#3d-printing #resin #elegoo #saturn-4-ultra #leveling #calibration # Overview Step-by-step procedure for getting the Elegoo Saturn 4 Ultra 16K build plate flat and parallel to the LCD. The machine's "auto-leveling" is really **auto-zeroing** — a downward-facing force sensor in the cantilever finds contact before every print. It corrects Z height only. It cannot correct **tilt** (plate not parallel to screen) and it cannot correct **flatness** (plate dished or crowned). Both of those are mechanical and must be fixed by hand. There is **no Z=0 / Z-offset menu item** on this printer. Anything telling you to go to `Tools → Z=0` is describing a Mars 3 / Saturn 2-era UI that doesn't exist here. Companion note: [[Resin Printing Notes]] **Where I am in this:** plate already lapped flat on a granite surface plate, shim washers already printed. That puts me at [[#Stage 5 — After lapping the plate]] — re-texture check, then re-level, then verify. The earlier stages are here for reference and for the next time the machine drifts. # Design ## What actually adjusts | Fastener | Tool | Count | What it does | |---|---|---|---| | Build plate corner adjusters | **2.5 mm hex** | 4 (the **inner** screw of each corner pair, not the outer bolt) | Sets each corner's height against a spring preload | | Handle retaining screw | **4.0 mm hex** | 1 | Holds the plate clamp handle on the cantilever | | Cantilever junction block screws | **4.0 mm hex** | 4 | Re-trams the whole arm. Thread-locked — needs heat | The plate itself slides into a connecting block and is clamped by the lever handle. Elegoo's own store copy confirms the plate has *"built-in leveling shims and springs, combined with an advanced mechanical sensor."* Elegoo publishes no exploded view or teardown of what is under the plate. The "spring preload, screw sets height" model below is inferred from Elegoo's warning about deforming the plate, from Chris Osgood's washer work, and from RetroGameBoyz — not from an Elegoo diagram. ## Screw direction — the one rule This trips everyone up because sources look like they contradict each other. They don't: | Turn | Corner moves | Gap to LCD | Paper feel | |---|---|---|---| | **Tighten / CW** | **up** | larger | **looser** | | **Loosen / CCW** | **down** | smaller | **tighter** | ## Tilt vs. flatness — diagnose before you adjust These are different defects with different fixes, and the wrong fix makes things worse. | Symptom | Defect | Fix | |---|---|---| | One corner loose, others fine | **Tilt** | Corner screw; shim that corner if out of travel | | Can't get all four corners to match — screws bottomed or maxed | **Tilt + no range left** | Equal shim on all four, then re-adjust | | Four corners equal but the **center** prints thin/thick | **Dish or crown** — a flatness error | **Lapping only.** Screws and shims cannot fix this | | Gross tilt that corner screws can't reach | Cantilever out of tram | Stage 6 — re-tram the arm | ==Failure mode to avoid (inferred, but the mechanics are sound): shimming a plate that is *warped* rather than *tilted* applies bending moments at four point loads. You rotate a curved plate about its center and end up with "warped **and** tilted" — one diagonal crushing into the FEP, the opposite region not sticking at all.== This is almost certainly what happened to Battle Brother Sam when he stacked 2× M6 washers per post and it made printing worse. # Procedure ## Stage 0 — Prep - Plate and vat clean of resin (IPA + lint-free cloth). Resin on the plate ends up on the LCD. - Level the **printer itself** front/back and side/side with a spirit level. This does nothing for plate-to-screen parallelism, but it stops resin pooling to one side of the vat. - Do the leveling in the printer's **final location**, on a solid surface. - Cut four paper squares **noticeably smaller** than a quarter sheet so they don't touch each other or hang over the LCD edge. 300 gsm cardstock gives a better feel than copy paper; keep one full A4 sheet aside for the full-plate drag test. - **Pre-loosen all four corner screws ~2 full