Various peeling mechanisms are used to peel off an object from vat surface.

1. Methods to peel off 3D object
from vat floor in DLP 3D printer

2. Contents
• Additive Manufacturing
• Additive Manufacturing with DLP
• DLP 3D printer
• Digital Light Processing
• Photopolymerization
• Advantages
• Disadvantages
• Why does sticking take place?
• Solutions to sticking problem
• Active mechanism3 February 2016 2

3. Contents(continued)
• Passive mechanism
• Free Radical Photopolymerization
• Continuous Liquid Interface Printing
• Controlled Free Radical Polymerization Oxygen
Inhibition
• Dead zone thickness
• Cured thickness
• Advantages
• Disadvantages
• Photopolymerizable resins
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4. Additive Manufacturing
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5. Additive Manufacturing with DLP
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• DLP projector
• Photopolymer
• Linear actuator
• Vat
• Stepper motor
• Bed
• Chassis

6. Digital light processing
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7. Photopolymerization
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• Curing- by polymerization rather than vaporization
• Photopolymer: Light sensitive resin that cures when light
hits it
• UV light of 320-400nm

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• A black and white image or “slice” is a way to
selectively cure the resin

9. Advantages
• consistent build time independent of layer
complexity or number of parts
• Reduced positioning errors
• High resolution of 3D printed parts
• Minimal or no supports required
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10. Disadvantages
• Continuous 3D object manufacturing
• Sticking problem peeling mechanism
• Limited range of photopolymers and their shelf
life
• Photopolymer resins that are used for DLP
printing are quite expensive($80 to $210 per liter)
• Limited build volume
• Support has to be of the same material as the
build material
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11. Why does sticking take place?
• Adhesiveness
• Atmospheric air pressure
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12. Solutions to sticking problem
• Anti-stick solution
1) A layer of PDMS on a solid vat floor
-transparent at frequencies (240-1100nm)
-can not sustain at high temperature
-cloudiness of the PDMS
-degradation if PDMS due to prolonged
exposure
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13. 2) Flexible film of FEP (Fluorinated ethylene propylene)
on vat floor
-requires silicon gasket to clamp the FEP film
-can not be used with polycarbonate, polyethylene
EnvisionTEC Perfectory
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14. Active mechanism
• Gliding the printed object(shearing the part)
• Ex. B9Creator
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15. • Tilting mechanism-Various mechanisms can be used
such as tilting mechanism ex. four bar mechanism,
eccentric cams, spindles, etc.
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16. • Rotating vat
• Ex. Little RP
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17. • Rotating build platform
• projected images also have to be rotated in
synchronization with the bed rotation
• Ex. Pimaker 3D printer, Blacksmith genesis
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18. Passive mechanism
• Using spring for tilting- use of high stiffness
springs
• No need to use extra motor
• Reduced precision
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19. Free radical polymerization
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20. Continuous Liquid Interface Printing
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• Controlled free radical polymerization

21. Continuous Liquid Interface Printing
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22. Oxygen transmissibility
𝑂𝑥𝑦𝑔𝑒𝑛 𝑡𝑟𝑎𝑛𝑠𝑚𝑖𝑠𝑠𝑖𝑏𝑖𝑙𝑖𝑡𝑦 =
𝐷𝑘
𝑡
• Dk- oxygen permeability function
• t- thickness of the semipermeable membrane
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23. Dead zone thickness
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• Φ0 - number of incident photons
• αPI - photoinitiator absorption coefficient
• Dc0 - resin reactivity of a monomer-
photoinitiator combination

24. Cured thickness
• α- resin absorption coefficient
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26. Advantages
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27. • Surface finish
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29. Technology Time taken
SLA 11½ Hours
SLS 3½ Hours
Polyjet 3 Hours
CLIP 6½ Minutes
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• Producing a 51mm diameter complex object

30. Disadvantages
• Need to maintain dead zone
• Continuous provision of resin in Vat
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31. Photopolymerizable resin
• Photocurable hydrogel
• Photocurable silicon resin
• Biodegradable resins
• Photocurable polyurethanes
• High performance resin
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32. References
• Stephen T. Newman, Zicheng Zhu, Vimal Dhokia, Alborz
Shokrani, Process planning for additive and subtractive
manufacturing technologies, CIRP Annals -
Manufacturing Technology 64 (2015) 467–470
• Erlita Mastan, Xiaohui Li Shiping Zhu, Modeling and
Theoretical Development in Controlled Radical
Polymerization, Progress in Polymer Science (2015)
• P. B. Morgan, C. Maldonado-Codina, Contact lenses:
the search for superior oxygen permeability, Page No.
280-304
• Continuous liquid interphase printing,US WO
2014126837 A2.
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