unprintable models

One surefire way to have your day ruined is to get an email from your 3D-printing service entitled “Help us resolve issues with models in order 12345.” This happened to me recently for 3 models (pictured below) that had already been printed successfully in other materials, but were somehow not printable in a new material I was trying, a transparent plastic. How can this even happen?

The answer is that there are many different 3D-printing technologies. This is fabulous because it means models can be printed in a dazzling variety of materials…transparent resins, precious metals, elastic rubber-like materials, multicolour plastics and sandstone. Check out the materials at shapeways, i.materialise or sculpteo and be amazed! The tricky part, though, is designing for all of these materials because each printer has different design specifications. Wall thickness, wire thickness, minimum detail size, presence of interlocking parts, clearance between parts, overall size and other factors must all be taken into consideration before a model is printable in a specific material.

My transparent plastic models will be printed using a Stratasys Objet. This printer works by spraying a photopolymer resin in layers on a build platform and simultaneously curing the layers with ultraviolet light. It uses a gel-like support material during the printing that is removed after the print is finished. To remove it, the material is washed out with water jets through a hole in the model, and the hole must be at least 10mm in diameter. To make both the Spumellaria sculpture model and the Anthocyrtium earrings printable, I had to expand holes in the bottom of each model to 10mm. In addition, removal of the support material can damage delicate parts and so I also had to thicken up some walls in the Spumellaria pendant model. All three modified models are now on their way to the printers. Cross your fingers that it works!