US 10556381

I'll search for the specific patent number and any related 2026 litigation activity.

Let me run a couple of targeted searches to check specifically for any Federal Circuit 2026 appeal involving this patent.

US Patent 10,556,381 — Verification Summary

Search scope note: I searched for the literal identifier "10556381" (not variants or neighboring numbers). Results consistently returned the same record across Google Patents, FreePatentsOnline, Justia, the USPTO Patents-Review entry, and PTAB filings.

Bibliographic data

Sources: Google Patents; FreePatentsOnline; US10556381 PDF.

Uncertainty flag on term: Google Patents states a 1,002-day patent term adjustment and adjusted expiration of 2036-07-27, while a third-party aggregator (Patents-Review) lists 2038-07-24. The granted application is a continuation with an Oct 29, 2012 effective priority date, so 2036 is more consistent with a 20-year-from-2013-parent-filing term. I could not independently verify which is correct from the granted face.

Abstract (verbatim)

"An extruder or other tool head of a three-dimensional printer is instrumented to detect contact force against the extruder, such as by a build platform or an object being fabricated. The tool head may also be instrumented to detect deflection forces and the like acting on the tool that might indicate an operating error. The resulting feedback data can be used in a variety of ways to control operation of the three-dimensional printer during fabrication or diagnostics."

Claim 1 — the only independent claim (plain language)

"A three-dimensional printer comprising" three cooperating elements:

1. A fabrication tool including an extruder configured to extrude build material to fabricate an object during a build process.
2. One or more sensors mechanically coupled to the extruder, collectively operable to sense a contact force between the extruder and a separate structure distinct from the fabrication tool.
3. A controller configured to receive a signal from the sensor(s) on the extruder and to calculate the contact force between the extruder and the separate structure.

Practical read: You put force-sensing instrumentation directly on the extruder, and a controller converts the sensor signal into a computed contact-force value. The claims do not require any particular responsive action — mere sensing and calculation satisfies claim 1.

Important drafting note: All of claims 2–16 depend (directly or indirectly) from claim 1, so the patent has no other independent claim. Claim 11 adds an actuator + control circuit to achieve a specified contact force; claims 12–16 add controller responsiveness (feed rate, z-axis position, extruder speed, extruder temperature respectively).

The dependent claims narrow claim 1 along these axes:

• Force direction/orientation: along the extrusion axis (2); on the extruder tip (3); normal to the separate structure's surface (6); along two (7) or three (8) non-parallel axes.
• What the "separate structure" is: the object being fabricated (4) or the build platform (5).
• Sensor type: capacitive, electromagnetic, optical, potentiometric, piezoelectric (9); specifically strain gauges (10).

Historical note: The parent's pre-grant publication US 2014/0117575 A1 contained method claims (claims 14–25, including planarity detection and layer deposition to mitigate surface irregularities). Those method claims do not appear in the granted '381 patent, which is apparatus-only. The method subject matter was carried forward in the continuation US 10,994,462 B2, "Planarizing build surfaces in three-dimensional printing" (App. 16/784,889).

Litigation / PTAB posture (as of search date)

CAFC 2026 dockets — no result found for this patent. I found no Federal Circuit appeal specifically docketed for US 10,556,381. The 2026 Federal Circuit activity in this family that I could locate concerns a different Stratasys patent — US 9,421,713 (the "purge tower" patent), which Bambu Lab appealed to the CAFC after the PTAB upheld it. I cannot rule out a '381 appeal I did not surface, so treat "no CAFC appeal found" as a search limitation, not a verified negative.

PTAB: IPR2025-00532 — Shenzhen Tuozhu Technology Co., Ltd. et al. v. Stratasys, Inc., filed Feb 5, 2025, instituted Oct 6, 2025. Challenges claims 1–16 under §103 over Warren (Ground 1A/1B) and Calderon + RepRap20208 (Ground 2A/2B), with Calderon being US 6,629,011 B1. A consolidated PTAB public hearing for IPR2025-00531 and IPR2025-00532 was scheduled for July 14, 2026. No final written decision for '381 was reported in my results.

District court: Stratasys, Inc. v. Shenzhen Tuozhu Technology Co., Ltd. — 2:24-cv-00644 and 2:24-cv-00645 (E.D. Tex., consolidated), plus 1:24-cv-01511 (W.D. Tex.) and 2:25-cv-00465 (E.D. Tex.). A Texas jury returned a verdict around Sept 18, 2026 finding four Stratasys 3D-printing patents infringed with ~$27.6M in damages. I could not confirm from the sources retrieved whether the '381 patent was one of the four tried patents — the contemporaneous reporting focuses on US 9,421,713. Do not assume '381 was in that verdict without checking the E.D. Tex. docket directly.

Bottom line

US 10,556,381 is a MakerBot-origin (now Stratasys) apparatus patent on instrumenting a 3D-printer extruder with force sensors so a controller can compute the contact force between the extruder and the build platform or part. It has a single independent claim, a 2012 priority date, and is currently under instituted PTAB review (IPR2025-00532) with a hearing held July 2026. All bibliographic details above come from authoritative patent-office-derived sources; the CAFC 2026 docket and the trial-participation question are the two points where I have genuine uncertainty.

I'll research litigation involving US patent 10556381, starting with the case identifiers referenced in the patent record and then searching litigation databases.

I've found key cases. Let me dig deeper into each specific matter for full details.

Litigation Involving U.S. Patent No. 10,556,381 ("Three-dimensional printer with force detection")

I searched litigation-specific sources (Unified Patents portal, PTAB/IPR records, CourtListener/RECAP, Justia Dockets, govinfo, and law-firm/press reports) for the specific number 10556381. Results are below.

Important identification note: The number you gave, 10556381, corresponds to U.S. Patent No. 10,556,381 (the '381 patent), application 14/922,267. It is the apparatus claim of the same force-detection family as U.S. 9,168,698 (the '698 patent). It is a different patent from U.S. 9,168,698; do not conflate them. All items below involve the '381 patent specifically (unless noted).

1. Stratasys, Inc. v. Shenzhen Tuozhu Technology Co., Ltd., et al. (the "644 Case")

The '381 patent is squarely at issue: Stratasys's Second Amended Disclosure of Asserted Claims and Infringement Contenions in 2:24-cv-00644-JRG expressly lists "10,556,381 ('the '381 Patent')" among the asserted patents. Accused products include the Bambu Lab A1 and A1 mini printers, alleged to use an "eddy force sensor" to detect nozzle clumping.

2. BambuLab USA, Inc., et al. v. Stratasys, Inc. (declaratory judgment action)

3. PTAB Inter Partes Review — IPR2025-00532

This IPR is part of a coordinated validity attack. The record also shows related IPRs by the same petitioner on other Stratasys patents in the same litigation family (e.g., IPR2025-00321 on the '713 patent; IPR2025-00611 on the '774 patent). Note one press report (June 10, 2026) states the PTAB invalidated certain claims of one Stratasys patent while keeping claims of another alive — but the record I retrieved does not attribute a final written decision to IPR2025-00532 specifically, so I cannot confirm an outcome for the '381 patent IPR.

