My Heap

PART 01: RESEARCH - Last Updated 14 MAR 2006
PART 02: BENCHWORK - Last Updated 22 MAR 2006
PART 03: G CODE - Last Updated 21 MAY 2006
PART 97: PROJECT COST - Last Updated 30 APR 2006
PART 98: BUILD LOG - Last Updated 30 JUL 2006
PART 99: RESOURCES - Last Updated 14 APR 2006

If you are looking at this page, you may be wondering just what someone who likes to cast metal would want with a machine that cuts foam. Maybe you know why I would like to use foam in metal casting but are wondering just what a CNC Foam Mill is. Below you will find answers to these questions and why I think I want to undertake such a project.

What is a CNC Foam Mill? I think before answering that question I should first address what a CNC anything is, or more precisely, what does CNC mean. CNC is an abreviation for Computer Numeric Control. CNC in it's most basic definition allows a computer to control devices by using numbers. These numbers along with other codes tell the device to move something to some position. A Mill is a piece of machinery that allows you to shape metal. For example, you could cut ways, channels and a bunch of other things. If your Mill is equiped with a dividing head, you can further your endeavors by being able to cut things like splines on shafts and teeth on gear blanks. Now in my example, I said metal, but the same principal can be applied to other materials, like plastic, wood and even styrofoam. Now to answer the question as it was presented. A CNC Foam Mill is a milling machine controlled by a computer that will be used to Mill or shape foam into some usable thing. A Plaque for example.

Why or how would you use foam in metal casting? For hundreds of years. Artisians have been using a process called lost wax casting in making jewelry and a bunch of other items. The idea behind lost wax casting is that you design or carve out of wax what thing you are wanting to cast. A ring would be a good example. The wax ring once carved and designed how the artist wants it to look next takes the wax ring and attached sprues to it. The whole mess is then submerged in a refractory material and allowed to set up. (A simple refractory for lost wax casting can be made from plaser mixed with very fine silica.) Once the refractory has set up, it is placed in an oven and allowed to heat up slowly melting the wax from the refractory mold. Once most of the wax is melted out, the refractory is further heated until any wax residue is completely burned away. After this the caster would pour his gold into the cavity and when cooled would remove the refractory and uncover his/her new gold ring. But the end result is that the original wax pattern is gone forever or just plain ol' lost. Hence the name, 'lost wax casting'.

A similar process can be done by using foam instead of wax. When using foam for casting bronze, brass or aluminum, the foam is packed in a refractory (like dry or green sand) and the metal is poured directly into the foam burning it away. The void left by the foam is filled by the metal you are pouring and the end result is you have a replica of your foam pattern in metal. But like the wax, the original foam pattern is lost forever. The processes described above have been over simplified to show the point. I want to tell you that there are other things to consider when using foam for casting. There are a number of good web sites on the Internet that you can check out to see what all goes into it. One site that comes to mind is Bob's Metal Casting. It is because of pages like Bob's that I developed the courage to try a project of this magnitude. Additionally, I owe Bob a big thanks for the help he has provided me. THANKS BOB!!! ;-)

What made me decide to try a project like this? This is really a complicated question. I have plenty of reasons for doing this and a few against. Some of the reasons I decided that I wanted a CNC Foam Mill are; it gives me the ability to create a master with lots of detail over and over again with no variation, it allows me to make patterns that fit together well taking into account shrinkage from the specific metal I want to cast, and finally, depending on the stepper motors used, and the tool used to do the physical cutting, I would have the ability to make things from plastic and wood. And finally to be fair about why not to make one ... There are lots of things you have to learn about, CAD - CAM - G-CODE, electronics, computer interfacing, etc. Also there can be a hefty cost involved depending on how you want to go about doing the project.

Well those things aside ... I have to figure out just what it takes to make one of these beasts. I figure next comes a little research. To follow my progress, check the links below.