Preparing files for 3D printing: i.Materialise explains all

May 10, 2016 | By Benedict

i.Materialise, the consumer 3D printing service and marketplace of Materialise, has published a guide to preparing files for 3D printing. The guide, coming in the form of a blog post, tackles file-fixing terminology and provides an essential model-fixing checklist.

Belgian 3D printing behemoth Materialise, a company with a foothold in industrial 3D printing, medical 3D printing, and other fields, might be part of some pretty important goings-on in the additive manufacturing world, but that hasn’t prevented it from connecting with a key 3D printing demographic: you, at home, desperately trying to get to grips with your newly downloaded CAD and slicing software. Okay, so the i.Materialise guide to 3D printing file preparation might be geared at potential customers for its online 3D printing service, but the advice given is nonetheless useful for amateur makers looking to create printable, error-free 3D models at home, without breaking a sweat.

So how does one go about preparing a 3D model for 3D printing? 3D printers can do some incredible things, but their abilities are naturally limited. Extremely thin and complex parts may not print properly or may be too weak for purpose, and some models which look stunning on-screen simply will not translate into chunks of ABS or PLA. Although much can be learned about the printing process through simple trial and error, following i.Materialise’s eight-item checklist is a decent start for preventing failed and substandard prints. In condensed form, here it is:

First up on the checklist is the issue of watertightness. Put simply, a 3D model must not have any holes in its surface—these holes may not be immediately apparent onscreen, but your printer will not appreciate them. When 3D printing veterans talk about creating a “manifold” model, they are essentially referring to its watertightness. If there are holes in the surface of the 3D model, patch them up.

The second item to consider is wall thickness and volume. Every surface of a 3D model needs to be assigned a wall thickness—the distance between that surface and its opposite sheer surface. 3D models imported from, say, computer games, will not have wall thicknesses specified, as they are only designed to be seen onscreen. To get the model printable, however, wall thickness need to be considered, taking both the kind of 3D printing material used and the quality of the 3D printer into account.

The next item on the checklist is auto intersections, internal overlapping, and self-intersecting surfaces. Quite a mouthful, but not as scary as it seems. This step basically involves not creating overlapping elements within a design, as these overlaps will confuse your printer. That doesn’t mean that you can’t create 3D models that appear to consist of overlapping elements, though—just implement a Boolean operation to merge those overlapping elements first.

Fourth on the checklist is the issue of reversed faces, inverted normals, and surface orientation. A common issue in 3D printing, inward-facing or reversed faces are more-or-less what they sound like: surfaces facing the wrong way, typically facing inside the object when it supposed to be facing outside the object. Before sending anything to the printer, double check that no such reversed faces are affecting your 3D model.

An issue that only really applies to i.materialise customers or users of similar 3D printing services is that of grouped models. Single STL files which actually consist of several separate 3D objects. You aren’t going to fool them that easily! Fortunately, i.materialise offers a quantity discount for customers looking to print multiple copies of a single design.

If you’re looking to add a mark of identity to your 3D printed model, you might be considering a small detail or embossed/engraved text. While such details can add a touch of class to a design, they can be difficult to get right. It is important to make sure that any such details are large enough to be accurately represented by the 3D printer. Some materials are better than others for minute details, so it’s best to read up thoroughly on your filament options before opting for such a design.

The penultimate item on the 3D printing file prep checklist concerns hollowing and escape holes. Part of the beauty of 3D printing is its ability to create objects of varying levels of solidity, with denser prints being stronger and more durable and hollower ones being cheaper to make. That being said, care needs to be taken when creating a hollow 3D printed model. Excess 3D printing material can easily get trapped inside a hollow model, so it is sometimes useful to add “escape holes” to a design, ideally in an inconspicuous place, so that any residue can be removed from the inside after printing.

Last but not least is the issue of file resolution and file size. Most 3D printable objects come in STL (STereoLithography, or, more recently, Standard Triangle Language) format, turning a 3D model into a collection of—you guessed it—triangles. When converting to STL format, you will have to define the “tolerance”, the maximum distance between the original shape and the new STL mesh. Materialise recommends a 0.01mm tolerance for most prints, since smaller tolerances are hard for printers to handle and large tolerances result in visible triangles.

There you have it: eight points to consider when preparing a 3D printable file, courtesy of i.Materialise. Materialise customers can currently choose from 21 3D printing materials and a wide variety of colors on the i.Materialise 3D print lab.

Posted in 3D Design

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