This article is part 2 of a series about the Sandia Mountains carving project. Click here to read Part 1.
Welcome back! After completing the planning phase of our mountain sculpture project, we were ready to move to the shop and start cutting.
BUILDING A BLOCK
Our plan was to use a nice piece of solid maple which was roughly 1.6"x8"x24" in size. Because we wanted a mountain sculpture much deeper than 1.6", we broke our workpiece down into two strips with different heights.
Gluing our two pieces together with tall in back and short in front, our rough block made a rough stair-step shape. This shape decreases material waste and cutting time, since the mountains are shorter in the front with lots of air above them.
LITTLE THINGS CAN MAKE A DIFFERENCE
Before taking our square-ish workpiece and removing all the straight edges, it was a great time to add keyhole slots to the back of the piece. This allows our artwork to be hung on a wall, if desired. A keyslot cutter (shown in picture) makes the complete feature by plunging and moving sideways.
During the rough milling phase, the majority of the unneeded material is removed. Similar to sculpting out of stone, we start with aggressive cuts to remove large swaths of our block.
Because getting perfect fine details is not important at this stage, the stepdowns between each cut layer can be clearly seen. Looks kind of like the lines on a topographical map, doesn't it? That's actually not a coincidence. The same principle behind "elevation lines" on a topographical map defines how the layers in our rough-cut workpiece look.
GETTING TO THE FINE DETAILS
With the bulk of the unneeded material removed from our sculpture, the next step is to go back and remove more material, cutting in the fine geographical details.This operation is what we call our "finishing" operation.
Finishing was done with a 1/4" ball-end mill. Starting at the top and working its way down, we cut the intricate details of the mountains in miniscule slices, stepping down .015 inches for each layer. These narrowly spaced "passes" blend together from layer to layer, creating a smooth overall finish.
With the majority of the unneeded material in our block removed, the finish tool doesn't need to make very deep cuts into the workpiece. This allows us to make very high speed passes with the tool. Despite this fact, finish milling was the most time-consuming aspect of our CNC cutting, with a run time of around 3 hours.
Unfortunately we didn't snap any pictures of the engraving process. This was a simple operation which involved etching some words into the front of the piece. We opted to include the location, name of our mountain range, and max elevation.
After cutting in the letters, a light application of black paint into the words helps them "pop" against their background, contrasting nicely against the light maple wood.
Maple wood has a beautiful, shimmery grain structure that this type of carving exposes nicely. We opted to finish simply with a brushed-on danish oil coating. The untinted oil we used served to simply deepen the existing grain features without coloring them.
That's it! I think our finished product turned out very nicely. Total CNC time for this project turned out to be around 5 hours. It turns out, the most time-consuming element of the job was planning just the right way to fit a mountain into the wood we had to work with.
You can see the finished result of this project at this page.