Step 3: Choosing a Prototyping Technique

The Learning Factory currently has two rapid prototyping machines, a Helisys LOM 1015 and a Genisys concept modeler from Stratasys. In addition, the L.F. may soon acquire a 3D Systems SLA-250/30A stereolithography machine. Each technique has unique strengths and weaknesses. The descriptions below provide some qualitative guidelines, while Table 1 gives quantitative specifications for these three machines and four other commonly used ones.

Advantages of the LOM 1015

• Dependable, working
  The LOM has been running reliably for over a year, whereas the Genisys is somewhat inconsistent and the SLA-250 is still hypothetical.
  
• Biggest size capacity: 35 cm x 25 cm x 36 cm build envelope
  
• Best support for overhangs and thin walled sections
  
• Ideal for parts w/ solid, broad bases
  
• Ideal for parts w/o small, complicated details
  
• Wood-like texture
  

Disadvantages of the LOM 1015

• Most complicated, time consuming pre-processing
  
• Labor intensive, time consuming post-processing
  After building, the user must manually pick the part out of the excess material.
  
• Cannot build internal cavities
  If you want to remove the excess material from internal cavities, you will have to cut the model open.
  

Advantages of the Genisys

• Easiest, fastest pre-processing
  
• Virtually no post-processing
  
• Shorter build times than the LOM
  
• Polyester material is effective for flexible structures
  
• Water-resistant parts
  

Disadvantages of the Genisys

• Smallest size capacity: 20 cm x 20 cm x 20 cm
  
• Lowest accuracy: 0.36 mm
  
• Warpage problems
  Tall models with large footprints (area of base) are prone to warpage problems. The bottom edges tend to lift off the build platform during the build, leaving the model with a curved base. Warpage can usually be eliminated by making the model hollow, so that its base area is minimized.
  

Advantages of the SLA-250

• Highest accuracy: 0.20 mm
  
• Strongest, hardest parts
  
• Transparent material
  Models can be used for photoelastic stress analysis or visualization studies.
  
• Ideal for indirect rapid tooling
  When designing patterns for casting or molding, the Maestro pre-processing software can automatically make shrinkage compensation adjustments.
  
• Models are flexible enough for use in snap-fit assemblies
  

Disadvantages of the SLA-250

• Messy, time-consuming post-processing
  Models must be rinsed off and cured in UV oven.
  

Step 4 - L.O.M.
Step 4 - Genisys
Step 2

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