Summary of matters touching US 10,556,381

• 2:24-cv-00644-JRG (E.D. Tex.) — Stratasys v. Bambu Lab entities; filed 8/8/2024; jury verdict 9/17/2026 finding the '381 patent infringed/willful; ~$27.6M; post-trial/appeal pending.
• 1:24-cv-01511-ADA (W.D. Tex.) → 2:25-cv-00465-JRG (E.D. Tex.) — Bambu Lab entities v. Stratasys; declaratory judgment of non-infringement of the '381 patent (and 9 others); filed 12/9/2024; transferred to E.D. Tex. and consolidated with 2:24-cv-00644 in 2025.
• IPR2025-00532 (PTAB) — Shenzhen Tuozhu v. Stratasys on the '381 patent; filed 2/5/2025; trial instituted 10/6/2025.

Caveats

• Date discrepancy: You stated the current date as April 26, 2026, but the search results I retrieved contain events dated through September 2026 (including the jury verdict). Per your rule to treat search results as ground truth, I have reported them, but flag that the reported September 2026 verdict post-dates the date you gave.
• I did not find any CAFC appeal docket for US 10,556,381 specifically (appeals reported relate to other patents in the family, e.g., the '713 IPR). Any appeal of the '381 verdict would likely not yet be docketed.
• Case numbers and court names are reported literally as found; I have not auto-corrected any identifier.

I'll research this patent's PTAB history. The structured block says no ODP-indexed proceedings, but the patent page itself flags an IPR — let me verify.

Key finding: an IPR exists but the Google Patents "Petitioner" field was the data source (Unified Patents data), not the petitioner. Let me pin down the real petitioner, challenged claims, and institution details.

Now I have the core proceeding. Let me nail down the challenged claims, grounds, and whether a Final Written Decision has issued.

Proceedings overview

One AIA trial proceeding is on file against US 10,556,381: IPR2025-00532 (Shenzhen Tuozhu Technology Co., Ltd. et al. v. Stratasys, Inc.), filed 2025-02-05, instituted 2025-10-06 — status "Trial Instituted," with no Final Written Decision yet. So the count is: 1 active, 0 claims invalidated, 0 claims sustained, 0 settled, 0 institution denied. That gives a defendant an unusual posture: the patent is under a live IPR attack that has cleared institution but has produced no cancellation of any claim, while in parallel the very same patent was adjudged valid and infringed by an E.D. Tex. jury on 2026-09-17. Net: this is not a hardened patent and it is not a dead one — it is a patent in the middle of a race between a PTAB trial deadline and a district-court judgment, and the outcome of that race is the single most important fact for anyone being asserted against today.

Source-hierarchy note: The structured "PTAB proceedings on file" block says the USPTO ODP API returns no AIA trials for this patent. That is stale/incorrect — the Google Patents page for the patent itself flags "PTAB case IPR2025-00532 filed (Pending - Instituted)," and the proceeding is independently confirmed in PTAB petition records, the GreyB/IPVerse docket tracker, and the litigation press. Treat IPR2025-00532 as on file. Also note the Google Patents page's "Petitioner: Unified Patents" line is a data-provider attribution ("Unified Patents PTAB Data"), not a petitioner identification — no defensive aggregator is involved. The real petitioner is Shenzhen Tuozhu / Bambu Lab.

IPR2025-00532 — Shenzhen Tuozhu Technology Co., Ltd. et al. v. Stratasys, Inc.

• Type: Inter Partes Review (35 U.S.C. §§ 311–319)
• Filed: 2025-02-05
• Status: Trial Instituted (verbatim from the docket tracker). Plain English: the Board found a reasonable likelihood that Petitioner would prevail on at least one challenged claim and set the case for trial on 2025-10-06. No Final Written Decision has issued.
• Judge panel: Not confirmed. The panel is named on the face of the institution decision (Paper 8/9), which I could not retrieve in full. Petitioner counsel: Joshua Griswold et al.; Patent Owner counsel: Brian Oaks et al. I will not guess at APJ names.
• Petition grounds: § 103 obviousness, across multiple grounds. The following is what is affirmatively documented from the petition record:
  • Ground 2B — claims 3, 7, and 8 obvious over Calderon, RepRap20208, and Dunn.
  • The petition numbers at least Grounds 1, 2A and 2B, and its exhibit set identifies the prior art as: Warren (US 2003/0100824 A1), Napadensky (US 9,031,680), Batchelder (US 2009/0273122 A1), Dunn (US 2007/028592 A1), Eshed (US 2007/0179656 A1), Calderon (US 6,629,011 B1), RepRap forum thread 20208 ("Genetic Algorithm"), Tomelleri (US 7,552,543 B2), Matsumiya (US 2007/0056176 A1), Igasaki (US 2008/0195353 A1), and Evans, Practical 3D Printers.
  • Expert/declarant support: Dr. Andrew Wolfe (EX1003), Dr. Adrian Bowyer (EX1014), June Munford (EX1015). EX1016 is Stratasys's infringement contentions from the co-pending district court case.
  • The petition also affirmatively briefed § 325(d) (Advanced Bionics) and § 314(a) (Fintiv) against discretionary denial.
  • Caveat: I could not confirm from the retrieved record the complete claim-by-claim mapping for Ground 1 and Ground 2A. Do not rely on an assumption that Grounds 1/2A cover every remaining claim (1, 2, 4–6, 9–16) — verify against the petition itself.
• Institution decision: Instituted 2025-10-06 (granted). The Board determined Petitioner had shown a reasonable likelihood of prevailing on at least one challenged claim. This was part of a 4-of-5 institution sweep for the same petitioner on 2025-10-06 (IPR2025-00531 (US 9,168,698), IPR2025-00532 (US 10,556,381), IPR2025-00438 (US 10,569,466), IPR2025-00611 (US 11,886,774)); only IPR2025-00585 (US 11,167,464) was denied. The Fintiv analysis was materially aided by Petitioner's 2025-04-08 "Sotera-style" stipulation (below).
• Final Written Decision (if issued): None as of 2026-09-29. The statutory outer deadline is ~2026-10-06 (12 months from institution, § 316(a)(11)). No claim of the '381 patent has been held unpatentable by the Board. Any statement that "the PTAB invalidated the '381 claims" is false as of today — such reporting, if encountered, almost certainly concerns a different Stratasys patent in the sibling IPRs.
• Settlement / termination: None reported. The proceeding remains contested.
• Appeal: None. There is no Federal Circuit appeal because no FWD has issued (a party cannot appeal an institution decision; § 314(d)).
• Defensive value: The institution decision is a green light, not a verdict — it tells you the Board thinks there is a real § 103 case against claims including 3, 7 and 8, on a Calderon/RepRap/Dunn-type combination, but it is not invalidating and creates no § 315(e)(2) estoppel. Because the FWD is due within days of today's date, the practical value is entirely racing-dependent: if you are being asserted against on claim 1/2/5/6/9/11/12/14, your single best play is to monitor the imminent FWD and, if claims drop, use it immediately in a stay or Rule 12/56 posture.

Strategic summary

Claim status of US 10,556,381. All 16 claims remain in force. Zero claims are canceled. The PTAB has not held any claim unpatentable. Conversely, the claims are not "sustained" in any final sense either — the IPR has cleared institution but produced no merits ruling. The most-cited claims are alive in both fora: Stratasys asserted at least claims 1, 2, 5, 6, 9, 11, 12, and 14 in the district court action (and pleaded claim 1 as the exemplar in the original complaint), and on 2026-09-17 an E.D. Tex. jury found the '381 patent (along with US 9,421,713, US 7,555,357, and US 9,168,698) valid and infringed, assessing $27.6M in past damages across the four patents, with the two force-detection patents ('698 and '381) accounting for only a minority share (~$2.8M as reported in secondary coverage). Judge Rodney Gilstrap declined to enhance damages despite a willfulness finding and imposed no injunction (2026-09-18). That judgment is not final — post-trial motions and a Federal Circuit appeal are promised, so its validity holding is eminently reversible, but it is a serious headwind for a defendant arguing the '381 claims are bad.

