Designed to Print
Great 3D Prints aren't simply a matter of printer quality. Great prints start with great design, a field that while growing still see a gap in the demand versus the supply . Whether your cranking out gadgets in Skethup for your own use, or engineering a rocket component in Solidworks at Kennedy Space Center, consistent design principles hold true for anyone intent on printing a 3D model. Continuing advances in design software are making the practice increasingly user friendly; however, it's always better to build foundational CAD skills for quality design before you rely on that new button which runs an automatic feature. Here's our list of do's and don'ts for 3D Design:
Do Create Manifold Models
If you're new to the term, a manifold 3D model is one with uniform, solid faces throughout its volume. Think about it this way: As a designer you have the task of creating something that exists digitally, which can also exist physically. A 3D Printer does nothing more than translate mathematical information from digital points in an x,y, and z plane to a physical x,y, and z plane using real material. CAD software on the other hand, can model geometry that can't exist in the physical world. A manifold, or "watertight" model is one with defined three dimensional geometry.
Infinitely Thin Planes: Also known as one-dimensional planes, these are any instance of a model with no quantified thickness. Surface modeling can result in this design-to-print problem when surfaces used to build an object are not actually merged with one another, or not defined as having a real thickness. Since software will render a plane with no actual thickness, using surface modeling for 3D Printing means you need to be thorough and run your due diligence, retoplogize, or remesh your final model so that all vertices are fused. Simply lining up flush edges is generally not enough to ensure a watertight model.
Double-sided faces: Any instance of a model in which information about a single surface also applies to it's inverse, parallel surface is a double-sided face. It can be a problem if the model doesn't have a defined volume or if such faces are layered against your model, but not fused. This has the potential to create flakes or floating sections of print instead of a uniform solid.
Holes and Cavities: Missing faces generally occur if planes and surfaces have not been properly aligned or if layered planes have not been properly fused. Intentional holes and internal cavities will print so long as the volume around them is defined.
Overlapping Planes: There's a big difference between overlapping planes and interlocking or nested planes and model geometry. As long as you've taken care to follow all the preceding principles any interlocking surfaces that aren't welded should print just fine -that's exactly how you create joints and other functional features. Overlapping planes that aren't defined as two separate surfaces or welded into a single solid can create critical print errors if not corrected. This occurs because when planes cross, the results contain infinitely thin points of intersection or reversed exterior and interior faces. Resulting models can look "blown out" or like Swiss cheese in such areas.
Don't Just Copy and Paste Sections of a Model
Some software allows very fluid replication of parts, but when you copy and paste sections of a model unless you also take the time to align and fuse, there can be problems. Even then, unless copied parts are placed mathematically rather than visually, they may not line up precisely. Copied sections of a model can create print issues like floating and detached surfaces, as well as inverted faces and normals. Mirroring or designing with symmetry as a means to duplicate parts of a model is a generally better practice. Most CAD software contains these features, while some even allows them in multiple and radial axes. If you do copy and paste sections of a model, make sure you also retoplogize or remesh.
Do Exaggerate Fine Detail
Depending on your model, the best method to achieve fine detail may be to exaggerate that detail. This is generally more true for artistic models rather than functional models. Cutting textures deeper, making ridges more pronounced, and increasing the physical contrast tends to result in prints that better reflect a model's appearance in a digital rendering. Renderings are great tool but can be deceptive and cannot account for the physical limitations of a printer.
Don't Rely Solely On Printer Resolution
A similar principle. Resolution is an important consideration, especially if your model is going to be moved across a couple types of software before printing. When the time comes to print, models created at too low a resolution can lose detail and features, while models at too high a resolution may be too large for a slicing software to process. Well crafted forms and details are more important to a good print than resolution. Depending on the model resolutions ranging from 100k to 1 million polys generally perform well across an array of technologies.
Do Design for the Printer and Material You're Using
A filament printer like the Airwolf Axiom, an SLA printer like the Form 2, and a powder printer like 3D Systems' Projet 660 are wildly different machines. Even in the case of a model all three can produce, the results couldn't look more different. Even among similarly classed technologies a model that looks great on one printer might not on another.
Every 3D Printer has its limitations and its strengths. Familiarize yourself with the one you plan on owning or using and then design your models with that printer in mind.
Do Account for Tolerances, Fit, and Offset
Even if you're not an engineer, don't forget that any kind of functional designs can be affected by the printer used. While high end printers are "True-to-CAD" filament printers, as well as a few others, are affected by the physical mechanics, dimensions, and offsets, created by their material or process. As above: Get familiar with the printer you plan to use before or while you design.
Do Design to Scale
While it may seem obvious, careful consideration to final scale , particularly in artistic applications like jewelry design is critical. Something that looks great zoomed in on a 16" monitor may be completely invisible on a necklace pendant, or in a tabletop model of a building. Conversely, smaller details not careful crafted into a large design might look muddy or undefined. While it's largely a nuanced and stylistic aspect of design, having sense of what makes a model of any kind look good at any given scale can make or break an aesthetic.
Do Check Your Model Before Printing
Finally, before you click print, or send the model of too a service provider, take the time to go back through it and run an automated check of the model's integrity. Even if there's nothing visibly wrong, some of the issues mentioned here can still present problems. A lot of design software offers quick, automated fixes for many basic issues.
All in all, the most basic elements of designing excellent, print-ready 3D models is as simple as being thorough in your approach and having a solid grasp on the capabilities of your design software. This is the diving off point to any other topic and practice in 3D Design.