PTAB

IPR2025-00531

Shenzhen Tuozhu Technology Co Ltd v. Stratasys Inc

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Key Events
Petition
petition

1. Case Identification

2. Patent Overview

  • Title: Three-Dimensional Printer With Force Detection
  • Brief Description: The ’698 patent discloses a three-dimensional printer with a pressure-sensing fabrication tool, such as an extruder. The system uses one or more sensors to detect the contact force between the fabrication tool and a separate structure (e.g., a build platform), generating feedback data to control the printer's operation during a build.

3. Grounds for Unpatentability

Ground 1: Claims 1-6 and 8-15 are obvious over Warren

  • Prior Art Relied Upon: Warren (Patent 6,986,739)
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that Warren, a single reference, teaches all limitations of the challenged claims. Warren discloses a 3D printing system for creating engineered tissue constructs using "direct-write deposition technology" (DWDT). This system includes a dispenser (fabrication tool) with a "vibro-sensoric" system that detects the intensity of contact force between the dispenser tip and a substrate. Warren explicitly teaches using a feedback signal, proportional to the detected contact force, to create a control signal that adjusts the z-positioning of the dispenser via a z-controller processor and step motor, all while depositing material. Petitioner asserted that Warren’s description of generating CAD/CAM program data for the build meets the "identifying build instructions" limitation, and its various dispensers, such as the through-nozzle dispenser, function as the claimed "extruder." Dependent claims related to controlling feed rate, z-distance, comparing forces, and detecting planarity were also argued to be disclosed within Warren's comprehensive system.
    • Motivation to Combine (for §103 grounds): Although a single reference, Petitioner argued for the obviousness of combining different disclosed embodiments within Warren, such as applying the vibrating force sensor (shown with a capillary dispenser) to Warren’s through-nozzle dispenser. The motivation was based on Warren’s explicit statement that its technology has a "plurality of aspects that...combine to make a tool" and that the capillary dispenser was shown "by way of example only." A POSITA would combine the precise flow control of the through-nozzle dispenser with the force-sensing capability to improve deposition control and prevent damage.
    • Expectation of Success: A POSITA would have a high expectation of success as it involved integrating complementary teachings from within the same reference related to the same core technology.

Ground 2: Claims 1-5, 7-10, and 12-15 are obvious over Calderon in view of RepRap20208

  • Prior Art Relied Upon: Calderon (Patent 6,629,011) and RepRap20208 (a 2009 online public forum discussion thread)

  • Core Argument for this Ground:

    • Prior Art Mapping: Petitioner argued that Calderon discloses an extrusion-based 3D modeling system that performs a z-axis initialization routine by detecting contact between the nozzle tip and the substrate using a "sensing means." However, Calderon's sensing is primarily for pre-build calibration. RepRap20208, a public forum discussion among 3D printer developers, was argued to supply the missing elements by suggesting the use of a "strain gauge on the extruder mount" to perform two key functions: z-axis calibration ("finding the bed height automatically") and real-time collision detection during a build. The combination, therefore, taught a method of using a sensor (a strain gauge) to detect contact force and create a control signal in response to that force while depositing material (i.e., for collision detection). This combination was alleged to meet the limitations of claim 1, including initiating a build, using a sensor to detect force, and creating a responsive control signal during the build.
    • Motivation to Combine: A POSITA would combine the teachings to improve upon Calderon's system. RepRap20208's strain gauge offered a more precise method for z-axis initialization than Calderon's suggestion of monitoring servo drive current, which suffered from "slop/backlash." Furthermore, the combination was motivated by the desire to add the significant and well-understood benefit of real-time collision detection during printing, a feature discussed in RepRap20208 but absent from Calderon's initialization-focused disclosure.
    • Expectation of Success: A POSITA would have a reasonable expectation of success because it involved applying a well-known sensor (a strain gauge) to a known system (Calderon's printer) to achieve predictable improvements in both calibration accuracy and operational safety.

  • Additional Grounds: Petitioner asserted additional obviousness challenges, adding Eshed (Application # 2007/0179656) to the Warren combination to explicitly teach terminating a build upon detecting a fabrication error (Ground 1B for claims 3, 7, 9), and adding Napadensky (Patent 9,031,680) to the Calderon/RepRap20208 combination to teach leveling a deposited layer to decrease irregularities (Ground 2B for claim 11).

4. Arguments Regarding Discretionary Denial

  • Petitioner argued that discretionary denial would be inappropriate. Under §325(d), Petitioner contended that its grounds raised new issues, as the Examiner never considered Warren or RepRap20208, and the asserted combinations provided the very features the Examiner mistakenly believed were missing from the prior art during prosecution.
  • Under the Fintiv factors for co-pending district court litigation, Petitioner argued for institution because the petition was filed early in the litigation timeline, before an answer or significant investment from the district court. Petitioner also cited a stipulation not to pursue the IPR grounds in district court, eliminating concerns of overlapping issues and duplicative efforts.

5. Relief Requested

  • Petitioner requests institution of an inter partes review and cancellation of claims 1-15 of the ’698 patent as unpatentable.