Over the past few years, as I've urged woodworkers to consider adding CNC equipment to their workshop, I've heard objections like these:
- CNC routers are only useful for processing sheet goods.
- CNC systems cost too much, I wouldn't get a good return on my investment.
- I don't have the computer skills to run a piece of CNC equipment.
- I already have a shop full of great equipment, the perfect shop in fact, why do I need a CNC router?
- Automation is the enemy of creativity; I don't want my projects to look like they came out of a cookie cutter.
The CNC Experience
As I think about the best way to answer these questions I always come to the same conclusion. You have to experience CNC woodworking to really understand the advantages, the power, and the pure fun involved.
First, let me say that I'm not an expert furniture designer or a world renowned woodworker, or even an author with several successful woodworking books in print. So, why am I writing a column on CNC woodworking? I know CNC equipment and processes. For the past 30 years I've used many different types of CNC equipment and CAD/CAM software to solve manufacturing problems and produce profits.
Purpose of This Column
Obviously, the very best way to experience CNC woodworking is to come to our factory and test drive a Legacy CNC woodworking system. Nothing beats real "Hands-on" experience; however, not everyone can make the trip to Utah, so I'll endeavor, in this column, to share the experience with you in print form. To do this I'll be building a series of projects.
What is Involved in CNC Woodworking
Before we start on the first project we need to take a look at the entire CNC manufacturing process. CNC operations can be broken down into three steps:
- CAD - The process of creating a complete drawing of your project.
- CAM - the process of turning your drawing into instructions for your CNC equipment.
- Setup - the process of getting the material setup in your CNC equipment and ready to process.
Note: Some software packages combine the drawing program (CAD) and the computer aided manufacturing (CAM) programs into a dual purpose package. These are referred to as CAD/CAM programs.
Don't let thie list intimidate you. If you can send an email to your family and friends or sort and file away your digital photo collections, you have the computer skills to get started.
To help you polish your computer, CAD, CAM and setup skills, Legacy offers live, webinar style, training sessions each week. If you see something that you don't understand you can join one of these classes to ask your questions and get your answers. Follow this link to see the class schedule.
Project One - Curved Front Cabinet
As you can see from my plan my first project has a re-curved front. The trim on the base and top and the door front follow a re-curved line. The cabinet sits on bracket feet and this is where we will begin working on this week's project.
Step One - The Bracket Feet (CAD)
The drawing shows the foot, an end view of the contour on the face of the foot, and the shape of the finished foot. I created this drawing with a CAD program. (I use a three dimensional modeling program called inventor but if you are just getting started you can create the same drawing with TurboCAD 2D for under $40.00). Chris Anderson teaches our online TurboCAD classes.
Step Two - Preparing the Code (CAM)
I built the bracket feet in two steps, milling the contoured face and then cutting out each foot, one as seen in the drawing and one, a mirror image of that foot. I used Aspire, a 3D milling and carving CAD/CAM program to create the program. Aspire has a simple tool called a two rail sweep which allowed me to import the end view of the bracket foot and create a three dimensional tool path along the surface.
I used a 1" diameter ball nose (core box) router bit with a 0.040" step-over. That just means that each time a cut was made along the face the router was moved forward 0.040" and an adjustment made in the cutting depth before another pass is made. (This technique is mostly used when carving a 3D picture or graphic but I like it for more practical jobs like milling a short run of custom molding.) John Hennen teaches our online Aspire classes.
Next I imported the face view of the foot and created a profile tool path. A profile tool path is simply a cutting path that follows a line. It can be on top the line or inside or outside of a group of lines that make up any geometric shape. Aspire allows me to control he amount of material removed each time around the line. I chose to cut 5/16" (0.3125") deep each time around so it tool several passes to cut completely through the material. Aspire has another great feature called tabs. That means that a small web of material is left behind in two or three places to hold the part in place until the cutting is complete. I used tabs that were 1/2"(0.5") wide but only 3/32" (0.09375") high. These were easily removed after all the cutting was done.
Step Three - Miter and Rabbet
These steps were completed on my chop saw and my table saw. I want to be able to add the feet to the cabinet after it is all finished so I glued and screwed a triangle of 1/2" plywood for stability and easy mounting later.
Next week I'll build up the sides of the cabinet on my CNC router table and then I'll show you how I created the re-curved molding for the top and base of the cabinet. After the cabinet is assembled we will move onto week three, the re-curved and raised panel door.
Until then, happy woodworking
Legacy Woodworking Machinery