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Turner's Cube

posted Nov 16, 2012, 6:08 PM by Sean M. Messenger   [ updated Dec 30, 2013, 5:39 PM ]
This is a project that I started at the beginning of my sophomore year at Mudd. I saw a similar design and thought it would be cool to make something like it, so I designed my variation up in Solidworks, ordered the material ($22.00 from Amazon), and made it. Here is a final render and the drawing:

The design took a couple hours to get the proportions right. The whole design is intended to look like there is a cube inside a cube with the vertices fused together. In other words, I wanted the corners of each inner cube to be embedded in the wall of the outer cube. Then I repeated this, so there are a total of four "cubes." 

I ordered the 3.5" cube of aluminum from Amazon because it was the cheapest price for such a "small" quantity of stock and I have free shipping (Amazon Prime). My first design was actually for a 2.25" cube as a final product, which I was intending to get from a 2.5" cube stock. Then the 3.5" cube ended up being just $2.00 more expensive, so I opted for a "larger project." 

I went into the project knowing that I would do all the operations on the mill, rather than the lathe. Typically, projects like this are done on the lathe because of the added complexity of mounting and working with a non-cylindrical piece. I wanted experience, and chose to use the mill because I could get it done a lot faster that way. Each hole lends itself to be cut out as a pocket. 

First, though, I have to square up each face. To do this, I ground my own lathe tool bit from square 0.1" tool steel for use on a flycutter. The flycutter let me mount the lathe bit in the mill, which was then essentially a very large facing tool (a tool bit that cuts one whole side, or face, of a material). I used this to get a little over 3.5" of cutting surface, so that one pass would face the entire side. This is one of the passes:

Facing Operation

After squaring up all the sides, I had a perfect 3.4" cube of machined aluminum. Working on a CNC Mill, I had the advantage (or, more appropriately, the necessity) of the pocket feature. This feature lets the user specify a center, diameter, feed rate, and spindle speed such that the machine will automatically cut a circular hole out of the material. I started working in 2-axis mode for manual experience, so I set the program, manually lowered the spindle 0.1" into the material for each pass, and then let the machine run. I repeated that for four of the six faces, then automated the process for the last two sides. 

To do this, I loaded the code up in Mastercam X6*, did the toolpathing, and then got g-code to run the machine with. That process basically let me specify what the tool would do before hand, convert it to code, and then load it as a single program into the machine. Mastercam gave a simulation of what the toolpathing looked like:

Mastercam Toolpathing

Which then got loaded up onto the machine, and ran to give this (entirely automated):

Pocket Machining

The final product looks great, and is exactly how I wanted it. To clean things up, I used a deburring tool on the edges and then sanded with 360 grit. I finished with some 600 grit, and it looks quite nice. 

Started: 30 September 2012
Finished: 13 November 2012

*I got Mastercam X6 for free by contacting the educational department of Mastercam. My license is a Demo/HLE that lasts for a year. It includes everything except for post-processing. I did the toolpathing up, saved the file, and then Machine Shop Manager Paul Stovall converted it to g-code for the machine.