On 6/16/2011 1:27 AM, gene heskett wrote: > On Thursday, June 16, 2011 12:56:34 AM Kent A. Reed did opine: > > >> Gentle persons. >> >> Recall that, on 6/3/2011 3:41 PM, Viesturs Lācis wrote: >> >>> Hello, gentlemen! >>> >>> I would like to ask, if anyone can suggest me a way to generate a >>> g-code for a single-time situation: >>> The part consists of 3 pieces of tubes - 2 of them need to be welded >>> to main piece. >>> What I need is to get a g-code that describes the intersection lines >>> of each 2 tube pieces. >>> I have SolidEdge model, IGES, STEP and STL models for the whole part. >>> >>> Does anyone have any idea, how do they usually generate toolpaths for >>> such kind of machines? >>> >>> Viesturs >>> >> I replied that it seemed pretty straightforward to work up and Gene >> Heskett then suggested I put my workup on the Wiki. >> >> I realize this may be moot since Viesturs received g-code to play with >> from Stuart Stevenson but I still like the intellectual challenge. >> >> I assumed that any two intersecting cylinders (aka tubes or pipes) have >> equal diameters and that their centerlines lie in a plane. If that isn't >> so, then the following must be replaced by something much more >> complicated. >> >> With my assumptions, working out the analytic geometry for the >> intersection lines and for the normals to those lines was >> straightforward, but I've discovered that I don't understand the g-codes >> available to emc2 as well as I thought I did. (Do you think the fact >> that I've never touched any 5-axis machine, let alone a PUMA-like >> robotic arm, has anything to do with this?) >> >> With my assumptions, the intersection lines Viesturs seeks are two >> half-ellipses, each lying in its own plane, with the two planes >> perpendicular to one another. I had in mind an elegant g-code solution >> which would, for each half-ellipse, define the plane containing the >> curve to be a working plane, and then send 2D-points and 2D-vectors >> (actually, these would be mathematical functions defined in subroutines) >> that define the half-ellipse and its normal in the working plane. In >> this solution, the welding head would trace around the curve while >> rotating about an axis perpendicular to the plane so as to remain >> pointing inward along the normal. >> >> Now that I've read and reread the relevant material in the Users Guide, >> I'm not sure I can do that. Am I just misunderstanding or do I have to >> send 3D-points and 3D-vectors that define each half-ellipse and its >> normal in space? >> >> Also, is there any purpose served if I post my analytic geometry to the >> Wiki as a "first half" score to the problem, so to speak? My wife is >> going under the surgeon's knife next week and it may be a while before I >> get to the "second half". >> >> > I don't see why not, maybe someone else will finish it while you are > tending to the missus. > > You folks are concentrating on the welding, but before you can weld it, the > ends of the pipes must be prepared. If they butt meet at an angle, and are > the same size, then its a simple miter saw problem. If however a space > frame where the pieces are triangulated, even with dis-similar sized pipes, > then again it seems like a simple jigging setup problem, one where you want > to drag the end of the tube being welded to the side of the other, slowly > past a ballnose that is tracing a half circle whose diameter matches the > other pipe. Once one pipe is properly seated on the other, and all such > pieces are assembled, then rather than welding, I would be tempted to > 'furnace braze' the whole assembly in one pass through the oven. Obviously > not as strong as properly welded, but done in one swell foop, and with less > stored stress than welding would leave. > > For the weld by emc, it strikes me that this same profile of motion could > be done, with the 'wrist' holding the migs wire feeder being auto turned so > that it always splits the angles. I can visualize it, but I have no clue > how the math that controls the 'wrist' angle can be done in real time as it > moves around the joint. Don't forget too, that generally speaking, one > must move the fire in a 'j' stroke, always pushing the heat ahead of the > puddle. Maybe it can be done, but I've had relatively poor luck just > trying to push the puddle in a straight line, so I usually revert to a j > stroke of about 3/16" out& back, with the dwell at the 'bottom' of the j > on the heavier gauge metal if there is a difference. > > OTOH, I've never tested for a cert for arc welding of any kind, so take > that with a suitable measure of salt. My work with a smith wrench has > stood the test of time quite a few times though. One has so much more > control over the composition of the weld puddle with gas that you can do > almost anything with it. Even magnesium, but you'd need to be better than > me. A lot better. ;-) > > >> Regards, >> Kent >> >> >> ------------------------------------------------------------------------ >> ------ EditLive Enterprise is the world's most technically advanced >> content authoring tool. Experience the power of Track Changes, Inline >> Image Editing and ensure content is compliant with Accessibility >> Checking. http://p.sf.net/sfu/ephox-dev2dev >> _______________________________________________ >> Emc-users mailing list >> [email protected] >> https://lists.sourceforge.net/lists/listinfo/emc-users >> > > Cheers, gene > One of the problems with tubing and pipe is that there is oftentimes a lot of stress in the pipe or tube when you get it.
I have slit lengthwise some 3x8" 3/16 wall tubing only to have it pop open or clamp shut on the saw blade depending on the tube. Also welding rectangular tubing can be a trick (at least steel) as the heat of the welds expanding and contracting can cause further problems that can interact with the stresses already in the tube. I would not be surprised if a length of steel tubing placed into a normalizing furnace hot enough to braze would result in a tube "noodle" rather than a straight tube. Thicker tubing, 3/8" wall and heavier seems to have fewer issues. Dave ------------------------------------------------------------------------------ EditLive Enterprise is the world's most technically advanced content authoring tool. Experience the power of Track Changes, Inline Image Editing and ensure content is compliant with Accessibility Checking. http://p.sf.net/sfu/ephox-dev2dev _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
