Creating a Wood Carving with a CNC

There have been a number of inquiries into my process for creating a wood carving. Following are the steps involved for my “Shelter” piece. (Click here for a preliminary description of getting started with a CNC.)

God created the trees. All the rest is the work of Man. My use of these trees starts at a sawmill. So sorry, but 3/4″ lumber company or Home Depot / Lowe’s lumber at $1 per inch is NOT acceptable. I use a semi-local mill which practices responsible tree harvesting. The acquisition requires about 5 hours of drive time, selection and loading. The wood is typically rough sawn and looks something like this:

The lumber is then run through a planer to give nice smooth surfaces on both sides. This process typically takes about 1 hour for each 12-15 board ft. (1′ x 1′ x 1″). A typical trip to the sawmill will result in about 3 days of planing. This will not endear one to their neighbors. Below are some pieces of “junk” wood before and after planing. Surprise, that is some exquisite walnut hiding in there.

The next step is laying out the design on a computer. I have found Vectric software’s VCarve (eventually upgraded to the very expensive Aspire) to be indispensible for layout. It’s full featured, very flexible and after the inescapable learning curve, very user friendly. This is not cheap, but there aren’t any cheap options that yield similar results as quickly and easily. No, the free options Carbide Create, Easel and Fusion 360 are not viable replacements for this kind of work. And I have tried them all.

The initial design of the Shelter piece yielded the following result :

Design involves inspiration, selection and creation of 3d models and assembly of the models and text. Each feature, dog, deer, house, smoke, etc. is a separate model. This piece contained 56 (eventually 57) different models. Fortunately, these models can be individually saved and used on other projects. The models must be sized for length, width and depth and then arranged for proper perspective amongst all of them. They can also be tilted to allow for differing overlaps. This is demonstrated by the dog in the picture. The feet must blend into the grass while the remainder of the dog must remain above the grass.

This is a very painstaking and involved process since there is a very limited space in which to fit everything. A typical workpiece is about the size of notebook paper and carving a 1″ thick piece is limited to about 5/8″ of depth, including any frame.

After the initial design, toolpaths must be generated to use the appropriate bits in the appropriate manner for the CNC. The software does most of this and you simply have to input the correct settings.

This Shelter piece design initially took about 3 days.

After the design, a workpiece must be selected. Since wood is a natural material and since one typically has a limited stock on hand, there is not always a perfect choice for the workpiece. Often the design must be resized to fit any available workpiece. If necessary, toolpaths need to be regenerated. I chose a 12″ wide by 15/16″ thick piece of maple for this project. I hadn’t used maple and wanted to, so I did.

The piece is secured into the CNC and the job is run. The Shelter piece required 5 different bits over 9 different toolpaths. Machine time was about 7 hours with appropriate supervision (securing the workpiece, setting the machine up for the cut, changing bits, making sure the job doesn’t crash, etc.). Luckily other things can be done during this most of this time, such as sanding and staining other “completed” pieces or preparing new pieces.

After removal from the machine, some sanding is required as wood will usually have some rough edges or fibers that don’t cut and need to be smoothed. Then comes stain and finish selection. A natural wood finish can usually be beautiful just with a sealer, but unfortunately, 3d detail and text usually require at least a minimal stain to reveal features and depth.

For this piece, I loved the look of the maple and wanted to just seal it. Alas, after lacquering, the text was hard to read and the 3d detail didn’t jump out. I had some poly stain mix (pecan color) that was close to the maple in tone. After adding that on top of the lacquer — which surprisingly worked well –the above mentioned problems were resolved, but I wasn’t fond of the color.

After the piece is “completed” comes the appraisal stage. I wasn’t a bit happy with this piece. There were a number of things I didn’t like. First, it was carved from a 1″ thick piece of wood, yet the frame and a significant part of the background were only 3/8″ thick or less. I like a more solid piece. Second, the water was too deep in comparison and the clouds, sun and house were too far out. The house also needed tilted to blend in at the base. The eagle morphed into the frame and was completely unacceptable. The text was not precise either. Finally, I wanted to add a few missing touches and that cloud/sun combo “would look so much better behind the mountains.”

These revisions took another 2 days to complete as I also wanted to include a few more original models. Although the changes seemed minor and subtle, it ended up being a major redesign. Eagle, house, clouds sun and water were revised. The entire cut was thickened and the frame was redone to thicken the edge. One of my favorite techniques is to let the carve spill out onto the interior of the frame and I was able to preserve this with the redesign. Computer generated preview was:

After the redesign comes another workpiece selection. Luckily this was from the same piece of maple so no resizing was necessary. Then more machining (another 7 hours). Then staining. For the second piece I chose a cherry Varathane stain which yielded better results than the original pecan color. Finally, 2 coats of satin lacquer were applied.

Approximately 7 days of work, but I’m fairly happy with the results. Additional copies will take about 7 hours for the machine, an hour for sanding and staining and 10 minutes for 2 coats of lacquer (spread over 2 hours for drying). With machine supervision (securing the piece, changing bits, etc.), wood selection and preparation, and finishing, my time will be about 4-5 hours each. Note that until I have more CNC machines available (if ever), the machine time will limit me to a maximum of 2 pieces per day.

Edit: No longer happy with this item. The tool paths from earlier versions resulted in diagonal lines so I fixed this and then carved a larger 17″ x 14.25″ version which revealed some additional problems:

No diagonal lines, but the deer stuck out much too far, the left side was boring and things needed to be repositioned, the water was now too high with respect to the river banks and it extended too far onto the frame. Also, the entire project was not sharp enough so a more precise bit was substituted. Spent another half day resolving these issues in the design and another day carving, sanding, staining and finishing a normal size (13.75″ x 11.25″) version. For this iteration, I had a piece of wood appropriately sized with the grain running vertically. This was the result:

Much better, but even after this, it became obvious that the outer frame was still too thin so I revised the layout to alleviate this last issue. Also, not to nit-pick, but I could have flipped the piece top to bottom to have the grain pointing upwards to complement the mountains. I have yet to cut a new version, but based on the results from this picture, I am satisfied that these two minor revisions will end my struggles with this piece. It is now ready to sell.

2nd Edit: New piece with the final version of this work finally created. I had a beautiful piece of cherry wood available so this time, I chose to use that with a golden oak stain (for variety).

I’m finally happy with it…. for now. And NOW it is ready to sell.

Just one more thing…

It is not unheard of for a piece to get destroyed by a machine crash where a dull bit doesn’t feed fast enough or when a bit is not quite secure enough and gets pulled out of the router, eventually cutting through the middle of the workpiece. This usually happens at the end of a very long job and leaves one with a wasted day and a piece of expensive firewood. “Dear Lord, please secure my tongue to prevent the escape of those words!”

That should adequately explain the whole starving artist thing ; )