PTAB

IPR2025-00532

Shenzhen Tuozhu Technology Co Ltd v. Stratasys Inc

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Petition
petition

1. Case Identification

2. Patent Overview

  • Title: Three-Dimensional Printer With Force Detection
  • Brief Description: The ’381 patent discloses a three-dimensional printer having a fabrication tool, such as an extruder, that is instrumented with one or more sensors. These sensors are mechanically coupled to the extruder to detect contact forces between the extruder and a separate structure, like a build platform or the object being fabricated, allowing a controller to use the resulting feedback data to control the printer's operation.

3. Grounds for Unpatentability

Ground 1A: Claims 1-6 and 9-16 are obvious over Warren

  • Prior Art Relied Upon: Warren (Application # 2003/0100824).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that Warren, which discloses a 3D printing technology for creating engineered tissue constructs, teaches all elements of the challenged claims. Warren describes a dispenser (extruder) equipped with a vibration-based force sensing system (a vibration sensor and transducer) mechanically attached to the dispenser. This system senses the intensity of physical contact with a substrate, creating a proportional feedback signal. A controller then uses this signal to adjust the z-position of the dispenser to maintain a desired contact force.
    • Motivation to Combine (within a single reference): Warren discloses multiple types of dispensers, including a capillary vibro-sensor dispenser and a through-nozzle dispenser with precise flow control. Petitioner contended a person of ordinary skill in the art (POSITA) would combine Warren’s vibrating force sensor with its through-nozzle dispenser. The motivation stems from Warren’s own suggestion to combine aspects of its technology to create a comprehensive tool. A POSITA would seek to gain the precise material flow control of the through-nozzle design while adding the force-sensing capability to improve deposition geometry and prevent damage to the nozzle or substrate.
    • Expectation of Success: A POSITA would have a high expectation of success, as this involves integrating complementary teachings from within a single reference related to the same overall system, which is a predictable modification.

Ground 2A: Claims 1-6 and 9-16 are obvious over Calderon and RepRap20208

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

  • Core Argument for this Ground:

    • Prior Art Mapping: Petitioner asserted that Calderon discloses an extrusion-based 3D printer that uses a sensor on the extrusion head to detect contact force against the substrate for a z-axis initialization routine. Calderon suggests various "sensing means," including monitoring servo drive current. RepRap20208, an online forum discussion among 3D printer developers, explicitly suggests using a "strain gauge on the extruder mount" to detect head collisions and to "find[] the bed height automatically." The combination of Calderon's system with RepRap20208's superior sensor allegedly renders the claims obvious.
    • Motivation to Combine: A POSITA would combine these references to improve the accuracy and reliability of Calderon’s system. Petitioner argued that Calderon's suggestion to use servo drive current for sensing would suffer from mechanical "slop/backlash," leading to imprecise contact detection. The strain gauge proposed in RepRap20208 provides a more direct, precise, and consistent force measurement, located closer to the point of contact. This modification would overcome the imprecision of Calderon's method, prevent damage to various substrate types (e.g., rigid vs. foam), and provide a more robust system for z-axis calibration.
    • Expectation of Success: Success would be reasonably expected because the combination involves substituting a known, superior sensor (strain gauge) for a known, inferior one (servo current monitoring) to achieve a predictable improvement in a known system. This constitutes a simple substitution of known elements to yield predictable results.

  • Additional Grounds: Petitioner asserted two additional obviousness challenges (Grounds 1B and 2B) for claims 3, 7, and 8. These grounds added the teachings of Dunn (Application # 2007/0228592) to the primary combinations of Warren and Calderon/RepRap20208, respectively. Dunn discloses a "multi-axis sensor assembly" capable of sensing forces in the X, Y, and Z directions, which Petitioner argued would have been a simple and predictable addition to provide the multi-axis sensing required by these dependent claims.

4. Arguments Regarding Discretionary Denial

  • §325(d) - Same or Substantially the Same Art: Petitioner argued against denial under §325(d), stating that while Calderon was cited during prosecution, it was never substantively applied against the claims. Furthermore, the primary prior art references, Warren and RepRap20208, which disclose the key sensor configuration the Examiner believed to be missing, were never considered. Petitioner contended this constitutes a material error by the examiner that warrants review.
  • §314(a) - Parallel Litigation (Fintiv Factors): Petitioner argued that the Fintiv factors strongly favor institution. The petition was filed early in the parallel district court proceeding, a motion to dismiss is pending, and the trial date is distant (June 2026). Critically, Petitioner has stipulated not to pursue the IPR grounds in the district court action, which eliminates concerns about overlapping issues and duplicative efforts.

5. Relief Requested

  • Petitioner requests the institution of an inter partes review and the cancellation of claims 1-16 of the ’381 patent as unpatentable.