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. I 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.
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 $300 to $500 plus your time and labor. Depending on the price, you pay for the stepper motors.
Why Use Foam?
Larry Burns of BurnsModelAircraft.com has created several aircraft 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. However, all aspects of modeling can make use of foam in construction of model aircraft fuselages and wings. EPP comes in two typically used densities of 1.3 density, which is usually used for wings because of its lighter quality, but can be used for fuselages as well, and 1.9 density, which is usually used for fuselages because of its denser more rigid quality, but can be used for wings as well. Other foams are pink foam, which is very light and good for indoor flying. White foam, available in one pound and two pound densities, is good for making wings to be covered with balsa or Obichi wood (1/64th inch thin plywood). Blue foam is another popular foam. Since it is very light, it is also good for indoor flyers. 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. A modeler's choice is usually dictated by the project.
After searching the web for two years, I still had 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/Cists, hobbyists, and foam bashers. 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.
The following information is for the hobbyist who wants to make his or her own CNC Machine. In my design, almost all parts can be found in your local Home Depot or hardware store at surprisingly low prices. Special tools are unnecessary to assemble the CNC machine. You may follow my link, www.8linx.com/cnc/cnc.htm, which explains step by step how to put the CNC machine together.
My Design Is Comprised Of Three Main Parts.
- Mechanics - All parts can be found at your local hardware store.
- Electronics - These can be found in some surplus stores, or over the web.
- Software - The most popular foam cutting software is the Gilles Muller software.
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 slide I could find, which was 26", but I later found out that there are even longer slides available. The Y-axis uses 20" slides. A close look at the design shows that each X-axis uses two slides, for a total of six slides on the table. The reason for using two slides on the X-axis is to achieve the lowest possible vibration and backlash
Motor driver chips for 4-stepper motors are made by AllegroMicro. The drivers can work in full step and half step modes. The board connects to the PC via a Parallel printer cable. The following is a link to a PDF file on AllegroMicro's site with more information about the stepper controller. www.allegromicro.com/datafile/5804.pdf
To control the wire temperature, I chose to use a router speed control and a high current transformer that will provide isolation from the mains power.
Warning! Do not to use a variac alone to control the wire temperature! 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.
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, since most 5V and 6V motors draw about 1 amp. If you find 12V motors, then use the 12V rail on the PC power supply. (The wires are colored yellow (+12V) and black (Ground)). Try to use a 1.8deg/step motors, since they are usually higher in torque. Brand new motors can cost up to $100 and even more, so try your local surplus store or EBay for good deals on stepper motors.
The most popular software available is made in France by Gilles Muller. His software was designed to cut foam cores, but it can cut other shapes too. It is easy to use and a great bargain. 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.
For those who wish to save the time and get a fully assembled and tested cutter. A professional, "Precision-FoamCut" retails for about $800, and it can be purchased through FoamLinx.com or from the distributor BurnsModelAircraft.com. It 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 it 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 that no templates are required, ever.
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 Pro-FoamCut" is the end of all other foam-cutting requirements.
Warning! 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, and 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!
I built one of these in 2002 using the information on Tal's first CNC site and parts from Tal. http://www.8linx.com/cnc/cnc.htm
Since then almost all my planes have been built with foam wings. I've used it on wings as small as 15" and as large as 80". It's really made building wings a lot quicker and easier. Thanks Tal!
Here are a few of the planes that have wings made with the foam cutter.
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I'm interested too....
the detailed schematics for the board would be very useful, the parallel port connections are obscure, and there is a chip at the lower right part of the PCB (next to the Y2 connector) thats is unknown.
somebody has a link were this part is better explained??
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|Article||CNC Foam Cutting Machine||Tal Barnea||The Builders Workshop||1||Dec 20, 2004 05:12 PM|
|CNC Foam Cutting Machine||dave_lilley||The Builders Workshop||1||Feb 05, 2003 04:21 AM|
|CNC Foam Cutting Machine||dave_lilley||Sailplane Talk||0||Feb 04, 2003 11:54 PM|
|CNC Foam Cutting Machine||dave_lilley||Site Chat||0||Feb 04, 2003 11:53 PM|
|CNC Foam Cutting Machine||dave_lilley||Foamies (Kits)||0||Feb 04, 2003 11:53 PM|