Lecture 7 Vat Photopolymerization

Vat Photopolymerization (definition)

Liquid photopolymer selectively cured by light activation

1. Stereo Lithography Apparatus (SLA)

(acrylates & vinylethers convert one double bond into one single bond)

-relationship between process variables & their impact on the final product

-eliminate trial & error from determining best settings of the variables

1. The photo-polymer resin obeys the Beer-Lamberts Law of exponential absorption

3. The resin transition from liquid to solid is at the gel point specified by critical exposure = E_c

The laser scans along what direction? (x, y, or z)

What direction is lateral to the scanning direction? (x, y, or z)

What direction extends directly downwards from the laser scan axis & is measured normal to x-y plane? (x, y, or z)

mathematical model of cure depth as a function of hatch spacing to provide insight into the cure behavior of ACES

determine the number of scan vectors that provide significant exposure to P

-volumetric shrinkage due to residual stresses

occurs over unsupported portions of the part

Green Creep Distortion (definition)

if surface tension of liquid resin is higher than the surface energy of cured layer = liquid balls up

-surface tension of cured layer depends on degree of cure

infusion of liquid into the green part

-dipping part in resin & sweeping with blade to wipe off excess resin resulting in PRECISELY controlled layer thickness.

Used by early machines & thickness obtained as a result of sweeping velocity, viscosity of resin, etc.