I machined a fixture on the manual mill to bolt the shock mounts to before using the CNC. I drilled the bolt holes such that they were located using the edge finder off the same surfaces that would be probed using the CNC. Thus, all the coordinates of the model geometry that the CNC would use would be in reference to the bolt holes, eliminating the propagation of error caused by the lack of precision offered by metal 3D printing.
The four bolt holes were machined relative to the marked surfaces such that the coordinate origin is at the spot marked “X”. The CNC was also probed off these surfaces to use the same coordinate origin.
On April 6 I machined the two shock mounts. I encountered one issue: 3 of the 4 surfaces that we were going to use to touch off on for reaming the center holes of the two parts were not actually machined by the dimensions of the part, so I had to offset both of the top touch off surfaces and the side touch off surface for the left shock mount. The result is shown below.
The left and right shock mounts, showing the two touch off surfaces. The surfaces that needed to be offset in the CAM are circled.
The three offset surfaces
The top surface of the right mount, the top surface of the left mount, and the side surface of the left mount were offset by 0.025”, 0.03”, and 0.035”, respectively.
| Surface | Offset (how much more material was machined) |
|---|---|
| Right mount top | 0.025” |
| Left mount top | 0.03” |
| Left mount side | 0.035” |
^The hole positions need to be offset accordingly.