turns (or at minimum 180°)** before starting, so you have travel in both directions. Skipping this is the single most common reason people "run out of adjustment." ## Stage 1 — On-machine Manual Leveling wizard Menu path: **`Settings → Accessibility Features → Manual leveling`** (it's on page 2 of Accessibility Features — *not* under Tools). Remove the build plate first and leave the **latch in the up position**, or the wizard makes you cancel and restart. On-screen text, verbatim from the manual: > "Please slide an A4 paper and ensure that the four corners are evenly pressed with minimal resistance difference. If the resistance is too high or too low, adjust the leveling screws on the corresponding corners." Target feel: **the paper can be pulled out, but cannot be pushed back in.** Two things the wizard doesn't tell you: - **Corner feel is misleading.** The LCD's outer edge has a bulky taped section housing electronics, so a corner paper can drag on *that* rather than register the true plate-to-screen gap. After the four-corner pass, slide **one full A4 sheet** under the whole plate and feel tension across the entire area. - **Running out of range?** Hit **Cancel** mid-process so the plate rises, adjust that screw the opposite direction *while the plate is up*, then re-run. This resets the usable adjustment window without adding shims. ## Stage 2 — Elegoo's load-bearing fine-tune This is Elegoo's official method and it's arguably more accurate than the wizard, because it levels **under actual exposure pressure**. > ⚠️ **This prints with the resin tank removed — bare metal plate onto a bare LCD.** Put a sacrificial FEP sheet over the screen. Also note Elegoo's warranty language about self-disassembly. 1. Slice any model; set **Bottom Exposure Time to 60 s (or 90 s)** — purely to buy yourself time to turn screws. Save to USB. 2. Tear an A4 sheet into four; place at the four LCD corners. Install the plate. 3. `Print → USB File`, select the model. **No vat, no resin.** 4. If a **"Print Abnormal"** popup appears → **Mandatory Printing**. 5. While the first layer is exposing, pull each corner paper. Find the one that's obviously loose. 6. **Loosen that corner's screw slightly, counterclockwise, 2.5 mm hex.** 7. **Re-test all four papers after every single screw adjustment.** Elegoo's warning, verbatim: *"Loosen the screw slightly. It is forbidden to tighten the screws drastically to prevent abnormalities of the build plate."* ## Stage 3 — Reload the leveling parameter patch If Stages 1–2 don't converge, Elegoo pushes a small gcode that rewrites the auto-level parameters. It's a **machine-parameter patch, not a firmware image**. 1. Download **https://elegoo-supportcenter.oss-us-west-1.aliyuncs.com/GCODE.zip** 2. Open the **`Saturn 4 Ultra 16K/`** folder — ==not the `Saturn 4 Ultra/` folder, the files are different==. The wiki text says to look for "Saturn 4 Ultra-ChituGcode.gcode"; that's a wording slip, the file inside every folder is just `ChituGcode.gcode`. 3. Copy `ChituGcode.gcode` to the **root of the USB drive**. **Do not rename it. Do not put it in a folder.** 4. Insert, power on, print that file. Parameters load automatically. 5. Power off at the side switch, unplug 10 s, restart. 6. Re-run Stage 1. For reference, the 16K file contents: ```gcode M5000 I205 B-4.000000 ; M5000 I205 E12000 M5000 I206 C15000 M5999 I0 ``` `M5000` writes a Chitu machine parameter, `M5999 I0` commits. ==The letter meanings aren't documented by Elegoo; they line up structurally with auto-level start/end position and the correction/blocking force thresholds, but that's inference.