Obviousness

Obviousness Analysis of US9421713B2 under 35 U.S.C. § 103

This analysis identifies combinations of prior art references that would render claims 1-5 of US9421713B2 obvious to a person having ordinary skill in the art (PHOSITA), along with the motivations for such combinations. The analysis strictly relies on the prior art explicitly cited within the US9421713B2 patent document itself.

The Invention of US9421713B2

US9421713B2 primarily claims a method for additive manufacturing that incorporates a "purge tower" into the build process. Specifically, the method involves:

• Printing a three-dimensional (3D) part and a support structure using multiple print heads or deposition lines and a layer-based additive manufacturing technique.
• Switching the print heads or deposition lines between stand-by and operating modes between the printing of layers.
• Performing a purge operation for each print head or deposition line switched to the operating mode.
• Crucially, this purge operation comprises printing at least one purge tower in a layer-by-layer manner from the print head or deposition line that has just switched to operating mode.

The patent highlights the problems with conventional purge stations, which include requiring sufficient material to fall into a purge bucket, occupying valuable build footprint, and needing periodic manual emptying, thus hindering full automation, especially in "printer farm" settings. The purge tower, in contrast, aims to address these issues by integrating the purge directly into the build environment.

Identified Prior Art References (from US9421713B2)

The patent explicitly references the following prior art that is relevant to the elements of its claims:

1. Turley et al., U.S. Pat. No. 7,744,364: Discloses conventional purge operations in additive manufacturing systems, involving moving a print head to a purge station to extrude material into a purge bucket. This reference details the various desired functions of a purge operation, such as freeing adhered filament, removing entrained gases and degraded materials, bringing the print head to a known operating state, and removing variable ooze.
2. Swanson et al., U.S. Publication Nos. 2010/0283172 and 2012/0164256; Leavitt, U.S. Pat. No. 7,625,200; LaBossiere et al., U.S. Pat. No. 7,604,470: These references describe additive manufacturing systems employing multiple print heads or deposition lines for printing 3D parts and support structures. They also disclose the concept of switching these print heads between "operating modes" (where the liquefier assembly is heated) and "stand-by modes" (where it is cooled), and the associated physical movement (lifting, pivoting) of the print heads.

Obviousness Combination and Motivation

A person having ordinary skill in the art (PHOSITA) would have been motivated to combine the teachings of Turley et al. (U.S. Pat. No. 7,744,364) with the multi-material additive manufacturing systems described in references such as Swanson et al. (U.S. Publication Nos. 2010/0283172 and 2012/0164256), Leavitt (U.S. Pat. No. 7,625,200), and/or LaBossiere et al. (U.S. Pat. No. 7,604,470).

Reasoning for Obviousness:

1. Known Components and Techniques: The elements of printing 3D parts and support structures from multiple print heads using a layer-based technique, and switching these print heads between operating and stand-by modes, were well-established in the prior art, as evidenced by the numerous patents cited within US9421713B2. The necessity of performing a purge operation when a print head transitions to an operating mode was also known, with Turley et al. providing a detailed explanation of its purpose and a conventional method involving a purge station and bucket.

2. Motivation to Combine/Modify: The US9421713B2 patent itself explicitly articulates the shortcomings of conventional purge stations: they consume significant build volume, waste material that could otherwise be contained or recycled, and require manual intervention to empty purge buckets, thereby hindering the automation desired for applications like "printer farms."
   A PHOSITA, familiar with these known problems and possessing the collective knowledge of multi-material FDM systems (from Swanson et al., Leavitt, LaBossiere et al.), would have a strong motivation to improve upon the conventional purge operation (from Turley et al.). The goal would be to find a more efficient and automated purging method that conserves space and enables continuous operation.

3. Predictable Solution - Printing a Purge Tower: Given that the additive manufacturing system is designed to "print" material in a layer-by-layer fashion onto a build platform, it would be an obvious engineering choice to adapt the purging process to deposit the purged material directly onto the same build platform, rather than into a separate, space-consuming bucket. Creating a simple, non-functional structure, such as a "purge tower," that grows layer by layer alongside the actual 3D part and support structure offers a straightforward solution:

   • Space Saving: It utilizes otherwise unused areas of the build platform, eliminating the need for a separate physical purge station.
   • Automation: It integrates the purge process directly into the automated build sequence, removing the need for manual emptying of purge buckets and facilitating continuous, unattended operation.
   • Z-height Synchronization: Building the purge tower layer-by-layer ensures that the print head operates at a consistent Z-height relative to the ongoing build, simplifying control and maintaining stable printing conditions.

4. Claim 4 Specifics (Tool Path): The design of a purge tower with a perimeter wall to "at least partially encase" the initial purge extrusion (as described in claim 4) is a predictable refinement. A PHOSITA would understand that the initial extrusion during purging can exhibit stringing or oozing. Creating a contained path to capture this excess material within the purge tower itself, preventing interference with the main part, is a logical design optimization for any structure built with extruded material. The patent itself notes that various simple perimeter wall geometries could be used, implying that the specific diamond shape is an optimization rather than a fundamental invention.

5. Claim 5 Specifics (Removal): The act of "removing the at least one purge tower after the printing operation is complete" (claim 5) is an inherent and obvious step for any auxiliary structure printed on a build platform in additive manufacturing.

Therefore, the combination of existing multi-head additive manufacturing systems (Swanson et al., Leavitt, LaBossiere et al.) with the known practice and purpose of purging (Turley et al.), motivated by the recognized disadvantages of conventional purge stations and the capabilities of layer-by-layer extrusion, would have led a PHOSITA to conceive of and implement a purge tower on the build platform. This renders claims 1-5 of US9421713B2 obvious under 35 U.S.C. § 103.