I was hating the way my old bumpers were looking on my 1968 vw bug so I made my own AR15 replacement bumpers! I was able to create the entire project using the machines and tools at techshop menlo park. I used the old bumper brackets, 3/16 mild steel, the cnc plasma cutter, corel draw, sandblaster, MIG welder and powder coating system to make these one of a kind bumpers.
Step 1: Plasma cutting the AR15s out
After creating my file and l uploaded it into the Torchmate software for the CNC plasma. I then entered all the different settings provided for the amperage and thickness of material into the machine. Once that was all settled I ran the gcode to ensure my parts would cut out in the correct order. I then enabled the torch to cut and ran the file. After everything was all cut out and my parts were cool enough to touch I started in on the removing of slag.
Step 2: Removing the slag and sharp edges
After cutting there is a thin layer of slag that needs to be removed. I used a chisel and a hammer to chip the slag off my parts. A light tapping of the hammer is all that should be needed to remove the slag. Too much pressure from the chisel will leave gouges in your material which will show through when you powder coat.
The edges are also ragged and sharp after cutting them out so I used some different types of files to smooth them out. I used several types of files because of all the different nooks I had to get in to.
I also took the bracket and cut off the tabs that the bolts for the old bumper went through. I wanted to see as little as the bracket as possible so I also cut out the center of the bracket.
Once every thing was filed and cut I prepared the surfaced that I would be welding by using the sandblaster to remove paint and mill scale from my parts.