3D Resin Printers

Notes on making 3d printers based on polymerizing resin.

Modifying a projector
Projector mods site
3dprinter Projector mods site

May need to remove UV filters, replace with a Hot Mirror Filter / IR filter.

MakerJuice selling reasonably priced UV curable resin. SubG+
Bucktown Polymers, $176-$310 / gallon

Mouser, $28 385-390nm 500mW
LHUV-0390-0450, 2W UV LED, 470-1000mW $39

Other resin printer projects
Chris Marion, DLP printer and 3DLP Host Software
Gary Hodgson DLP resin printer
Video of resin printer testing/build
3 D L P rint
DLP printer less than $200
Very simple DLP printer: Chimera
Bo Pang with PDMS membrane

Top down of bottom up polymerization?
The surface layer of the resin resists polymerization due to oxygen. So top down polymerization requires a stronger light (running through the resistant layer to the resin below. It also presents challenges in 1) getting the resin layer the correct depth. The part may need to be dipped then raised. 2) Some printers include a wiper to set the liquid layer thickness. 3) Bubbles can form as liquid moves around the part, 4) The part can only be as tall as the tank depth, and enough resin to fill the tank must be used, 5) The resin surface height must be calibrated after filling the tank.

Continuous Top-Down DLP Experiments

Option: Print resin from a ink jet printer head

Bottom up printing presents a challenge because the part will stick to the bottom of the tank. This is handled by 1) using a non-stick surface (Sylgard 184 polymer $60 0.5 kg, PDFE sheet, FEP sheet), 2) using a tilt / raise action between layers to break the adhesion and allow resin to move between the tank bottom and part.

Tests of materials to coat vat floor

Option: CLIP, uses “an oxygen-permeable membrane lies below the resin, which creates a “dead zone” (persistent liquid interface)”.

Possible membranes:
PTFE FEP, oxygen permeability 11.6 X 10^3 (cm3/m2·24 hr·atm)
PTFE PDA, oxygen permeability 6.7 X 10^3 (cm3/m2·24 hr·atm)
PDMS (mechanically weaker), oxygen permeability est. 1380 X 10^3 (cm3/m2·24 hr·atm), 600 Barrers

Oxygen permeability table
, another, another, another

TPX film (Mitsui) / Polymethylpentene, or PMP, 25 Barrers, “slight haze”
Polyimide clear, strong, oxygen permeability 3800 mL/m2 ⋅ 24 hr MPa, 25 cc/(100 in2 ⋅ 24 hr ⋅ atm) (1/4 of PDMS?) 0.5 – 7 Barrers
Cytop, ~oxygen permeability 8 Barrers

High >50 Barrers, but not commercially available: PTMSP, TR 450-1, PIM-1
1 Barrer=1×10-10 cm3 ×cm/cm2 ×sec×cm Hg

PDMS Elastosil Superclear Silicone Sheet – 200mm sq
PDMS Ultra Thin Silicone Film – 30 Shore – 250mm Wide
Best would be Teflon AF2400, second best Teflon AF1600. Oxygen permeable, fairly strong

Making PDMS films

Option: Add a non-miscible liquid layer between the tank bottom and the part. For example, tetrachloroethene, or perchloroethylene (dry cleaning fluid, sold on Amazon, $15) which is denser than water (1.622 g/cm3) and has low solubility (0.15 g/L (25 °C)). Or perhaps even an oil layer (lighter than water, but may adhere to the bottom). One problem with this is the flow of resin into the gap between the part and tank could pull this fluid away from its layer.

Or add a sandwich–glass, circulating oxygen carrier fluid (water or perfluorocarbon), PDMS sheet. This oxygenates the PDMS while providing a solid support. This is a bit complicated and the layers will affect the image quality.

Perflurocarbons: Perfluorodecalin, 25g / $25

Another option is to support the PDMS with air pressure from below to equal the fluid pressure from above. This would require a glass / pressurized air / PDMS sandwich, again affecting the image quality.

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