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Plastic 3D printer robot on printer

3D Printing Frequently Asked Questions

3D Printing is a new way of manufacturing custom designed objects.  CIRT houses a Makerbot Replicator 2, which is an additive manufacturing 3D printer. An additive 3D printer is basically an intelligent, robotic glue gun that follows the ‘commands’ of your model and builds a solid object in layers from the bottom up.  

successful 3d print of a set of spheres

How does it print?

The Makerbot melts PLA (cornstarch based) or ABS (plastic based) filament and extrudes it into thin, defined lines through a heated nozzle. It gradually builds the melted material into an object layer by layer. This process often takes a significant amount of time, but allows for exponential levels of customization. 

How does it know what to print or where?

Just like a regular printer needs an image or text to print, a 3D printer needs a model to give it the right information to build an object. A computer generated 3D model saved in .stl, .obj, or other common formats, informs the printer of the desired end result. The model is sliced into even layers defined by the user (the thinner the slice, the greater the amount of detail, but also the amount of time it takes to print) and the slicing software generates Z-code which is what controls where the print nozzle goes  (and the pattern it runs in) to extrude filament. 

What are the limitations? 

Just because you create a beautiful, seamless 3D model in a modeling software, does not mean it is able to be 3D printed successfully.  There are certain guidelines to keep in mind when designing & modifying an object to print. Following these pointers will increase the amount of successful prints!  failed 3d print of a male figure

Water-tightness– “Watertight” is a term used to describe a 3D mesh suitable for 3D printing. It means that there are no holes, cracks or missing features on the mesh. The easiest way to describe a good mesh for 3D printing is to think of it as a skin, and filling the inside with water. It is important to create watertight meshes, so that it is clear to the 3D printer what is the “inside” (which needs to be made up of 3D print material) and what is the “outside”. 


Overhang Additive Manufacturing printers build from the bottom up. There is little allowance for overhang, due to gravity. If you are printing a giraffe for example, its neck has nothing to build upon because it is out in space. You can either create thin supports to hold the extended piece (or have the software do it for you automatically) & then remove them later, or you can have a very gradual build up at an angle to support the object as it extends upward.  The latter is a more challenging technique than the former, but gives a cleaner print. 


Geometry/Orientation of Objects on Print Bed – The printer moves on X, Y, & Z axes. With that in mind, certain angles are more difficult for the printer to manage. You will want to avoid jagged lines leading into curves or extremely small circles without using a raft (rafts are thin bottom supports for the printed model). 


Keep It Simple– Do yourself a favor, keep your models simple at first. This means using basic shapes to build objects. It is surprising how many designs can be created from combining shapes & it also orients you into the 3D landscape. It takes time to get used to thinking in 3 dimensions—practicing is the key!