Far too often we have seen engineers and designers come up with a part design that is “unprintable” because they were unaware, or overlooked the 3D Printing design guidelines while designing. This is then followed by a plethora of design changes amidst a lot of to-and-fro communication, which really isn’t the most efficient, nor the most productive way of doing things. We thus decided that, it was imperative that we write an article that addresses these concerns and presents a better approach, and a checklist of things that one should consider while designing for 3D Printing. So here are the 6 things that you should consider while designing for 3D Printing:
Choose the right 3D Printing Technology:
Prior to designing, it is important to get some perspective of what the final application of the product will be and what manufacturing conditions will be conducive for the product. Some of the 3D Printing technologies have support structure generation which lead to excessive post-processing operations; some have smooth surface finishes; some take longer time to print; whereas some might just not be viable for your product owing to process characteristics like heating, UV curing etc. It is important to set your expectations straight and design accordingly. For e.g: If I opt for Selective Laser Sintering(SLS) technology, I am bound to get an inherent grainy surface finish irrespective of the kind of material I am running on the machine. I may need polishing on it, for which I may need to give some allowance in the design.
Pay heed to the Material Data-sheets:
Long before you actually start manufacturing the parts, you must figure out the material in which you will later fabricate them, instead of it being the other way round. There are numerous materials in 3D Printing, each catering to unique applications. One thing to note is that, 3D Printing materials are different from their conventional counterparts. For e.g: 3D Printed Nylon is different from the conventional Nylon material. So it’s always advised to have a look at the material data-sheets which will help in accounting the material properties while designing the load bearing, critical features. You may explore different materials for more insights.
Do NOT ignore the Design guidelines:
Each 3D Printing material has its own unique properties: Some are rigid, some are flexible, some are heat-resistant, and so on and so forth. Each of these materials have their unique set of design guidelines that talk about the minimum wall thickness, allowances, maximum overhang length, etc. While designing a particular part, one must refer to these design guidelines so that the part design can be made “printable” in a given material. Ignoring these guidelines could prove detrimental while manufacturing the same. Have a look at our design guidelines (mentioned on the Materials’ page).
Wherever possible, make the models hollow:
Traditionally, 3D Printing was only used for prototyping hence the name Rapid prototyping. But lately, that scenario is changing ever so quickly as people have now started adopting 3D Printing for Low volume production runs. When it comes to iterating the part design, you want to reduce the part cost as much as possible. This is where 3D Printing comes in handy. In 3D Printing, you can make the models hollow. Read our blog on how to make models hollow in 3D Printing. What hollowing does is, it not only makes your model lightweight but also reduces the manufacturing cost, owing to less material consumption as opposed to what would have been consumed had the part been fully solid.
Most of the 3D Printers accept files in *.stl file format. While exporting a 3D CAD file into a *.stl format, the polysurfaces are converted into triangles. If the polygon count while exporting is low, the file size will be low, but you will get bigger triangles which lead to facets on the part (as seen in the image below). While printing such a part, the 3D Printer will detect these facets and print accordingly. This results in discrepancy between what is desired and what is printed. By exporting the file in higher polygon count, although the file size will be bigger, the triangles will be denser thereby mitigating the facets. Our tech. platform – COCO, can handle files up to 50 MB in size and for good quality parts, we recommend a tolerance (the maximum distance between the original solid and the polygon mesh created for the *.stl file) of 0.01 mm.
Fix your CAD Files:
Invariably the 3D CAD files when exported to the *.stl file format have errors relating to meshing. There are mainly two types of errors viz. Naked edges and Non-Manifold edges. It is important to repair the files before placing them for print.
Naked edges: Naked edges are those openings left in the models when the surfaces/meshes don’t weld properly to each other and when there’s a slight gap left in them. To put it simply, if there is a naked edge in the part, then the part geometry isn’t watertight i.e. it isn’t fully sealed. To give you an analogy, if your part geometry were a bottle, the bottle would leak.
Naked edge (Marked in Red) Non-Manifold edges: When two or more parts intersect each other such that they share one common edge between them, the printer cannot figure out which part that edge belongs to. This leads to an error while printing. There are some freewares like Netfabb Basic which help in basic file repairs related to naked and non-manifold edges.
Non-Manifold edge (Marked in Red)
We hope these aforementioned steps come in handy the next time you design for 3D Printing. We would love to hear your feedback. For more information and queries, kindly write to us at firstname.lastname@example.org