3d rectangle with medium squish.8/12/2023 ![]() Since we are not limited by what shapes we can cut out of a solid chunk of metal we can optimize the shape and get rid of material. The classic example used for this is parts designed for commercial airplanes such as the bracket below. But if we simplify things a bit, complexity is "free". Granted, a simple cube doesn't use any retraction or many travel moves to speak of, so print time will be slightly lower. What we mean by this is that the printer doesn't care if it creates a cube or an intricate set of shapes. After the print is done the ball is simply broken free from the rest of the print and is free to rattle around inside of it. One very common example is the whistle where the little ball is printed inside of the whistle from the start. Of course you're not limited to creating parts that interlock or interact directly. You can read more about stringing and what you can do to lessen its impact here. The one problem that you may run into is with stringing which can cause the parts to fuse together. We've created parts with as little as 0.2mm of clearance. In the X-Y direction this isn't nearly as big a problem and you can design parts with quite tight tolerances. This makes it easy for the printer to handle but we also completely avoid the problem of sagging that could cause the two parts to fuse. ![]() As you can see we've respected the 45degree rule by making the overhangs of the hinge stay at 45 degrees. The top part of the image shows the entire part while the lower image shows a section cut of the hinge. In the example below is a hinged dust filter that is printed as a single piece. Create a small test part so that you don't have to waste more time and plastic than you need. By far the easiest way to figure out how much you need is to simply print out a test piece and see what happens. If it's longer or if it has an intricate shape you may find that it sags down considerably more and you'll have to compensate for this accordingly. If the overhanging part is very small, say 10mm across, you may get away with a clearance as small as 0.5mm. How big that clearance needs to be is difficult to give a straight forward answer to. Because of this it is important that you leave enough clearance between the two parts to allow of this sagging. It is much harder to control a strand of plastic that is extruded into mid air as it will sag unpredictably. This is mostly a problem on the areas of the print where one part is lying on top of another. The biggest challenge when creating designs for this purpose is to make sure that the different parts do not stick together and are unable to move relative to each other. That is, instead of creating multiple separate pieces that you then mount together, you can (in some cases) print the pieces already assembled. ![]() One such thing is to print assemblies in place. Given that objects in a 3d printer are built layer by layer there are some interesting things you can do by taking advantage of this fact. This way you'll have better control over it. But what if you were trying to make a square part fit into a square hole, such as a lid? This extra build up could prevent that from being possible without adding additional clearances all around the part.īecause of this it can be a good idea to make the corners or your parts slightly rounded at the design stage. Now, the corner become slightly rounded is probably not a problem in most cases. What's worse is that there is some slight material build up. This corner was designed to be perfectly square in CAD but as you can see the machine is not capable of creating this edge. During the slow down the builtup pressure in the nozzle causes some excess plastic to sneak out creating a slightly thicker extrusion. Depending on your print speed there's also a very good chance that you'll get some additional oozing at the corners since the print head needs to slow down in the curve. Since the printer nozzle is round it is impossible to create a perfectly sharp outer corner on your parts. Here's some thoughts and suggestions on ways to improve your prints by designing them in a way that makes them easier to print. ![]()
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