Print speed isn't a single number — it's the smallest of three different limits: how much molten plastic your hotend can push per second, how much surface area your fan can cool per second, and how fast your motors can change direction without shaking the machine apart. Cura's "100 mm/s" setting means nothing if any of these limits is hit first.
Your printer's real speed limit is the lowest of: max volumetric flow (mm³/s), max acceleration (mm/s²), and cooling capacity . Stock Ender 3 = ~8 mm³/s, ~500 mm/s². Bambu X1 = ~28 mm³/s, ~20 000 mm/s². Run the max volumetric flow test in OrcaSlicer to find yours, then set max volumetric flow in your filament profile and let the slicer cap speed automatically.
Volumetric flow is the volume of melted plastic flowing through the nozzle per second, measured in mm³/s . It's the most fundamental limit because if your hotend can't melt plastic fast enough, the extruder gear simply skips and you get under-extrusion.
Flow rate = layer height × line width × print speed. So at 0.20 layer / 0.45 width / 150 mm/s, flow = 13.5 mm³/s.
Filament also matters — PLA flows easier than PETG, which flows easier than ABS. High-flow PLAs (Bambu PLA-HS, Polymaker PolySonic) push flow rates up by 30–50%.
OrcaSlicer's "Max Volumetric Speed" calibration is the standard. It prints a tower at increasing flow rates; you measure where the print starts under-extruding and set max volumetric speed slightly below that number. Most people are surprised — their printer's real limit is far below what they assumed.
Part cooling solidifies fresh extrusions so the next layer doesn't melt them or sag onto soft plastic. The faster you print, the more cooling you need to keep up. When you outrun your fan, you see overhangs droop, small-part details slump, and stringing increase.
If you increase volumetric flow and overhangs start sagging, you're cooling-limited. Options:
Acceleration controls how quickly the toolhead changes speed. At 1000 mm/s², going from 0 to 100 mm/s takes 0.1 seconds (a 5 mm distance). Higher acceleration = the printer reaches and holds target speed for more of each move = shorter actual print time, even if the target speed is the same.
Input shaping (or "resonance compensation") measures your printer's natural vibration frequencies and tells the firmware to pre-compensate for them. It lets you run much higher accelerations without ringing/ghosting. Klipper, Marlin 2.1+, Prusa Buddy firmware, and Bambu firmware all support it. Re-run the calibration any time you change major mechanical components (belts, frame, hotend).
The companion to input shaping. It pre-emptively increases extrusion before corners and decreases after, compensating for melt-zone pressure lag. Without it, you get blobs at corners and gaps after them. Test prints take ~10 minutes; the impact on print quality is substantial.
Old-school "jerk" is the instantaneous speed change allowed at corners. New-school "junction deviation" is a smarter, geometry-aware version. Both control how much the printer slows for corners. Higher = faster but rougher; lower = smoother but slower. Most users leave the defaults alone (jerk 8–10, junction deviation 0.05–0.1).
Speed isn't always the goal. Print slow when: