Fix PLA stringing: retraction settings for Cura and PrusaSlicer

Stringing is molten plastic leaking out of the nozzle while the print head travels, and retraction is the fix: the extruder pulls filament back to drop the pressure in the melt zone before the move starts. On a direct-drive extruder that takes far less movement than most profiles suggest, roughly 0.5-2 mm, and Bambu Lab’s troubleshooting page warns that going much past 2 mm mostly buys you clogs. Bowden machines need more: Prusa ships its Bowden MINI with a 3.2 mm retraction length against 0.8 mm on its direct-drive printers.

This guide names every retraction setting as it appears in Cura and in PrusaSlicer, gives the default each one actually ships with, and runs the test tower that turns those defaults into a number for your machine. The values come from UltiMaker’s Cura settings definition, PrusaSlicer’s configuration source and Prusa’s own printer and filament profiles, the OrcaSlicer calibration documentation and the Bambu Lab wiki, all linked at the end. Anything that is a starting range rather than a published figure is labelled as one.

Stringing fix in six steps

1. Dry the filament. Bambu Lab lists damp filament as the first cause of stringing and oozing, ahead of any slicer setting.
2. Lower the nozzle temperature in 5 °C steps while layer adhesion still looks good. Hotter plastic is thinner and leaks faster.
3. Read the retraction distance your profile is really using, not the one you assume it has.
4. Print a retraction tower and take the shortest length that comes out clean.
5. Sweep retraction speed with that length locked, watching for ground filament at the extruder.
6. Only then touch combing, wipe, coasting and Z-hop. They hide or trim ooze; they do not stop it.

Retraction settings by name in Cura and PrusaSlicer

The same handful of controls exists in both slicers under different names, units and defaults. Cura’s figures below come from the generic fdmprinter definition that every machine profile inherits; PrusaSlicer’s are the built-in defaults from its configuration source, with the values Prusa ships in its own printer profiles in brackets.

What it controls	Cura name (default)	PrusaSlicer name (default)
How far the filament is pulled back	Retraction Distance – 6.5 mm	Retraction length – 2 mm (Prusa profiles: 0.8 mm on MK3.5, MK4 and XL, 3.2 mm on the MINI)
How fast it is pulled back and pushed in again	Retraction Speed – 25 mm/s; separate retract and prime speeds inherit it	Retraction Speed – 40 mm/s, Deretraction Speed – 0, meaning the same as retraction (Prusa profiles: 35 mm/s out, 25 mm/s back)
Shortest travel that still triggers a retraction	Retraction Minimum Travel – 1.5 mm in the definition, but calculated as twice the line width unless you override it	Minimum travel after retraction – 2 mm (Prusa profiles: 1-1.5 mm)
Extra material pushed in on restart	Retraction Extra Prime Amount – 0 mm³	Deretraction extra length – 0 mm, called extra length on restart in older builds
Keeping travel inside the part instead of retracting	Combing Mode – All; options are Off, All, Not on Outer Surface, Not in Skin, Within Infill	Avoid crossing perimeters – off, and off in Prusa’s shipped print profiles too
Lifting the nozzle during travel	Z Hop When Retracted – off, Z Hop Height 1 mm (Creality profiles set 0.2 mm)	Lift height, in the Lift Z group – 0 mm (Prusa profiles: 0.2-0.4 mm)
Using leftover nozzle pressure at the end of a line	Enable Coasting – off, Coasting Volume 0.064 mm³	No coasting setting exists; the nearest tool is Wipe while retracting, off by default and on in Prusa’s profiles

The 6.5 mm trap. Cura’s retraction distance is a Bowden-era value inherited from UltiMaker’s own machines, and machine definitions do not always override it: Creality’s definition in the Cura repository changes combing, Z-hop height and minimum travel, but leaves the distance alone. Run that on a direct-drive Ender-class printer and you pull melt back towards the cold zone on every travel move. Open the setting and read the number before you blame the printer.

Two settings that look identical and are not. Cura’s Retraction Extra Prime Amount is a volume in mm³; PrusaSlicer’s deretraction extra length is a length of raw filament in mm. Copying 0.1 from one into the other copies two different amounts of plastic. Both ship at zero, and should stay there until you can see gaps at the start of lines.

Direct drive or Bowden: where to start

The distance between the drive gears and the melt zone decides everything. A direct-drive extruder grips the filament a couple of centimetres above the nozzle, so a short pull relieves the pressure at once. A Bowden extruder pushes through a long PTFE tube, and the filament inside behaves like a spring: part of any retraction is spent unloading the tube before the nozzle notices.

