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racerxky's blog
Posted by racerxky | Nov 19, 2013 @ 02:58 PM | 1,930 Views
I know some of you in out there do CAD/CAM development. I'm starting up a project where I would need to make some molds of an organically shaped fuselage. Until now I have stayed away from curved surface modeling because my favorite modeling tool, Sketchup, doesn't property model curves.

Sketchup can model line segments, triangles and things made up out of triangles (meshes or poly meshes). Meshes can be derived from lines but once these meshes are created they cant be easily or accurately modified. Also the resolution of a triangular mesh impacts what you can do with it. Imagine taking the cross section of an SR-71 fuselage to make bulkheads. If the mesh that makes up the fuse skin is composed of flat triangles the bulkhead edges will have flat spots. That might be OK if the flat spots are smaller than the resolution of your CNC equipment but on a large model (say 2M) that wont be the case.

So the answer is to use a CAD program that models curved surfaces using a mathematical representation called NURBS. With NURBS you can compute exactly the x,y,z location of any point on a surface. So when you slice a bulkhead through a curvy part you get a curve of infinite resolution no matter how large you scale up the part. The same model could be used for the full scale airplane with no loss in resolution.

NURBS programs tend to be 2 things: Difficult to use and Expensive. The cheapest one that's often pointed to is Rhino which will set you back a cool $1K. I played with Rhino all...Continue Reading
Posted by racerxky | Mar 15, 2012 @ 06:42 PM | 2,417 Views
My research into vinyl cutters has its first tangible results. I really like the Silhouette Cameo. It's only 12" wide but it is the cheapest cutter I was looking into and its performance with our materials and ease of use are great. I would like to find a wider cutter that has similar cost and performance. I may get to evaluate one of the chinese cutters from USCutter.

Evaluating these machines is expensive and time consuming. If something is not going well it can take a lot of messing around to decide if the problem is your setup, the machine or the software. Many test cuts have to be made changing just one variable at a time. I'm not keen on wasting my time like that too often.
Posted by racerxky | Oct 19, 2011 @ 11:56 AM | 2,527 Views
I'm doing some research into a cheap/effective vinyl cutter. I've been wanting one to cut covering and vinyl for a while. It really speeds up a lot of things, even repairs. The thread is here, if you have any experience please do contribute.
Posted by racerxky | Jan 22, 2011 @ 11:22 AM | 7,575 Views