Material Extrusion operates in a similar fashion to a hot glue gun; plastic filament is heated to a malleable state and extruded through a nozzle. In order to create a part, a CAD model is sliced into layers. The nozzle uses g-code to draw each layer, one at a time, with the heated plastic, which then cools and transitions back into a solid state.
If the part has large overhangs, support material is required to prevent sagging and protect part integrity. This support material is created either through thin, breakable trusses of the build material or a second soluble material.
Material Extrusion of ABS allows for:
- Strong parts (Tensile strength of ABS is 5,000 psi)
- Material Extrusion ABS is machineable, sandable and paintable
- Can be treated with resins to strengthen the plastic and increase heat resistance
- Relatively cheap compared to other AM processes (~$250.00 per 56 in3 of material)
Stratasys Dimension SST 768
The Stratasys Dimension SST system is located in the Mechanical Engineering Department’s CAD Lab in Randolph 114. A fused deposition modeling technology, the system creates artifacts by selectively extruding a plastic filament. The Dimension SST works with an ABS polymer and a water-soluble support material.
In addition to the Dimension SST printer, the DREAMS Lab contains the technology’s supporting equipment including a water bath that is used to assist with the removal of the support material.
The Stratasys FDM 1600 system, a fused deposition modeling technology, creates artifacts by extruding a plastic filament. The FDM 1600 works with a ABS polymer and a separate support material that is manually removed after the build is complete.
FDM is relatively slow and cannot compete with full-scale production requirements. However, it is a useful tool for certain situations such as:
- Low volume production
- Optimization of complex components
- Custom molds
- Unique internal geometries
Stratasys Dimension uPrint
The Dimension uPrint is the smallest of the Stratasys Dimension product line. It is available to students through Virginia Tech’s Engineering Education Department and is located in the Frith Lab in the basement of Randolph Hall. Four additional uPrints are open to ME senior design teams in Goodwin 140.
The Fortus 250mc is an industrial Material Extrusion system with a larger build area, more material options, a higher resolution. It is available to students through Virginia Tech’s Mechanical Engineering Department and is located in the Machine Shop in the basement of Randolph Hall.
The Fortus 400mc is a larger version of the 250mc located in the DREAMS Lab. It offers the same properties as the 250mc, but can also print in ULTEM, a much stronger and durable plastic material.
The Benefits of Desktop Fabricators
Desktop fabricators give individual users the ability to print their own part designs or those of others’ from websites like MakerBot Industries’ Thingiverse. These small-scale systems open the door for widespread personal use of additive manufacturing technologies.
Fab @ Home
The Fab@Home system is an open source desktop fabrication technology. Using off-the-shelf components, the system creates prototypes via the selective extrusion of material. The extrusion subsystem is composed of a stepper motor, a lead screw, and a syringe.
In its current embodiment, the Fab@Home system is only able to work with materials which can be extruded at room temperature: frosting, silicone RTV, and modeling clay.
The Afinia is a basic printer that you might see introduced into k-12 school systems. The printer is fairly basic, easy to use, and fairly reliable. The Afinia can print ABS or PLA plastic. The part is printed on a removable bed where the parts are printed directly on the removable bed and have to be removed after the print.
Residing in the atrium of Goodwin Hall, the DreamVendor 2.0 offers a unique opportunity for students in which they are able to use a 3D printer free of charge. In contrast to the cartesian style printing of the Afinia and Fab@Home, the DreamVendor utilizes a delta style of printing through three linear rails situated in a triangular formation. More information is available on the DreamVendor through its banner button at the top of the site.
Direct Writing (DW) involves a controlled selective deposition of material according to a pattern. The material is usually patterned through a nozzle, whose movement is controlled and set-up to follow a specific pattern. This can be achieved through different ways such as extrusion of liquid ink, ejecting material-droplets onto a substrate or through aerosol jetting. DW Techniques are capable of single or multi-layer patterning of material onto flat as well as conformal surfaces. The process can achieve high-resolution in material-deposition. DW enables development of embedded circuitry and rapid manufacturing of sensors. The advantage over conventional fabrication of electronics is in elimination of masking and etching steps.
An extrusion based direct write process has been developed specifically to pattern conductive inks. A Nordson EFD Ultimus V high precision dispenser is used to extrude the conductive ink (DuPont 5201) and the translation of the nozzle is controlled, using an Arduino program which interprets the g-code. The system can be integrated with PolyJet process and hence deposit conductive ink into PolyJet structures.