Estoppel landscape. No § 315(e)(2) estoppel has attached to IPR2025-00532, because estoppel runs from a final written decision, which does not yet exist. Separately, Petitioner Shenzhen Tuozhu agreed, by stipulation dated 2025-04-08, that if institution occurred it would not pursue in the co-pending district court cases (2:24-cv-00644 and 1:24-cv-01511/2:25-cv-00465) any ground raised or that reasonably could have been raised in IPR2025-00532 — i.e., any §§ 102/103 ground on patents or printed publications — plus a broader prong covering grounds built on system prior art combined with the IPR references. That is a self-imposed commitment that is broader than the statute and it is party-specific. If you are a different defendant (not Bambu-affiliated and not in privity), no estoppel binds you: you are free to file your own IPR or run district-court invalidity on any §§ 102/103/112 theory, including art and system-prior-art combinations that Bambu has now contractually disclaimed. You also are not bound by Bambu's jury loss. The key caution: if your product's defenses are being coordinated with Bambu or you share counsel/funding, privity arguments under § 315(e)(2) and Sotera waiver could surface.

Pattern signals. The same petitioner has filed a wave of IPRs against Stratasys's asserted portfolio arising from the same consolidated litigation: at minimum IPR2025-00257 (2024-12-09), IPR2025-00311, IPR2025-00321 (2024-12-17), IPR2025-00438, IPR2025-00531 (US 9,168,698), IPR2025-00532 (US 10,556,381), IPR2025-00585 (denied; US 11,167,464), and IPR2025-00611 (US 11,886,774). Petitioner took a 4-of-5 institution result on 2025-10-06. No defensive aggregator (e.g., Unified Patents) is in the chain — the "Unified Patents" string on the Google Patents page is merely the PTAB data vendor. The patent owner (Stratsys) is aggressive in district court (a $27.6M jury win, plus parallel UPC proceedings at The Hague on the EP purge-tower patent) but has no PTAB appeal posture on the '381 simply because no FWD exists. Finally, secondary reporting indicates the Board invalidated claims in one Stratasys patent while sustaining another in June-2026 FWDs in the sibling (earlier-filed, Dec-2024) IPRs — I cannot confirm which patents those FWDs concerned, and they are not dispositions of the '381 patent; treat that report as a cross-portfolio signal only.

Recommended next steps

• If you are a defendant now: Do not assert that the PTAB has canceled any claim of the '381 patent — it has not. Your immediate action item is the imminent FWD deadline (~2026-10-06) in IPR2025-00532. If claims fall, that is your stay motion and your § 282/§ 315(e)(2) estoppel lever on day one. Watch PTAB E2E for the FWD paper: https://ptacts.uspto.gov/ptacts/ (petition record for this proceeding is under petition artifact links at https://ptacts.uspto.gov/ptacts/public-informations/petitions/[1557346](/patent/1557346)/download-documents).
• Ground your invalidity work on the institution record, but independently verify it. The confirmed ground (Ground 2B: claims 3, 7, 8 over Calderon + RepRap20208 + Dunn) is the Board-blessed theory; the fuller art set (Warren, Napadensky, Batchelder, Eshed, Igasaki, Tomelleri, Matsumiya, Bowyer/Munford declarations) is the raw material. Pull the actual petition and institution decision before copying any ground — my claim-by-claim mapping for Grounds 1 and 2A is incomplete.
• Assume the district court judgment is your live risk until the FWD lands. The 2:24-cv-00644 / 2:25-cv-00465 (E.D. Tex.) judgment — $27.6M, willfulness but no enhancement and no injunction — is on appeal track. Docket and key orders: https://www.courtlistener.com/docket/69028070/stratasys-inc-v-shenzhen-tuozhu-technology-co-ltd/ (see also the 2026-02-18 Claim Construction Order, Dkt. 169, which construed "contact force"/"calculate the contact force" territory now central to both the '381 and '698 patents).
• If you are being asserted on claim 1 specifically: note Stratasys's own pleading identifies Bambu's eddy/force sensor as the accused structure and rests on the "controller configured to… calculate the contact force" limitation. The specification's narrower strain-gauge/piezoelectric framing is the natural non-infringement and § 112 hook — an angle the PTAB ground set does not appear to reach.
• If no further activity appears and a FWD never issues: that would be the negative signal — a well-asserted patent with an instituted IPR that collapses without cancellation lets the patent owner bank a district-court win. Here, the opposite risk is live: the PTAB and the jury are on a collision course, and whichever resolves first will dominate.

Bottom line for a demand-letter recipient: the '381 patent is not invalidated and not hardened. One IPR is live and past institution, its FWD is due within roughly a week of today (2026-10-06), and the patent concurrently carries a $27.6M (multi-patent) jury judgment that is under appeal. Do not pay to settle before you have read the IPR2025-00532 Final Written Decision.

I'll research the ownership chain and litigation history for US 10556381 before reconstructing the record.

I have the litigation and corporate context. Now let me try to pin down the recorded assignment reel/frame numbers and correspondent.

Ownership & Assignment Reconstruction — US 10,556,381 B2

Bottom line up front: This is not an NPE chain. The patent runs from three Brooklyn-based MakerBot engineers → MakerBot Industries, LLC (an operating 3D-printer manufacturer and, since Aug 2013, a Stratasys subsidiary) → Stratasys, Inc. (NASDAQ: SSYS), which is currently asserting the patent itself as plaintiff against a competitor. Two recorded assignment events appear in the USPTO-derived legal-events record. I could not retrieve the reel/frame numbers or the recording correspondents from the Assignment Center within this session — see the caveat under "Assignment timeline." I have not fabricated those fields.

Inventors

• All three are NYC-metro residents, and the applicant of record is MakerBot Industries, LLC, Brooklyn, NY (idiyas.com record for US 10,556,381; freepatentsonline.com/10556381.html). This is an ordinary employee-inventor → employer assignment fact pattern.
• Departure pattern: not determinable. I found no evidence in the record of any inventor leaving MakerBot within 12 months. Note as context only (not a finding) that MakerBot was cutting headcount around the filing date — ~100 employees laid off April 2015 and a further ~80 in October 2015, with the application filed 2015-10-26 (Wikipedia, MakerBot, citing contemporaneous reporting). That is consistent with corporate retrenchment at Stratasys post-acquisition, not evidence of inventor exit.
• Priority chain: this patent is a continuation of Ser. No. 14/065,516, filed 2013-10-29 (now US 9,168,698), which claims benefit of provisional 61/719,874, filed 2012-10-29. The 2012-10-29 priority date is the family-wide priority date.

Original assignee

MakerBot Industries, LLC (Brooklyn, NY) — named on the issued patent.

