Getting design to GCode

[dfranks]

Let me start by saying that I am new to the CNC world, I'm about 1/3 of the way thru my 1st table build. Even though I am very familar with computers and software apps, worked in the field for the last 20 years, I have fallen short in the Cad Cam area.
I have downloaded the Alibre software and have gotten thru the 1st tutorial. I feel that I will indeed be able to catch on to it pretty easy, at least basic deisigns. But I'm not familar with the options you have for saving or exporting the designs to. I guess I was assuming (bad thing to do) that I could export the design to a dxf format , or similar, and then on to GCode.
I don't think that I am grasping the differences between Cad and Cam. Could someone explain the differences for me as well as what I do with the design when I have completed it?
At this point I am thinking that my Alibre design is Cad, it needs to be converted to Cam, save it as a dxf file and then convert to GCode. Or am I way off base here?

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[HuFlungDung]

CAM is the software tool that helps you create toolpaths over your model. While simple 2d outlines are quite readily offset for tool radius and then converted to dxf and then to gcode with some convertor type applications, this covers only the simplest machining applications. Such convertors may be quite deficient in supplying Z axis control codes to permit your tool to safely enter and/or clear the work at the proper moment.

Now, if you do much more toolpath drawing manually, you can improve the entry into the part with ramps, helical entry and so on. Good CAM will give you these options and add them to your gcode automatically.

While it can be quite entertaining and interesting to draw your toolpaths manually for a while, this can get to be a bothersome chore. Tweaking the toolpath to bring the part into tolerance basically means "start over" with your toolpathing. That gets irritating after you get to the point of wanting to see some output from your machine.

Beware of cheap cam software that does not create and simulate toolpaths from a solid or surface model. Those programs are simply outdated in today's world, kind of like the DOS operating system. If you are using something like Alibre, chances are you are doing more than sketching a few lines on the screen, but everyone has different requirements to achieve what they want. If you can better describe what you intend to machine, then better advice can be given for what to look for, for cam software.

[dfranks]

Yes, I guess it would help if I described the type of projects I have in mind As I am new to CNC routing here is what I envisioned being my progression, suggestions in this area are appreciated as well.
Starting out with 2 dimensional wood objects, cutting out yard art, bird houses, engraving small signs, etc. to get the hang of it. For these items I would probably be using 1/8" - 1/2" pine material. In most cases these could probably be cut in a single pass. Then moving on to 2 1/2 dimensional wood routing such as raised letter signs and eventually solid electric guitar bodies. The guitar bodies are typically 1 3/4" in thickness and various types of wood may be used - ash, maple, basswood, etc. and would require multiple passes, increasing the depth on each pass.

[ger21]

Starting out with 2 dimensional wood objects, cutting out yard art, bird houses, engraving small signs, etc. to get the hang of it. For these items I would probably be using 1/8" - 1/2" pine material. In most cases these could probably be cut in a single pass. Then moving on to 2 1/2 dimensional wood routing such as raised letter signs and eventually solid electric guitar bodies. The guitar bodies are typically 1 3/4" in thickness and various types of wood may be used - ash, maple, basswood, etc. and would require multiple passes, increasing the depth on each pass.

I'm assuming you're using the free version of Alibre, Xpress? This is really not the right type of CAD program to do what you want. Cutting out 2D shapes and engraving are usually done with 2D CAD. These export a 2D .dxf drawing which is converted to toolpaths (g-code) with something like ACE converter, or SheetCAM. Even the more expensive CAM programs will do it.

Alibre Xpress creates 3D models. These are usually exported as .stl files. A CAM program like MeshCAM or other far more expensive programs can take the 3D model and create the toolpaths.

Even a simple 2D .dxf can be made to cut in multiple passes. I haven't played around with Alibre enough to know if it can output 2D .dxf's, though. A good free 2D CAD program is A9CAD from http://www.a9tech.com

[tjones]

Alibre Xpress free version is limited on import and export abilities. If you were the lucky 100k then you have the capability now.

If not then you can purchase this as a module for $99 and you will get many export features including 3D exports like iges,stp,acis,rhino,dwg and stl. Oh yes and 2D dxf.

However the nice thing is that there are relly cheap programs out there to do what you want. Bobcad lists for $1000 but just a little chat with the salesman and in about a week you may be able to get it for $250-$300.

Good Luck.