Methods for photocuring liquid resin with reduced heat generation

A method for printing a cross section of a three-dimensional object in a photocuring region of a vat polymerization printer that includes (i) a tank configured for containing a photo-curable liquid resin, (ii) a flexible membrane defining a bottom boundary of the photocuring region, (iii) a light source configured to emit a light beam, (iv) a beam scanner configured to scan the light beam, and (v) a mask disposed between the beam scanner and the flexible membrane and having pixels configurable to be individually transparent or opaque to portions of the light beam, wherein a diameter of a cross section of the light beam is greater than a cross-sectional dimension of each of the respective pixels, the method comprising:

• controlling, during an exposure time duration, a first subset of the pixels to be transparent at locations corresponding to the cross section of the three-dimensional object, and a second subset of the pixels to be opaque at locations not corresponding to the cross section of the three-dimensional object;
• and
• scanning, during the exposure time duration, the light beam across at least one region of the mask having at least some pixels that are controlled to be transparent and into the photocuring region, wherein at most ten percent of the pixels that are controlled to be opaque are scanned by the light beam during the printing of the cross section of the three-dimensional object,
• wherein, during the exposure time duration, and as a result of the control of the first and second subset of the pixels, (i) a first region of the mask includes at least some pixels that are controlled to be transparent, the first region of the mask being surrounded by a first border with pixels that are controlled to be opaque, (ii) a second region of the mask includes only pixels that are controlled to be opaque, and (iii) a third region of the mask includes at least some pixels that are controlled to be transparent, and
• wherein the scanning of the light beam comprises repeatedly scanning the light beam across the first region of the mask and into the photocuring region through pixels of the first region that are controlled to be transparent, repositioning the light beam from the first region of the mask to the third region of the mask without scanning the second region of the mask, and repeatedly scanning the light beam across the third region of the mask and into the photocuring region through pixels of the third region that are controlled to be transparent,
• wherein the first border is illuminated by the light beam.