CAD (computer-aided design) and CAM (computer-aided manufacturing/machining) refer to programs that you can use to design and mill objects on the Bantam Tools™ Desktop PCB Milling Machine.
CAD programs provide the design tools necessary to create two- and three-dimensional (2D and 3D) renderings of the object you will eventually cut (the “model”) on the milling machine.
For example, here’s a CAD model for a coffee pot, designed in Autodesk Fusion 360:
The coffee pot was made by creating and modifying shapes in the CAD program, similar to how you might create an image in a graphics program such as Illustrator or Inkscape. Once the object you want to make is finalized in CAD, you can import it into your CAM program.
CAM programs allow you to select tools, materials, and other variables for your cutting job. Even though you’ve done all your CAD and know what you want your part to look like, the milling machine doesn’t know what size or shape of milling tool you want to use or the specifics of your material size or type.
CAM programs use the model you created in CAD to calculate the movement of the tool through the material. These movement calculations, called toolpaths, are automatically generated for maximum efficiency by the CAM program. Some CAM programs can also create on-screen simulations of how the machine will cut the material with the tool you’ve chosen. Running simulations instead of cutting a piece over and over saves on tool wear, machining time, and material.
Bantam Tools™ Desktop Milling Machine Software, the motion-control program for the milling machine, can create the CAM for circuit board files in EAGLE .brd and Gerber format.
Once a file is imported, it appears in the software as an imported plan file window, and a representation of the object to be milled appears on the rendered machining bed. You can then select the tools and material you’d like to use, and the software will calculate the toolpaths for you.
CAD and CAM programs are usually separate, although programs that offers the functionality of both are increasing. Every CAD and CAM program has a different user interface, ease of use, and learning curve. It’s important to find the one that’s right for you and your projects and to learn it well.
A post-processor is software that works with your CAM program to optimize your file for the specific machine with which you’ll mill the object you’re making.
Each post-processor has to be developed to work for both the CAM program you’re working with and the machine you’re using.
If you’re not using a program that has a post-processor especially for the milling machine you can use a generic one that exports in mm/arcs. Note that the milling machine uses the G55 coordinate system, which may not be the default for your CAM.
Using CAD and CAM Together
Although different programs may have differing setups and features, here’s the basic process:
1. Create a design in CAD.
Draw something in a graphics program or create something new directly in CAD.
Once you’re done modeling, if you’re using a CAM program, save your file in a format your CAM software can read.
If you’re using a 2D file format that the software can import directly (EAGLE .brd or .svg), import the file into the software and set up the CAM side of your file there.
2. Make your design into a toolpath with CAM.
Import your file into CAM software if you’re using a separate CAM program.
CAM software will require information about the tool you want to use, the material dimensions you’re cutting, where and how you’d like to cut, the locations of the axes, the size of the raw material you’re cutting, and other variables that factor into how your finished product machines. You’ll also define the x, y, and z origins of the G-code you eventually produce.
The milling machine requires one tool per G-code file, so be sure to program separate files for every tool you’d like to use for your project.
If your CAM program has a simulation feature, running it before your export your code might warn you about potential issues. For example, the tool might not be able to cut a certain area on your model, or the tool might not cut the part the way you were expecting. If you need to adjust anything, you can do it before you ever turn your mill on.
Save or export your file as G-code with an .nc or .tap extension. As mentioned previously, if you don’t have a post-processor for the milling machine in your CAM program, you can use any generic post-processor labeled “mm/arcs.”
3. Cut your toolpath on the milling machine.
Import the G-code file into the software. The G-code file will be rendered on the virtual machining bed in the software. If you don’t already have it selected, turn on the motion plan in the View menu by selecting Show Motion Plan.
Verify that your G-code file is placed correctly and that your dimensions and origins look identical to how you programmed them in CAM.
When you select your tool, use the same tool you selected in your CAM program.
Set up your material in the software. Measure the material with digital or dial calipers to verify that the dimensions you enter in the software match the actual dimensions of the material.
Then attach the material to the machining bed on your milling machine. This is called fixturing. Generally, material can be attached to the milling machine with double-sided tape or the Precision Fixturing and Toe Clamp Set, depending on the project and material. Advanced users can also use what are called T-slots, which are underneath the flat spoilboard on the machining bed.
Verify all your settings one last time, and make sure you can stay with the mill for a while before you click on Start Cutting. Never leave a milling machine unattended!
For more information, see our Fusion 360 tutorial to get an idea of how one CAD/CAM program handles files for the milling machine.
Suggested CAD/CAM Software
Different CAD and CAM programs can be specifically designed for specific applications. You should choose the right option for your project.
For printed circuit board (PCB) prototyping, the software can directly import the data provided in the standard files produced by circuit board design programs, which are also known as electronic design automation (EDA) programs.
The CAD portion of PCB design is done in any number of PCB programs, while the software provides the CAM support by generating the traces, holes, outlines, and components footprints automatically.
Commonly Used Circuit Board CAD Programs
Osmond PCB is an OS X-based circuit board design tool, free for smaller boards. This program, like most other programs, exports Gerber format files, which can be imported directly into the software.
KiCad is an open-source professional-grade suite for board design.
Altium is a widely used professional-grade circuit board design program.
Fritzing is an open-source program and community with a mission to make PCB design more accessible.
2D design files can be more than enough to create parts and projects on the milling machine. For designers, programs like Adobe Illustrator and Inkscape are simple to use, inexpensive, and flexible. Engineers may be familiar with drafting tools such as AutoCAD. In either case, a 2D CAM program will be necessary to create toolpaths for the milling machine.
Powerful 2D CAD and CAM Programs
QCad is an open-source program that also exports Gerber format for circuit board design.
Illustrator is a popular graphics program that can export .svg files.
Inkscape is a free, open-source program that produces .svg files natively.
Sketch is a lightweight, easy-to-use, powerful graphics program that exports .svg files.
Making a 3D part on the milling machine requires both a 3D CAD and CAM program. The resulting file is written in G-code, the format understood by most CNC machines. Some 2D CAD programs can generate G-code, and you can use 3D CAM programs to produce 2D models.
3D CAD and CAM programs offer functionality specifically for 3D parts. For example, a 3D program will allow you to create smooth contours, where a 2D CAD program cannot.
Popular CAD Programs
TinkerCad is simple-to-learn, accessible software for novice designers.
SketchUp is 3D CAD streamlined for ease of use.
SolidWorks is powerful, professional-grade software.
Autodesk Fusion 360 includes its own CAM functionality, plus a tool library and post-processor designed especially for the milling machine.
Popular CAM Programs
HSMWorks, an add-on to SolidWorks, also includes a tool library and post-processor for the milling machine.
MasterCAM is a professional-grade, established CAM program.
BobCAD-CAM is a suite of professional-grade machining and EDA CAD and CAM programs.
Cut3D is a streamlined 3D CAM program by the makers of VCarve.
MeshCAM is 3D CAM software optimized for ease of use.
These programs run the gamut from perfect for the novice milling machine user to complex, feature-packed software that allows the advanced user to establish finely detailed parameters for a project. Parameters that are common to most CAM software include the length of your cutting tool, spindle speed, and feed rate.
Some programs, however, include dozens of settings that allow you to optimize your toolpaths, extend the life of your tools, and obtain fantastic surface finishes and dimensional accuracy. Learning how to manipulate these settings is the basis of the art of machining.