Re: Newbie question about homing and coordinates and CAM

[Ray <rehenry-at-up.net>]

Barry (Comments mixed in.)

On Thursday 08 November 2001 12:48 am, you wrote:
> I apologize in advance if this is a FAQ or something I should otherwise
> be able to derive....however...I am a newbie with machining.  This may
> not even be the right forum for the following questions, if so please
> advise.
>
> Since installing the home switches (mechanical snap switches) the system
> of course resets itself to 0 on all axis.  I have the home switches set
> at the extremes of each axis with the table all the way left and forward
> whilst facing the machine, and the spindle all the way at the top.  I
> prefer to work with Z 0 being the highest point on the work piece just
> because I find it easier to think about things in that fashion when
> creating the tool path. Plus, anything with a -ve in the Z is going to
> be a cut so it seems to make checking the code a bit easier.
>
> Before the switches just initialized EMC with the piece set up and ready
> to go, and set the tool height to the topmost surface of the part.
>
> How to I set the machine coordinates for a piece to be machined?  Or, do
> I need to adjust my practices now and generate tool paths with the new
> home position in mind?

Some use the g92 set of codes to offset zero for this kind of thing.  I 
prefer to use the coordinate systems g55+.  There is a little script, 
Set_Coordinates, that will let you move to a position and then teach it 
into one of these.  Then just put a g5? code at the head and a g54 x0 y0 
z0 at the end. 

> I had been considering putting +/- limit switches and placing optical
> home switches in the center of the machine's envelope, but I am not sure
> if that is a good idea or not.  What is typical or standard practice?

These could be anyplace that you want them.  In fact, you could offset the 
apparent switch location by putting whatever values you want for the home 
location in your ini file as HOME [AXIS #] .  These values are loaded when 
the homing routine has finished.

> Last question, although I have successfully used BobCAD/CAM 17 to create
> workable tool paths, I find the program obtuse and buggy and frankly
> fallling short of the mark for what is sold as a professional software
> package.  BobCAD definitely has some nice features but it is very
> clunky. Most stuff so far has been easier to do by hand in IntelliCAD,
> but I will need a good CAM package for more complex parts.  Are there
> affordable or better yet free CAM solutions for linux?  Even a Win32
> version would do the trick.

I use Vector but for drawing, the brothers who wrote bobcad and vector had 
some of the same thoughts about how to do that part of it.  Vector does 
have an EMC config available.   For more information about Vector and 
related products contact  "Fred Smith" <imserv-at-vectorcam.com>

Hope this helps.

Ray