[CAD_CAM_EDM_DRO] Re: Gcode standards (Was: easy to learn use cad/cam cnc software?)

Interesting. What I have been doing is writing a macro language for
gcode. I have written a set of macros that allow you to insert a line
like:

engrave({0.5},{0.5},{0.9},{Part #2X534C 10/31/2004})

Where the first two parameters are and x and y offset to use as the
start point, the third parameter is the scaling factor, and the
fourth is the text to be engraved. You can insert this macro into a
normal EMC program and it will generate the thousands of gcode lines
to engrave the part. The example I sent earlier was the output
generated to engrave two characters. The #nnnn calculations allow the
macro to start at the x and y offsets and increment them based on the
max width of each character as it is drawn.

It seems to work and work well, but as you saw, it does use #nnnn
variables to do it's job. To define a variable, I created a macro

defineVar({maxCutPerPass})

That generates a new #nnnn number and defines a macro, in this case
maxCutPerPass, that you can use anywhere in your gcode program.
maxCutPerPass will then expand out to the proper #nnnn variable.

This is all done with a standard macro pre-processor called m4. m4 is
available on all UNIX machines and I think that it runs on PCs too
since it is used by the 'make' process when you do a ./configure.

The news that many gcodes do not support #nnnn variables is thus not
great news.

That is why I was asking the question about standards. Sounds like
the answer is that only the basic stuff is standard and beyond that
there is nothing. Thanks for your insight. -Chuck-



At 10:17 AM +0000 11/2/04, Fred Smith wrote:

>--- In CAD_CAM_EDM_DRO@yahoogroups.com, Chuck Rice <Chuck@W...> wrote:
>> At 1:11 PM -0800 11/1/04, Chris DeHut wrote:
>
>If you have written a G-code program over 30-40 lines, you are
>wasting time that could be better spent designing parts, planning
>process and making chips. DXF converters are free and cad-cam
>programs are very inexpensive.
>
>G-code is supposed to be man-readable. It started out as all hand
>coded.
>
>> #4708=[#4708+[#4706*0.8379]]
>
>Use of varables and expression evaluation is not standard g-code.
>This is the EMC developer's isolated interpretation of a machine
>controller, selecting the features he wanted. Fanuc Macro language
>(an expensive optional add-on) uses the cryptic # symbol for
>variables, but in many versions does not permit mixed expression
>evaluation and motion commands on the same line. It was a hardware
>issue when all the controller logic circuits were hand wired,
>discrete components and simple logic chips.
>
>Most controllers use subroutines and repeat statements, with absolute
>and incremental modes to make hand written code more legible, thus
>eliminating a lot of the need for cryptic code. EMC does not support
>subroutines or repeat commands.
>
>A decent cad-cam program will permit you to produce many more parts
>per hour spent developing programs, reduce your mistakes, and permit
>much more efficient changes to your part designs. It will also
>permit you to connect your drawing and design skills directly to the
>CNC controller, without restricting your programming to the speed at
>which you type.
>
>For example, Engraving Text is a very simple process with a CAD
>system, but a gut wrenching task when manually programming.
>
>3D surfaces can easily be processed by nearly any hobby class
>controller. I doubt 1 in 10,000 would even try to manually program
>these parts. Pocketing, the process of clear cutting a closed shape
>to a defined depth, is a very tedious manual process. With a cad-cam
>program, a perfect toolpath and the associated g-code can be created
>in a few seconds.
>
>In addition to the commands that others have mentioned as
>standardized, also learn (for milling)
>
>G90 Absolute mode
>G91 Incremental mode
>G41, G42, G40 cutter comp control
>
>G81 and G83 are drilling cycles that are very similar between
>controllers, with an ocassional swapping of letters for the various
>parameters. All the other drill cycles will be more
>machine/controller manufacturer dependent.
>
>Fred Smith - IMService - Vote Early and Often
>
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>http://www.cadcamcadcam.com/hobby
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