DCT

2:24-cv-00644

Stratasys Inc v. Shenzhen Tuozhu Technology Co Ltd

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Key Events
Amended Complaint

I. Executive Summary and Procedural Information

  • Parties & Counsel:
  • Case Identification: 2:24-cv-00644, E.D. Tex., 09/17/2025
  • Venue Allegations: Venue is alleged to be proper as Defendants are foreign entities that have committed acts of patent infringement within the Eastern District of Texas.
  • Core Dispute: Plaintiff alleges that Defendant’s 3D printers, accessories, and associated software infringe five U.S. patents related to multi-material purging, heated build platforms, void-filling toolpaths, and force-detection systems.
  • Technical Context: The lawsuit concerns additive manufacturing, commonly known as 3D printing, a technology sector with significant consumer, "prosumer," and industrial market applications.
  • Key Procedural History: The complaint notes that Defendants initially filed a declaratory judgment action in the Western District of Texas seeking a declaration of invalidity for the asserted patents. That action was subsequently transferred to the Eastern District of Texas and consolidated with the present case.

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 Alleged Launch of Accused Bambu Lab Printers
2024-08-05 Alleged Date of Notice Letter to Defendants
2024-12-09 Defendants File Declaratory Judgment Action in W.D. Tex.
2025-09-17 First Amended 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”

Issued August 23, 2016

The Invention Explained

  • Problem Addressed: In multi-extruder 3D printing, when switching between materials (e.g., model material and support material), the newly activated nozzle must be purged of old or oozed material to ensure a clean start. The patent’s background indicates that conventional methods, which often involve moving the print head to an off-platform "purge bucket," can be inefficient and consume valuable build area (’713 Patent, col. 4:40-50).
  • The Patented Solution: The invention proposes a method where, instead of using an external station, the printer constructs a dedicated "purge tower" on the build plate itself, alongside the primary object being printed. Each time a print head is activated, it first deposits a layer of material onto this tower to prime the nozzle before moving to print its designated layer of the part or support structure (’713 Patent, Abstract; col. 8:8-13).
  • Technical Importance: This approach integrates the material purging process directly into the build volume, which may reduce the time required for material changes and maximize the usable area on the build platform (’713 Patent, col. 9:8-14).

Key Claims at a Glance

The complaint asserts independent Claim 1 (Compl. ¶93). Its essential elements include:

  • A method for printing a three-dimensional 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.
  • Performing a purge operation for each print head or deposition line switched to the operating mode.
  • The purge operation comprises printing at least one purge tower in a layer-by-layer manner from the newly activated print head or deposition line.

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 materials requires a heated build surface for proper adhesion and to prevent part warping. The patent background describes that parts can adhere too strongly, making them difficult to remove without damage, and that consumable surfaces like polyimide tape are prone to tearing, trapping air bubbles, and creating uneven surfaces (’660 Patent, col. 1:12-65).
  • The Patented Solution: The patent describes a build apparatus comprising a heated platform, a separate thermally conductive plate placed upon it, and a polymer coating attached to the plate's surface. This coating is engineered to provide strong adhesion while the part is printing at high temperature but also permit easy removal of the part once it cools. The claims explicitly state that this polymer coating is "not a polymer tape" (’660 Patent, Abstract; col. 2:50-3:1).
  • Technical Importance: This system provides a durable and reusable build surface that resolves the conflicting requirements of strong adhesion during fabrication and easy part release after fabrication, particularly for high-performance thermoplastics (’660 Patent, col. 3:5-10).

Key Claims at a Glance

The complaint asserts independent Claim 1 (Compl. ¶109). Its essential elements include:

  • A build apparatus for printing a 3D object of thermoplastics.
  • A build platform with a temperature control unit for heating.
  • A thermally conductive plate disposed adjacent to the build platform.
  • A polymer coating attached to the plate's surface, which is capable of facilitating adhesion during printing and permitting removal after cooling without chemical or mechanical removal of the coating itself.
  • A negative limitation: "wherein the polymer coating is not a polymer tape."

