Re: [RE: emc really needs a copyleft cad/cam package]

[Matt Shaver <mshaver-at-erols.com>]

Anne Ogborn wrote:
> 
> Hmm...
> 
>    I think before we can go very far with a features list we
> should clarify if we're expecting this to be a CAM package that
> takes a model from elsewhere and produces a tool path from it,
> or an integrated CAD package and CAM package.
> 
>   Personally I'd rather we do the former, for the very practical
> reason that it's a more do-able size project, if nothing else.

I. I was going to address this issue in my last post, but it got too
late.

  A. I would think (and I could easily be wrong), that a CAM package is
going to have a lot of the elements necessary to build a CAD package.

    1. You'll need a canvas upon which you can display entities in the
drawing database, and which can be zoomed and panned. 

    2. You'll need object snaps.

    3. You'll have to be able to pick (select) entities and snap points
with the mouse to specify the starting and ending points for moves in
the cnc program.

    4. Having said all that, I'd be happy to start with the CAM
functions first and import our geometry. CAD functionality could be
added later if we adopt a modular approach to building the program so
that it can be extended by folks who need those extensions. Examples of
extendable programs:

      a. TkEMC will automatically add items to one of its menus when you
put new script files in a certain directory.

      b. EMACS can be extended to do almost anything (and has been...).

  B. We could probably do without:

    1. New entity creation commands (line, circle, arc, etc.).

    2. Text and dimensioning.

    3. Printing (maybe).

II. Direct DXF to g-code converters:

  A. Work OK for extremely simple jobs where there are no ambiguities,
but you really need lots of user input to create tool paths from complex
geometry.

  B. Usually generate code that runs the cutter centerline along the
geometry.

  C. I don't know how it decides which direction to go. If it takes its
cue from the start and end points of lines and arcs in the DXF file,
it's going to be pretty confused.

Matt