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100 hours of print time, and what I’ve learned...
When dealing with flipped normals and hidden faces there are some things you must consider. Many people say the best way to deal with this is to import the .stl of the model into a yet another program and do a “clean” or “repair.” I personally have opted to be stubborn and figure out what I’m doing wrong in the first place! To self-diagnose, first identify the faces that are “inside” your mesh but are not intentional.
The best example of this issue happening is when you extrude 4 vertices on one side of a cube. When you do this you are given 4 new vertices, and 5 new faces. The model on the outside looks fine and you just made the square a rectangle. But what was left behind was a face between those 4 vertices. At no point did we tell blender to remove that face, so it remained to throw things off later. Be aware of what you are leaving behind when extruding. Also consider a “remove all doubles” just to be safe. In dealing with normals it is important to make sure that normals are facing outward, otherwise the print will attempt to print up to where the normals face. That may sound confusing but if an object has three faces on one side and one face happens to be flipped, then that flipped face will be bypassed because there is no printable area behind where the normal is facing. Most of the time that I have run into this problem is when I was joining meshes with boolean unions. At the intersection of two meshes you may have faces flipped randomly. I’m sure there is a reason to this madness, but I just assume the role of inspector after each union.
Now you may have the need to make something “functional” for real world. Or something really awesome, but it has to fill a certain space. The way I personally have addressed this, after lots of tests, is to assume the default cube is a 2’ x 2’ x 2’ cube. So, if you press “s” for size and type .5, you now have a one inch cube. If you remember my list earlier, in ReplicatorG i select “scale” and then “inches -> mm.” this allows me
BLENDERART - ISSUE 40 | NOV 2012
to work flawlessly with default blender units and have a mesh in 3D view that isn’t unbearably huge! So modeling sections are easy enough now, as long as you are comfortable typing in your measurements in inches. So if I want to move a vertex 2.75 inches, I just select the vertex, press the “g” button, then press “x”, “y”, or “z” depending on the axis I want to move on and then immediately type “2.75”. That principle is carried throughout the model. If you are modeling around a real world object (like an LED) then make a model with the dimensions using this method, and then artistically make the model fit around the modeled template of the real world object.
The last thing I’ve had the privilege of working on was dual extrusion prints. And I’ve included a file to be used. When you create a dual color print, at least with ReplicatorG, you will find that you have to create an .stl file for each color, and when being printed each color will have no awareness of each other. It is possible to have the printer print twice in the same 3D space. Sounds cool I know, but can cause the printer to get jammed up.
And it is a pain to clean at times. You may also notice particles of each color found on the outside edges due to the nature of plastic melting and expanding inside the print heads “nozzle.” One way to address this is to enable a profile to build a “skirt” around the model to catch all the loose particles of plastic. This is an advanced setting to handle, but alternatively, it is easy to scrape off most of the loose plastic. My best advice: try things, take chances, and have fun!
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