Three-dimensional (3D) printing is widely used for building objects, such as models or prototypes. In 3D printing, an object is constructed by deposition of material in a controlled manner so as to form the object. Instructions for guiding construction of the object may be derived from a digital representation of the object to be constructed. Such a digital representation may, for example, be generated by a computer-aided design or computer-aided manufacturing program or application.
Commonly used 3D printers use inkjet printing heads for selectively dispensing material such as photopolymer material. The photopolymer material is deposited layer-by-layer to form a 3D model. Different photopolymer materials may be deposited to form different parts of the object being printed. The photopolymer material may be stored in a liquid or gel form within the inkjet printing head. After the photopolymer material is dispensed by the inkjet printing head, the material may harden or may be cured (e.g. by exposure to light or ultraviolet radiation) in order to cause the material to harden.
An inkjet printing head may include piezoelectric elements. Application of an electrical pulse to a piezoelectric element may generate a pressure wave in the material that is within the printing head. The pressure wave may cause the printing head to jet or expel a drop of the material.
Under some circumstances, a pressure wave may form small cavities (cavitation) within the material. Components of the material may fill the formed cavities in a gaseous state to form gas bubbles within the material. Air bubble generation in ink-jet printing heads is a well-known phenomenon (see e.g., H. Wijshoff, “The dynamics of the piezoelectric inkjet printhead operation”, Physics Reports, v. 491 (2010), pp. 77-177). Ink-jet printing heads are preferably used in conventional printing machines for two-dimensional printing. In such application bubble formation in ink drops is considered a parasitic or negative side-effect, and much effort is invested in order to suppress such bubble formation completely or significantly decrease it.