Recently we held a webinar on three of the main software programs available that help prepare a CAD design for 3D printing / additive manufacturing (Magics, Rhino3DPRINT, and Spark). Our presenters* offered a number of suggestions, which are condensed here.
As our presenters noted, 3D printing is not yet living up to its potential or its hype. Part of the problem is the link between software and hardware for 3D printing, which needs improvement. Software must translate the digital content into the right format to be produced by the printer, but there are many potential failure points in this process.
The most fundamental question you can ask is “can your design actually be printed on your printer?” Meaning, have you considered the needs of the equipment that will be used to create your design? One of the issues with 3D printing is that because these needs are still being determined, it can be a challenge to design for your 3D printer.
The next question is “how can you optimize your design for your 3D printer? What steps can you take to ensure you are not sacrificing print quality while still meeting your performance criteria? And also factor in the time it takes to print. Are there changes you could make to the design that speed up the printing?
The way in which you handle meshes can affect the answers to these questions. All 3D printers take in some sort of mesh format for building a part. The most common program used to convert CAD data into 3D printable (mesh) data is the Standard Tessellation Language (STL) format. STL is basically little more than triangles, so it is a simple representation of your model.
Another mesh language choice is the Additive Manufacturing Format, which is a bit smarter that STL. In addition to handling meshes, it also condenses your files and can handle color and texture information.
Even though these formats will help make your CAD data more easily 3D printable, there are steps you can take with the aid of programs like Magics, Rhino3DPRINT, and Spark. Thus the following tips:
–Be aware of the amount of mesh data you are sending to your 3D printer. A common issue for 3D printing is that mesh data do not always fit the confines of the printer volume. Some CAD designs or programs go over a 3D printer’s limit, with obvious consequences. A companion issue is the number of triangles in a design. Some 3D printers have limits as to the number of triangles they will handle.
Mesh reduction features automatically reduce the number of triangles sent to the printer. In an example given in the webinar, in less than a minute, you can reduce a design that has about 850,000 triangles to 203,000 triangles without too much change in the actual shape of the part.
–Data coming from scanners or other devices may be incomplete. In some cases, the data is from an older design or part and so no solid model is available. These programs can automatically analyze and repair gaps in the data. Programs like Magics, Rhino3DPRINT, NetFabb and Spark offer mesh stitching functions that will stitch the data to deliver one solid mesh model.
With mesh analysis tools you can check and fix the edges, triangle, and vertices. Some of this software has pre-print checks built in that will check the printer volume. It helps you fit the model in the printer volume, detect thin walls, and checks the overhangs where you will need supports.
–3D printers also have a limit regarding data density. An STL file may be true to the model, but the amount of data may be dense. Obviously, you don’t want to reduce the data too much and compromise design integrity.
–Part data should be water-tight. That means no holes in the data, or edges that are disjointed.
–Data should be regularized. The aspect ratio of the triangles that you’re sending in mesh data should be “nice,” no long skinny triangles, for example. These programs have tools to refine meshes; they will take mesh data that’s coarse and reduce and smooth the triangles to a very nice mesh.
–Your design cannot have features that are too small for the printer to handle. These features include thin walls and features that the resolution of the printer will not print.
–Another important consideration is to optimize the design for printing in a sense of saving material and print time. For example, one suggestion is to print thin walled shells rather than fully dense parts, especially for prototypes.
–How you position multiple parts within the printer volume is another way to optimize a design. Several of these programs have a function that will suggest the best way to stack or place multiple parts for the most efficient use of the print material. Whenever possible, print more than one part at a time. When printing parts larger than a printer’s print volume, you may want to segment them to fit within the printer volume or machine them in multiples runs.
–Offsetting and shelling. Shelling is a difficult challenge for solid modelers. One solution is to take a solid mesh model and either perform inward or outward offset by uniform distance, and create shells by splitting these offset models. Features in some 3D printing preparation and repair software also let you design additional geometry for support.
You can see the whole webinar here
*Our presenters were Anthony Nguyen, application engineer and technical instructor at Materialise; Joe Anand, president and CEO of MecSoft Corporation, and James Page, senior product manager at Autodesk, Inc.
Leslie Langnau
llangnau@wtwhmedia.com
