Kent Chasson wrote:
ballbanjos wrote:
.... The main thing I can see from your approach is that you are seeing the machine table with material on it when you start out working a design in CAD while I'm just seeing a piece of raw material. ....
Dave
Is another way of saying that that Andy's drawings all have the table (and zeroed fence) included and yours are just the part?
Big picture, conceptual stuff like this is really helpful to a beginner.
My original thought was to have a few dedicated auxiliary tables with indexing for each part. Maybe one for multiple fretboards, one for headplates, one for necks, etc. Each table indexes into the machine table. Would that make sense?
Seems like half the point of this is being able to set it up and let it run while you are doing other things. If I have to stand around and plug in parts every ten minutes, I might as well machine them myself.
Not to answer for Andy--but my understanding of his approach is that he does his CAD drawings with the 0,0 origin in the same corner as his home position on the machine and measures everything relative to that. He does a centerline for his fingerboards in the CAD design so that he has something to sync his workpiece to, and all of the indexing pins to keep it consistent--all relative to his 0,0 that matches his machine. What I've done is to design something without regard to the machine itself, and habit has me setting my 0,0 point to the center of the work. It doesn't take the machine into account at all--I zero the machine to the jig, wherever the jig happens to sit on the table.
From my point of view, each approach has pros and cons. I think that Andy's more integrated method is a more logical solution all in all than mine. But mine has the advantage of being able to put a bunch of different fixtures on the table wherever I can fit them and set the 0,0 where ever I need to. With the handwheels and index hole for zeroing the machine out, it's quick and easy, but not as logical or as automated as Andy's approach.
One fixture that I use a lot makes necks, fingerboards and peghead overlays. Three separate vacuum jigs on one secondary table. It fits in index holes on my main table. I zero the machine to the center of the middle jig on the table. This becomes offset G54. I have also set up G55 and G56 for the other two jigs on this fixture. This same setup would work well (probably better) using Andy's approach, but I would assume he would use G55, G56 and G57 or else he would have made the entire fixture as one big CAD drawing with the whole thing in G54.
I leave this fixture on my machine a lot, since I can do so much of a banjo using just this one fixture. But I also have other fixtures that I use for other things--some banjo related, some not. I'm basically lazy and don't want to take my main fixture off just to do a quick job on something else, so I just find an open place on my table, and put the other jig wherever it will fit. I re-zero the machine to the zero point on this jig, use G54 and I'm good to go no matter where on the table it's sitting. Of course, if I zeroed like Andy does, I could still re-zero manually for the extra jig.
Guess it's all a matter of habit. I like Andy's approach, and I suspect it is probably the more common way of doing things out in CNC land. It's also a lot easier to find a CAM solution that will work with it--pretty much any CAM out there will let you set up a corner origin, but finding one that will inherit the non-corner origins I'm using from a CAD drawing is not as easy. MadCAM does a great job of taking whatever origin I use in Rhino, but most of the other CAMs I tried weren't so forgiving. Starting from scratch, I'd use Andy's method. As it is though, I've got a lot of CAD designs, fixtures, etc. that I don't want to re-engineer. Going forward, I might well change my ways, but for the stuff I'm already doing, I have too much time invested to re do it now, especially since it's not a big deal to zero the machine manually anyway.
Even though I've done mechanical design work for years and I've worked with servo systems for years, I'm a newbie in the CNC world. Trial and error is my game, and sometimes I get it right and sometimes I smack my head and say, "Dang why didn't I think of that!"
Of course, on the other hand I might have completely misunderstood what Andy's doing! The work he's turning out is sure looking good whatever it is he's doing, and that is after all the bottom line!
Dave