It sounds like you are considering reversing the tool path of an additive machine. That can't work. The tool end would have to pass through solid material.
If the goal is to have your additive machine create different surface properties for material near the edges then this is typically done in the slicer software. All slicers to this. They lay down the material that can be seen and touched differently from the material inside the part. The simplest example is "infill". All slicers can creat low density infill. Another example is what they call "ironing" where they move the hot extruder over the exterior surface while not extruding any more plastic. The hot metal flattens out any bumps. It should be possible to add other surface treatments to the slicer software. On Sun, Mar 11, 2018 at 5:36 AM, Gene Heskett <ghesk...@shentel.net> wrote: > On Sunday 11 March 2018 05:54:08 Andy Pugh wrote: > >> > On 11 Mar 2018, at 06:03, a k <pccncmach...@gmail.com> wrote: >> > >> > i want reverse tool path. >> >> No, you don’t. >> >> A reversed tool path will still put the tool outside the part >> material. >> >> Just use a 3D printer slicer and configure your machine with a dummy >> extruder axis that does nothing. > > That to me, still doesn't quite get the job done. He needs to hook up the > extruders wire feed to the plastic feed, and some way to turn off the > fire when jumping across an opening in the pattern, and restarting the > fire when its moved across the empty opening. The fact that the machine > can lay down a much thicker line of metal in one pass than the 3d > printer can should just be a matter of programming the slicer for a > thicker slice. In fact it may be worthwhile in reduced "finishing" work > to design a new smaller "extruder like" mechanism to handle say .015" > diameter wire, as that would reduce the final pass to size to a single > pass, possibly with EDM if its a thin walled and easily distorted item.. > > It might even be helpfull to replace the drive motor on the "extruder" > with a reverseable motor so that the wire can be withdrawn far enough to > extinguish the arc. The rest of this I see as a hal file composition > exercise, hooking up SSR's to control the arc, and some sort of a THC > like arc starter. In fact, let the THC output control the x/y feed speed > as a way of laying down a consistent thickness of metal. > > It would also be a good idea to have the workspace flooded with the near > inert CO2/Argon atmosphere. The CO2 adds carbon to the puddle, making > the resultant metal layer much harder than straight argon by itself > would. It wouldn't matter if it leaked, as long as the working envelope > was flooded to keep slag at bay because that would make the arc restart > simply a matter of fireing the SSR and extending the wire until contact > was made again, letting a feedhold hold the starting position until the > arc was started, long enough to make sure the metal was being > transferred. The flooding gas would ensure a clean, oxide free > interface, making the arc so much easier to restart you'd wonder why you > ever bothered trying w/o it. The initial startup might need a delay > after gas turnon to assure its well flooded else the weld would slag > over once the head had moved on, at least long enough for the weld to > cool. > > Or perhaps I don't fully understand the problem. Its certainly something > LinuxCNC can do once the slicer has created the laydown paths from the > 3d model. > > Aram hasn't given us any hint at how big the working envelope of the 3d > metal printer might have to be as that will determine the gas economics. > In the size bottles I use, a big box can get expen$ive to flood. > > -- > Cheers, Gene Heskett > -- > "There are four boxes to be used in defense of liberty: > soap, ballot, jury, and ammo. Please use in that order." > -Ed Howdershelt (Author) > Genes Web page <http://geneslinuxbox.net:6309/gene> > > ------------------------------------------------------------------------------ > Check out the vibrant tech community on one of the world's most > engaging tech sites, Slashdot.org! http://sdm.link/slashdot > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users -- Chris Albertson Redondo Beach, California ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