Multi-Patent Capsule: U.S. Patent No. 7,555,357

  • Patent Identification: U.S. Patent No. 7,555,357, “Method For Building Three-Dimensional Objects With Extrusion-Based Layer Deposition Systems,” Issued June 30, 2009 (Compl. ¶122).
  • Technology Synopsis: The patent addresses the technical problem of small gaps or "void regions" that can form between toolpaths in a printed layer, which can compromise the object's structural integrity. The patented solution is a method for generating a special "remnant path" to fill these voids, which are smaller than a standard deposition road, often using varied deposition rates to match the void's dimensions (’357 Patent, Abstract; col. 2:5-17).
  • Asserted Claims: Independent Claim 15 (Compl. ¶125).
  • Accused Features: The complaint alleges that Defendant's Bambu Studio software generates, and its printers execute, build paths that create void regions and then fill them with remnant paths of a different width (Compl. ¶126).

Multi-Patent Capsule: U.S. Patent No. 9,168,698

  • Patent Identification: U.S. Patent No. 9,168,698, “Three-Dimensional Printer With Force Detection,” Issued October 27, 2015 (Compl. ¶138).
  • Technology Synopsis: This patent addresses printing failures such as nozzle clumping, where filament accumulates around the extruder. The invention is a method that uses sensors mechanically coupled to the fabrication tool to detect a contact force between the tool and a separate structure (e.g., the heatbed or a clump of filament), and then creates a control signal—for instance, to pause the print—in response to that detected force (’698 Patent, Abstract; col. 12:47-62).
  • Asserted Claims: Independent Claim 1 (Compl. ¶141).
  • Accused Features: The Bambu Lab A1 and A1 mini printers are accused of infringing. The complaint alleges these printers use an "eddy force sensor" to detect nozzle clumping and automatically stop the print job based on the detected force (Compl. ¶142).

Multi-Patent Capsule: U.S. Patent No. 10,556,381

  • Patent Identification: U.S. Patent No. 10,556,381, “Three-Dimensional Printer With Force Detection,” Issued February 11, 2020 (Compl. ¶154).
  • Technology Synopsis: Related to the ’698 Patent, this patent claims an apparatus rather than a method. It describes a 3D printer comprising an extruder, one or more sensors mechanically coupled to it to sense a contact force, and a controller configured to receive the sensor signal and calculate the contact force between the extruder and a separate structure (’381 Patent, Abstract; col. 13:1-4).
  • Asserted Claims: Independent Claim 1 (Compl. ¶157).
  • Accused Features: The Bambu Lab A1 and A1 mini printers are accused of being the claimed apparatus. The complaint alleges these printers contain an extrusion nozzle, an "eddy force sensor," and a controller that uses the sensor's signal to detect and react to forces caused by nozzle clumping (Compl. ¶158).

III. The Accused Instrumentality

Product Identification

The accused instrumentalities include the Bambu Lab A1, A1 mini, P1P, X1-Carbon ("X1C"), P1S, and X1E 3D printers; the Automatic Material System ("AMS") accessory; and the Bambu Studio software (Compl. ¶¶20, 92, 108).

Functionality and Market Context

The complaint describes the accused products as additive manufacturing systems used for printing 3D objects (Compl. ¶¶94, 110). Specific functionalities highlighted include multi-material printing using the AMS, which houses multiple filament spools that feed into the printer's extruder (Compl. ¶¶34, 37). The complaint references a marketing image for a "Dual-Nozzle Double Flexibility" feature, suggesting advanced multi-material capabilities (Compl. p. 10). The printers are also alleged to use heated build platforms ("heatbeds") (Compl. ¶49), employ temperature control features for the print chamber and heatbed (Compl. ¶¶56-58), and incorporate force sensors for detecting print failures like nozzle clumping (Compl. ¶¶59, 61). The printers are controlled by the Bambu Studio software, which processes 3D models into printable instructions (Compl. ¶65).

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... The accused 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 layers of a 3D part. ¶94 col. 8:8-13
switching the print heads or deposition line between stand-by modes and operating modes in-between the printing of the layers... The Bambu Studio software instructs the printer to switch deposition lines between printing part material and support material. ¶94 col. 8:14-18
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 accused printers to perform a purge operation to a "prime tower" when a deposition line is switched between materials. ¶94 col. 8:19-25

’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 accused printers have a heated build platform ("heatbed"). ¶110 col. 1:12-14
a thermally conductive plate disposed adjacent to the build platform; Defendant sells thermally conductive build plates (e.g., Textured PEI Plate, High Temperature Plate) that are placed on the heatbed. ¶110 col. 2:50-52
a polymer coating attached to a surface of the thermally conductive plate which is capable of (i) facilitating adhesion... and (ii) permitting removal... without chemically or mechanically removing the polymer coating... The accused build plates are made by coating a polymer (e.g., polyetherimide) onto a steel sheet. This facilitates adhesion, and the 3D object is removable by flexing the plate after it has cooled. ¶¶110-111 col. 2:53-65
wherein the polymer coating is not a polymer tape. The complaint alleges the accused build plates are polymer-coated steel sheets, distinguishing them from a polymer tape. ¶110 col. 3:1-2