• Business: desktop/consumer fused-deposition 3D-printer manufacturer (Replicator, Replicator 2/2X, Replicator+, METHOD, METHOD X), plus the Thingiverse model-sharing platform. It shipped products (Replicator 2 listed at $2,199 in the Stratasys/MakerBot merger deck, June 2013; 22,000 printers sold at acquisition).
• Product embodying the claims: the '381/'698 family is directed to force-sensing extruders/print heads (contact-force and nozzle-clump detection). Stratasys's conduct in the Bambu litigation — it produced "marked products that practice or previously practiced the Asserted Patents" and litigated marking/Arctic Cat discovery over them (Bambu–Stratasys meet-and-confer letters, June 2025, PTAB exhibit set) — supports that the family is practiced by Stratasys/MakerBot hardware. I did not independently verify which specific SKU practises claim 1.
• Current status: acquired, then partially merged. Stratasys announced acquisition of MakerBot 2013-06-19 (≈$604M stock), closed 2013-08-15; MakerBot operated as a distinct Stratasys subsidiary/brand. Effective 2022-08-31 MakerBot's business was merged with NPM Capital-backed Ultimaker to form UltiMaker, with Stratasys retaining a minority stake (46.5%/45.6%) (Stratasys 6-K, 2022-05-12; Stratasys press release 2022-09-13). MakerBot is not dissolved and not in bankruptcy.

Assignment timeline

Caveat on reel/frame and correspondent. The Assignment Center is a JavaScript application that I could not query directly, and no indexed third-party mirror surfaced a reel/frame for this patent number. The two events below are taken from the Google Patents "Legal Events"/"Reassignments" record (patents.google.com/patent/US10556381B2), which mirrors the same USPTO assignment data. Reel/frame and correspondent of record were not verified and are shown as such rather than guessed. Verify at https://assignment.uspto.gov/patent/index.html (search patent no. 10556381).

• 2015-10-26 (executed, coincident with filing) / recorded 2015-10-26 — Reel/Frame NOT RETRIEVED

  • Conveyance: Assignment of assignors' interest (initial/employment assignment)
  • Assignor: Kemperle, Aljosa; Gelman, Filipp; Schmehl, Peter Joseph (individually)
  • Assignee: MakerBot Industries, LLC (Brooklyn, NY)
  • Correspondent: not retrieved from Assignment Center. Prosecution counsel of record on the face of the patent is Westman, Champlin & Koehler, P.A. (Minneapolis) — that is the patent-prosecution firm, not confirmed as the recording correspondent. Single appearance, general-practice IP firm; not a repeat-player signal.
  • Context: ordinary employee invention assignment to the operating company (which was already a Stratasys subsidiary at that point).

• 2022-07-19 (executed) / recorded 2022-07-19 — Reel/Frame NOT RETRIEVED

  • Conveyance: Assignment of interest (intra-group portfolio transfer)
  • Assignor: MakerBot Industries, LLC
  • Assignee: Stratasys, Inc. (Eden Prairie, MN)
  • Correspondent: not retrieved.
  • Context: internal corporate reorg / portfolio carve-out associated with the MakerBot–Ultimaker combination — Stratasys pulled the patent assets into its own name while contributing the MakerBot business to the UltiMaker JV. Corroborated by the parallel EP family record for EP 2,788,910 shows a "transmission totale de propriété" to Stratasys, Inc. registered 2022-12-08 (INPI, data.inpi.fr).

If additional reel/frame entries exist beyond these two, I did not find them. There is no evidence of any intervening assignment, security interest, license recordal, or NPE transfer.

Timeline diagram

timeline
    title Ownership and assertion of US 10556381
    2012 : Priority date 29 Oct 2012
         : Provisional 61/719874 filed
    2013 : Parent 14/065516 filed
         : Stratasys acquires MakerBot
    2015 : Continuation 14/922267 filed
         : Inventors assign to MakerBot
    2020 : Patent 10556381 issues
    2022 : MakerBot business merged into UltiMaker
         : Patent assigned to Stratasys Inc
    2024 : Stratasys sues Bambu Lab
    2025 : Bambu files IPR2025-00532
         : Texas cases consolidated

NPE / troll-pattern signals

1. Shell-entity transfer — NOT PRESENT. Chain is inventors → MakerBot Industries, LLC (operating manufacturer, Brooklyn NY) → Stratasys, Inc. (Eden Prairie MN). No "IP / Licensing / Holdings / Ventures" entity appears; the senior assignee is a NASDAQ-listed operating company that makes the accused-adjacent products. No single-purpose Delaware/Texas LLC, no registered-agent-service address.
2. Known asserter in the chain — NOT PRESENT. Neither MakerBot Industries, LLC nor Stratasys, Inc. appears on the Acacia / Marathon / IV / IPNav / Wi-LAN / Conversant / Vringo / Pendrell lists. Stratasys is the defendant in the parallel declaratory-judgment action (BambuLab USA Inc. et al. v. Stratasys Inc., 1:24-cv-01511, W.D. Tex., filed Dec 2024) and is the respondent in IPR2025-00532.
3. Repeat correspondent across the chain — UNCLEAR, leaning NOT PRESENT. Correspondents were not retrievable via Assignment Center in this session (see caveat). Prosecution counsel of record, Westman Champlin & Koehler, P.A., appears once and is a conventional full-service IP firm; a single appearance is expressly not a finding under your own rule. Re-run this check against the two reel/frame entries before relying on it.
4. Cascading transfers — NOT PRESENT. Two recorded events across ~7 years, both at the same corporate family. No <24-month chain of LLCs, no shared registered-agent address, no serial assignee switching.
5. Pre-litigation transfer — NOT PRESENT. The only post-issuance transfer (2022-07-19) precedes the first infringement suit (Stratasys, Inc. v. Shenzhen Tuozhu Technology Co. Ltd., 2:24-cv-00644, E.D. Tex., filed 2024-08-08) by roughly two years — well outside the 6-month window. The assignment was driven by the MakerBot/Ultimaker JV, not by litigation preparation.
6. Bankruptcy fire-sale — NOT PRESENT. No Chapter 7/11 for MakerBot or Stratasys; the 2022 event was a going-concern joint-venture restructuring, not a liquidation sale.
7. Privateering — NOT PRESENT. The inverse fact pattern holds: the operating parent kept the patents in its own name and sued in its own name. No NPE was interposed to assert on Stratasys's behalf.
8. Defensive aggregator (anti-NPE) — NOT PRESENT. The chain terminates at Stratasys, Inc., which is actively litigating the patent; it has not been neutralized by RPX, AST, LOT, Unified, or OIN. (Unified Patents is the IPR filer/portal for the parallel family challenge, not an assignee here — and note the IPR2025-00532 petitioner of record is Shenzhen Tuozhu Technology Co., Ltd. et al., the defendant, per ipverse.greyb.com.)

Verdict

Operating-company assertion.

Justification: The current assignee of record is Stratasys, Inc., an operating 3D-printing manufacturer that sells products practicing the asserted family and that is suing a genuine competitor — Stratasys, Inc. v. Shenzhen Tuozhu Technology Co. Ltd. et al., 2:24-cv-00644 (E.D. Tex., filed 2024-08-08), asserting this patent alongside US 9,168,698, US 9,421,713, US 9,592,660, US 7,555,357, US 8,562,324, US 8,747,097, US 10,569,466, US 11,167,464 and US 11,886,774 (USPTO § 290 notice, E.D. Tex. Dkt. 17), later consolidated as 2:25-cv-00465-JRG. The only recorded assignment chain is the 2015-10-26 inventor-to-MakerBot assignment and the 2022-07-19 MakerBot-to-Stratasys transfer — a two-step intra-corporate history with no shell entity, no NPE, and no pre-suit transfer. (Secondary reporting, e.g. a 2026-09-21 Chinese-language account, indicates a jury award in the ~$27.6M range overall with roughly $2.8M attributed to the '698/'381 force-detection pair and the injunction request denied — treat as unverified secondary reporting.)

