System and method for three dimensional model printing

1. A scanning 3-D printing system comprising:

a printing platform movable in a printing direction and in an indexing direction, the printing platform comprising a printing head configured for dispensing building material while the printing platform is moving in a printing direction one pass at a time, and layer by layer, and for shifting in the indexing direction prior to dispensing a subsequent pass of a layer, wherein at least one layer includes multiple passes;

a roller configured for accumulating excess dispensed building material in a current printed pass of a layer prior to printing an additional pass of that layer, wherein the roller is rotatably mounted on a Y rail and both the roller and the Y rail extend over all passes of the printing system and are stationary in the indexing direction;

a scraper configured for scraping excess building material off the roller; and

a trough configured for collecting the building material scraped of the roller, wherein at least one of the scraper and the trough extends over all passes of the printing system and is stationary in the indexing direction.

2. The system according to claim 1 , wherein the Y rail is mounted at each end to a carriage movable in the printing direction, wherein the carriage is configured to support and couple the Y rail on each of its ends to an X rail aligned with the printing direction.

3. The system according to claim 1 , wherein the scraper is mounted on the printing platform.

4. The system according to claim 2 , wherein the printing platform is mounted on the Y rail.

5. The system according to claim 1 , where the printing platform and the roller move together in the printing direction while dispensing the building material from the printing head.

6. The system of claim 1 , wherein the scraper and the trough are configured to move together with the roller in the printing direction while the roller accumulates the excess dispensed building material from the printed pass.