Over the past three years I have been experimenting with different designs to achieve the best quality, lowest cost and easiest to build automatic foam cutter.

It all started when I got my first flying wing, and decided I wanted to cut my own wing, which I believed would be much better than the one I purchased. Eventually, I succeeded in achieving a simple low cost automatic foam cutter, which will cut any desirable shape using an "X-Y" configuration.

Surprisingly, I found that foam is used for a wide variety of hobbies and businesses, such as: making surfboards, hovercraft, architecture, advertising and aero-modeling, just to name a few.

Comparison Review: Conventional gravity operated foam-cutting machines with all table accessories, vertical cylinder cutters and crosscutting equipment, power supplies and bows cost at least $650 plus for a complete setup. You can "make your own" CNC machine from purchases made at local hardware stores, electronic stores and/or the Internet for about $250-$300 plus your time and labor. Depending on the price you pay for the Stepper motors.

Our professional, "Precision Pro-FoamCutÒ ," retails for $800 and can be purchased through http://burnsmodelaircraft.com and does not require as much space nor added accessories as the gravity machines. It will cut vertically, horizontally, any degree angles, compound curves, and multiple wire cuts and will cut ANY desired airfoil possible including cylinders and fuselage shapes. It will even do multiple wing cores at one time if desired. The big plus is, NO TEMPLATES REQUIRED, EVER.

The "Precision Pro-FoamCutÒ " is machined from stainless steel components with TeflonÒ sliders and laser-cut powder-coated steel brackets and high quality stepper motors and electronic driver circuit board with cutting wire and power supply included.

These will be available to be shipped worldwide plus shipping charges. Overseas charges may cost $200 plus for shipping and tariff charges.

Why use foam? Larry Burns cuts and sells planes like these at:  http://www.BurnsModelAircraft.com

They are made from Expanded Polypropylene Foam (EPP), a very good and forgiving material to use that has "memory" which means it will spring back to its original shape.

These planes are nearly indestructible. Therefore, EPP foam is especially important for use with combat wings and combat airplanes. But, all aspects of modeling can make use of foam in construction of model aircraft fuselages and wings.

EPP comes in two typically used densities: 1.3 density (usually used for wings because of its lighter quality but can be used for fuselages as well) and 1.9 density (usually used for fuselages (because of its denser more rigid quality, but can be used for wings as well). Other foams are: Pink foam (very light and good for indoor flying), White foam (In one pound and two pound densities, good for making wings to be covered with balsa or Obichi wood (1/64th inch thin plywood) and blue foam (very light and also good for indoor flying). Except for EPP, these other foams are more rigid, making them brittle and easily broken in a crash. There are many and varied uses for the different foams used on R/C planes and the modelers’ choice is usually for whatever the project they use them on dictates.

Searching the web for two years, to date, I still have not found a simple design for a low cost automatic foam cutter. For this reason, I decided to share my experience with all fellow R/Cist, hobbyist and foamies. I knew what I was looking for – Construction articles with "LOTS" of pictures, but I never found them. On my site you will see lots of pictures with a few words.

In my design, almost all parts can be found in your local Home DepotÒ or hardware store at surprisingly low prices. Special tools are unnecessary to assemble the CNC machine. You may follow my link, that explains step by step how to put the CNC machine together. www.8linx.com/cnc/cnc.htm

The machine is comprised of three main parts:

Mechanics – All parts can be found at your local hardware store for about $150.

Electronics – Can be found in some surplus stores or here: www.8linx.com/cnc/day2.htm.
Software – The most popular foam cutting software: http://gm.cnc.free.fr/index_en.html for about $32.

Nichrome cutting wire and cutting bows can be purchased from: http://burnsmodelaircraft.com (a bow can be used with the CNC if you have a special need for it. Although it is unnecessary for most of the cutting, some cutting with a bow may be required if you are doing finish work on some fuselages or some other creative work that an X-Y machine cannot do.) You may find that the "Home-built CNC" or the "Precision-FoamCutÒ " is the end of all other foam-cutting requirements.

In order to keep the design as simple and cost effective as possible I decided to use drawer slides. On the X (horizontal) axis I used the longest I could find – 26" but later I found out that there are even longer ones out there. A close look at the design shows that each X-axis uses two slides, total of 6 slides on the table.

Since I chose to use the French software, I had to find a way to make the hardware work with the software. There are a few designs out there that work well with the French software, but I could never get it working to my satisfaction. For that reason I chose the simple cost effective solution, a board that controls only the motors but not the wire temperature. To change the temperature of the wire I use a router speed control with a high current transformer http://www.8linx.com/cnc/day5.htm

The Software: I chose to use the most popular software available. It is made in France by Gilles Muller http://gm.cnc.free.fr/index_en.html

 His software was designed to cut foam cores, but it can cut other shapes too. It is easy to use and a great bargain - $32

A warning here!!! Do not to use a variac!!! A variac does not provide isolation from the main power; you can get electrocuted if you touch the wire. If you do choose to use a variac, make sure that you use another isolation transformer after it. Again, in order to provide a safe and cost effective solution I chose to use a router speed control and a high current transformer that will provide isolation from the mains power

Motors: can be found in most surplus stores. Try to use 5V 6V or 12V unipolar (6 wire) motors. Use of these motors will enable the use of a low cost PC power supply.

Both 5V and 6V motors will work fine using the PC power supply 5V wires Red (+5V) and Black (Ground). An ATX power supply can supply 20A, which is more than enough to drive these motors – most 5V and 6V motors are about 1Amp.

If you find 12V motors, then use the 12V on the PC power supply – wires colored yellow (+12V) and Black (Ground). Try to use a 1.8deg/step motors they are usually higher in torque [picture of the motor] & [picture of the power supply]

Brand new motors can cost from $40 to $100 and even more, try your local surplus store or EbayÒ for good deals on stepper motors.

The reason for using 2 slides on the X-axis is to achieve the lowest possible vibration and backlash

Stepper Motor Software

It is worth the extra time to visit his site for more information about the software and pictures of other machines that were built mainly in France.

http://gm.cnc.free.fr/index_en.html

When cutting foam, beware of the hazardous fumes because they are toxic. Make sure to work in a well-ventilated area. Always double check the voltage, make sure that there is no water around the electrical parts. Keep your hands away from all moving mechanical parts as well as the hot wire. Make sure there are no small children around!

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