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In Rhino 4.0 Essential Training, author Dave Schultze shows how the 3D NURBS-based modeling tools in Rhino 4.0 are used to engineer products from toy robots to full-sized aircraft. This course concentrates on using Rhino 4.0 for industrial design and rapid prototyping, with a review of common 3D terminology using specific examples. Along with a comprehensive exploration of the Rhino interface, the course includes an introduction to building 3D objects with Rhino's three primary entities: the curve, the surface, and the solid. Exercise files are included with the course.
In this video, we'll take our robot arm and review the steps required to send out a file for prototyping. Our goal is to export the 3D data to a file format called STL, which stands for Stereolithography. This term is used for both the machine and the process. This is a very cool machine. It will build your model using a laser and liquid resin. A quick recap, a NURBS model is by definition very smooth. This is great to edit and design and visualize, but it's not intended for prototyping. Instead, we're going to create a polygonal mesh and then save that mesh in the STL file format.
Now Rhino has a direct way to do this via the File > Export Selected, which will generate a mesh and export it, but I feel that you lose too much control. So, I'm going to add one extra step. We'll kind of do a quality control, review the geometry before it goes out and then save it, of course, if it passes the test. Let's turn off the robot. Focus on the arm. Now another reminder here. We've already verified that this entire model is closed and clean via some of the strategies discussed earlier. Okay.
Let's take a visit to a brand- new menu. It's called Mesh. There are lots of options here. We're going to just pick the first one available. Mesh > From NURBS Object. We're going to select this entire object here, right-click and switch over to Simple Controls, which is usually the default. So, this process, just to make it a little more clear to understand, I'm going to crank it down. We can do a preview. Sometimes, it's hard to tell what's going on because this mesh is generated right on top of the NURBS object. I'm going to leave it as acceptable and hit OK.
Now to analyze this, we're going to have to select the mesh. I'm just going to nudge it over a few places and we'll take a look at what we got. Right off the bat, you can probably tell that's not what we're wanting to do here. This has got a lot of large facets. There are also some problem areas here as circle is turned into a square. We've got all sorts of pinching and puckering all over the place, but this is good to check out the difference between a NURBS surface and a polygonal mesh.
This is not all that editable. In fact, we probably wouldn't want to touch it. However, you can't turn control points on, as you can quickly see, there is nothing you'd want to mess with. So, we're going to go ahead and turn the control points off, delete it. We're going to do this one more time in higher setting. So, I'm going to select the object one more time. Go to Mesh > From NURBS. We're going to go quite a bit higher to the opposite end. Check the Preview button. This is actually looking much better. I'm going to go a little bit further.
I'm going to select the mesh. I'm going to nudge it over for inspection. I'm going to use the Zoom Selected button here. Now we can see that this is much more round. You don't have any pinching on these interior spots. That's still round, to have--- nope! That looks pretty good. So, the question always arises, how dense should I make the mesh? Well, if it's going to appear solid black in your viewport, that's too dense. At some point, you've got to remember that the tolerance of the machinery, the Stereolithography machine, it can only builds things to a certain size.
If you've way below that, you're just doing unnecessary detail that it cannot capture. Let's say that this has passed the inspection. I'm going to mention one more thing, just in case there were any problem areas. This is where you'd catch that. Occasionally, we'll see surfaces or polygons flipped, turned inside out, or just missing. So, that's your opportunity to fix that file, in which case, I recommend just throwing this whole mesh away and addressing whatever part was causing the problems, and then just building the mesh one more time.
It's ready for export. I'm going to select. I'm going over to the File > Export Selected option. Call this the robo arm. One great thing about Rhino is it has got a million formats you can export to. For this, we're going to pick Stereolithography, go ahead and click Save. I'm just going to accept the defaults here. So, if I were to skip these steps of generating the mesh and reviewing and regenerating, I might have missed some error, because what happens is that mesh would get exported all in one step, and I'd be left just with this NURBS surface.
Any problems would be in an external file that I might not catch, and that could be a potential problem if you're on a tight deadline. I'm going to jump over to the folder and do another couple of recommended steps. Here is my exports folder. Here is the Rhino file. Notice the size gets considerably smaller. That's because the polygons don't have that much data. It's a lot of points, yes, but since it's no longer editable, it does tend to be quite a bit smaller. However, this is a critical step I'm going to mention. I'm going to go ahead and ZIP this. If you're going to send this out to a prototype service bureau, you can potentially have errors creeping into the data.
So, it wouldn't make a difference on most file formats, but this you might actually have a seam open up or have a problem which would prevent it from being built at all. So, it's simple to solve just by compressing it into a ZIP format. Notice the file sizes get considerably smaller each step. So, this is almost 7 megabyte Rhino file is under 1 megabyte. It's a third of that size when we ZIP it. So, that is ready to be sent out. So, here is the custom robot arm we just finished modeling and exporting.
For something of this size and complexity, the service bureau would print it out within a few days. Parts like this will be used for testing or reviews prior to manufacturing. However, many prototype parts do not get manufactured. They're used to find problems before a million parts are made or just to make a single custom paperweight for your desk.
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