Identified Points of Contention:

  • Scope Questions: The infringement analysis for the ’713 Patent may raise the question of whether switching between multiple filament "deposition lines" that feed a single extruder, as the AMS system does, meets the claim limitation of switching "print heads or deposition line[s]." For the ’660 Patent, a central issue may be the scope of the negative limitation "not a polymer tape" and whether Defendant's polymer-coated flexible steel plates fall outside that exclusion.
  • Technical Questions: A key technical question for the ’713 Patent is whether the accused "prime tower" functions as the claimed "purge tower," which involves priming a nozzle for a clean extrusion start. For the ’660 Patent, the analysis may focus on whether flexing the build plate to remove a part constitutes "mechanically removing the polymer coating from [the] 3D object," an action the claim language proscribes for the removal step. A visual in the complaint of the accused heatbed unit provides context for the physical apparatus at issue (Compl. p. 17).

V. Key Claim Terms for Construction

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

    • Context and Importance: Plaintiff's infringement theory rests on the allegation that Defendant's "prime tower" is a "purge tower." The construction of this term will be critical to determining infringement.
    • Intrinsic Evidence for Interpretation:
      • Evidence for a Broader Interpretation: The patent abstract describes the invention functionally as a "method for printing...with purge towers," and the claim recites "printing at least one purge tower" as part of a "purge operation" (’713 Patent, Abstract; Claim 1). This functional language may support a construction that covers any structure printed on the build plate for the purpose of priming a nozzle.
      • Evidence for a Narrower Interpretation: The specification's preferred embodiments and figures illustrate a specific diamond-shaped tower geometry (e.g., ’713 Patent, FIG. 4, col. 9:51-54). Arguments may be made that the term should be limited to structures sharing these or similar geometric characteristics.

  • Term: "not a polymer tape" (’660 Patent, Claim 1)

    • Context and Importance: This negative limitation is central to distinguishing the patented invention from the prior art. Whether the accused polymer-coated plates are excluded by this term will be a focal point of the dispute.
    • Intrinsic Evidence for Interpretation:
      • Evidence for a Broader Interpretation (of what constitutes a "tape"): The term is not explicitly defined. A party could argue that any thin polymer film applied to a substrate, regardless of manufacturing method, could be considered a "tape" in the functional context of a 3D printer build surface.
      • Evidence for a Narrower Interpretation (of what constitutes a "tape"): The patent's background section specifically discusses problems with "polyimide tape," such as trapping air bubbles during application and tearing upon part removal (’660 Patent, col. 1:49-65). This context may support an interpretation that "polymer tape" refers to user-applied, adhesive-backed films, distinguishing them from the pre-manufactured, integrated polymer-coated plates described in the patent.

VI. Other Allegations

  • Indirect Infringement: The complaint alleges both induced and contributory infringement for all five asserted patents. The inducement allegations are based on Defendant's affirmative acts of encouraging infringement by providing instructional materials, user manuals, marketing, software, and training for the accused products (e.g., Compl. ¶¶96, 112, 128, 144, 160).
  • Willful Infringement: Willfulness is alleged for all five patents. The complaint asserts that Defendants had knowledge of the patents and their infringement at least as early as August 5, 2024, via a notice letter, and continued their alleged infringing activities thereafter (e.g., Compl. ¶¶100, 116, 132, 148, 164).

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

  • A core issue will be one of definitional scope: Does switching filament feeds to a single nozzle via the AMS system constitute switching "print heads or deposition lines" as required by the ’713 patent? Further, are Defendant's polymer-coated, flexible steel build plates properly distinguished from the "polymer tape" that is expressly excluded by the ’660 patent?
  • A second central question will be one of technical operation: Does the accused "prime tower" function as a "purge tower" by priming a nozzle before it prints a layer, as claimed in the ’713 patent? For the force-detection patents ('698 and '381), a key evidentiary question will be whether the accused printers' eddy current sensor system, which the complaint alleges detects nozzle clumping (Compl. p. 23), performs the specific steps of detecting and calculating a "contact force" as required by the claims.