Report on Stratasys' Genisys Fused Deposition Modeling Machine

by David Garner and Alexandra Atkins

Objective

• Characterize the system of fused deposition.
• Investigate imperfections to develop stratagies for future prevention
• For a given set of parameters, use this model to predict the sample quality, build time, ideal build orientation, and ideal material for a part.

Background

Fused Deposition Modeling (FDM) is a thermal process using non-toxic materials for rapid part creation. It allows a simple virtual computer model to be used to create a 3-D model in a matter of minutes or hours. Depending on the sophistication of te part, minor errors including rough surfaces, bowed frames, and jagged edges may occur.

How It Works

• Uses CAD wireframe, surface, or solid models
• Imports CAD file into a PC or UNIX-based workstation
• Slices file into horizontal layers
• Downloads layers to a 3D modeler
• Builds parts by depositing ultra-thin layers of molten thermoplastic one layer at a time
• Plastic solidifies in 0.1 seconds

Stratasys Genisys

ICES (Institute for Complex Engineering Systems) purchased the Genisys 3D printer (by Stratasys) during the summer of 1998. This machine is the basis of all of our experiments.

Process

• Create 3D geometry.
• Observe time, quality, and material usage for each build.
• Document results.
• Note imperfections.
• Create hypothesis based on build results.
• Refine models to test hypothesis in an interative manner until conclusion can be made.

Factors to Evaluate

• Build Quality
• Time
• Parameters
• Minimum radius
• Minimum slot width
• Sharpest build angle
• Height vs. thickness

• Support Structure

Shapes/Geometries

• Spheres
• Vertical Planes
• Inclined Planes
• E-Shapes
• Complex Parts

Results

• Slots begin to merge and fuse under thicknes of .03125
• Spheres severely deform at diameters smaller than 0.35"
• Support structure is only needed for overhangs and very sharp angles
• Vertical Plates (up to 6”) need no support structure; adherence to base provides adequate support/anchor.

Conclusion

The Genisys FDM printer is a convenient method of rapid prototyping parts, however, the quality of these parts are not satisfactory for real production. As long as models are built according to the above stated parameters, parts printed by the Genisys 3D modeller exhibit limited deformation. Sanding and laquer can be applied to improve surface finish and conceal minor ridging.

Future Work

• Develop simple user’s manual detailing specific parameters to ensure optimum part quality.
• Examine influence of density on build time and create spreadsheet to better estimate build time based on total print volume.
• Design more models to test support structures and overhang. 
• Determine limits for the sharpest build angle.