Here at the Foundery we want to provide our members the tools, education, and encouragement to build anything they can dream. And while we will do our best to educate and support members in their endeavors, it’s all meaningless unless we provide the right tools for the job. To that end we have amassed quite a collection of tools. From the simple, but versatile, hammer all the way up to the Abrasive Waterjet, and everything in between. Today’s post, however, will pull from the higher end of that spectrum and aim to educate you as well.


CNC Plasma Cutter

What you see here is a CNC plasma cutting system. And while I already know your first question, why is it red, I’m not going to answer that question just yet. But what I will do is answer the first question you should have asked, which is what does CNC mean. CNC stands for computer numerical control, which is just an elaborate way of saying that a computer controls this machine. This, of course, is only half the puzzle to understanding this machine. The other part being what is plasma cutting.

I could go into a long explanation about how plasma cutting works and an even longer explanation into plasma (The Fourth State of Matter), but I’ll leave you to research those topics for yourself. But in the simplest technical sense, plasma cutting utilizes an accelerated jet of hot plasma to cut through any electrically conductive material. In layman’s terms, super hot gas slices through metal like a hot knife through butter! Pretty cool, right.

Photo by Brown Photography – Retro Systems LLC (CC BY-SA 3.0)

Photo by Brown Photography – Retro Systems LLC (CC BY-SA 3.0)

Putting this all together, what we have here is a machine that is computer controlled and can cut through metal. Basically this machine can be used to cut almost any 2-dimensional shape out of metal.  Again, I already know what you are going to ask, don’t you already have a machine that can do that. Yes we do, but there are major differences in the capabilities of these machines and that is why we have both.

Plasma Cutting System Abrasive Waterjet
Faster Slower
Can only can metals Can cut just about anything
Cheaper to operate More expensive to operate
Lower precision High precision


Beyond the basic differences of the two systems, there are more specific differences in our machines. For example, our plasma cutter cannot cut metals thicker than half an inch. While the waterjet can easily cut materials which are much thicker.

This post is getting pretty long and I still haven’t even covered the question I know you want answered, why is it red? The answer is quite simple; to make it watertight. However, the explanation for why we decided to do this is a bit more involved.

When using a plasma cutter, a lot dust and smoke is generated in the process. This dust and smoke must be captured and redirected away from the operator and occupied spaces. Our plasma system had a downdraft ventilation system. Basically, the bottom of the table had a large hole which was hooked up to an external exhaust system used to pull all the smoke and dust away. When Jason purchased this used system several years ago our current location and facilities didn’t exist. Once the new location was established Corey and Jason quickly realized that using a downdraft ventilation system was not a viable option. But fortunately for us there is more than one solution to this problem.

Corey, having personally built a smaller CNC plasma cutter in his garage several years ago, already had the solution. Convert the system to a water table. A water table will capture the dust and smoke before it’s able to leave the cutting area.

There were, however, several issues with this approach. Firstly, filling the table will 1,000+ lbs. of water would exceed weight capacity of the table. So Audrey put on her welding helmet and welded several additional support members to the table and frame.

Secondly, what should we use to make the table watertight? After much research and debate, we decided to use an unlikely material. RedGard® is a membrane typically used in construction for waterproofing under tile flooring. (That is spelled RedGard not Redguard for all you Elder Scrolls fans out there) But, as it turns out this product was perfect for our waterproofing application. So we plugged the bottom of the plasma table, leaving only a small drain hole, and proceeded to add several layers of RedGard. And finally we ended up with a watertight and very red plasma cutting system.


The first coat

Ok, this post has gone on long enough, and you should now know why we have a red CNC plasma cutter. I also hope you learned something about plasma cutting systems. I know I didn’t cover any of the motion control hardware, software, or general repair of aspects of the system that we performed to get this used equipment back up and running. If you’re interested leave a comment and I can always write another post on those topics.