Now, how to get from plan to reality.
Back in an earlier post I posted an image of a widget. This widget is actually a zeroing fixture for my minimill.
A note about my minimill. One of my other hobbies is CNC machining. The minimill is a heavily modified Harbor Freight 44991 minimill and is a work in progress. Some of the modifications include an extended Y axis, precision cut ways, brass gibs, belt drive, computer controlled spindle and a stepper/ball screw driven CNC conversion.
The second image is of a tooling plate, also for the minimill. It took a month of sundays to drill/tap 105 10-32 holes on a 1x1 grid. The tooling plate bolts to the stock table on the minimill and provides a convenient platform upon which a variety of fixtures can be mounted. The third image shows the zero fixture mounted on the tooling plate. The indicator is a coaxial indicator and is used to align the center of the spindle with the hole in the zeroing fixture. Once that's done, the machine XY zeros can be accurately set.
The fourth image shows the milling fixture which will be used to machine the avbay bulkheads and internal mounting components. The fixture serves several functions. First it secures the workpiece to the table. Secondly, it protects the tooling plate from inadvertent damage should I make a programming error or if something bad happens. In this respect it is sacrificial.
Next are a stack of .75x6" blanks from which the bulkheads will be machined. They were predrilled to allow mounting to the milling fixture.
Each bulkhead will receive two machining sequences. The first is the pocketing. The last image is of the pocketing toolpath as generated by the madcam Rhino plugin. The second sequence will cut the partially machined bulkhead out of the blank and is written in simple g-code.
Given the size of the minimill, one cannot make very aggressive cuts. Each cut was .050" using a 1/4" carbide endmill at a fairly slow feed rate. Needless to say, it takes some time to machine a bulkhead.