== ## Stage 4 — Shims Shims are **not step one**. They're the workaround for corner screws running out of travel. Only reach for them after Stages 1–3. - **One shim at one corner** = tilt correction (Chris Osgood's 0.45 mm case). - **Equal shims at all four corners** = adjustment-range extension only. Cannot change tilt. - **Shims on a dished plate** = worse, per the table above. **On printed resin washers:** they compress and creep under spring preload. The designer of the parametric one says so himself in writing — *"a metal version like stainless steel would be nice"* — and worries about them cracking under the pan-head. Use printed ones to find the right thickness, then buy that thickness in stainless. **Stainless equivalent:** DIN 988 shim washers, **4 × 8 × t mm** (assuming M4 — see below), in 0.1 / 0.2 / 0.3 / 0.5 mm. Search term "DIN 988 shim washer" gets you real precision parts instead of generic flat washers. > **Measure your screws before ordering.** M4 is the best available evidence — Chris Osgood replaced his stock M4×5 with M4×10, and his SCAD clearance hole is 4.1 mm. But Elegoo publishes no thread spec, and nobody has confirmed M4 on the 16K specifically. Calipers on the shank, or try an M4 nut. ## Stage 5 — After lapping the plate This is where I am. Order matters here. ### Does removing material change Z zero? **No, and there's nothing to re-zero anyway.** The force sensor re-derives contact before every print — the self-check runs "Calibrating the sensor → detecting resin → automatic leveling." Take 0.2 mm off the plate and the machine just finds contact 0.2 mm lower. Invisible. **What does need re-checking is corner-to-corner uniformity**, because hand lapping never removes material perfectly evenly. Re-run Stage 1 after any lapping session. Consider re-running Stage 3 as well. ### Surface finish — flat is necessary, smooth is harmful Resin cures **into** surface scratches. That's the adhesion mechanism. A mirror-finish plate is a plate that drops prints. MatterHackers' canonical sequence, on a flat reference surface (granite is ideal), plate face down, **let gravity do the work — no downward pressure, or you'll induce a bend in the plate**: 1. **120 grit** — flatten. Slide away and back ×4, rotate the plate 90°, repeat through all four orientations. Done when there are no visible unsanded low spots. 2. **80 grit, diagonal strokes** — deliberately cut deep gouges. This is the adhesion texture. 3. **120 grit again** — knock off the burrs from the 80 without erasing its gouges. Burrs will chew the FEP, so don't skip this. 4. IPA + lint-free cloth, reinstall, re-level. **Don't finish finer than ~120.** Target finish is uniform dull grey with visible directional gouges, not shiny. If you already went finer while chasing flatness, one 80-grit diagonal pass plus one 120-grit deburr pass restores the tooth and removes almost no material. Media: wet/dry **silicon carbide**, PSA-backed so it stays put on the granite. Gloves and a respirator — aluminum dust. A working data point from [[Resin Printing Notes]]: *"Sanded my build plate… 80 grit then 180 grit"* with bottom exposure 28 / exposure 1.975 / 0.03 layer height, reported zero failed prints. Slightly finer final grit than MatterHackers, so 120–180 is the usable window. ## Stage 6 — Re-tram the cantilever (last resort) Only if the plate is flat, the corner screws are in range, and it's *still* grossly tilted. This is disassembly — weigh the warranty language. 1. Remove the handle: **4.0 mm hex**, one screw. 2. Pull the protective cover off gently. 3. **The 4 cantilever screws are thread-locked with screw glue. Heat them with a hair dryer for 2–3 min to about 80 °C** before touching them. *"Do not disassemble violently."* If they're still stiff, keep heating. 4. Loosen the 4 cantilever junction block screws, 4.0 mm hex (2 on each face). 5. Refit the handle, tighten its screw, install the plate. 6. Four paper quarters on the LCD corners. `Tools → Manual`, lower the plate 50 / 10 / 1 / 0.1 mm until the paper is pressed. 7. Pull all four papers — you want **significant resistance** at all four. 8. **Tighten the 4 cantilever screws in a diagonal pattern.** 9. `Home` — Z homes. Remove the paper. 10. Remove plate, remove handle, clip the cover back on, refit handle (4.0 mm). 