The plasma table CNC build has officially gone into fabrication phase. I have sacrificed multiple, sleepless, nights coming up with a game plan and determining the best sequence to build the table in. I have opted not to use any existing plans but instead engineer the table my way. I have a “big picture” in mind however all the details that are required to ensure the concept will be completed are yet to be determined.
Most tables are typically started by building the main frame. Since there are so many unknowns as far as gantry sizes and, more importantly, X,Y,Z travel dimensions I decided I am going to start from the center of the universe. In this case I am going to build the entire table around the tip of the plasma torch. This would mean I begin with my Z axis.
Since part of the construction of the Z-axis involves its ability to move along the X-axis I needed to come up with a linear movement system. X and Y axis linear movement methods are obviously nothing new. There are multiple systems that a proven to work well. My favorite has always been the Dualvee Bearing design coupled with the Vee rails. It takes care of both the radial and axial movements all in one shot and it does it in a fairly compact set up.
Since the whole point of fabricating the CNC is to actual “fabricate” I wanted to avoid purchasing as many components as possible and instead build the items. Coming up with a simple linear motion system that I had the skills, and equipment, to build was tough. I didn’t want to clutter up the sliders with aluminum plates housing 8 bearings each just to keep things smooth and straight.
After much thought I took some inspiration from the Vee bearing design and opted to build my own version but without the Vee. My version would incorporate a radius bearing that would ride along a 4140 alloy rod. If the design works it will control the radial and axial loads just like a Vee bearing does.
Weight of the table is a huge factor and this will become evident why later on in the build. So after a bit of experimenting I came up with a system to accurately machine radius bearings out of aluminum. Aluminum is not exactly the first choice for bearing material however in my case the loads are not massive plus the ability to anodize aluminum will certainly add a layer of hardness. The following outlines the first steps in building the CNC table by starting with the axis bearings.