3D Printing: A Step-by-Step Overview

Smith College owns two 3D printers, a Zcorp 3D printer Model 310, and a Dimension BST 768 3D printer. Both are housed in the Center for Design & Fabrication in the basement of McConnell Hall. They were purchased jointly by the Departments of Computer Science and Engineering, partially funded by the National Science Foundation (Grant CNS-453208). They both have similar "build volumes": 8"x10"x8" for the Z-printer and 8"x8"x12" for the Dimension. Although these volumes represent the largest objects that can be printed, we rarely run the printers at full volume. (Here is a photo of one full-volume run.) Usually a single "print run" includes several distinct objects.

The two printers use different technologies, and result in rather different types of objects.The Z-printer uses powder that has the consistency of starch, and binds in thin layers with an agent that cures to a hard but breakable object. The objects can be "post-processed" by immersing in parafin or coating with cyanoacrylate [Krazy Glue] to make a more durable object. The ingredients for both printers are rather expensive, a cost currently being absorbed by the College. The Dimension printer deposits a thin trail of ABS plastic in layers. The result is hard and durable, and can be used in machines.The Z-printer has somewhat finer resolution, and prints faster than the Dimension. A typical Z-printer run is 5 hrs; a typical Dimension run is 10 hrs.

Although it would be nice if the printers print, and then you just walk away with the objects, in reality there is considerable post-processing for each printer. When the Z-printer finishes, the objects are embedded in a block of powder in the machine. The objects must be extracted from the powder carefully, the powder blown off in the depowdering station, and then the clean objects perhaps further processed by dipping into melted parafin or coating with cyanoacrylate or painting with acrylic paints. When the Dimension printer finishes, the objects are fastened to the build platter with glue. They must be snapped off. Then a substrate remains, not only where the part touched the platter, but also structural elements are built to support overhangs. All of these must be removed, a somewhat tedious and difficult process.

Use of the printer involves five main steps:
- Creating a 3D model in any of several different pieces of software.
     - Saving the model to a special file format, .stl (stereolithography).
- Checking the .stl model file for reversed normals and other problems. We use MeshLab, and Z-edit for the Z-printer.
- Loading and editing the file with the printer software.
- Preparing the printer.
- 3D Printing.
- Post-processing.
By far the most time-consuming and difficult step is #1: creating the model. Depending on which software is used to create the model, "fixing" problems in the model (Step #2) can be technically tricky. Printing itself (#4) is relatively straightforward, but the post-processing (#6) can be challenging.

Each of these steps is described in more detail, and illustrated with examples, by following the links above.