Too much material coming out (over-extrusion)
Over-extrusion ruins the finish and, above all, the tolerances: if a part needs to fit into another, an extra half-tenth of plastic spoils it.
What the failure looks like
Surfaces with blobs and ridges, bulging corners, nozzle dragging over previous layers and the part measuring over size.
Causes, most likely first
- 01
Flow above 100%
Legacy profiles or old tweaks that nobody reverted.
- 02
Incorrectly set filament diameter
The slicer expects 1,75 mm and the filament is actually 1,70: too much plastic goes in.
- 03
High temperature
The plastic oozes and expands on exit.
- 04
E-steps set too high
The extruder pushes more than it thinks.
Step-by-step fix
1. Reset flow to 100%
And work from there.
2. Measure and input the real diameter
Average of three measurements with callipers.
3. Single-wall test
20 mm cube, 0 infill, 0 top layers, 1 perimeter. Measure the wall: it should match the line width (0,42-0,45 mm with a 0,4 nozzle).
4. Adjust flow using the formula
New flow = current flow x (target width / measured width).
5. Lower by 5-10 °C
If the material allows it without losing layer adhesion.
So it doesn't happen again
- One profile per material and brand; do not reuse the cheap PLA profile for technical PETG.
- Recalibrate the flow when changing nozzles.
Related questions
Over-extrusion or low Z-offset?
If it only happens on the base, it's Z-offset. If it happens across the entire height of the part, it's flow.
Keep reading
What if it isn't worth your time?
Sometimes the part is more urgent than the learning curve. We're a workshop in Viladecavalls: send us the file and we'll print it with the right material and settings.
Still not working?
Tell Marco which printer and material you use and he'll tell you what to change.
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