Thursday, July 9, 2015

Keeping Tabs

The CAD file is complete and I have the CNC mill reserved for tomorrow. And I've run into two critical problems while setting up the actual tool paths.

The first is the growing realization that I won't be able to achieve the shapes that are on the CAD. Not, at least, without significant hand-work. There are too many curves and angles to make traditional milling possible, and the contour milling leaves too many fillets behind. So there is going to be time-consuming clean-up.

The critical one, at this moment, is a seemingly tiny problem. I can't set up support tabs in Fusion 360. Within, say, Cut3D the available tabs are primitive but they do the job:

Fusion 360 doesn't have that easy option. There are tabs in some of the milling operations, but they aren't global. And there are also some operations that can be instructed to stay clear of objects that could be part of a support structure. It may even be possible to define a set of tabs as a "fixture" -- I'm looking into that now.

But basically, I'm at a point of crawling through forums and watching endlessly slow, fatuously self-pleased instructional videos hoping that one of them may happen to mention this essential work-holding issue, and that it will be appropriate to the version of the software that I'm running (a perennial issue with Fusion 360, as they are re-writing it faster than anyone can document it).

Fortunately my fall-back is looking more plausible.

Cura (which is a freeware multi-platform "slicer" for 3d printing) estimates 1:58 to print the largest of my pieces. Which based on experience is about 1/2 the time the printer will actually take, but that still makes it just possible within a single machine reservation.

Even better, they all fall into the "within the density where calculations are performed on the bounding box" at Shapeways, to the point where all the major parts can be printed for under a hundred bucks total! If I had any spare cash at the moment, I'd probably put an order out right now just to be on the safe side...

I'm also depressed because I'm working sixteen hours a day trying to complete this commission and I'm flat broke. Can't even go look for work because, well, sixteen hour days trying to complete an existing commission. And the thing is really scaring me now. I don't know if I will be able to complete it (and it is already well behind on the delivery date I wanted.)

Well, maybe. If this thing gets done, I'll move on to the Jubal Early (which will be a lot easier based on what I've learned now). Heck..from what I've learned already, a PPG would be straight-forward. Perhaps even more straight-forward! If I can just survive a few more months, I just might be able to move on to some of the machined props people have been asking for. And one or two of those would pay my way for a considerable period...

No comments:

Post a Comment