2.8 Nozzles
Module 2 · Lesson 8 of 10 · about 5 min
Every printer in the room normally has a 0.4 mm nozzle, and all nozzles here are hardened steel. The one change members may make is on the H2S: if your job already qualifies for an H2S (2.9 The H2S: use it only when you need it), you may swap to a 0.8 mm high-flow nozzle. For big, chunky parts it can cut the print time considerably. Speed alone is never a reason to use an H2S.
How nozzle size changes a print
The nozzle's hole decides how wide each printed line is, and so how thick each layer can be. Doubling the nozzle size roughly doubles both, so each line carries about four times as much plastic.
0.4 mm (standard) | 0.8 mm high-flow (H2S only) | |
|---|---|---|
Line width | about 0.4 mm | about 0.8 mm |
Typical layer height | 0.1–0.3 mm | 0.2–0.6 mm |
Print time | The baseline | Much shorter for big, chunky parts |
Surface and detail | Fine detail, crisp small text, smooth curves | Visible layer lines. Small text, sharp corners and thin features lose detail. |
Walls | Each wall loop is about 0.4 mm | Each wall loop is about 0.8 mm, so the same number of loops gives a wall twice as thick. Even at the same thickness, fewer and wider lines usually make a stronger part. |
The bow of the same boat printed with two nozzle sizes. Left, 0.4 mm: fine layers, crisp edges and a clean porthole. Right, 0.8 mm: thicker layer lines, rougher edges and a ragged porthole
Left: 0.4 mm nozzle. Right: 0.8 mm nozzle.
A bigger hole already prints faster, because each line is wider. But the hotend also has to melt all that extra plastic in time, and that soon becomes the limit. A high-flow nozzle has an insert inside that splits the filament into three channels as it melts, so the heat reaches all of it faster, and it can print faster still. That is why the room's large-print option is a 0.8 mm high-flow nozzle, not just a 0.8 mm one.
Cutaway of a high-flow nozzle: inside its copper tip, an insert splits the melting filament into three channels before the nozzle opening
When to use 0.8 mm: large parts where strength and speed matter more than fine detail, such as boxes, brackets, stands and big enclosures. When to stay on 0.4 mm: anything with small text, fine detail or a surface you want smooth.
✅ Hard rule. The only nozzle change members may make is swapping the hotend on an H2S between the standard 0.4 mm and the 0.8 mm high-flow. Only make the change if you know how. If you have never done it, ask in Slack and do your first one with someone who has.
⛔ Hard rule. Never change the nozzles on an X2D.
Changing the hotend on an H2S
The drawer under the left H2S with the spare hotends in their boxes, and the box labels close up: Hotend with hardened steel nozzle 0.4 mm, and High Flow Hotend 0.8 mm
Six photos of an H2S hotend change, left to right and top to bottom: front cover off, silicone sock off, hotend out, new hotend seated with the buckle closed, sock back on, cover back on
On the H2S, the nozzle is built into the hotend, the heated block that melts the filament, so you swap the whole hotend as one unit. The steps below summarise Bambu Lab's own guide, Replace H2S Silicone Sock and Hotend. Keep it open while you work. The video Changing the HotEnd on the Bambu Lab H2S (fbrc8) shows the whole change from start to finish. If the hotend won't come out, stop and ask in the Slack channel #3D-Skrivare. The spare hotends are in the drawer directly under the left H2S.
Unload the filament first. Run Unload on the screen (1.9 Loading filament into the AMS) and take the spool out.
Wait until the hotend has cooled to room temperature. It prints at well over 200 °C and stays hot for a good while after a print. Touching it before then will burn you.
Cut the filament if any is still in the hotend after the unload, using the filament cutter on the print head.
Remove the print head's front cover. Press firmly on its bottom edge and pull it gently towards you.
Pull the silicone sock straight down off the hotend, holding it on both sides.
Unlock the hotend buckle. Hold the heat sink at the top and bottom and pull the hotend out.
Fit the new hotend. Open its buckle fully and push it all the way onto the heating assembly. Close the left buckle plate first, then press the buckle in and lock it.
Refit the silicone sock. Slide it on from below until it sits flush. It must not touch the plastic around it.
Refit the front cover. Line up the clips at the top and press down until it clicks into place.
Check the fit. Gently wiggle the nozzle. It should not move. If it does, go back to step 7.
After the change
The printer screen's Left Nozzle Type settings: Standard or High Flow, Hardened or Stainless, and the nozzle size
The same nozzle in two places. Left: the H2S screen's Nozzle & Extruder page, showing Standard, Hardened, 0.4 mm. Right: Bambu Studio after a sync with the H2S, showing nozzle 0.4, Standard
Tell the printer. Set the new nozzle size and type on the printer's screen.
Set the H2S's nozzle size indicator to match, so the next person can see at a glance which nozzle is fitted.
Re-sync in Bambu Studio and check that the slicer shows the nozzle that is actually fitted. A job sliced for 0.4 mm but printed with a 0.8 mm nozzle comes out a mess, and the opposite can jam the nozzle.
Put the old hotend back in the drawer directly under the left H2S, cleaned.
When your print is finished, swap back to the standard 0.4 mm hotend the same way, and set the screen, the indicator and Bambu Studio back to 0.4 mm. The next person should find the standard nozzle fitted.
Image sources: nozzle comparison and high-flow nozzle cutaway, Bambu Lab product images; hotend change and nozzle type screen, from Bambu Lab's Replace H2S Silicone Sock and Hotend.