By: Kashif Vicente Laurie

Date: 2/13/2018

• Stereolithography is one of the oldest forms of additive manufacturing which creates solids in a layer-by layer fashion using UV light to cure (harden) photopolymers. Objects made from this process are typically used for "Show & Tell" production models, prototypes, & patterns for molding techniques

• The termed was first coined in 1984 by Charles "Chuck" Hull who then patented the process in 1986.
  • • Hull went on to co-found the world's first 3D printing company, 3D Systems Inc where he commercialized Stereolithography.

• In the early 1980's, before Hull coined the word, Dr. Hideo Kodama invented the modern layer process of using UV-light to harden photosensitive polymers.

• Types of designs made from this process:
  • "Show and Tell" type of models for:
    • Prototypes
    • Production Models
    • Master patterns for injection molding, blow molding and other metal casting process. 

• Characteristics/Restrictions: 
  • Maximal Build Envelope: 2,100 x 700 x 800 mm^3
  • Minimum Feature Size: 0.1mm
  • Typical Tolerance: +/-0.15 mm
  • Minimum layer thickness: 0.016 mm

• Advantages:
  • Build large parts with good accuracy
    • Can print up to 2 meters long depending on the printer being used. 
  • Great surface finish
  • Create complex geometric shapes
  • Quick process depending on the size and complexity of the piece (hours to a few days)

• Disadvantages:
  • Expensive material to own. (Usually have to outsource to a company that can make the parts)
  • Not good for mechanical testing. 

• Compared to other manufacturing methods:
  • Fused Deposition Modeling:
    • Limited in the size you can make
  • Selective Laser Sintering:
    • High Strength and Stiffness
    • Create  complex parts with interior components 
    • Depending on the material used, fabricated parts can be porous and have a rough surface
    • Thermal distortion which can cause shrinking and warping 

• Examples of the output of this process.

• What is the step by step processes?

1. A UV laser is curing a liquid photopolymer in a vat.
2. The laser scans the surface of the solidifying vat and the build platform is lowered gradually into the vat where the part is built layer by layer.
3. Once the piece is done, the support structures are removed from the final model. 
4. The model is finished. 

• How does it work?
  • In order to make the solid, there is a layer by layer method called "Photo-polymerization" where light causes chains of molecules to link forming polymers.
  • In order to stabilize the solid while it is forming, support structures are built at precise locations to:
    • All details have something to attach to
    • Resist lateral pressure from the  resin filled blade
    • Prevent deflection from gravity
    • Help retain newly created sections during the peeling process.  

• How many people are needed and what skill sets are necessary to run the process?
  • Only one person is needed for this process. The individual needs to create a 3D-model using CAD software and save it as a "Standard Tessellation Language" (STL) so the machine can read the file. 

• What is the typical equipment cost?
  • $250,000+ for a machine
  • $800 per gallon of resin
  • There are commercial machines for less than $4,000 however they are limited in the quality and size of the piece. 

• Outsourcing
  
  •  Companies usually have to outsource to 3D Printing companies if they want a piece made.
  • PT Cam:
    • $55/hour to print out the piece.
    • $30/hour for company to use the machine. 

• 3D Printer Comparison Cost: 
  • Fused Deposition Modeling (FDM):
    • Professional Machine: $10,000 - $300,000
    • Consumer Models: $1,000 - $10,000
  • Selective Laser Sintering: N/A