Chris Ghent Posted February 17, 2004 Share Posted February 17, 2004 (edited) Things to keep in mind when CADing for laser or waterjet output is that all the lines must be either straight lines or arcs (no Bezier, Cubic, etc. curves), all must meet at vertexes, circles must "pigtail" in to start, and the lesser number of vertexes the less expensive will be the production of your part (the laser/waterjet equipment has to "think" at each vertex which adds an appreciable amount of time to perform the cuts). Richard, While I have had problems with the shapes of curves in the design phase and have touched on this in dialogue with Dana, I had not realised there were restrictions on the shapes of curves in the cutting process. A bezier curve is one with a shifting radius, right? Isn't it a total limitation that a curve like this cannot be cut? And a cubic one sounds like the same only with a logarithmic based lengthening or shortening of the radius? "All must meet at vertexes" means when a geometric shape, say an arc with fixed radius, meets a similar, you can't round off the corner, it must come to a point? And "circles must pigtail in", well I'm stumped there..? I just checked a pic of a Jeffries end and of course the shapes rarely follow these rules. In fact the most pleasing curves (in every part of life!) are those described as flowing! I don't have expertise in AutoCad, I am just used to sitting down and learning new programmes. Your warning is heard. I suspect R2V progs have come along recently, one I tried yesterday (AlgoLab R2V) did create arcs, but could not decide how to handle a vertex consistently. Also, as it was drawing a line without physical width (steady down the back) it wandered around inside the width of the rasterised line it was converting enough to be disconcerting. I found it much easier to import a scanned image into my CAD program and draw (CAD) right over it. That way you create what you want without having to "fix" stuff you don't want. When you say draw, if you are meaning you can freehand over the top in vectorspeak, then that would be great, and I'll do whatever you are doing. However, I suspect you mean arrange arcs and lines by means of inserting points and influencing the line produced between them between into a curve? I entered this particular area of concertina building (cad) believing I would be able to show a computer a line drawing and it would accurately replace the lines with some sort of "software guidance tracks". I now know that idea is so divorced from the way it all actually works it is risible. Just another compliment to the human brain I guess. As regards .4mm offsets, would the "jobber" (great word, I usually try to de-Australianise the speech in my posts, maybe I shouldn't) be able to act on an instruction like, "cut .4mm to the inside of all closed shapes?" Hope you might have a minute to continue my education, no hurry... regards Chris Edited a couple of times to remove evidence of carelessness and stupidity... Edited February 17, 2004 by Chris Ghent Quote Link to comment Share on other sites More sharing options...
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