post processor

Message: 1
Date: Fri, 09 Mar 2001 14:18:36 -0500
From: Brian Fairey <bfairey@...>
Subject: post processor

Is there a post processor on the web that doesnt cost an arm and a leg
for converting DXF files into G code.
There used to be a program that worked inside ACAD R13 but I have not
seen anything for R14.
Brian.
--
Brian Fairey
Fairey Mfg, Waterloo,
Canada.------------------------------------

[DXF (Autocad's Drawing eXchange Format, which has become a generic format
used by many non-Autodesk programs) encompasses both 2d drawings and 3d
surface meshes. Conversion programs will generally work on one or the
other, but not both. For 2d drawings, there are some freeware programs on
the web that will probably work: check out
http://members.aol.com/andrewc119/index.htm for one.

Surfaces are trickier, but there are some some relatively inexpensive
programs that deal with them in "rasterizing" fashion, converting them to a
series of tool passes which are parallel in x or y and vary in z. I sell a
couple of them; Millwizard from Delcam of the UK, and DeskProto from Delft
Spline in the Netherlands, which is more expensive but also more capable.
The beta version of DeskProto 3.0 (available to purchasers of version 2.0)
supports rotary parts made using a 4th ("A") axis parallel to the x axis.
It does this two ways; either running down the x axis varying in z, then
rotating a variable increment in A and coming back up x; or rotating in A
varying in z, then reversing at 360 degrees, incrementing in x, and going
back to zero degrees in A again. This works well when no area of the part
drops below the center of the rotary axis (z=0); unfortunately it tends to
gouge the part when the z value is negative- but they're working on it
(that's why they call it a beta).

"Post-processing" is another issue. While G-code is fairly standardized,
there are many "flavors" of g-code used by different manufacturers, and
different machines want their data presented slightly differently. Some
want line numbers for each command, some require spaces or commas between
directional commands, others will execute a certain g-command entirely
differently than the rest. The job of the post-processor is to take the
g-code the program generates and put it in the form suited to a particular
machine. Usually this is fairly simple, but some machines require extensive
(and expensive) massage of the code in order to execute it correctly.
Fortunately, these simple rasterizing programs generally use a very
restricted command set, so major compatability problems are rare. ]

Andrew
http://www.computersculpture.com

Andrew Werby - United Artworks
Sculpture, Jewelry, and Other Art Stuff
http://unitedartworks.com