11. Install plate and vat, power on, `Print` → let the self-check run. # Verification Paper feel is a proxy. This is the actual measurement, and it distinguishes tilt from dish. **J3D-Tech Build Plate Calibration** — five flat plates arranged in a **dice pattern** (TL, TR, Center, BL, BR). Prints in under 15 minutes. - Instructions: https://docs.mango3d.io/doc/j3d-tech-s-guide-to-resin-printing/printer-calibration/build-plate-calibration/ - Model: https://cults3d.com/en/3d-model/tool/j3d-tech-s-bed-of-calibration - XL / RERF version (better fit for the S4U's 218.88 × 122.88 mm area): https://cults3d.com/en/3d-model/tool/biuld-plate-calibraion-xl-designed-for-rerf-or-whatever Measure each raft **at its thinnest section** with digital calipers. Nominal is 1.00 mm each. | Reading | Verdict | Action | |---|---|---| | All five within **0.15 mm** | Level and flat | Done — move on to exposure | | Corners agree, **center thin** | Still dished | More lapping. Screws won't help | | One corner off | Tilt | That corner's screw, or shim it | | Diagonal pair off | Tilt about the diagonal | Two corners | > ⚠️ The J3D docs include a Z-offset correction step. **Ignore it** — this machine has no Z-offset control. Use the numbers as a flatness/tilt diagnostic only. **Not a leveling test:** Elegoo's own `S4U16K_Testing.zip` is six chess piece STLs plus a pre-sliced rook. It's a "does the printer work" smoke test with a single small footprint — it tells you nothing about corner-to-corner level. # Configuration Elegoo factory defaults for the S4U 16K (manual EN-V3, p.15): | Parameter | Default | Notes | |---|---|---| | Layer height | 0.05 mm | Range 0.01–0.2 | | Bottom layer count | 5 | | | Normal exposure | 2.3 s | | | **Bottom exposure** | **32 s** | Elegoo resins ~25–35 s at 0.05 mm | | Wait before cure | 1.2 s | | | Wait before/after lift | 0 s | | Third-party resins span much wider — Liqcreate's official S4U16K table runs 15–60 s base / 2.0–12.0 s normal depending on resin and layer height. ## Order of operations, and why it matters **Flatness → level → *then* exposure.** Not the other way around. Cranking bottom exposure absolutely does mask a leveling problem, and both Elegoo and the community confirm it from opposite directions: - Elegoo's own fine-tuning procedure sets bottom exposure to 60–90 s purely as a *timing convenience* — proof that bottom exposure is decoupled from level. - Elegoo's FAQ prescribes "add more bottom exposure time" as the first fix for adhesion failure, with no reference to level at all. That's the band-aid. - J3D-Tech says the opposite: calibrate burn-in downward in 4 s steps until parts release easily but hold firm; if models still fall off and you're already above the manufacturer's recommendation, *increase raft surface area and slow retract to ≤40 mm/min* rather than burning LCD hours. - Battle Brother Sam did the math on Elegoo support's "raise it to 70 s" advice: 6 bottom layers × 70 s = 420 s per print against a ~2,000-hour screen rating, and it over-bonds the raft so it shatters on removal (the "exploding rafts" problem). If you calibrate exposure before level, you bake permanent over-exposure into your profile — elephant foot, hard part removal, accelerated FEP wear, dead LCD sooner. # Decisions - **Stainless over printed shims.** Printed resin washers creep under spring preload; the parametric washer's own author says he'd prefer stainless and worries about cracking. Use printed to *find* the thickness, buy DIN 988 stainless to *keep* it. - **Lapping before shimming.** Shims correct tilt; only lapping corrects flatness. Shimming a warped plate makes it warped *and* tilted. Already done here — plate lapped on granite. - **Don't chase the cantilever re-tram unless nothing else works.** It's thread-locked disassembly with warranty implications, and the corner screws plus the parameter patch cover most cases. - **Skip the DIY3D guide's gcode link.