DCT

2:24-cv-00644

Stratasys Inc v. Shenzhen Tuozhu Technology Co Ltd

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I. Executive Summary and Procedural Information

  • Parties & Counsel:
  • Case Identification: 2:24-cv-00644, E.D. Tex., 08/08/2024
  • Venue Allegations: Plaintiff alleges venue is proper in the Eastern District of Texas because Defendants are foreign entities that have committed acts of patent infringement within the district through online sales and distribution.
  • Core Dispute: Plaintiff alleges that Defendant’s 3D printers, software, and related accessories infringe five U.S. patents related to multi-material printing processes, heated build platforms, void-filling toolpath generation, and force-detection safety mechanisms.
  • Technical Context: The lawsuit concerns technologies in the field of fused deposition modeling (FDM), a prominent form of additive manufacturing used for rapid prototyping and producing end-use parts.
  • Key Procedural History: The complaint alleges that Defendants were notified of their alleged infringement via a notice letter on August 5, 2024, three days prior to the filing of the lawsuit. This notification forms the basis for the allegations of willful infringement.

Case Timeline

Date Event
2006-01-31 '357 Patent Priority Date
2009-06-30 '357 Patent Issue Date
2012-10-29 '698 and '381 Patents Priority Date
2013-03-08 '713 Patent Priority Date
2014-12-17 '660 Patent Priority Date
2015-10-27 '698 Patent Issue Date
2016-08-23 '713 Patent Issue Date
2017-03-14 '660 Patent Issue Date
2020-02-11 '381 Patent Issue Date
2022-01-01 Accused Bambu Lab Printers Launch (by this date)
2024-08-05 Plaintiff Sends Notice Letter to Defendants
2024-08-08 Complaint Filing Date

II. Technology and Patent(s)-in-Suit Analysis

U.S. Patent No. 9,421,713 - "Additive Manufacturing Method For Printing Three-Dimensional Parts With Purge Towers"

  • Patent Identification: U.S. Patent No. 9,421,713, "Additive Manufacturing Method For Printing Three-Dimensional Parts With Purge Towers," issued August 23, 2016.
  • The Invention Explained:
    • Problem Addressed: In multi-material 3D printing, switching between materials (e.g., a part material and a dissolvable support material) can lead to print failures. When a print head is idle, the material inside can degrade, ooze, or entrain gases, requiring a "purge" to ensure the nozzle is primed with quality material before it resumes printing ('713 Patent, col. 4:48-62).
    • The Patented Solution: The patent proposes a method where, after a print head is switched from a stand-by to an operating mode, it performs a purge operation by printing a dedicated, separate structure called a "purge tower" in a layer-by-layer fashion. This tower contains the purged material, preventing it from contaminating the actual 3D part and its support structure ('713 Patent, Abstract; col. 2:1-7).
    • Technical Importance: This method improves the reliability and quality of multi-material prints by isolating waste material and ensuring the print nozzle is in a ready state before depositing material onto the part ('713 Patent, col. 4:40-62).
  • Key Claims at a Glance:
    • The complaint asserts independent claim 1 (Compl. ¶26).
    • The essential elements of claim 1 are:
      • A method for printing a 3D part with an additive manufacturing system.
      • Printing layers of the part and a support structure from multiple print heads or deposition lines.
      • Switching the print heads or deposition lines between stand-by and operating modes between printing layers.
      • Performing a purge operation for each print head or deposition line that is switched to the operating mode.
      • The purge operation involves printing at least one "purge tower" layer-by-layer, using the print head or deposition line that was just switched to the operating mode.

