Allowing for destruction in your creative process
As a CAD modeler, your practical sense can be easily lulled to rest by the graceful shapes bursting out of your imagination. And sure enough, when the rendering is complete, when you and or your customer are feeling pleased with numerical beauty, nobody is thinking much about compromise.
But then one of you remembers things like design alterations and manufacturing processes. Once those considerations hit, you realize that the technical aspects of manufacturing will likely violate your artwork in the name of actually making something real.
Fortunately enough, 3D printing allows the modeler to experience more freedom with his or her virtual shapes. Creativity has never been unleashed in such an exhilarating manner since virtuoso sculptors. But while Michelangelo’s art took years, many hands, revisions, and prototypes, 3D CAD and additive manufacturing, theoretically, takes only imagination and a 3D printer.
But, none of this will ensure the consistency of your system, or its sustainability. The matter of cohesion on a macro and micro level is compulsory to take into consideration while designing your CAD model.
Once outside the abstract, your model is subjected to failure
If you want your model to endure outside of your head and your computer, you should always have failure and defects in mind. A shape could surely look beautiful on your part and serve its functionality perfectly well, but it might also invite in defects and failure that could spread to the rest of the shape.
Failure is not a phenomena that can be predicted or thoroughly monitored, you can be as sure as you want from your material and the manufacturing process, there will never be a complete guarantee that a simple disparity of temperature in a certain microscopic spot didn’t initiate a disparity of layers in your creation. Failure needs only a microscopic flaw as an extremely tiny scratch and a hazardous event as someone discharging a heavy load on the ground within the perimeter to be initiated.
You can only dimension your mechanical system to known failure classic paradigms. You’ll never be able to dimension something perfectly. The essence of nature is decay, and so is the case for your models. Once you acknowledge this fact and are aware of it throughout the process of modeling, you will be able to prevent some aspects of failure and have a peaceful mind as to the quite predictable but not guaranteed lifecycle of your component.
Coping with failure on the analysis and expertise scales
While analysis helps to narrow in on the critical zones of a model and improve it, an experienced modeler/manufacturer would be able to guess, from the shape of a component, which part or feature would be fragile or would present a defect. Certain practices are unconsciously performed by the modeler to avoid stress concentration, and therefore the most immediate cause of failure.
Sure, you understand that edgy corners aren’t the best, but it’s mainly because a radius breaks down the concentration of a force and helps induce a slower spread of the packed stress. You are also quite careful not to load your system and instead leave room within, as this actually helps with a wide array of problematics on the mechanical level, such as giving slots to "inaccuracies," leaving space to parts to dilate or retract as a thermal release result…etc, etc.
Get your CAD failure ready
Within the R&D departments of the industry, we can’t afford to throw away all the parts that show failure within the early stages of manufacturing or have a minor defect, especially when they are expensive to make or to study. Therefore, we learn to adapt our CAD models to the failure scenario so as to be able to adapt the "perfect" virtual model to the "flawed" manufactured one. From there, we study its lifecycle liability, its sustainability, and its immediate failure impact.
This is achieved by several and combined ways which can be summed up in one idea: making the CAD tree very, very flexible. This can be as obvious and easy as creating all features with feature options instead of sketching them. Or, it can be as elaborate as knowing beforehand the manufacturing process you intend to use along with all the possible screw ups it might generate and allowing the area prone to be affected by said screw-ups to be available on the CAD tree.
All in all, solutions can be as inventive as the problems which gave rise to them. But the main challenge is to allow them to come up to you. And this is the main reason why being aware of failure and defect impact regardless of the virtual model at hand is so important. Because failure can’t be put into a square and, therefore, can’t be monitored by just one way. Failure has several aspects and manifests in random ways. Therefore, having a set of classic solutions at hand is a comfort to start on but it is in no case a reliable value.
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About the author: (Khadija Ouajjani)
Mechanical design engineer working for the aeronautics industry, obsessed with improving CAD to improve analysis, doesn't accept numbers without a precision scale, bookworm and aspiring writer, obsessed with garlic and Mandelbrot, loves tea with mint and coffee with cinnamon. When not writing for GrabCAD, she's probably drawing fancy propellers and coloring cube trees in a coffeeshop.
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