Shenzhen Tuozhu Technology Co Ltd v. Stratasys Inc

1. Case Identification

• Case #: IPR2025-00321
• Patent #: 9,421,713
• Filed: December 17, 2024
• Petitioner(s): Shenzhen Tuozhu Technology Co., Ltd.
• Patent Owner(s): Stratasys, Inc.
• Challenged Claims: 1, 2, 5-7, 9, 16, 17

2. Patent Overview

• Title: Additive Manufacturing Method for Printing Three-Dimensional Parts with Purge Towers
• Brief Description: The ’713 patent describes a method for additive manufacturing using multiple print heads or deposition lines (e.g., for part material and support material). The method’s key feature is printing a sacrificial “purge tower” on the build platform to prime a print head and clear old material after it switches from a standby mode to an active operating mode.

3. Grounds for Unpatentability

Ground 1: Obviousness over Leavitt and RepRap - Claims 1, 2, 5-7, 9, 16, and 17 are obvious over Leavitt in view of the RepRap Article and RepRap Video.

• Prior Art Relied Upon: Leavitt (Application # 2009/0035405), the RepRap Article (an online publication from Oct. 2012), and the RepRap Video (a YouTube video from Oct. 2012).
• Core Argument for this Ground:
  • Prior Art Mapping: Petitioner argued that Leavitt discloses a dual-extruder 3D printer that prints a part and support structure in a layer-by-layer manner, with print heads switching between active and idle states. Leavitt explicitly acknowledges the problem of material oozing from the idle nozzle. The RepRap references (an article and accompanying video) teach a solution to this exact problem in a dual-extruder system by printing a "purge tower" (termed a "parking space") adjacent to the primary object. This tower is used to prime the extruder nozzle each time it becomes active, ensuring a consistent flow and purging degraded material. The combination of Leavitt's system and RepRap's purge tower method allegedly meets all limitations of independent claims 1 and 16.
  • Motivation to Combine: A person of ordinary skill in the art (POSITA) would combine RepRap's purge tower with Leavitt’s system to solve the known oozing problem that Leavitt itself identifies. The motivations included improving print quality by avoiding defects from oozed material, ensuring a consistent material flow after an extruder becomes active, and efficiently managing waste material in a compact, disposable structure.
  • Expectation of Success: A POSITA would have a reasonable expectation of success because both Leavitt and RepRap describe conventional extrusion-based 3D printing systems, and implementing a purge tower was a predictable software and mechanical modification.

Ground 2: Obviousness over Priedeman and KISSlicer - Claims 1, 2, 6, 7, 9, 16, and 17 are obvious over Priedeman in view of KISSlicer.

• Prior Art Relied Upon: Priedeman (Application # 2003/0004600) and KISSlicer (a 2012 software quick-start guide).
• Core Argument for this Ground:
  • Prior Art Mapping: Petitioner asserted that Priedeman discloses an additive manufacturing system with multiple nozzles for printing a model and a support structure, and it acknowledges that material can "drain uncontrollably" from an idle extruder. KISSlicer is a contemporary software program designed to control such multi-extruder systems. Critically, KISSlicer expressly teaches that it is "extremely important" to clean extruder tips "before every layer" by printing a purge tower, which it refers to as a "wipe pillar." The combination of Priedeman's hardware and KISSlicer's control software and purging strategy allegedly discloses all limitations of the challenged claims.
  • Motivation to Combine: A POSITA would be motivated to use control software like KISSlicer to operate hardware like Priedeman's. The motivation is straightforward: to implement a known solution (printing a purge tower, as taught by KISSlicer) to solve a known problem (oozing from an idle nozzle, as acknowledged by Priedeman).
  • Expectation of Success: Applying specific control software to its intended type of hardware to achieve a predictable result was well within the skill of a POSITA, who would have reasonably expected the combination to function as intended.

Ground 3: Anticipation by Boyer - Claims 1, 2, 6, 7, and 9 are anticipated by Boyer.

• Prior Art Relied Upon: Boyer (Application # 2014/0034214).
• Core Argument for this Ground:
  • Prior Art Mapping: Petitioner argued that Boyer, under an alternative claim construction, anticipates the challenged claims. Boyer discloses a 3D printer that uses a single extruder with a single output tip to print with multiple materials fed to it sequentially. When the system switches from a first material to a second, it prints a "transition segment" to purge the residual first material before printing the desired object segment with the second material. Petitioner contended these "transition segments," when printed layer-upon-layer, constitute the claimed "purge tower." Boyer discloses printing a part and support structure, switching between materials (standby/operating modes), and printing the purge structure layer-by-layer, allegedly meeting all limitations.
• Additional Grounds: Petitioner asserted an additional obviousness challenge for claim 5 (Ground 2B) based on Priedeman, KISSlicer, and the RepRap references, arguing RepRap's disclosure of a wider base for its purge tower would have been a simple, predictable design choice to improve stability.

4. Key Claim Construction Positions

• Petitioner argued for two constructions of the term "from multiple print heads or deposition lines" (claim 1), which it contended was central to the invalidity analysis.
  • The primary construction requires a system with multiple physical deposition output ports (e.g., a dual-extruder printer), under which Grounds 1 and 2 are applicable.
  • An alternative, broader construction includes systems with a single output port that deposits different materials at different times. This construction is necessary for Ground 3 (Boyer) to be applicable.

5. Arguments Regarding Discretionary Denial

• Petitioner argued that discretionary denial under 35 U.S.C. §325(d) is unwarranted because the petition relies on new prior art (RepRap, KISSlicer, Boyer) that was never before the examiner. Petitioner asserted this art corrects a material error in prosecution, as the examiner allowed the claims based on the mistaken belief that no prior art taught printing a purge tower.
• Petitioner argued that discretionary denial under Fintiv is also inappropriate. The parallel district court litigation is in a very early stage, with minimal investment of resources. Furthermore, Petitioner has stipulated that it will not pursue in the district court any invalidity ground raised or that could have been reasonably raised in this IPR.

6. Relief Requested

• Petitioner requests institution of an inter partes review and cancellation of claims 1, 2, 5-7, 9, 16, and 17 of the ’713 patent as unpatentable.