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Rapid Prototyping

Contact: Bryan Smith,  510 486 4956

Rapid prototyping is the automatic construction of physical objects using solid freeform fabrication. While primarily used to produce models and prototype parts, the technology is also capable of short-run production quantity parts. The Shops employ:

  • ProJet 3500: MultiJet Printing (MJP)

    The MJP machine uses a series of printer heads aligned with the y-axis to deposit a photopolymer resin and casting wax onto a build surface to construct a part. The build platform moves along the x-axis and the printer heads move along the z-axis resulting in print layers being uniaxial. Although the layers form a uniaxial structure, the material response in the xy-plane is relatively isotropic. Each individual material drop is about 0.075 mm (0.003 in) in diameter and approximately 0.030 mm (0.0012 in) thick allowing for fine high resolution features. Due to the printer heads moving in the z-axis rather than the build platform there is no way to purge the printer heads during printing meaning that the more material that must be deposited, the higher the risk for printer heads to become blocked and the print fails. Since the material is deposited in a fluid form and rapidly cured utilizing UV light, unless a significant fillet is applied, a lip will forms on all edges of the bottom surface and all edges become rounded on the top surface. 
    The ProJet is recommended for printing of functional parts that have small volumes (< 8 in3), desired tolerances no smaller than 0.25 mm (0.010 in), and in which transparency is not a concern.
  • Dimension Elite: Fused Deposition Modeling (FDM)
    The FDM machine uses a single printer head with two extrusion nozzles to deposit the build and support material. The printer head moves in the x- and y-directions while the build platform drops in the z-direction. Each layer of the internal structure is deposited in an alternating orientation to improve material response in the xy-plane, but the layer-by-layer construction in the z-direction means that the final printed part is highly anisotropic. The layer-by-layer construction also results in ribbed surface finish corresponding to the layer thickness, 0.178 mm (0.007 in), for vertical faces and a stair step like surface finish for angle faces. Since the build platform drops in the z-direction, the extrusion nozzle can be cleaned throughout the printing process making it is possible to print parts with large volumes. The dual nozzles for the build and support material on a single print head results in a slow print process, especially for large, fully solid parts.

  • ZPrinter 650: ColorJet Printing (CJP):

    The CJP machine uses five printer heads (clear, yellow, magenta, cyan, and black) to deposit a water based color binder onto a plaster based powder bed. The printer heads move in the x- and y-directions while the build platform drops in the z-direction resulting in a uniaxial internal structure corresponding to the x-direction. As a plaster based printing technique, the printed parts are highly brittle and prone to chipping; to increase the durability, a super-glue type bonding agent is applied to the part through either soaking or directed surface application. The finished parts have a very rough surface finish that can be sanded to achieve a smoother finish.The ZPrinter is recommended for printing of prototypes where functionality and durability are low priorities.

 

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