Practical guide
How to 3D print faster without losing quality
The speed a printer advertises (500, 600 mm/s…) is almost never what you see on a real part. What actually limits how long a print takes is how much plastic the hotend can melt per second, and from there, a few slicer decisions. Here's which ones move the needle and which ones only promise to.
The real limit: volumetric flow
Bambu Lab explains it with a formula: plastic out per second (mm³/s) is layer height × line width × speed. Every hotend-filament combination has a maximum; for example, Bambu sets 25 mm³/s for its PLA Basic on an H2S. The slicer knows that maximum and slows down on its own when you'd reach it, so raising speed beyond it achieves nothing.
The chart shows the consequence: with thinner layers, each line carries less plastic and you can move faster before hitting the limit.
| Layer height | Top speed at 25 mm³/s |
|---|---|
| 0.16 mm | 347 mm/s |
| 0.20 mm | 278 mm/s |
| 0.30 mm | 185 mm/s |
Being able to move faster at 0.16 mm layers doesn't mean finishing sooner: you need many more layers for the same height, and Bambu warns total time rises sharply. The key is different: make every setting work without exceeding the limit. Flow is explained in what is a hotend.
1. A bigger nozzle (the strongest lever)
A wider nozzle puts out more plastic per line and allows taller layers. Prusa measured it: with a 0.6 mm nozzle, parts like headphone stands, holders, racks or planters print in up to half the time, and the difference in looks on a planter is nearly impossible to see. It allows layers up to 0.48 mm (80% of the diameter) and, in its tests, parts absorbed up to 25.6% more energy than 0.4 mm ones. Bambu Lab gives a figure in the same direction: on its H2 printers, going from a 0.4 mm to a 0.6 mm high-flow nozzle raises max flow from about 35 to 40 mm³/s.
The downsides, per Prusa: worse detail on text and small parts, and supports that are harder to remove. And a catch: on a vase printed with a single wall at the same layer height, you won't gain any speed.
2. Layer height
Prusa names it the main factor in print time: taller layers shorten the print a lot at the cost of more visible lines. Within the 80%-of-nozzle limit, going from 0.12 to 0.2 mm on a functional part is one of the easiest ways to save time. And for the best of both worlds, variable layer height puts thin layers only where they show. We explain it in layer height: which to choose.
3. Infill
10-20% infill is what Prusa considers the ideal balance, and it almost never makes sense to go above 40%. For decorative parts, the lightning pattern uses the least time and material of all. If you need strength, add perimeters before infill. Details in infill: which pattern and percentage.
4. Speed modes
Bambu Lab printers have four: Silent (slower and quieter, ideal at night with a good finish), Standard (the default balance), Sport (faster while keeping functional parts reliable) and Ludicrous (speed above all, for drafts and test pieces where looks and strength don't matter). Bambu stresses they make more sense once you know your filament's flow: a mode that pushes past max flow brings under-extrusion and clogs.
5. Temperature: the last resort
When working close to the flow limit, raising the nozzle temperature by 5-10 °C makes the plastic runnier and buys some headroom. Bambu frames it as the last adjustment, after looking for signs the hotend can't keep up (gaps in walls, rough infill, layers splitting), because overdoing it brings stringing, drooping overhangs and colour shifts.
What happens if you overdo it
Exceeding max flow doesn't give faster parts, just worse ones. Bambu Lab lists the symptoms: dimensions that don't add up (a 0.45 mm wall coming out at 0.35 mm), under-extrusion, weak overhangs and bridges, uneven gloss and poorly bonded layers that crack. And over time, clogs and extruder gears chewing the filament.
Frequently asked questions
- Does raising the speed in the slicer make it print faster?
- Only up to a point. The slicer caps speed so it doesn't exceed each filament's max volumetric speed, which is what the hotend can melt. Once you hit that limit, raising speed no longer speeds anything up.
- What saves more time, the nozzle or the layer height?
- They go together. Prusa explains that a 0.6 mm nozzle allows layers up to 0.48 mm and that parts without fine detail can print in half the time. With a 0.4 mm nozzle, raising the layer height also shortens the print a lot.
- Does a bigger nozzle make weaker parts?
- The opposite, according to Prusa: in its tests, parts printed with a 0.6 mm nozzle absorbed up to 25.6% more energy than those from a 0.4 mm one. What you lose is fine detail, such as small text.
- Can I raise the temperature to print faster?
- A little, and as a last resort. Bambu Lab says raising it 5-10 °C leaves a bit more flow headroom, but recommends checking other things first, because overdoing temperature brings stringing, drooping overhangs and colour shifts.
Sources
- Bambu Lab Wiki — Volumetric speed and how it impacts 3D printing (formula, limits, speed modes and symptoms)
- Prusa Blog — Everything about nozzles with a different diameter
- Prusa Knowledge Base — Layers and perimeters
- Prusa Blog — Everything you need to know about infills
- Our own chart, computed with Bambu Lab's formula.