U.S. Patent No. 9,592,660 - "Heated Build Platform And System For Three-Dimensional Printing Methods"

  • Patent Identification: U.S. Patent No. 9,592,660, "Heated Build Platform And System For Three-Dimensional Printing Methods," issued March 14, 2017.
  • The Invention Explained:
    • Problem Addressed: Printing with high-temperature thermoplastics requires a heated build surface to ensure part adhesion and prevent warping. The patent’s background section notes that the common solution, applying polyimide tape to the build plate, is unreliable; the tape can trap air bubbles that create an uneven surface, can be damaged during part removal, and can permanently adhere to the part ('660 Patent, col. 1:40-65).
    • The Patented Solution: The invention is a build apparatus featuring a heated platform, a separate thermally conductive plate placed on it, and a polymer coating bonded directly to the plate's surface. This coating is specifically designed to adhere to the 3D object during printing but allow for easy, non-damaging removal once the object has cooled. The claims explicitly state the "polymer coating is not a polymer tape" ('660 Patent, Abstract; col. 2:63-65).
    • Technical Importance: This design provides a durable, reusable, and more reliable printing surface for high-performance materials, overcoming the deficiencies of single-use adhesive tapes ('660 Patent, col. 2:5-10).
  • Key Claims at a Glance:
    • The complaint asserts independent claim 1 (Compl. ¶42).
    • The essential elements of claim 1 are:
      • A build apparatus for printing a 3D object of thermoplastics.
      • A build platform with a temperature control unit for heating.
      • A thermally conductive plate located adjacent to the build platform.
      • A polymer coating attached to the plate's surface that both facilitates adhesion during printing and permits easy removal of the cooled object without damage to the object, plate, or coating.
      • A negative limitation: the polymer coating is not a polymer tape.

Multi-Patent Capsule: U.S. Patent No. 7,555,357 - "Method For Building Three-Dimensional Objects With Extrusion-Based Layered Deposition Systems"

  • Patent Identification: U.S. Patent No. 7,555,357, "Method For Building Three-Dimensional Objects With Extrusion-Based Layered Deposition Systems," issued June 30, 2009.
  • Technology Synopsis: The patent addresses the problem of small gaps or "void regions" that can form within layers of a 3D-printed object, which are often too small to fill with standard toolpaths and can compromise the part's structural integrity ('357 Patent, col. 2:57-65). The invention is a method for generating a special "remnant path" with a varying deposition rate specifically to fill these voids ('357 Patent, col. 2:10-17).
  • Asserted Claims: The complaint asserts independent claim 15 (Compl. ¶58).
  • Accused Features: The complaint alleges that Defendant's "Bambu Studio" software generates toolpaths that fill voids between walls by modifying parameters like the "wall distribution count," which is alleged to be a method of generating remnant paths with varying widths (Compl. ¶59).

Multi-Patent Capsule: U.S. Patent No. 9,168,698 - "Three-Dimensional Printer With Force Detection"

  • Patent Identification: U.S. Patent No. 9,168,698, "Three-Dimensional Printer With Force Detection," issued October 27, 2015.
  • Technology Synopsis: This patent addresses the need to detect and respond to operating errors in 3D printers, such as when the extruder collides with the object being printed ('698 Patent, col. 1:15-22). The invention is a method wherein sensors detect a "current contact force" on the fabrication tool and, in response, generate a control signal to alter the printer's operation, such as by pausing or terminating the build ('698 Patent, col. 12:8-14).
  • Asserted Claims: The complaint asserts independent claim 1 (Compl. ¶74).
  • Accused Features: The Bambu Lab A1 and A1 mini printers are accused of infringing this method by using an "extrusion force sensor" to detect "nozzle clumping" and automatically stopping the print job in response (Compl. ¶75).

Multi-Patent Capsule: U.S. Patent No. 10,556,381 - "Three-Dimensional Printer With Force Detection"

  • Patent Identification: U.S. Patent No. 10,556,381, "Three-Dimensional Printer With Force Detection," issued February 11, 2020.
  • Technology Synopsis: This patent, a continuation of the application that led to the '698 Patent, describes a system for detecting forces on an extruder ('381 Patent, col. 1:25-33). The invention is an apparatus (a printer) comprising a fabrication tool, one or more sensors mechanically coupled to it, and a controller that calculates the contact force based on the sensor's signal ('381 Patent, Abstract).
  • Asserted Claims: The complaint asserts independent claim 1 (Compl. ¶90).
  • Accused Features: The Bambu Lab A1 and A1 mini printers themselves are accused of infringing these apparatus claims, based on the inclusion of an "extrusion force sensor" to detect nozzle clumping and a controller that stops the print based on the detected force (Compl. ¶91).

