For twenty plus years, my boss has had this piece of live edge Myrtlewood sitting in his garage hoping one day to carve a design in it that would represent its character and beauty. Having a really nice friend give me a one year membership to the TechShop allowed me the opportunity to use my knowledge of SolidWorks in combination with PartWorks (the software that that writes code to control the ShopBot) to create this beautiful piece. The tree design itself was drawn by my boss. My love for detail and the beauty that objects behold gave me the idea to use the ShopBot to carve the tree design into the wood. The challenge that presented itself was whether or not I could get the Shopbot to carve the tree design where intended it to emerge/sprout from the piece itself.
Step 1: Materials
1 - section of wood (in this case I used a piece of myrtlewood)
1 - scrap piece of MDF or wood that is about the same size as your project piece of wood
a couple pieces of sketching paper
a couple scrap peices of wood for anchoring to Shopbot
sand paper or sanding block
handfull of screws (approx. 1" to 1 1/2")
1 - Flat bottom bit (recommend a 1/4" up-cut bit)
1 - V-carve bit (used a 90 degree bit)
1 - Shopbot
Step 2: The Design - Getting the Idea Down on Paper
Next up, start drawing the design on paper, this doesn't have to be a perfect drawing it just has to be close to what you have in mind. Again, you will clean up the image in the next step, so don't worry to much about neatness at this point. Note: try to keep your design from coming to close to the edge of the wood that way you give yourself a little wiggle room. Also I should encourage you to draw three small circles at random places on your drawing, this will help you align your piece of wood on the Shopbot later.
Step 3: Perparing for Partworks- Part 1
The first thing I suggest is laying your drawing down flat on the floor. You will want to place something in the picture that you know the absolute size of (like a quarter or small measuring tape), preferably in a blank spot on the drawing so that you don't cover any part of the design. This is so you'll have something to reference in size and scale the picture appropriately. Using a digital camera take a picture of the design with the scale object in place. Make sure to take the picture from as straight above as possible so there is no skew to the image. You could also use a scanner here if your drawing is small enough to fit in one or if you feel like compiling the images together in a composite, using a program such as Photoshop.
Step 4: Preparing for Partworks - Part 2
If you are like me and you have used any CAD drawing/modeling programs then you might think PartWorks is a little basic. So this step will just explain how to import an image into SolidWorks, size it appropriately, and then export the drawing into something PartWorks recognizes.
So lets first open a new file in SolidWorks. Next go under your options and make sure that you have the right type of units that you want to use (i.e., inches or mm). Now create a sketch on one of the three major planes (i.e., front, top, right). Now to insert a picture into SolidWorks, go to Tools>Sketch Tools>Sketch Picture... browse to find the image of your drawing, then click open. Once the picture loads, click the check mark and then you are ready to begin determining your scaling factor.
To find this scaling factor you first need to draw a line over whatever you placed in the picture for a reference. In most cases, the item you used for your reference will not be straight up and down, so when you go to Smart Dimension, make sure you move your mouse around until you get the perpendicular dimension (example in pictures, I made my line from one inch mark to another). Since I used a measuring tape it was simple; whatever the Smart Dimension came to be, 1 divided by the Smart Dimension measurement gives you the scaling factor. If you use something else its simple:
(The actual length of the object) / (Smart Dimension measurement) = Scaling Factor
Now that you have that, double click on the image. You should see a vertical and horizontal length of the actual image (these should be automatically linked). To scale it, all you need to do is multiply your scaling factor by one of these lengths and type this result into the appropriate box. (example in picture below)
After having scaled the picture, its time to start tracing. If you're going to have a lot of spiraling curves, I recommend playing with the spline tool. Just remember that all shapes have to be closed (meaning no gaps can be left in-between end point of lines). Remember to trace out those circles you put in your drawing.
Once you're done tracing out your entire drawing, you can move on to extruding the drawing. Now when I got to this step I knew I wanted to have multiple layers of cutting in my final piece so I extruded my main layer in one thickness and what I called the new growth buds on the end of each branch in another thickness. By doing the various thicknesses you create more fine detail that can be in the final carving.
Now that you have finished all of the extrusions, click on all the surfaces (by holding shift or control) that you would like to bring into Partworks (I only clicked on the top surfaces). To export this data go to file Save As, then go the pull down menu and select .dxf format.
Step 5: Partworks
So, moving on as if you have done the CAD step previously, you will need to start a new PartWorks file. Make the material size a little larger than the actual wood size. To import the .dxf data there is a simple button to the side of the screen. (Refer to the chart below)
Now that you have your art in PartWorks you need to clean it up a bit. You may have multiples of the same line, this usually happens when making .dxf files from multiple thickness parts in SolidWorks, but trust me when I say its easier to bring in all the details of your drawing at once. All of your lines will need to be joined together to make closed loops, that way the V-carve tool paths will work. If you are going to have different cut depths, I suggest you divide up your various designs on different levels.
If I haven't reminded you enough of the circles you should have had in your drawing, I'm reminding you again. Use the button in the second row under Flie Operations that I have indicated in the chart below to change the origin to the center on one of these circles. If you are not sure of the exact location of the circle, use the move control button under Edit Vectors and set the command to tell you the absolute location.
The last thing you will need to do in PartWorks is set your tool paths. I recommend the V-carve tool path for all artistic drawings, the bit will cut all the space inside of the drawings without going outside the lines. It's a great tool! Remember to save all tool paths to a file type that the ShopBot recognizes, using the simple button indicated in one of the charts below.
Step 6: Now for the ShopBot
Once you are satisfied with your cuts and you feel you're ready, take your pieces of wood and place it upon the Shopbot cutting deck. Place your original drawing on top of your piece of wood carefully aligning it to match the surface. Align the drill bit over the circle on the drawing that was set to the origin of the PartWorks file and set the origin of the Shopbot (the command should be z2). You should now place one of the anchors near the bottom of the wood you are cutting, this will lock in the X position of your origin (this is how this Shopbot was set up).
Next up go into PartWorks, find one of the other circles that is not at the origin. Click on it and then click on the move command, you have a choice of relative or absolute movement, you want absolute. This will give you the location of the circle in comparison to the origin. You can now tell the ShopBot to move to that location by using the command "mx" then typing in the x distance and then the command "my" and then the y distance. Now you can adjust the wood on the table until that circle lines up under the drill bit, then repeat the same move commands for the last circle. This should align everything so that when the ShopBot starts cutting everything will be where you intended it to be. Make sure that you anchor the wood down tightly.
I would suggest that you run a planing tool path with a flat bottom bit as your first cut, I took off about .025" but my piece of wood was fairly flat. All I can say from here is make sure that you zero your bit every time you change it (the command should be c2) and suggest that you run you flat bottom cuts first. I feel that in the long run it is better on the tips of your V-carve bits.
***Note: While you are cutting you want chips to be flying not dust (dust means you are wearing out your bit faster). This can be regulated by the feed rate of the bit and the RPM's of the bit.