3D Printers, and to a lesser extent laser cutters, get a lot of attention as computer-controlled maker tools. As great as they are for small parts with light materials, if you want to cut on an industrial (or combat robotics) scale, perhaps a plasma cutter is what you need. In order to facilitate his pursuit of robotics, David Randolph built his own for the bargain price of around $3000 (and it only took two months of his time, much of it spent waiting on parts)!
According to Randolph,
I was building my 1st heavyweight combat robot “Simba’s Revenge” and I needed some parts plasma cut. They wanted a fortune for the parts so I was determined to do it for less. I used the opportunity to learn how to do CNC work and how large CNC machines worked. I continued to use it for my next robot “Super Fluffy Pink Bunny from the land of candy and rainbows”
When asked about his build process and his practice of not using a drawing, but instead having the design in his head, he said that,
Generally when I build I tend to look at the whole project and I identify the problems that will limit the build and then I build around that. So with the plasma cutter I wanted a 4ft x 4ft cutting area and the problem is a gantry needs room at the front and back and left to right so I knew the base would need to be 5ft wide and 5ft deep to clear all the assembly and give room for the torch to move around.
This kind of theme is certainly familiar to most makers on a budget. There’s an awesome device you want to build (a robot in this case), but in order to build it you need an expensive tool. The question is always whether you build the tool yourself, learn, and perhaps save some money, or buy something that you know works. In Randolph’s case, it seems like his DIY answer was the right one, as it looks great, and he reports that, “All in all it worked like a charm.”
One thing that I wondered about this build was why he chose to include a Z-axis? In theory, plasma cutters work with flat material, much like a laser cutter, so this would seem to be unnecessary. He replied that,
You don’t have to have a Z-axis, but it’s helpful in the same way that a Z-axis helps with a laser cutter. You need to be a specific distance away from the surface and that varies depending on the material’s thickness. I also had planned to add in AHC which is auto height control but never got around to it. AHC allows the cutter to monitor the arc and move the Z-axis up and down to keep the plasma arc perfect. Really good when cutting thin metals that will warp over time.
This plasma cutter is controlled using the Mach3 software package, familiar to many home-CNC builders including myself. He’s even been able to use it with both a PlayStation 3 and Xbox 360 controller, which simply required finding the appropriate software plugins for the controllers. As he puts it, “It was a far cheaper an option than most of the professional controllers out there and a lot more fun.”
Perhaps the next logical question is that since there are three axes and a large work surface, why not use this as a CNC router when needed? According to Randolph, he’s not going to make this into a mill, as it’s not strong enough to handle the router with the back pressure from the bit. He reports that he has “a few smaller mills” for that work. Apparently he has one of the best-equipped home shops of anyone I’ve been able to feature on Make:.
You can see his cutter in action cutting out a logo in the video below. If you’d like to see how his combat robots turned out (the ultimate goal of this build), images and video of “Simba’s Revenge” can be seen here, and images from the later “Super Fluffy Pink Bunny from the Land of Candy and Rainbows” (also known as SFPBFLOCAR) are found here.
If that wasn’t enough to convince you of Randolph’s maker cred, he casually mentioned that he also built his own laser cutter, pictured below in his dining room. The result: A 1200mm x 900mm 100 watt laser in a nicely finished package that looks great— though the cost of the build was still around $6000.