Additive Manufacturing Strategies

Hollow Prints Save Money and Resources, i.materialise Reminds Us

ST Medical Devices

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logoEver since I started writing about 3D printing over a year ago, I find that one of the developments I get most excited about in the 3D printing space is the ability to move toward more environmentally sustainable practices. Like any emerging technology, the space plays host to a variety of competing visions, with some caring more and some caring less about environmental impacts. As it turns out, the same sustainable practices used by individuals and companies can also result in reducing costs. This is definitely the case with i.materialise‘s reminder that 3D printed hollow objects cut costs by reducing the amount of unnecessary materials used, thus reducing negative environmental impacts too.

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i.materialise is the 3D printing marketplace of Materialise — a Belgium-based 3D printing company. Materialise runs the biggest 3D printing service in Europe with over 100 machines that produce over 300,000 parts a year. i.materialise is the marketplace where artists can upload models and consumers can go to order designs and have them printed and delivered. Making hollow objects is beneficial due to the fact that the costs of 3D printed items are based on volume and amount of material used in the print. Think about it: there are many 3D printed items that don’t have to be solid. And this can also help avoid warping. But, printing hollow objects takes it own kind of skill set.

As explained in a recent blog post:

“…creating a 3D model with an empty interior can be a bit tricky: you need to know how to hollow your model in the 3D modeling software you’re using, you need to define a wall thickness that is strong enough for your model not to break, and it probably makes sense to add so-called ‘escape holes’ to your model… since our printers print layer by layer, 3D printing material can get trapped in the interior of your model…If you would like to avoid this… Material that is not used for building your 3D print can then be removed.”

hol2That makes enough sense–particularly as to why i.materialise would refer to this method as the “#1 hack” to lower costs in 3D printing. Hollow prints sound good for many projects and escape holes for built-up material sounds like a good solution to the problem of printing hollow objects. Another aspect of designing for hollow objects is the need for walls. Object walls vary in required thickness: stainless steel for example can be quite fine at 0.3-0.4 mm, but ceramic would need to be at least 3-4 mm thick, by comparison. Leaving no stone unturned, i.materialise has provided a guide for 3D designers about wall thickness here.

While SketchUp’s platform is complicated for hollowing objects, 123Design software is recommended for designing hollowed models because it provides a function that allows you to “modify” and “shell” objects. The post from i.materialise also recommends Meshmixer as perhaps the easiest software to use; it allows users to “edit” and “hollow” objects.

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As for how many “escape holes” you should include per object, there’s not a universal answer. Multi-colored prints should have at least two with gold, brass, silver and bronze prints needing more. Ceramic objects need holes at least 10 mm in size. Here’s an individual design guide that can help you with these decisions. The idea to create a “cylinder at the bottom of your model and extrude or subtract from its wall” is the same for each design, but wall thickness and number of escape holes differ depending on a variety of factors.

Discuss this story in the Printing Hollow forum thread on 3DPB.com.

Happy Hollowing!

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