In the articles I have written for ShopBot in the past, what I tend to talk about are the types of signs we make here at Lincoln Sign Company, and how we use the ShopBot to achieve them.
What I would like to do for this article, is to concentrate specifically on the design software that we use to program the ShopBot; ArtCAM Pro. While I don’t want to specifically do a “step-by-step” through all the minutia of the software process, I do want to show someone that might not be familiar with ArtCAM (or toolpath design software in general), what setting up tool-paths looks like in the program and get an idea of how ArtCAM and the ShopBot work together to help us create signs.
There were a great number of software choices when it came time for us to decide what software we were going to use with our ShopBot (many of which are profiled on the ShopBot website here). I was fortunate in that I was already very familiar with ArtCAM Pro, so it was a simple choice for me, but there is a wide selection of software you could choose to work with, and it is important that each ShopBot owner make a selection based on software features and price.
There are three types of carving that can be done with a 3-axis CNC Router.
* 2D Cutting: Traditionally, 2D carving is achieved using basic, end-mill bits, and all that is required of the ShopBot is plunging the bit to a specific depth into the material, and then following a vector to create a shape. This creates a cut-out shape in the substrate. In some cases, a hole, or pocket, might be cut out of a substrate as well.
* 2.5D Carving: 2.5D Carving, is when a specialty bit (like a V-shaped bit) is used to create angles or curves in a material by virtue of the shape of the bit itself. The most common example of this would be v-carved lettering, and this is a capability we use at Lincoln Sign Company every day.
* 3D Carving: True 3D carving, is the “high-end” of what can be done with a ShopBot, and is what we love the most about the machine. 3D carving begins as a 3-dimensional model which one creates with software, that is then translated into a series of toolpaths that are cut with a ballnose, 3D bit. In this type of carving, an endless variety of shapes and angles can be cut out with the exact same bit, as the shapes are not coming from the physical shape of the bit, but rather, the 3D moves that the router makes to “trace” out the shape. (For a more involved explanation of 2D, 2.5D and 3D, click here)
The project that I am going to talk about today, is going to be a traditional, New England carved sign which utilizes 2.5D carving and 2D cutting. We used ArtCAM Pro for this project (but we could have also completed the project using ArtCAM Insignia or ArtCAM Express)
This is a custom carved sign for a historic home in New England. It is a wooden sign, constructed of Western Red Cedar, and will be hand gold-leafed with 23k gold. The sketch above is what we would normally submit to a customer for approval.
Here is what the ArtCAM interface looks like when the design is viewed as a line drawing. If you look on the left hand side of the screen, you can see the various carving icon controls for 2D and 3D cutting. If you look at the second icon under “2D”, you will see the control for “area clear”. This is traditionally used to create a pocket in material or for creating the illusion of raised, flat-lettering (by cutting away the background to a certain depth).
Here, I am going to use the Area Clear Control to “mill” the surface of the material before I 2.5D carve it.
So why do I need to “mill” the surface of the material?
One thing you learn pretty quickly when you start working with any CNC router, is that NO material is a consistent depth. Even 2″ thick High Density Urethane is not a consistent thickness throughout the entire sheet. This inconsistency causes V-Carve lettering to vary in depth, which looks terrible. The strokes and serifs will appear to vary in width, in some places too wide, and in others, not wide enough.
The solution to this problem is to have a flat-bottomed bit (an “end-mill” bit), travel over the entire surface of the project to make sure the material is cut to a consistent height. If you look to the left of the screen, I have opened the Area Clear dialog box, and have selected a 1/2″ wide bit. I set the speed which bit travels over the material, and how much of an overlap I want the bit to have as it makes each pass (you can’t see it in this view, but I have set the overlap to 0.25″). The red lines over the design show the path that the bit will take when I am ready to run all of the toolpaths.
In the screen-capture above, I am selecting a 100 degree V-bit, which I am going to use to carve the lettering and the border.
The red lines show the actual path that the 100 degree bit will follow as it cuts.
One of the great things about ArtCAM Pro, is how it will show you a simulation, in 3D, of how the actual carving will look. Here is a view of this simulation, and again you can see the red lines that represents where the tip of the v-bit will make contact with the material. In this angled view, you can get an idea of how much vertical movement the router bit does to achieve a carved 2.5D letter.
Here is another view of that same simulation. Believe me, it is great to see the simulation, and be confident you made all the right carving choices, before you start cutting into an expensive sheet of material.
In this screen capture, I am choosing a 1/4″ end-mill bit, and I have selected the outside vector of the sign to cut the sign away from the sheet of material.
When cutting a shape out of 1.5″ thick Western Red Cedar, you need to make multiple passes, cutting deeper on each of the passes (unless you like to collect broken bits and ruined signs). Here I believe I am having the router only cut .25″ of material at a time.
Another nice thing about this view, is that you can confirm that you are not cutting deeper than your material is thick, which would mean accidentally cutting into the router table surface itself.
Here is what the finished simulation looks like.
Here is the sign as it appears after we are finished carving it. (I’ll stack the firewood later, I swear)
The sign is primed (seen here) and then painted with a background color. We use a top-quality outdoor latex paint, and put anywhere from 3-5 coats on the sign before we start lettering it.
We actually need to letter the sign (that is, hand-paint the letters) before we gold-leaf it to make sure we have a smooth, friendly surface to paint the gold-size onto.
Gold-Size is what allows us to gold-leaf the letters of a sign. Size is a varnish that dries very slowly (over a 24 hour period) and allows us to place gold on the letters and adhere it without ruining the shine of the gold. We need to start leafing at just the right moment as well, when the Size is just about dry, but not quite. It is a pretty short window of opportunity.
It is a time and labor intensive technique, but it yields fantastic results!
I hope this has been able to give you a taste of what it is like to work on a project within ArtCAM Pro. If you are interested in learning more, you can always go to ArtCam.com.