[jcolley]

Well, where to start.

I have a concept in mind for a 5-Axis machine I would like to build. I have the basic design layed out, but I'm thinking further down the road as to how to program it.

I know very little about the workflow of CNC machining, but here's how a understand it works so far.

CAD -> CAM -> G-code -> machine

Now, my question is, how does the stuff know the physical dimensions and capabilities of the machine? Is this what a postprocessor does? For example, if I use an 'A' axis, how does the machine know where to position the z axis while the 'A' is turning?

I guess there is no easy book on all this stuff, huh?

Jim

[Al_The_Man]

In most CNC machines, the machine itself has to be taught where it is upon switch on, in other words you 'home' the machine's axis, some are just simple limits, other methods if the machine has encoders, is to recognize a marker pulse on the encoder and set this as a certain point in space, the home position can either be set to zero or an actual distance or dimension can be automatically entered. The machine will then know where it is in space and can move accordingly, it will keep track as to where it is, either by the number of steps (stepper) or encoder count in the case of servo's.
In the case of interpolated moves, the motion control processor does the actual arithmetic to control the coordinated move.
Al

[ger21]

A bigger concern might be that unless you want to spend $10,000+ for software, you're only option to generate 5 axis code is this. http://www.rainnea.com/cnc_toolkit.htm

[DareBee]

A couple of points.
A book that you need to get..CNC Machining Handbook
by James Madison, published by Industrial Press Inc.
This book will put you in the know on CNC right from the concept of how CNC works and explains right up to programming.

Also VisualMill 5 is a 5 axis CAM program. I have not used 5 axis but I understand that it is 4axis full movement and the 5th is a positioning axis. You would have to contact MecSoft for confirmation or more info.

[Torsten]

Yes you are correct the Postprocessor will contain the details
of the geometrical relations of you moving axes's.
I will have to be customised for your machine.
The CAM part uses genetic information relating just the tool to part
information It is your responsibility as a programmer to ensure that
this relationship can be obtained on your machine tool.
Good Luck

[jcolley]

Well,

I stand a little more educated than before. I have limited access to Delcam's PowerMill documentation and read a little bit about Ductpost, the postprocessor. It seems that was the question I was asking, as the postprocessor has the exact design in it that I was thinking about, I would just have to change the dimensions in a file.

Thanks for the responses guys, I will take the recommendation on the book as well. 14 bucks on amazon...

Thanks again,
Jim