III. The Accused Instrumentality

  • Product Identification: The accused instrumentalities are primarily the Bambu Lab family of 3D printers, including the A1, A1 mini, P1P, X1-Carbon ("X1C"), P1S, and X1E models (Compl. ¶19). The allegations also extend to associated software ("Bambu Studio," "Bambu Handy") and hardware accessories, such as the Bambu Engineering Plate, Textured PEI Plate, and High Temperature Plate (Compl. ¶¶27, 43).
  • Functionality and Market Context:
    • The accused products are extrusion-based (FDM) 3D printers marketed to both consumer and professional users. The complaint alleges these printers, in conjunction with their controlling software, implement features for multi-material management, build surface preparation, toolpath generation, and error detection (Compl. ¶¶27, 43, 59, 75).
    • Specifically, the complaint alleges the "Automatic Material System (AMS)" enables multi-material printing, and the "Bambu Studio" software directs the creation of a "prime tower" to manage material changes (Compl. ¶27). The printers are alleged to use heated "heatbeds" in combination with removable, polymer-coated steel build plates (Compl. ¶43). The A1 series printers are alleged to incorporate an "eddy force sensor" to detect nozzle clumping and halt printing (Compl. ¶75).
    • No probative visual evidence provided in complaint.

IV. Analysis of Infringement Allegations

'713 Patent Infringement Allegations

Claim Element (from Independent Claim 1) Alleged Infringing Functionality Complaint Citation Patent Citation
printing layers of the three-dimensional part and of a support structure for the three-dimensional part from multiple print heads or deposition lines... Bambu Lab's 3D printers use an Automatic Material System (AMS) that supports multiple filament spools, each with an independent deposition line coupled to the print head, to print parts and support structures. ¶27 col. 1:40-44
switching the print heads or deposition line between stand-by modes and operating modes in-between the printing of the layers... Bambu Studio software instructs the printer to switch deposition lines when changing between printing part material and support material. ¶27 col. 4:1-12
performing a purge operation for each print head or deposition line switched to the operating mode, the purge operation comprising printing at least one purge tower in a layer-by-layer manner... The Bambu Studio slicer software instructs the printer to perform a purge operation by creating a "prime tower" when a deposition line is switched between materials. ¶27 col. 2:1-7

'660 Patent Infringement Allegations

Claim Element (from Independent Claim 1) Alleged Infringing Functionality Complaint Citation Patent Citation
a build platform with a temperature control unit configured to control heating of the build platform; The Bambu printers have a heated build platform, referred to as a "heatbed." ¶43 col. 4:19-22
a thermally conductive plate disposed adjacent to the build platform; Bambu Lab sells thermally conductive build plates (e.g., steel sheets) that are placed on the heatbed for printing. ¶43 col. 5:15-16
a polymer coating attached to a surface of the thermally conductive plate which is capable of (i) facilitating adhesion to the 3D object during printing and (ii) permitting removal of the 3D object...without damaging the polymer coating... The accused build plates are coated with a polymer (e.g., polyetherimide) that facilitates adhesion. The 3D object is removed by flexing the plate after it has cooled, which does not damage the coating. ¶43 col. 5:28-44
...wherein the polymer coating is not a polymer tape. The complaint alleges the build plates are made by "coating a polymer...onto a steel sheet," which is distinct from an adhesive-backed polymer tape. ¶43 col. 2:63-65
  • Identified Points of Contention:
    • Scope Questions: A primary issue for the '713 Patent will be whether Bambu Lab's "prime tower" constitutes a "purge tower" as the term is used in the patent. For the '660 Patent, a central question is whether the accused polymer-surfaced build plates are "a polymer coating" and, critically, "not a polymer tape," as required by the claim.
    • Technical Questions: The infringement theory for the '713 Patent raises the question of whether a single-nozzle printer fed by multiple filaments via the AMS technically meets the claim language of switching between "multiple print heads or deposition lines." For the '357 Patent, a key technical question will be whether the accused software's method of adjusting "wall distribution count" operates in the same way as the claimed method of generating a "remnant path...based on deposition rates that are configured to vary."

