Rapid prototyping is an additive process used to build models in contrast to traditional fabrication methods (i.e. machining )that are subtractive. Rapid prototyping can cut costs and decrease lead and production time. Since the models are built up layer by layer, design complexity is rarely an issue and allows the user to construct models that would be impossible to make using traditional means.
In our current projects we are investigating the production of sand casting molds. Areas of interest are:
Dimensional accuracy of castings made by Rapid Prototyping.
Strength molds made by Rapid Prototyping.
Surface finish of the castings.
A Z Corporation ZPrinter 310 was acquired with a DURIP Award from the USAF. The ZPrinter 310 is a three-dimensional printer also known as a powder binder printer. A 3-D computer model is loaded into the software that divides it into multiple layers. Each layer is printed on the sand using a proprietary binder. The operation of the printer is as follows: the printer rolls out a layer of powder onto the build-base. A print head sprays out binder in a pattern specific to the current layer of the computer model. Another layer of powder is rolled out again and is again printed on. This vertical build-up process continues until the 3-D piece is complete. The piece is then transferred to a depowdering station and the loose powder is removed. The molds are baked to remove excess water and are ready for casting. The printer has a build envelope of 8x10x8. Parts larger than 7.5x9.5x7.5 must be built in sections and glued together.