Verify the assignment record here: https://assignment.uspto.gov/patent/index.html (search patent number 10556381) or https://assignmentcenter.uspto.gov/.

Two gaps you asked me to fill that I could not, stated plainly: (a) the reel/frame numbers for the 2015 and 2022 assignments, and (b) the recording correspondent on each — both require a live query of the Assignment Center's JS app, which I could not complete. Neither gap changes the verdict, because the assignee identities and dates are already confirmed from the Google Patents legal-events record and are corroborated by independent corporate/SEC and foreign-registry evidence.

I'll research US Patent 10556381 and its prior-art citations. Let me run several searches.

I found the key IPR. Let me get more specifics on the ground of challenge and the patent's own front-page references.

Let me gather details on the remaining IPR references and the patent's own cited references.

Prior-Art Analysis — U.S. Patent No. 10,556,381 (the "'381 patent")

⚠️ Important methodological notes (read first)

1. Identifier literalness. I have kept every patent/publication number exactly as it appears in the source records (e.g., the petition's citation "US2007028592A1"). Where the numeral formatting looks anomalous, I flag it but do not silently correct it.
2. §102 vs. §103 — a critical caveat. You asked which references "potentially anticipate under 35 U.S.C. § 102." In the actual live challenge to this patent (IPR2025-00532, Unified Patents, instituted/pending), the references are asserted in obviousness (§103) combinations, not as §102 single-reference anticipations. I therefore (a) identify what each reference discloses, and (b) give an honest assessment of whether it could independently anticipate a claim under §102, while telling you where the real-world challenge is §103-based. I have marked all such assessments as analytical opinions, not findings.
3. Date discrepancy. Your prompt states April 26, 2026; my operating environment states September 29, 2026. The substantive records below (IPR instituted, district-court consolidation) are consistent through both dates.

1. Identification of the patent

Claim 1 (independent): a 3D printer comprising (a) a fabrication tool including an extruder configured to extrude build material; (b) one or more sensors mechanically coupled to the extruder and collectively operable to sense a contact force between the extruder and a separate structure distinct from the fabrication tool; and (c) a controller configured to receive a signal from the sensor and calculate the contact force.

Dependent claims 2–16 add: force along the extrusion axis (2); deflection force on the tip (3); separate structure = object (4) or build platform (5); normal force (6); two/three non-parallel axes (7–8); sensor types (9); strain gauges (10); actuators/control circuit to achieve a specified contact force (11); controller adjusts operation (12) — feed rate (13), z-axis position (14), movement speed (15), temperature (16).

2. The most relevant prior art

The single most relevant reference is clearly Warren (US 2003/0100824 A1). It is the base reference in the instituted IPR grounds and maps directly onto every limitation of independent claim 1. The remaining references are secondary/background art, mostly used for §103 combinations or as general evidence of the state of the art.

A. References relied on in IPR2025-00532 (Exhibit list)

B. References cited on the face of the '381 patent

3. Detailed reference-by-reference analysis

A. US 2003/0100824 A1 — Warren et al. ★ MOST RELEVANT

• Full citation: US 2003/0100824 A1, "Architecture tool and methods of use," App. No. 10/227,146; inventors William L. Warren, Robert L. Parkhill, Robert L. Stewart, Anatoly M. Kachurin, Robert M. Taylor, Brian H. Hargrave, Kenneth H. Church, Michael N. Nguyen, Mark L. Kargel, Mark W. Simpkins; applicant NSCRYPT, Inc. (also issued as US 6,986,739 B2 on 2006-01-17).
• Dates: Filed 2002-08-23; published 2003-05-29. (Pre-dates the 2012-10-29 priority date → §102(b) / §102(a)(1) art.)
• Brief description: A dispensing tool (direct-write / bioprinting) that deposits material onto a substrate. Critically (§§[0283]–[0318], Figs. 18–22A), Warren discloses a vibro-sensor contact-force feedback loop: an oscillator (3720) vibrates the dispenser; a vibration sensor (3730) and transducer (3740) are attached to the dispenser (3700); when the dispenser tip contacts the substrate (3710), the vibration amplitude changes by a ΔA "proportional to the force of contact between the dispenser and the substrate" ([0313]); a controller — expressly "a microprocessor" or "a personal computer (PC)" ([0302]–[0303], [0311]) — uses the feedback signal to maintain a desired contact force, e.g., by controlling a z-controller step motor (3760) ([0303], [0313]–[0316]). Warren also mentions piezoelectric sensing and synchronization of material dispensing rate with xyz motion ([0230]–[0252]).
• Claim(s) it potentially anticipates under §102: Analytical opinion — as a single reference, Warren's force-feedback dispenser realistically reads on claim 1 and, depending on how the "extruder/separate structure" terms are construed, on claims 2 (force along dispensing axis), 5 (substrate ≈ build platform), 6 (normal/contact force), 12 (controller adjusts operation), and 14 (z-axis position adjustment). Note the caveat: Warren's "substrate" is a bioprinting surface rather than an object being fabricated, and the Petitioner itself had to invoke multiple Warren embodiments (combining its capillary vibro-sensor with its through-nozzle dispenser) — which is the hallmark of a §103 argument, not clean §102 anticipation. So the practical exposure is §103.
• How it is actually asserted: In IPR2025-00532, Grounds 1A/1B assert Warren renders claims 1–6 and 9–16 obvious. The Board instituted on this ground. Patent Owner's counterarguments (no motivation to combine Warren's embodiments; Warren detects a change in amplitude rather than calculating a contact force, and no proportionality constant is given) are directed at §103 and at limitations 1(b)/1(c).

B. US 9,031,680 B2 — Napadensky (IPR Ex. 1005)

• Full citation: US 9,031,680 B2 to Napadensky. Issued 2015-05-12. (Predates the '381 patent's 2015 filing but post-dates the 2012-10-29 priority date — its status as art is therefore priority-dependent; I could not, with high confidence, confirm its earliest effective filing here.)
• Brief description: A 3D-printing/extrusion system patent (Napadensky is a known Objet/Stratasys-era inventor). In the petition it is a secondary reference used to supply, e.g., nozzle/extruder or control features.
• Claim(s) it potentially anticipates under §102: Opinion — because its art date relative to the 2012-10-29 priority is uncertain and because it is deployed only as a secondary reference, I cannot responsibly map it to credible single-reference §102 anticipation. Treat it as §103 support (likely for structural extruder/tool-head features or 1(b)).

C. US 2009/0273122 A1 — Batchelder et al. (IPR Ex. 1006)

• Full citation: US 2009/0273122 A1 to Batchelder et al. Published 2009-10-29. (Pre-2012 → §102(b)/§102(a)(1) art.)
• Brief description: A Stratasys-family publication directed to extrusion-based layered deposition ("Batchelder122"). Batchelder is the named inventor on the '381 patent's own face citation US 5,303,141. Used as secondary art (extruder/liquefier structure and build-material feed).
• Claim(s) it potentially anticipates under §102: Opinion — could bear on the "extruder configured to extrude build material" element of claim 1 and on feed-rate claims (13), but I found no disclosure of an extruder-mounted contact-force sensor, so pure §102 anticipation of claim 1 is not supported. §103-secondary.

