Making a [very cool looking] Dome Plate

As I get the second R2-D2's build back on track, one piece I did not have was the dome plate.  This is the part where all of the gadgets will mount to inside R2's dome.  For example, the periscope, the life form scanner and other things.

The one I have in the first R2 is a 1/8" inch thick dome plate.  While it works fine, I wanted something thicker the next time around. 

The great thing about being part of an R2 Building Club is the way people share their ideas with one another.  Another builder shared with me a drawing of a dome plate that was really well laid out and looked great.  Using the 1/4" inch aluminum, it has numerous grooves, holes and cut outs that reduce the weight of the finished piece.

Once I had a chance to review the drawing with my machinist friend, it was pretty clear we had a good amount of work ahead of us.  We had to tell the software what to cut thru, what parts to cut down an 1/8" of an inch, where to place tabs and so on.  This took about two hours to do.  Once we were happy with the calculations and previews of the end result, we created the g-code for the Mach 3 software.  The Mach 3 software takes that code and controls the X, Y and Z axis of the CNC machine.

Software loaded, everything is calibrated....

I purchased a 17 inch by 17 inch piece of aluminum plate from my local metal supplier.  Once the piece was clamped in and the CNC machine was calibrated, it was time to sit back and watch it work.

And watch, we did.  Since our CNC machine can only use one tool at a time, it did the entire piece with its 12mm cutting bit.  More advanced machines could change tools to remove move material with larger bits, getting the job done much quicker.  However, for us hobbyists, this works just fine despite taking a lot longer.

Specifically, this took 8 hours and 41 minutes to cut!  Then, another hour or so to remove all the tabs that hold many pieces in place until completed.

8 hours and 41 minutes later!

Once all the pieces that were no longer needed were removed, you can see how neat this part looks!

The original metal plate weighed just over 6 pounds.  After all the excess material was removed, the dome plate weighs 1.87 pounds.

To remove all the metal scratches and lines left from the cutting bit, I had a friend bead-blast it.

To protect the finish, we clear coat the dome plate...

Granted, the only time people will see this part is if R2's dome is off.  But, it was a great challenge to see if the CNC machine could make this piece!