A nozzle that drags across a print leaves a mark that looks different from most defects on this site. It isn’t a hair of stringing, and it isn’t the rough texture vibration leaves on a wall. It’s a scrape, a gouge, or a knocked-over blob, usually on a top surface or wherever the printer just traveled over the tallest point of the job. The cause is almost always the same: the nozzle passed through a spot where the print was taller, or closer, than the slicer expected it to be.
Why the nozzle catches on the print
Between extrusion moves, the printer retracts a little filament, lifts the nozzle, travels to the next start point in open air, then drops back down and resumes printing. That lift is the entire safety margin between the nozzle and everything already on the bed. If it’s too small, switched off, or the print underneath has grown taller than the slicer thinks it is, the nozzle clips the top of a wall, a blob, or a curled corner on the way past. At low speed that leaves a scratch. At normal print speed it can knock a feature loose, skip a step, or drag molten plastic sideways across whatever it caught on.
Not enough Z-hop clearance
That lift has a name: Z-hop in most slicers, Lift Z in PrusaSlicer, Z Hop When Retracting in Cura. Ultimaker’s own documentation for the Cura setting is direct about its job: it moves the nozzle up before a travel move so it can pass over the print without touching it, which is exactly what stops it from leaving blobs or scratches on the surface. Set it to zero, or set it lower than the tallest feature it needs to clear, and dragging is the direct result.
OrcaSlicer splits the setting into several controls that are worth understanding before you just raise the height and hope:
- Z-hop height (
z_hop) sets how far the nozzle lifts on every retraction. - Z-hop type (
z_hop_types) chooses the path: Normal Lift moves straight up and back down, Slope and Spiral move up at an angle to cut down on stringing, and Auto switches in depending on whether the travel move crosses an overhang. - Traveling angle (
travel_slope) sets the angle used for Slope and Spiral; at 90 degrees it behaves like Normal Lift. - Only lift Z above and Only lift Z below (
retract_lift_above/retract_lift_below) restrict the lift to travel moves above or below a specific height on the Z axis, worth checking if the dragging only happens in one section of a tall print.
A height that matches or slightly exceeds your current layer height is a reasonable place to start. PrusaSlicer keeps the equivalent setting under Printer Settings, Extruder, Retraction, labeled Lift Z. Cura keeps it under Travel settings as Z Hop When Retracting. Different name in every slicer, same job.
The bump might not be where the slicer expects it
Raising Z-hop is a real fix, but it only treats the symptom if something on the print grew taller than the current layer height in the first place. A slicer plans its travel moves around the model it sliced, not the plastic actually sitting on the bed, so anything that pushes a feature higher than expected can defeat even a generous hop. The usual suspects are a blob or zit left behind by a retraction or coasting issue, a corner lifting off the bed from warping, or a squashed, over-wide first layer that widens into the travel path. Fixing the bump at its source is more durable than compensating for it with a taller hop on every travel move for the rest of the print. See Fix Blobs and Zits, Fix Mid-Print Curling, and Fix Elephant Foot on 3D Prints.
A tight Z-offset shrinks the margin everywhere
Z-hop height gets added on top of wherever the nozzle already sits. If the Z-offset is dialed in too close (a first layer that’s slightly over-squished is usually the tell), every travel move for the rest of the print inherits that same reduced clearance, and a Z-hop that would normally be plenty stops being enough. Check the offset itself before compensating with an even taller hop. Z-Offset Calibration covers the paper test and the probe-based routines most printers use.
When the travel path itself is the problem
Z-hop only has to do its job if the nozzle travels directly over the print in the first place. Combing settings, sometimes called Avoid Crossing Perimeters, route travel moves around the outside of already-printed walls instead of straight across the top of them. Turn combing off, or leave it set to allow travel over the top surface, and the nozzle takes the shortest path even when a longer route around the outside would have avoided the tall feature entirely. Ultimaker’s documentation for Cura’s travel settings notes that when there’s no way to route around a part, the printer performs a Z-hop over it anyway, which is why the two settings work together instead of replacing each other. Cura Combing Mode covers what each option actually changes.
Ruling out the similar-looking defects
Dragging gets confused with a few other surface problems that come from completely different causes:
- Fuzzy skin is a texture across the whole wall from vibration, moisture, or heat, not a single scrape from a collision.
- Z-banding, also called Z-wobble, is a horizontal ripple that repeats at a regular height because of a bent leadscrew or loose coupler, not a one-off gouge from a travel move.
- Pillowing shows up as bumps and gaps on top surfaces from thin top layers or weak infill support, not from the nozzle physically catching on anything.
If the mark follows a straight line where the nozzle would have traveled, and it lines up with a blob, a warped corner, or the tallest feature on the plate, that’s dragging.
Quick checklist
- Raise Z-hop (Lift Z / Z Hop When Retracting) past your current layer height and see if the marks stop.
- Check whether the drag lines up with a blob, a warp, or an elephant foot, and fix that feature at the source.
- Re-run Z-offset calibration if the nozzle seems to ride close to the bed for the whole print.
- Turn on combing or avoid-crossing-perimeters so travel moves route around tall walls instead of over them.
- Rule out fuzzy skin, Z-banding, and pillowing before assuming every top-surface mark is a collision.
None of these fixes fight each other. A taller Z-hop, a clean Z-offset, and combing turned on all lower the odds of the nozzle ever getting close enough to drag, and most printers are better off with all three set well regardless of whether dragging has shown up yet.
Sources
Settings behavior described here comes from official slicer documentation, checked in August 2026: OrcaSlicer wiki, Z Hop; Ultimaker Support, Travel settings.