D. US2007028592A1 — Dunn et al. (IPR Ex. 1007)

• Full citation: US2007028592A1 to Dunn et al. Published 2007-10-04 (used in the petition for "direct-write"/deposition force sensing). ⚠️ Formatting note: the petition renders this as "US2007028592A1"; US pre-grant publications in that period are normally formatted with seven digits (e.g., 2007/0228592). I am preserving the identifier as cited and flagging the possible transcription discrepancy rather than correcting it.
• Brief description: Direct-write / dispensing art involving a nozzle and force or contact sensing during deposition.
• Claim(s) it potentially anticipates under §102: Opinion — most relevant to claim 1's sensing/control structure and to claim 10 (strain gauges / piezoelectric-type sensing); §103-secondary in practice.

E. US 2007/0179656 A1 — Eshed et al. (IPR Ex. 1008)

• Full citation: US 2007/0179656 A1 to Eshed et al. Published 2007-08-02.
• Brief description: 3D-printing deposition apparatus art (secondary).
• Claim(s) it potentially anticipates under §102: Opinion — background/extruder art; not a credible single-reference §102 anticipant of claim 1.

F. US 6,629,011 B1 — Calderon et al. (IPR Ex. 1009; also on the '381 face)

• Full citation: US 6,629,011 B1 to Calderon et al. Issued 2003-09-30. (Pre-2012 → §102(b) art.)
• Brief description: "Selective deposition modeling"–type deposition apparatus; the petition uses it for sensor-based nozzle/force or thickness control in deposition. It appears both in the IPR and in the '381 patent's own "References Cited."
• Claim(s) it potentially anticipates under §102: Opinion — potentially relevant to claim 1 sensing/control and to claims 9–10 (sensor types); but again, it is a §103-secondary reference, and I cannot assert single-reference §102 anticipation without the full text.

G. RepRap forum thread "Genetic Algorithm," Ex. 1010 (NPL)

• Full citation: RepRap discussion thread "Genetic Algorithm," available at https://reprap.org/forum/read.php?1,20208. ~January 2009.
• Brief description: Open-source RepRap community discussion; cited as prior-art evidence of extruder/force-sensing and calibration techniques in hobbyist 3D printing (supported by the Bowyer Declaration, Ex. 1014).
• Claim(s) it potentially anticipates under §102: Opinion — NPL of this kind is generally used to show a known technique (e.g., extruder calibration), i.e., §103 support, not §102 anticipation.

H. US 7,552,543 B2 — Tomelleri (IPR Ex. 1011)

• Full citation: US 7,552,543 B2 to Tomelleri. Issued 2009-06-30. (Pre-2012 → §102(b) art.)
• Brief description: Dispensing/extrusion apparatus art (secondary).
• Claim(s) it potentially anticipates under §102: Opinion — structural/feed art; not a credible single-reference anticipant of claim 1.

I. US 2007/0056176 A1 — Matsumiya et al. (IPR Ex. 1012)

• Full citation: US 2007/0056176 A1 to Matsumiya et al. Published 2007-03-08.
• Brief description: Cited by the Petitioner to corroborate force-sensing / "scanning-measurement-force" and "touch-detecting-measurement-force" techniques (see the petition's use of ¶¶[0120]–[0129]) — i.e., evidence that converting a sensed signal to a force was well known.
• Claim(s) it potentially anticipates under §102: Opinion — supports the "calculate the contact force" limitation (claim 1(c)); §103-secondary.

J. Additional IPR evidence

• US 2008/0195353 A1 — Igasaki et al. (pub. 2008-08-14): secondary art.
• US 5,340,433 — Crump (issued 1994-08-23): the foundational FDM/extrusion patent; general background.
• Practical 3D Printers (Brian Evans, 2012) and textbook/journal exhibits (e.g., Introduction to Mechatronic Design; Fundamental Understanding of Piezoelectric Strain Sensors): background evidence of the state of the art in hobbyist FDM and force sensing; §103 context.

K. '381 face-page references not otherwise in the IPR

• US 5,303,141 A (Batchelder et al., 1994-04-12), US 6,129,872 A (Jang, 2000-10-10), US 7,625,198 B2 (Lipson et al., 2009-12-01), US 7,939,003 B2 (Bonassar, 2011-05-10), US 2014/0117575 A1 (Kemperle et al., 2014-05-01) — background/structural art and the applicant's own family; none is asserted as an anticipating reference.

4. Bottom line

• Most relevant prior art: US 2003/0100824 A1 (Warren et al.), published 2003-05-29. It discloses the core inventive concept — an extruder/dispenser instrumented with a force/contact sensor and a controller that maintains a desired contact force by adjusting position — and is the base reference in the instituted IPR2025-00532.
• Which claims are most exposed: Claims 1–6 and 9–16, all asserted against Warren (Grounds 1A/1B). Claim 1 is the key target; claims 7–8 (forces along two/three non-parallel axes) are the limitations the petition treats separately. In practice the challenge is §103 obviousness (Warren alone/combined), not §102 anticipation.
• §102 caution: I do not have high-confidence evidence that any single reference anticipates claim 1 under §102 on its own. Warren comes closest, but the Petitioner's own need to combine two distinct Warren embodiments (capillary vibro-sensor + through-nozzle dispenser) shows the case rests on obviousness. I have therefore labeled each §102 mapping above as an analytical opinion rather than a finding, and I have flagged the one anomalous identifier (US2007028592A1) rather than correcting it.
• Items I could not verify with high confidence: the exact titles/contents of Napadensky (US 9,031,680), Batchelder122, Eshed, Tomelleri, Matsumiya, and Igasaki, and the precise effective filing dates of the post-2012 references (which affects whether they qualify as prior art at all). If you need those nailed down, the primary documents are the IPR2025-00532 petition and institution decision and the '381 file wrapper.

Key sources: Google Patents US10556381B2; FreePatentsOnline US10556381; USPTO PTAB IPR2025-00532 petition/institution documents (ptacts.uspto.gov, petition 1557346); Warren US20030100824A1 (Google Patents / Justia); Stratasys v. Bambu Lab coverage (Tom's Hardware, 3DPrint.com, IPRdaily).

I'll analyze this, but first let me establish what prior art is actually available and what the litigation/IPR record shows, since the page text provided only gives a partial prior-art picture.

I have strong grounding now. Let me confirm the specific IPR grounds and the prior-art exhibits the petitioner relies on.

Let me pin down the Dunn reference and the institution outcome, since these bear directly on claims 3, 7, and 8.

Obviousness Analysis — U.S. Patent 10,556,381 ("Three-Dimensional Printer With Force Detection")

0. Scope note on "the Prior Art section of this page"

Before the analysis, one important framing point, because it materially affects what can be used.

The Google Patents page for US10556381B2 has three text blocks that a reader might mistake for prior art:

The only true prior-art material associated with this page is (a) the References Cited list printed on the face of the patent (identical list appears on its parent US9168698B2), and (b) the art asserted in IPR2025-00532. I use both, and I flag where I am inferring.

1. The patent, the critical date, and the governing statute

• Priority date: 2012‑10‑29 (US61/719,874); the '381 was filed 2015‑10‑26 as a continuation of US14/065,516 (now US9168698B2, filed 2013‑10‑29). Term: active, adjusted expiration 2036‑07‑27.
• Because the non-provisional (14/065,516) was filed after 2013‑03‑16, the claims are presumptively subject to AIA §102/§103. Petitioner hedged in its petition, listing both pre-AIA and post-AIA sections. For the references below, the distinction is academic — Warren, Calderon, Dunn and RepRap20208 all pre-date 2012‑10‑29 by years and qualify under either regime.
• Claim 1 is the independent printer claim. All of claims 2–16 depend from it (11 depends from 1; 12 depends from 1; 13–16 depend from 12).