• Direct drive, start at 0.5-2 mm. OrcaSlicer’s retraction test sweeps 0 to 2 mm in 0.1 mm steps and calls that range suitable for most direct-drive extruders. Bambu Lab, whose machines are direct drive, recommends keeping the length no greater than 2 mm because longer retractions invite clogs. Prusa’s direct-drive profiles sit at 0.7-0.8 mm.
• Bowden, start at 3-6 mm. OrcaSlicer suggests sweeping 1 to 6 mm in 0.2 mm steps for Bowden setups. Prusa’s Bowden MINI ships at 3.2 mm and 70 mm/s: four times the distance and twice the speed of its direct-drive siblings. A very long tube may need more, but treat anything past 6 mm as a reason to check the tube and couplers first.
• Minimum travel scales too. Prusa’s MINI and XL profiles skip retraction below 1.5 mm of travel, where MK3-era profiles use 1 mm. A higher value means fewer retractions and less chewed filament, at the cost of the odd string across a small gap.

These are starting points for the tower, not answers. If the extruder layout itself is in question, we compare the trade-offs in whether a direct drive conversion is worth it.

Set nozzle temperature before retraction

Heat sets how runny the melt is; retraction sets how much pressure is left pushing it out. A retraction value found at one temperature stops being right at another, so settle the temperature first and tune retraction on top of it.

• How far to drop. Prusa’s stringing guide suggests lowering the nozzle temperature by 5-10 °C and checking whether the strings thin out. For reference, Prusa’s generic PLA profile prints the first layer at 215 °C and the rest at 210 °C.
• Where to stop. Take the lowest temperature that still bonds layers well, not the lowest one the hotend will push through. A temperature tower shows both limits in a single print.
• Speed moves the target. Bambu Lab’s filament guides make the point for PETG, and it holds for PLA too: a slower profile melts less plastic per second, so the same temperature leaves it runnier. If you slow a print down to fix something else, expect more ooze until the temperature comes down with it.

Too cold trades strings for weak, splitting layers. If a part snaps along the layer lines after the change, come back up in 5 °C steps.

Print a retraction tower

A retraction tower is a vertical model whose retraction length changes every few millimetres of height, so one print shows a whole range of values under identical conditions. OrcaSlicer generates one from a menu; in Cura and PrusaSlicer you get the same result with a height-range modifier, a change-at-Z script, or a stringing test printed several times with one value each.

1. Settle everything else first: dry filament, a temperature you have already chosen, and constant print and travel speeds. One variable at a time.
2. Set the sweep. 0 to 2 mm in 0.1 mm steps for direct drive, 1 to 6 mm in 0.2 mm steps for Bowden, following OrcaSlicer’s documented defaults.
3. Take the shortest clean band, not the tallest. The optimal length is the smallest one that produces a clean tower; every extra millimetre beyond it only adds wear and clog risk.
4. Turn height back into a value using the marker comments in the G-code preview rather than counting bands by eye.
5. Then sweep speed with the length locked, in 5-10 mm/s steps around the slicer default: 25 mm/s in Cura, 40 mm/s in PrusaSlicer, 35 mm/s in Prusa’s profiles. Stop as soon as the extruder grinds a flat spot onto the filament.
6. If the whole tower strings, stop tuning. OrcaSlicer’s own note says a tower still hairy at the top points to wet filament or a nozzle that is not seated tightly, not to a retraction value you have yet to find.

A tower that is clean from the first band is normal on low-ooze materials: OrcaSlicer notes PLA and ABS often need only 0.2-0.4 mm on a direct-drive machine. Cura guards the opposite extreme with Maximum Retraction Count, which allows 90 retractions inside a 4.5 mm window of extruded filament and ignores the rest, because retracting the same short piece of filament repeatedly flattens it.

Coasting, wipe and the blobs at the seam

Retraction deals with travel. Blobs and zits are a different defect: a local lump where a line starts or ends, left by pressure that is still in the nozzle when the extruder stops, or by too much material pushed in when it restarts.

• Coasting is a Cura feature. It cuts extrusion short and lets the leftover pressure finish the line. Off by default, with Coasting Volume 0.064 mm³, Minimum Volume Before Coasting 0.8 mm³ so short paths are left alone, and Coasting Speed at 90% of the print speed. Overdo it and line ends come up short.
• Wipe exists in both, differently. PrusaSlicer’s Wipe while retracting drags the nozzle along the finished wall as it retracts, and Retract amount before wipe sets how much of the pull happens first: 80% in the MK4 profiles, 70% on the MINI. Cura’s equivalent is Outer Wall Wipe Distance, which defaults to half the nozzle diameter, so 0.2 mm on a 0.4 mm nozzle.
• Extra prime is a last resort. Raise it only when you can see a gap where a perimeter restarts, in the smallest steps the field accepts. Overshoot turns the gap into a bump.
• Retract on layer change is off in PrusaSlicer’s built-in defaults and on in every Prusa printer profile. It costs one retraction per layer and removes the blob that otherwise lands at each layer start.

