This calculator answers a common slicing question: how fast can I print before the surface falls apart? Speed is limited by two different things at once — how fast the hotend can melt plastic, and how much the printer’s frame rings when it changes direction. The tool checks both.
How it works
There are two independent limits.
1. The melt (volumetric flow) limit. The plastic leaving the nozzle each second is a simple cross-section times speed:
Q = layer_height × line_width × speed (mm³/s)Every hotend can only melt so much per second. If Q exceeds that ceiling, the nozzle
under-extrudes — you get gaps, glossy patches and weak layers. Solving the equation for speed
gives the maximum speed for a given flow target:
speed = Q_limit / (layer_height × line_width)The tool reports two flow-based speeds: a derated clean-surface speed (around 65–75% of the ceiling, where walls stay smooth) and the absolute melt-limited ceiling.
2. The ringing (mechanical) limit. Ghosting is vibration from acceleration, not flow. On a stiff frame with input shaping enabled it stays invisible up to very high speeds; without input shaping it typically appears above roughly 80 mm/s. The tool flags this separately so you know whether your bottleneck is the hotend or the motion system.
Tips and notes
- If the verdict says “over the melt limit”, either slow down to the reported ceiling or raise nozzle temperature / fit a high-flow hotend.
- High-speed PLA and high-flow hotends shift the melt ceiling dramatically — that’s why the “PLA High-Speed” preset allows far faster printing than standard PLA.
- TPU has a low flow ceiling and prints slowly regardless of motion-system upgrades.
- Always confirm your real hotend ceiling with a flow-rate calibration before trusting any estimate — frame stiffness, nozzle bore and filament brand all shift the numbers.