Rafts, Brooms, Supports, And Skirts
Rafts: A raft is printed directly on the print bed under your model. They are primarily used to help with bed adhesion and can aid in reducing warping for a larger, flat prints. They are also useful to stabilize models with small footprints.
Brims: An alternative to a raft, a brim is attached to the part and extends out word on the print bed. They are useful to stabilize small parts or isolated sections of a model such as legs on a table. They are easily removed from the model after printing.
Supports: Supports are a crucial piece when a model has large overhangs four components of a model that do not have other structures beneath them. Supports can often be eliminated or reduced by proper orientation of a model prior to printing. Generally, supports can be easily removed but may require some finishing, such as filing, to fully remove them from your final model.
Skirts: A skirt is a single layer outline of your model that extends slightly past the actual model on the print bed. Skirts are useful because they help prime the extruder and start filament flow before printing your actual model. The skirt is not attached to the model at any time so it does not interfere with removal of the model from the print bed. It is a good idea to always print a skirt.
A 3D Printed Dog as a Demonstration of Supports and Brims.
The two most common filament types are ABS and PLA. Both of these are inexpensive and Suitable for classroom use. in general, PLA is easier to print with as it does not require the use of the heated bed and is not as susceptible to environmental changes. ABS also has a strong smell that may not be the best choice in classroom settings. ABS is a stronger plastic and is much more durable if dropped or handled, but for most applications in a classroom setting PLA is more than adequate. PLA is also biodegradable and is resistant to shrinkage, warping, or cracking.
There been a number of new filament types that have recently entered the market. Some of these include steel, copper, wood, stone, nylon, and a rubberized filament. Many of these will work in commercial printers, but may require the use of additional or supplemental print heads.
Each filament has advantages and disadvantages depending on what you are trying to accomplish. The best advice is to research and test these filaments prior to introducing them in your classroom.
How a model is placed on the print bed within the slicing software is crucial to successful printing. Considerations such as overhangs, components that must be round, holes, and having enough material to adhere to the print bed should be taken into account. Below is a model created in TinkerCAD to demonstrate the importance of orientation. To demonstrate this to your students, print out a similar model with and without supports. This will show the students that the model can be created with less filament and no support by properly orienting the table. You can also demonstrate how the model would look if no supports are added to overhanging components of the model.