Another project from our high school manufacturing class.
I could only get a few pics here, so I will comment again for more pics. Visit our class website for even more pictures.
This entire project was designed to test our ability to accurately 2 sided machine a part. Accurately aligning the second side to match up to the first side boggled my mind and I tended to steer students away from this. We settled on the Millennium Falcon from Star Wars. It has good detail on 2 sides, but we wouldn't be able to get the detail on the edge of it. Since most of the detail is on the top and bottom, this seemed acceptable. We had to make a new CNC table that easily and accurately aligns to the actual bed of the machine and has a home that can be aligned to without thought. Here is a link to the details of the table we made.https://penguinmanufacturing.wordpress.com/2016/04/12/new-cnc-routing-table/
Next, we brought in a 3D model of the Falcon into Vectric Aspire. We split the model in two in the software and had two 3D models of the Falcon. The top and bottom design. We realized that if it worked out perfect as planned, the Falcon would fall out of the wood near the end of the carve, so we needed a way to suspend the finished work in the wood. We designed in some sprues that will be cut on both sides of the carve. These sprues would get cut off with the bandsaw and sanded clean.
Since the dimensions we settled on was 20 x 13 x 3.5 inches, the next step for accurate flipping would be accurately creating these dimensions. The 20 inch dimension was less critical as that could be too long and not affect the flip. The 3.5 inches was critical to create the perfect meet up height on both sides. The 13 inch dimension was most critical to accurately align after flip. Unfortunately, we do not have accurate calipers that go that large, so we had to trust our fairly accurate Incra table saw fence that pulled this off. I still don't know how many .001's are off on the wood, but it can't be too many.
Side one: We roughed out the carve 3 times. 1/2 end mill with a .125 clearance. I didn't want the tearout to affect the final carve. a 1/2 ball end with .0625 clearance. and finally a 1/4 ball end with a .01 clearence. We did our final pass with a 3/16 ball end mill with 10% stepover. I would have love longer 1/8 inch bits, but finding 4 inch long 1/8 inch bits is expensive.
For the second side, we decided to try a new strategy. We did our first roughing pass with a 1/2 ball end mill with 30% step over and .06 clearance. This seemed to really cut down on the tearout. Second, we used a 1/4 ball end with a .03 clearance. We did our final pass with the 3/16 bit again, but shortly after starting it broke. We retried with a 1/4 ball end and it worked. The detail isn't as great, but since it is the bottom a slight difference in quality won't be noticed.
On to the base. We wanted a 1/4 steel base with the rebel logo. We CNC plasma cut the logo out also using Aspire. We added 3 posts made from some double hammered steel decorative bar we had.