About this tool
How fast an FDM printer can print is usually limited not by the mechanics but by the hot end: it can only melt a certain amount of plastic per second. This volumetric flow in mm³/s is the cross-section of the printed line times the speed. A line 0.45 mm wide at 0.2 mm layer height and 150 mm/s needs about 12 mm³/s.
In the second mode you enter your hot end’s limit and get the highest speed for your layer height and line width. The calculator also shows how fast the filament runs into the extruder and how many grams of PLA go through per hour.
How it works
- Choose whether to calculate the flow at a speed or the maximum speed.
- Enter the print speed or the hot end’s maximum flow.
- Enter layer height, line width and filament diameter.
- Read the volumetric flow or maximum speed, the filament feed and the throughput.
Frequently asked questions
How much flow can my hot end handle?
As a rough guide, classic hot ends with a short melt zone manage about 10 to 15 mm³/s of PLA, high-flow hot ends with a long melt zone 25 mm³/s and more. The real value depends on material and temperature; a flow test, as offered by OrcaSlicer for example, is the most accurate.
Why is the cross-section smaller than width times height?
A printed line has no sharp edges but rounded sides. PrusaSlicer and OrcaSlicer therefore use (width − height) × height + π × height² / 4. For 0.45 × 0.2 mm that is 0.081 instead of 0.09 mm².
What happens if I print too fast?
The hot end can no longer melt the filament completely. The result is under-extrusion, weak layer adhesion and in extreme cases a skipping extruder. If the amount extruded is wrong in general, use the Extruder Calibration (E-steps & Flow).
Where do I set the limit in the slicer?
In PrusaSlicer and OrcaSlicer in the filament settings as max volumetric speed. The slicer then slows every line down so that the flow is not exceeded.