Digital three-dimensional manufacturing, also known as digital additive manufacturing, is a process of making a three-dimensional solid object of virtually any shape from a digital data model. Polyjet three-dimensional printing is an additive process in which one or more printheads or ejector heads eject successive layers of material on a substrate in different shapes. The substrate is supported either on a platform that can be moved three dimensionally by operation of actuators operatively connected to the platform, or the printhead or printheads are operatively connected to one or more actuators for controlled movement of the printhead or printheads to produce the layers that form the object. Three-dimensional printing is distinguishable from traditional object-forming techniques, which mostly rely on the removal of material from a work piece by a subtractive process, such as cutting or drilling.
One process for producing three-dimensional objects with a three-dimensional printing system 10 is illustrated in FIGS. 5A-5D. As shown in FIG. 5A, at the beginning of a printing operation, a member 14 and at least one printhead 18 are positioned such that the at least one printhead 18 is spaced vertically above the member 14 by the height H, and the member 14 is to the left of the at least one printhead 18.
As shown in FIG. 5B, as the member 14 and the at least one printhead 18 then move relative to one another, the member 14 moves toward the right relative to the at least one printhead 18. As the member 14 passes underneath the at least one printhead 18, material 22 is ejected from at least one ejector 26 of the at least one printhead 18 toward various locations of the member 14 to form a first layer 30 of an object 34.
Next, as shown in FIG. 5C, when the first layer 30 of the object 34 has been completed, the at least one printhead 18 and the member 14 are moved relative to one another such that the at least one printhead 18 is spaced above the first layer 30 by the height H. In other words, the at least one printhead 18 and the member 14 are moved vertically apart from one another to accommodate a thickness T of the object 34 atop the member 14. Additionally, the member 14 is again positioned to the left of the at least one printhead 18.
As shown in FIG. 5D, as the member 14 and the at least one printhead 18 then move relative to one another, the member 14 again moves toward the right relative to the at least one printhead 18 in the same manner as described above. As the member 14 passes underneath the at least one printhead 18, the material 22 is ejected from the at least one ejector 26 of the at least one printhead 18 toward various locations of the member 14 to form a second layer 38 of the object 34 atop the first layer 30. Accordingly, the thickness T of the object 34 is increased by the material 22 of the second layer 38. This process can be repeated as many times as necessary to form the object 34.
This three-dimensional object printing process is an additive process, and material 22 is repeatedly added to the object 34 such that the thickness T of the object 34 increases throughout the process. Accordingly, to accommodate the increasing thickness T of the object 34, the height H of the printhead 18 relative to the member 14 is also increased after each layer is added to the object 34 and before another layer is added. In other words, the printhead 18 and the member 14 are moved vertically apart from one another after each layer is added to the object 34.
One issue that arises in the production of three-dimensional objects with a three-dimensional object printer in the manner described above is the possibility that the vertical position of the printhead 18 will not be properly adjusted relative to the member 14 to accommodate the increasing thickness T of the object 34 before the member 14 moves to the right relative to the at least one printhead 18. In this case, the object 34 may contact the at least one printhead 18 and the at least one ejector 26 on the at least one printhead 18, causing damage to the at least one printhead 18. Replacing or repairing a printhead is time-consuming and expensive. Accordingly, a three-dimensional object printer capable of protecting at least one ejector in a printhead from contact with an object or member would be advantageous because such a three-dimensional object printer would reduce expenditures of time and money to repair the printer.