mark the spot. Then use a center drill (short
stubby drill bit in the middle) to drill a starting hole. Then use
a twist bit to drill the hole. When you are done debur the holes.
I used the drill press to keep the holes square.
the four vertical axis brackets according to the images. Multiple
5/16" washers act as spacers. The ID of the bearings is actually
8mm (0.3149") and the bolts shoulders are 5/16" OD (0.3125"),
but once the bolt is tightened, there is little slop.
purchasing the "Super Strut" Pick out pieces that the
bearings will fit into. I had one piece that I had to open up using
a hammer and some plastic blocks. Test the brackets on the "Super
Strut" to make sure that the bearings ride on the top and side
of the rail. If the "Super Strut" is dirty, you may need
to clean and polish the areas that the bearings ride on. In the
picture on the right you can see most of the pieces for both vertical
axis laid out.
0.5" thick UHMW (Ultra High Molecular Weight Polyethylene)
plastic moves up and down the vertical axis and has the hot wire
attached to it via the 3" screw. It electrically isolates the
wire from the rest of the machine. The UHMW has a low friction coefficient
and is simple, eliminating the need for several more bearings.
3/4" steel tube takes the bending load from the wire by letting
the plastic block slide up and down. You will want to take some
000 steel wool and dish soap with warm water and polish it until
it is smooth (It doesn't have to be shiny). Having the lead nut
tight against the UHMW plastic ensures that the plastic won't bind
on the 3/4" steel tube.
to final assembling the vertical axis, you will need to install
the slack adjustors. The slack adjustors are two "L" shaped
pieces of aluminium with a 1/4" diamter screw in each one.
The 1/4" diameter screw is adjusted very close (without touching)
to the 3/4" steel tube. These screws prevent the plastic block
from rocking back and forth when the wire changes direction. Adjustment
of the screws will be covered in part 2, since it requires the hot
wire to be installed and under tension. The brackets are held on
the plastic block with (4) 8-32 screws and nylon lock nuts.
assembling the bearings to the bearing blocks and the lead screws,
parts should easily assemble and may require some light tapping
to assemble. If more force than light tapping is required, some
rework will be required for a good fit. If you force the bearings
onto the lead screws and the bearing blocks you will have excessive
friction that the stepper motor will not be able to overcome the
moving parts of the vertical axis are tied to the axis with 1/8"
thick 4" L brackets. You will need to drill holes to mount
the bearing blocks. Be sure to leave about 1/4" between the
bearing block and the bracket to leave room for the screw heads.
On the top add the 4" long aluminum for the vertical axis motor
where the lead screw needs to go through the vertical axis and cut
a "U" shape. Drill a 3/4" or larger hole with a hole
saw and then cut to the tangents of the circle with a jig saw. To
align the horizontal lead screw I used 2 pieces of wood that were
cut together so they had the same height. A table saw makes this
task easy. Simply place the wood under the bearing block and mark
the Super Strut to drill. Drilling the holes a bit oversize will
allow you some adjustment. Leave the screws loose so you can adjust
the lead screw later. Install the screws to attach the lead screw
nut to the vertical axis.
the vertical axis and the horizontal lead screws are installed,
you can align the horizontal lead screws. The easiest way is to
move the vertical axis to the front end of the horizontal axis and
then tighten the screws holding the bearing blocks on that side.
This will align the lead screw to the bearing block. When the front
side is done, move the axis to the rear and tighten those screws.
Repeat on the opposite side horizontal axis. I used a 1/4"
drill bit, a clamp and 1/4" ID fuel hose to move the horizontal
that the basic construction of the machine is complete, it's time
to add the HobbyCNC motors. I started by adding the vertical axis
motors by using the Precision Tech Machining motor mounts. You can
align the motor side to side visually, and I used a ruler to align
the motor fore and aft. Simply measure the shaft of the motor and
set the shaft of the lead screw to the same distance. Mark and drill
the holes. The 1/4" ID fuel line can tolerate slight misalignments.
the horizontal axis motors by drilling the mounting holes in the
aluminum stock. Drill the center of the mounting bracket just a
bit larger than the 1/4" ID fuel tubing. Make sure that the
clamp that is closest to the motor is 0.4" from the base of
the motor to clear the "Super Strut". Slide the second
clamp on the hose and install the motor. Drill a 1" circle
in the side of the "Super Strut" so you can tighten the
hose clamps. Insert the motor by sliding the fuel hose over the
motor shaft and tightening one of the hose clamps.
the wood that will form the base for the foam to sit on. To save
in cost of materials, I made 2 strips of wood to support the outer
edges. Nail the strips of the wood to the base. Now the basic mechanical
construction is complete.
that the mechanical construction is complete, it's time to build
the the HobbyCNC board. The first step is to organize the electrical
parts. You can identify the resistors by the color bands on the
body of the resistor. In addition I used the multi-meter to measure
each resisters resistance prior to inserting it into the board.
the far left picture, the basic construction of the board is completed.