V. Key Claim Terms for Construction

  • The Term: "purge tower" ('713 Patent, Claim 1)

    • Context and Importance: Defendant describes its accused feature as a "prime tower" (Compl. ¶27). The resolution of the case may depend on whether this feature falls within the legal definition of a "purge tower." Practitioners may focus on this term because the parties use different nomenclature for what may be functionally similar features.
    • Intrinsic Evidence for a Broader Interpretation: The specification describes the function of the purge operation broadly as freeing filament, removing degraded material, and bringing the print head to a known operating state ('713 Patent, col. 4:48-54). This could support construing the term to cover any separate, printed structure that achieves these functions.
    • Intrinsic Evidence for a Narrower Interpretation: The patent depicts a specific diamond-shaped tower and explains its structure is beneficial for containing stringing within its interior volume ('713 Patent, Fig. 5; col. 9:15-23). This could support a narrower construction limited to structures with specific geometries designed for waste containment.

  • The Term: "polymer coating" ... "wherein the polymer coating is not a polymer tape" ('660 Patent, Claim 1)

    • Context and Importance: This pair of limitations is the core distinction over the prior art use of polyimide tape. The dispute will likely center on the line between a "coating" applied to a plate and a "tape" or laminate affixed to it.
    • Intrinsic Evidence for a Broader Interpretation (of "coating"): The patent's background extensively criticizes "polyimide tape" for its unreliability, including issues with trapped air and tearing ('660 Patent, col. 1:40-65). This context suggests "coating" was intended to mean a more integrated, durable, and reusable surface, distinct from a disposable adhesive film. The specification also mentions spray coating as an application method (col. 4:36-37).
    • Intrinsic Evidence for a Narrower Interpretation (of "coating"): A defendant might argue that the term "coating" should be limited to substances applied in a liquid or powder form that cure in place, and that any pre-formed polymer sheet bonded to the metal plate, regardless of the bonding method, functions as a "tape" in the context of the patent.

VI. Other Allegations

  • Indirect Infringement: The complaint alleges that by providing printers, software (Bambu Studio), user manuals, and online instructional materials (e.g., wikis and YouTube videos), Defendants actively encourage and instruct their customers to operate the products in a manner that directly infringes the asserted patents (Compl. ¶¶ 29, 45, 61, 77, 93).
  • Willful Infringement: Willfulness is alleged for all five asserted patents. The basis for this allegation is Defendants' alleged continued infringement after receiving a notice letter from Stratasys on August 5, 2024 (Compl. ¶¶ 33, 49, 65, 81, 97).

VII. Analyst’s Conclusion: Key Questions for the Case

  • A core issue will be one of definitional scope: can the term "purge tower", as defined in the '713 Patent, be construed to cover the accused "prime tower"? Similarly, is the accused "Textured PEI Plate" a "polymer coating" that is "not a polymer tape" under the specific meaning of the '660 Patent?
  • A key technical question will be one of operational equivalence: does a single-nozzle printer fed by an automatic material system (as in the accused products) infringe claims written in the context of systems with physically distinct "multiple print heads or deposition lines"?
  • A central evidentiary question across multiple patents will be the comparison of algorithms: does the accused Bambu Studio software's method for filling small gaps by adjusting a "wall distribution count" infringe the '357 Patent's specific method of generating a "remnant path" with varying deposition rates?