Guidelines for Starting a CNC Project
1. Find a CNC tech at the beginning to discuss and troubleshoot the project. At this point you should have an idea of size and scale of the project, and what type of material you would like to use.
a. Materials – Our CNC router can drill, route, cut, etc. with the proper bit, all woods, plywood, laminates, foam, MDF, and Plexiglas. This is not a complete list of material possibilities. Materials all machine and react differently, so the tech can help you with the best material for your needs.
b. Size Limitations - We have a bed size that is 5' x 10'. That allows for a maximum cut area of @59" x 113". (note: the long dimension is shortened due to motor being located to one side of the machine gantry, which allows travel to about 9.5'). These dimensions are approximate to how the piece needs to be bedded. (note: bedding is the act of fixing the raw material down to the CNC table).
c. Height Limitations - the machine has a maximum height of @10.5". This can be rarely achieved due circumstances such as; length of the bit, stock sizes, surrounding cuts, etc. The tech can help explain in detail possible limitations of you project.
2. Digital Modeling Process. The CNC machine uses Rhino 5.0 as its primary software coupled with RhinoCAM 2012 as the software to write G-Code. (note: G-code is the language that instructs the CNC machine how to move) You can model in any software and it has a strong possibility that it will be compatible with Rhino. However, you will have a better finished project if your work is developed in certain way. The tech can help you with the specifics to your project.
a. 2D cutting - This process can be started in multiple software platforms. You can start with Illustrator, Rhino, Sketchup, AutoCAD, etc. and then take it to a 3DM file. (a Rhino native file) The key is to make sure that all lines are exploded, connected, on the same plane, and do not contain multiple overlaid lines. The cleaner your model is, the easier it will be to machine.
b. 3D machining - This is where the process becomes much more important. Depending on the project and your goals, there are a couple of software packages you could use. Rhino is always good, as is Solidworks (although very complicated for most projects), Revit works well for site modeling, and of course AutoCAD for more simple 3D forms. The tech can help you decide which is the most appropriate.
The key to this is similar with the 2D modeling. The cleaner your model, the easier it is to machine. The big difference is that a single line in 2D is easy for RhinoCAM to understand but a 3D surface that is not modeled cleanly will result in long delays and multiple fixes on the digital model. RhinoCAM needs to have one surface for it to function properly. If you have patched multiple surfaces together in Rhino or Revit, the possibility of small holes in the surfaces will cause RhinoCam to fail to find a machine path. You may not even see a hole in your digital model on your screen, but the CAM software could spend hours trying to process how to get a bit into that section to mill it, until the software gives up and you have to start over.
You should have your model 100% complete before beginning. It is very difficult to go back and machine a file onto an already previously milled piece. It can be done, but is very difficult and time consuming. Do it right the first time.
3. Milling process - At this point you should schedule an appointment with the tech that knows your project.
a. First, a short meeting to open the file and process it through the RhinoCAM software. This will tell two important things. One, that the digital model is OK and works, and how long it will take to machine.
You can then figure out a schedule to complete the project, based on completion date and how long it will take you to prepare your material.
b. Material preparation - The tech will tell you how to prepare the blank stock so that it can be bedded properly. Bedding is perhaps the most important aspect to having a good finished product. By following this advice, you could a lot of machine time (depending on the project).
4. General comments
- The CNC machine is not a "magic bullet" that will get you out of work. It is a time consuming process to get a one of kind project. The CNC excels in manufacturing, and is very useful for making many of the same object. This is often the exact opposite of how it is utilized by architecture students.
- There are certain things that the CNC can have trouble with as it pertains to certain scales and materials. Example: A site model, made out of glued layers of MDF, with small buildings on it can be problematic. The CNC can cut smaller objects, but the MDF as a material cannot handle the pressure and will shear laterally when the surface area becomes too small. Potentially, the same project run in another material would be fine. The CNC tech can help troubleshoot these issues, but if there is a doubt, run a small test piece before proceeding to a final project
- Depending on the project, there will always be some post hand work on your project. This could range from sanding to squaring up corners in 3D surfaces by hand (since we always cut with a circular bit)
- Give yourself plenty of time to get your project completed. This is not something to procrastinate, and then try and rush a day before your project is due.