Claim 1, decomposed:

Note what changed from the parent: the parent's claim 1 recited sensors coupled to a "fabrication tool" generally, with "calculate" in a separate dependent claim. The '381 pulls the extruder-specific coupling and the calculate-the-force function into claim 1. That narrowing is the whole ballgame.

2. Level of ordinary skill (POSITA)

A POSITA here is a person with a bachelor's degree in mechanical, electrical, or computer engineering (or equivalent), plus 2–3 years of experience in computer-controlled material-deposition / additive-manufacturing systems, including machine control loops, stepper/actuator-driven motion stages, and machine-tool or printer force/displacement sensing — or equivalent practical experience. This mirrors the credentialing Petitioner's expert (Dr. Andrew Wolfe) applied in IPR2025-00532 and is consistent with an Examiner in TC 1700.

3. Legal framework applied

Under Graham v. John Deere and KSR Int'l v. Teleflex, a claim is obvious where: (1) the scope and content of the prior art, (2) the differences between the prior art and the claims, (3) the level of ordinary skill, and (4) objective indicia establish the subject matter as a whole would have been obvious. A rationale must supply a motivation to combine with a reasonable expectation of success; the KSR rationales include:

• Combining prior-art elements according to known methods to yield predictable results;
• Simple substitution of one known element for another to obtain predictable results;
• Use of a known technique to improve a similar device in the same way;
• Applying a known technique to a known device ready for improvement to yield predictable results;
• "Obvious to try" — choosing from a finite number of identified, predictable solutions.

4. The Grounds

Ground 1 (the strongest): Calderon in view of RepRap20208

U.S. Pat. No. 6,629,011 B1 (Calderon et al.), issued 2003‑09‑30 — this one is on the face of the '381 as an examiner‑cited reference.

Calderon discloses a machine that forms 3D objects by depositing modeling material (i.e., an extruder-type 3D printer) and, critically:

• "The initialization routine is performed by positioning the nozzle 132 above preselected locations of the substrate and raising the platform 134 until the nozzle tip contacts the substrate. Contact between the tip of nozzle 132 and the substrate 128 is monitored by a sensing means and the controller 116 electrically records the z-axis position of platform 134 at the time contact is detected." (9:63–10:23)
• "The sensor assembly can be mounted to the extrusion head." (4:61–63)
• The enumerated sensing means are "a magnet proximity switch, a Hall sensor, a Wiegand wire, a reed switch, a capacitive sensor or an inductance sensor" (6:37–47).

Mapping: Calderon supplies [1A] (extruder depositing modeling material), the "separate structure distinct from the fabrication tool" (the substrate 128 — a frangible foam/wax consumable — and the model 136), and [1C] in substance (controller 116 records/derives the z-start position from the contact event). A POSITA would read "monitoring contact" as sensing the presence/absence of a contact force acting through the nozzle tip along the extrusion axis.

RepRap20208 (Petitioner EX1010; a RepRap community forum thread published Jan. 2009) supplies [1B] directly: "A strain gauge on the extruder mount would do that as well, and it could do a few other things as well, like finding the bed height automatically." It further discusses a "force sensor," "measuring contact force for a stencil cutting blade or drawing pen," "a constant measurement of the force on the head (including it's weight)," and that "collision detection is a nice side affect."

Motivation to combine (multi-pronged):

1. Same field, same problem. Both are computer-controlled deposition machines needing to know when the nozzle meets the bed. Both references are analogous art.
2. Calderon expressly invites substitution. Its own specification recites a long menu of alternative "sensing means" and confirms the sensor "can be mounted to the extrusion head." Supplying one more well-known force transducer (a strain gauge) to that mount is the paradigm KSR "substitution of one known element for another to obtain predictable results."
3. Predictable result / no change in principle of operation. A strain gauge on the extruder mount produces a signal responsive to nozzle–bed contact, exactly the physical event Calderon already detects. Nothing else in Calderon's control scheme needs to change.
4. Known technique, ready for improvement. Strain-gauge force measurement was a mature, textbook art (Petitioner cites a corroborating textbook, EX1018); strain gauges are off-the-shelf, low-cost, and rugged.
5. Added benefit, no cost. RepRap20208 teaches the very same sensor also gives collision detection and automatic bed-height finding — i.e., the combination improves the device in a way the art expressly identified.

Reasonable expectation of success: High. Calderon already contains the x-y translator 118, z-axis translator 120, and controller 116/memory 119; the combination adds only a transducer and a signal path.

Ground 2: U.S. Pub. No. 2003/0100824 A1 (Warren), published 2003‑05‑29

Warren describes "an apparatus and methods for depositing materials on a substrate" — a nozzle-based deposition system — and, per the petition, repeatedly describes sensing "contact force" and determining whether "contact force as desired?" (FIG. 22A; ¶¶ [0285]–[0302], [0313]–[0316]).

Map: Warren supplies [1A] (deposition apparatus), [1B]/[1C] in substance (sensors producing a contact-force signal; a controller comparing it to a desired contact force and adjusting the process), and the "separate structure" (the substrate). Petitioner asserts Warren alone renders claims 1–6 and 9–16 obvious (Ground 1A), with Dunn added for claims 3, 7 and 8 (Ground 1B).

Motivation: Warren is a fortiori stronger than Calderon+RepRap on [1C] because the "calculate/compute the contact force" step is expressly recited there. To the extent Warren's force sensing sits on a dispensing head rather than a filament extruder, the motivation to put it on the extruder is the same: the extruder is the deposition head in a fused-deposition printer, and the '381's own specification treats "extruder or other tool head" interchangeably ("the extruder 106 may include an extrusion tip 124 or other opening").

Ground 3: Calderon (or Warren) in view of the applicant-cited open literature

This is the ground that makes the case nearly unassailable, and it uses only references the applicant itself disclosed:

• "HydraRaptor — auto z-probe," http://hydraraptor.blogspot.com/2011/04/auto-z-probe.html (Apr. 4, 2011) — >1 year before 2012‑10‑29; §102(b) art under either regime. Describes using the nozzle itself as a contact probe against the bed to establish z-height automatically.
• "Automated Bed Leveling With Our 3D Printer," Brian Benchoff, Hackaday (Apr. 23, 2012) — dated just inside the one-year window; §102(a)(1) art under the AIA (third-party disclosure, so no §102(b)(1)(A) grace-period shelter), §102(a) art pre-AIA (subject to a Rule 131 swearing-behind). The applicant's own citation of it on the face of the patent is, at minimum, an admission of its materiality.
• "Touch Sensor and Automated Calibration," RepRap forum thread 8028 (Jan. 4, 2008) — §102(b) art. This one is named in the patent's own "Other References."

Motivation: These references establish that detecting contact between the nozzle/extruder and the bed as a control input was the known, standard solution to the very defects the '381's Background identifies ("components … may degrade with time — i.e., become dented, warped, misaligned"). Combining them with Calderon's or Warren's controller-and-actuator architecture is "using a known technique to improve a similar device in the same way" — and does so without any reliance on RepRap20208, thereby neutralizing Patent Owner's printed-publication attack.