The only remaining parts are the electrostatic sensitive stepper
chips and programmed PIC. At this point you will complete the TB5
test to check and make sure that 5 volts is present at the test
pad. This indicates that all the components are installed correctly
prior to installing the stepper chips.
HobbyCNC board is enclosed in a plastic case that is not included
in the HobbyCNC kit. The directions specified a part that could
be ordered from an electronics supplier, but I found that a case
from the local Radio Shack that worked (P/N 270-1809). Cut a hole
in the top case for the cooling fan in the location specified in
the directions. Here a hole saw or jig saw will work. Route the
wires for the fan to the inside of the case and use the supplied
template to layout the front panel. The front panel houses the switches
and connectors for the HobbyCNC board.
it comes time to install the heat sink to the stepper motor chips,
you will need to drill and tap the aluminum bar that is supplied
with the kit. It is a good idea to use some heat sink compound to
help transfer the heat from the chips to the bar. This is the same
stuff that is used on computer CPU's and can be bought at Radio
Shack. Once you tighten the heat sink on the chips, you should have
a little squeeze out from the heat sink compound. Make sure that
the bar does not extend down past the bottom of the chip, or you
will short the chip out.
the board in the plastic case and make the connections to the switches
and banana jacks. Also run the power into the box and hook the negative
side to TB5 and the positive lead to the 8 Amp fuse. Run the other
side of the fuse to the positive side of TB5. I installed banana
jacks between my power supply and the HobbyCNC box so I could use
same power supply to charge batteries when I was not cutting foam.
the HobbyCNC board is completed, you will need to complete the Vref
test before hooking up the motors to the board. With the stepper
chips installed, apply power to the board and adjust each axis potentiometer
(small blue adjustable part) to the correct voltage (see instructions
for the correct voltage). This will set the amount of current that
goes to each motor, so it's important to set it correctly. Do this
before hooking the stepper motors up!
the VRef test is complete, route the included hook up wire from
the HobbyCNC controller board to each motor. Make sure that you
plan your wire runs carefully, the kit includes just enough wire.
I located the HobbyCNC controller in the front center of the machine.
The horizontal axis wires are the shortest with the rest going to
the vertical axis motors.
soldering the wires of the motor to the hookup wire, the motor will
have 8 wires and the hook up wire will have 6 wires. Two pairs of
wires on the motors are "common" and must be twisted together
before connecting to the hookup wire.
some holes in the motor mounts and secured the hook up wire to the
mounts using a zip tie. This provides strain relief to the motor,
ensuring that the moving motor doesn't have it's wires pulled out.
the parallel cable and 12V power supply to the HobbyCNC board and
you are ready to fire the machine up. If you turn on the power supply,
all 4 motors should "lock up" and hum (with or without
the computer connected). This indicates that all four stepper circuits
are functioning correctly. Do NOT connect or disconnect the stepper
motor wires to the board with power on the board, you will blow
the stepper motor chips!
this first part of a two part series, we covered the construction
of a hot wire CNC foam cutting machine. The mechanical and electrical
construction was covered.
the next segment we will cover installing the hot-wire and hot-wire
power supply and how to setup and operate the GFMC software. Drawing
cutting shapes in the computer and the differences in types of foam
will also be covered.
a CNC Hot-wire Foam cutter you will be able to make many complex
shapes including wing cores and fuselage parts quickly and easily.
Using the HobbyCNC and Precision Machining Tech parts makes the
construction of this "scratch built" project fast and
The comments, observations and conclusions made in this review are solely with respect to the particular item the editor reviewed and may not apply generally to similar products by the manufacturer. We cannot be responsible for any manufacturer defects in workmanship or other deficiencies in products like the one featured in the review.