** Its Google Drive file is dead. Elegoo's `GCODE.zip` is the live source. # Troubleshooting | Symptom | Likely cause | Fix | |---|---|---| | "Ran out of screw adjustment" | Screws not pre-loosened before starting | Pre-loosen ~2 turns; or use the Cancel-mid-process trick to reset range; or equal shims all four | | Front half prints, back half doesn't | Tilt | Corner screws / single-corner shim | | Corners fine, center prints thin or won't stick | Plate dished | Lapping. Nothing else will fix it | | Prints stick too hard, elephant foot, rafts shatter | Over-exposed bottom layers, often masking a level problem | Fix level first, then walk bottom exposure down | | Parts drop off but level checks out | Plate too smooth after sanding | 80-grit diagonal texture pass, then 120 deburr | | Auto-leveling fails outright at self-check | Machine parameter or sensor fault | Run Elegoo's `Exporting.gcode` diagnostic → generates `100MachineParams.gcode` on the USB → email to Elegoo support with resin type and viscosity | | Tilt axis feels stiff / laggy | Resin leaked into the tilt platform groove | Elegoo's groove cleaning procedure — https://wiki.elegoo.com/saturn/saturn-4-ultra-how-to-clean-the-resin-leaked-in-the-groove-of-the-tilt-platform | | Release film whitened, scratched, no elasticity | Worn FEP | Replace. Firmware also warns at ~60,000 accumulated uses | # Resources ## Video guides — suggested viewing order | # | Video | Channel | Length | Why | |---|---|---|---|---| | 1 | [Bed Leveling Tip — Loosen 4 Set Screws FIRST!](https://www.youtube.com/watch?v=_lM0OY2p_Hc) | RetroGameBoyz | 2:20 | The prerequisite everyone omits. Pre-loosen ~2 turns. Direction convention at ~1:53 | | 2 | [Saturn 4 Ultra: Fine Tuning of Automatic Leveling](https://www.youtube.com/watch?v=_BG38q8jmzA) | Elegoo Official | 3:05 | Authoritative. The load-bearing method in Stage 2. Effectively hidden — doesn't surface in Elegoo's own channel search | | 3 | [The Ultimate Elegoo Saturn 4 Ultra Leveling Guide](https://www.youtube.com/watch?v=nvUwhhyUJ5U) | OleBrogger | 10:15 | Cleanest wizard walkthrough. Full-sheet A4 drag test at ~5:46. Pre-turn screws 180° at ~3:46. Menu path at ~4:25 | | 4 | [Why My Prints Kept Failing… (FIXED)](https://www.youtube.com/watch?v=gYutzU_VI1s) | LeyzarGamingViews | 8:03 | Best overall. The Cancel-mid-process range-reset trick at ~3:59. Lapping procedure at ~5:38. Why corner feel misleads at ~3:12 | | 5 | [How To FIX Your Brand NEW Saturn 4 Ultra 16k](https://www.youtube.com/watch?v=t5Bi3SyILjw) | Battle Brother Sam | 15:58 | The washer negative result at ~10:23. Plate disassembly at ~11:15. Sanding at ~13:21. Bottom-exposure argument at ~5:58 | | — | [Saturn 4 Ultra Manual Leveling Tutorial](https://www.youtube.com/watch?v=eGCmi9x0ieY) | Elegoo Official | — | Elegoo's version of the Stage 6 cantilever re-tram | | — | [Elegoo Replied to My Saturn 4 Ultra 16k Video](https://www.youtube.com/watch?v=dm3lHdA4TPc) | Battle Brother Sam | 10:19 | Same content as #5 without the support-welding filler | | — | [Saturn 4 Ultra Manual Level? No Auto Level?!](https://www.youtube.com/watch?v=vhehQW3ueno) | That Dude 3D Prints | 15:36 | Origin story — firmware 1.2.7 adding manual leveling. Documents the wizard's limitation (Cancel/Next only, no adjustment step) at ~8:51 | Not worth the time: [Stop doing THIS with your Saturn 4 Ultra!](https://www.youtube.com/watch?v=9yHHXfIUaJE) (Tuba Makes) ranks high in leveling searches but is entirely about drip adapters. [Saturn 4 Ultra 16K Review](https://www.youtube.com/watch?v=rpcsXHTAt0w) (FauxHammer) is a review, not a how-to — relevant only as the origin of the "auto **zeroing**" framing. ## Official Elegoo - [How to improve leveling results — ELEGOO Wiki](https://wiki.elegoo.com/saturn/saturn-4-ultra-how-to-improve-leveling-results) — the only leveling procedure page for the whole S4U family. ==Linked from the Saturn 4 Ultra hub but not the 16K hub; it applies to both== - [Saturn 4 Ultra 16K User Manual, EN-20260122-V3 (PDF)](https://elegoo-downloads.oss-us-west-1.aliyuncs.com/download.elegoo.com/04%20LCD%20Printer/24%20Saturn%204%20Ultra%2016K/Saturn%204%20Ultra%2016K-EN-20260122-V3.pdf) - [GCODE.zip — leveling parameter patch](https://elegoo-supportcenter.oss-us-west-1.aliyuncs.com/GCODE.zip) — use the `Saturn 4 Ultra 16K/` folder - [Exporting.gcode — auto-level failure diagnostic](https://drive.google.com/file/d/1wzAbd3kw3u7BBFXD_5688MDVh_wFMTsL/view?usp=drive_link) — via [Self Test: Auto-leveling Failed](https://wiki.elegoo.com/saturn/saturn-4-ultra-16k/self-test-auto-leveling-failed) - [Mechanical sensor replacement](https://wiki.elegoo.com/saturn/saturn-4-ultra-how-to-replace-the-mechanical-sensor) — force sensor must face downward - [Release film replacement](https://wiki.elegoo.com/saturn/release-film-replacement) — closest thing Elegoo gives to a torque spec: *"tighten to two-thirds of the required torque, then tighten completely, diagonal pairs each time"* - [Elegoo Download Center](https://www.elegoo.com/pages/download) - Annotated adjuster photo (Mars 5 Ultra page, identical plate design): https://wiki.elegoo.com/mars5ultra-bulid-plate-asjust.png - S4U adjustment photo: https://wiki.elegoo.com/saturn/saturn-4-ultra-fine-tuning-tutorial-after-the-automatic-leveling/image12.png ## Reference guides - [MatterHackers — How To: Perfectly Level (Flatten) Your Resin Printer's Build Plate](https://www.matterhackers.com/articles/how-to-perfectly-flatten-your-resin-3d-printers-build-plate) — the canonical lapping procedure - [3D Printerly — Scratches on Your Resin Build Plate?](https://3dprinterly.com/scratches-on-your-resin-build-plate-should-you-fix-or-replace/) — why texture aids adhesion, why burrs kill FEP - [J3D-Tech — Build Plate Calibration](https://docs.mango3d.io/doc/j3d-tech-s-guide-to-resin-printing/printer-calibration/build-plate-calibration/) · [Burn-in Layers](https://doc.mango3d.io/doc/j3d-tech-s-guide-to-resin-printing/printer-calibration/burn-in-layers-bottom-layers-calibration/) · [Levelling the Bed](https://docs.mango3d.io/doc/j3d-tech-s-guide-to-resin-printing/good-to-know/levelling-the-bed/) - [Liqcreate — S4U 16K resin settings table](https://www.liqcreate.com/supportarticles/elegoo-saturn4-ultra-resin-16k/) · [Mr Resin — 2026 Elegoo settings](https://mrresin.es/en/blogs/mr-resin-3d-blog/resin-settings-elegoo) - [DIY3D — S4U16K bed leveling](https://diy3d.in/blogs/news/saturn-4-ultra-16k-bed-leveling-guide) — ==its gcode Google Drive link is dead; use Elegoo's GCODE.zip== · [DIY3D — test file / anomaly check](https://diy3d.in/blogs/news/elegoo-saturn-4-ultra-16k-test-file-print-anomaly-check) - Exposure calibration (tests resin, **not** leveling — don't confuse them): [AmeraLabs Town](https://ameralabs.com/blog/town-calibration-part/) · [Cones of Calibration V3](https://www.tableflipfoundry.com/3d-printing/the-cones-of-calibration-v3/) · [Printables mirror](https://www.printables.com/model/1306590-cones-of-calibration-v3-r_e_r_f-exposure-finder-nu) # Build Log ## 2026-08-05 - Plate lapped flat on granite surface plate (done prior to this note — ==record which grits were actually used and the final finish==) - Shim washers printed (==which model? Jim Cheong's or the parametric one? record thickness==) - Research compiled into this note - Next: verify surface texture is coarse enough (see Stage 5), re-run Manual Leveling, then print the J3D 5-plate dice test # TODO - ==Confirm build plate screw thread with calipers before ordering stainless shims — M4 is likely but unconfirmed on the 16K== - ==Run the 30-second screw-direction test to confirm CW = raise on this specific machine== - ==Check final lapped grit; if finer than ~180, do an 80-grit diagonal texture pass + 120 deburr== - ==Download and print the J3D-Tech Build Plate Calibration XL test; log the five caliper readings here== - ==Decide whether to reload GCODE.zip parameter patch after lapping== - ==Order DIN 988 4×8 stainless shims in the thickness the printed washers prove out== - ==Consider the Shars granite plate + feeler gauges if not already owned — makes the whole loop measurable instead of feel-based== # References - [[Resin Printing Notes]] — general resin setup, cleaning, exposure test results - ==No Reddit / forum evidence in this note — r/ElegooSaturn, r/resinprinting and r/elegoo were unreachable during research. The shim tilt-vs-dish analysis is mechanism-based reasoning cross-checked against the model authors' own stated intent, not community consensus==