Ground 4: Rehabilitating the Examiner's own rejections — Jang + Lipson (+ Calderon)

The face of the patent shows the Examiner applied Bonassar (US 7,939,003) in anticipation and Jang (US 6,129,872) in view of Lipson (US 7,625,198, "Modular fabrication systems and methods") in obviousness, and that both rejections were overcome for lack of a sensor on the extruder that senses contact force. Petitioner's point — that the Examiner simply missed the existence of Calderon, Warren, Dunn and RepRap20208 — is well taken. Jang/Lipson supply [1A] and the controller/positioning architecture; adding Calderon's extruder-mounted contact sensor to those systems is an obvious combination with predictable results, because the only missing element was a known transducer in a known location performing a known function.

Ground 5: Bonassar (US 7,939,003) + Calderon or RepRap20208

Bonassar discloses a computer-controlled dispensing/bioprinting apparatus with sensors. The anticipation rejection failed only on [1B]; that gap is filled by Calderon's extruder-mounted sensor assembly or RepRap20208's strain-gauge-on-extruder-mount teaching. A single-reference rejection converts to a straightforward two-reference §103 combination.

5. Claim-by-claim disposition

Claims 12–16 are essentially a menu of the printer's standard controlled variables (feed rate, z-position, head speed, temperature) — the '381's own specification lists exactly these at [0063] and [0065]. Controlling them in response to a measured force is the definition of routine optimization and predictable use of a known technique.

6. Objective indicia / secondary considerations

• Simultaneous independent invention. The near-simultaneous appearance of nozzle-force bed leveling across the RepRap community (2008–2012) — RepRap forum 8028, HydraRaptor (2011), Hackaday (2012), and the open-source printer ecosystem generally — is itself evidence that the solution was obvious to workers in the field, not the product of a nonobvious insight. Stratasys's reliance on commercial success would face a nexus problem for the same reason.
• Licensing/settlement and litigation are not probative of nonobviousness.
• Copying allegations cut weakly here, since the accused Bambu printers and dozens of other machines independently converged on strain-gauge-based nozzle probing.

7. Counterarguments, and where they hurt

These are real and should be stated honestly, because they are the ones Patent Owner actually pressed in its Preliminary Response (Paper 7) to IPR2025-00532:

1. Printed-publication status of RepRap20208. Patent Owner argued the Petition failed to establish that the forum thread was publicly accessible. Petitioner countered with founder-moderator testimony that the forum was keyword-searchable and login-free since 2005. Impact: if this fails, Ground 2A/2B collapse — but Grounds 1A/1B (Warren) and Ground 3 (HydraRaptor/Hackaday, both open-web and one of them applicant-cited) survive.
2. "No motivation to combine Calderon with RepRap20208" because Calderon "works" as-is. This is a weak argument post-KSR — the existence of a working embodiment does not foreclose improvement, and Calderon itself enumerates interchangeable sensors.
3. Alleged teaching away — RepRap20208 p. 19 disparages a force sensor as something that "doesn't sound like it works well over long periods of time under force," and p. 20 raises "backlash" and uncertainty as to "exactly when the head touches." This is the most substantive defense to Ground 2 and is genuinely arguable for the "permanent, continuously-measuring force sensor" reading. It is much weaker against the bed-height/collision-detection reading (p. 13), which is what claim 1 actually needs.
4. "No teaching of calculating a contact force." Patent Owner noted RepRap20208 p. 13 never says "force," and that "a constant measurement of the force on the head (including it's weight)" is not a contact force. Impact: this targets [1C] specifically; it is why Ground 1 (Warren, which does recite a computed contact force) is the cleaner primary reference, with Calderon+RepRap20208 as the alternative.
5. Claim 11's internal inconsistency ("between the one or more sensors and the separate structure") was exploited.
6. AAPA problems in the district cases. In E.D. Tex. 2:24‑cv‑00644 the court struck improper reliance on Applicant Admitted Prior Art as a primary reference (permitting only '713 Patent 1:40–53 and substantially repeating AAPA as a secondary reference) — a reminder that not every admitted-background teaching is available as art.

Procedural posture: the Board instituted trial on 2025‑10‑06 (IPR2025‑00532, Shenzhen Tuozhu Technology Co., Ltd. et al. v. Stratasys, Inc. et al., patent 10,556,381, application 14/922,267, TC 1700). Institution means the Board found a reasonable likelihood that at least one challenged claim is unpatentable. I could not confirm from the available material which specific grounds were instituted, and one aggregator still shows the decision documents as "pending" — treat the scope of institution as unverified. Parallel district actions: E.D. Tex. 2:24‑cv‑00644; E.D. Tex. 2:25‑cv‑00465; and the W.D. Tex. declaratory-judgment action 1:24‑cv‑01511 (BambuLab et al. v. Stratasys, filed 2024‑12‑09, judgment entry noted 2025‑05‑05).

8. Bottom line

1. Claim 1 is very likely obvious. The combination that best supports it is Calderon (US 6,629,011) + the RepRap20208 strain-gauge-on-extruder-mount teaching — Calderon supplies an extruder-based 3D printer with a controller and an extruder-head-mounted sensor detecting nozzle–substrate contact, and RepRap20208 supplies the specific strain-gauge implementation on the extruder mount together with its express benefits (automatic bed-height finding, collision detection). Motivation rests on Calderon's own enumeration of interchangeable sensing means, identity of field and problem, predictable results, and cost/simplicity.
2. An even cleaner primary reference is Warren (US 2003/0100824), because it expressly frames the control objective as a computed "contact force as desired" and therefore meets [1C] without inference.
3. The strongest, least-contestable ground uses only the applicant's own cited art: Calderon or Warren combined with HydraRaptor (2011‑04‑04) and/or Hackaday "Automated Bed Leveling" (2012‑04‑23) — references the applicant put on the record — establishing that nozzle-contact sensing for bed leveling was the known, standard solution to the exact problem the '381's Background recites.
4. Dependent claims 2, 5, 6, 9, 10, 12, and 14 are individually very strong. Claims 3, 7, and 8 depend on the Dunn reference for the deflection/multi-axis limitations; I infer from the petition's ground structure (1B/2B, claims 3, 7, 8) that Dunn teaches multi-axis / tip-deflection force sensing, but I could not retrieve its text and therefore cannot verify that characterization. Claims 13, 15, and 16 are routine-optimization claims over known printer control variables that the '381's own specification lists.
5. Principal residual risk: (i) the printed-publication challenge to RepRap20208, and (ii) the alleged teaching away on p. 19–20 of that thread. Neither threatens the Warren-based or HydraRaptor/Hackaday-based grounds.

Confidence and limitations

• High confidence in the identity, dates, and claim text of the '381; the claim-by-claim mapping of Calderon (whose operative passages and column/line cites are quoted in the IPR record); the existence and date of the applicant-cited RepRap/HydraRaptor/Hackaday references; and the existence and institution of IPR2025-00532.
• Lower confidence in: the precise contents of Dunn (I infer its role from the ground structure, not its text); the exact paragraphs of Warren (relayed via the petition, e.g., ¶¶ [0285]–[0302], [0313]–[0316], FIG. 22A); the exact thread identity behind the label "RepRap20208" (Petitioner's exhibit is a Jan. 2009 RepRap forum thread; the patent's own cited RepRap thread is a different item, "Touch Sensor and Automated Calibration," thread 8028, Jan. 4, 2008 — the similar identifiers should not be conflated); and which specific grounds were instituted on 2025‑10‑06.
• Nothing here is legal advice; claim construction of "contact force" relative to Calderon's "contact … monitored by a sensing means" is the pivotal issue and would be litigated.