Those lumps all stack up in one place: the seam, where each perimeter starts and stops. Prusa’s print profiles default to an aligned seam, Cura to the sharpest corner. If what remains still bothers you, move it rather than chase it, using the options in our guide to Z-seam placement.

What changes for PETG and TPU

Prusa publishes its filament profiles as plain text, which makes the material differences readable instead of anecdotal. Each value below is a documented override sitting on top of the same printer profile.

Material	What Prusa’s profile changes	Why it helps
PLA	No retraction override at all; it runs the printer default, 0.8 mm on a direct-drive Prusa, 3.2 mm on the MINI	Low ooze, so the printer profile is already close enough
PETG	Retraction length raised to 1 mm, plus a 0.2 mm lift	A stickier melt, and lifting keeps the nozzle from dragging through it
Flexibles, direct drive	0.8 mm, wipe switched off, no lift	Elastic filament stretches instead of moving, so gentler is better
Flexibles, Bowden MINI	4 mm, minimum travel raised to 6 mm, deretraction slowed to 15 mm/s, wipe off	The tube demands a long pull, so the profile retracts rarely instead of often

The flexible profile is the instructive one. Faced with a material that punishes retraction, Prusa raises the minimum travel to 6 mm so the printer retracts far less often: the combing tactic applied to the material rather than the toolpath. Our guides to PETG print settings and to preventing TPU jams cover the temperature and flow side of both materials.

Symptom, cause, fix

What you see	Likely cause	What to change
Fine strings everywhere, worst between separate parts	Too little retraction, or too much heat	Run the tower, drop the nozzle 5 °C at a time, raise travel speed
Strings plus popping sounds and a rough surface	Damp filament boiling in the melt zone	Dry the spool, store it sealed with desiccant; no retraction value fixes this
Strings only across short gaps	Minimum travel set so high that no retraction happens	Lower Retraction Minimum Travel, or Minimum travel after retraction
Blobs or zits where perimeters start	Extra prime too high, or no retraction on layer change	Return extra prime to zero, enable retract on layer change
Gaps and thin starts straight after a travel move	Retraction too long, or deretraction too slow to refill	Shorten to the smallest clean tower band, raise deretraction speed
Clicking extruder, flat spot ground into the filament	Too many retractions over the same piece of filament	Raise minimum travel, enable combing or avoid crossing perimeters, lower retraction speed
Strings plus blobs, walls wider than the line width	Over-extrusion: flow too high, so extra pressure sits in the nozzle	Calibrate flow first; no retraction value outruns surplus plastic
Bulging corners and thin line starts, worse at speed	Pressure advance or linear advance untuned	Run a pressure advance test before shortening or lengthening retraction
Stringing got worse after enabling Z-hop	More time in the air on every travel move	Cut the hop to the minimum that clears the print, or switch it off while tuning
A clog appeared after raising the distance	Melt pulled up towards the cold end	Go back to the last good value; Bambu Lab’s ceiling for direct drive is 2 mm

When retraction is not the problem

Bambu Lab’s troubleshooting page lists six causes of stringing and oozing, and only one is a retraction number. Rule out the rest before printing another tower:

• Damp filament, which vaporises inside the nozzle and pushes plastic out whatever the pressure is doing.
• Nozzle temperature too high, which thins the melt until no retraction can hold it.
• Long travel distances, including models spread across the plate. Moving them closer, or printing one object at a time, removes the travel instead of managing it.
• A nozzle that is worn, or wider than the profile expects, which simply lets more material out. A partial clog gives the same erratic flow.
• The hotend itself. Prusa’s stringing guide also lists poor heat dissipation and an incorrectly assembled hotend. A nozzle that is not seated tightly against the heat break is the usual assembly fault to check.
• Travel speed. Cura’s default is 120 mm/s and PrusaSlicer’s built-in default 130 mm/s, while Prusa’s input-shaper profiles travel at 300 mm/s. Faster travel gives ooze less time to form a strand, if the mechanics can take it.

For a print already off the bed, settings help nothing: see how to remove strings and blobs from a finished print, then fix the profile for the next one.

Frequently asked questions

Why does Cura default to 6.5 mm of retraction?

That value lives in Cura’s generic machine definition, which every profile inherits, and it reflects UltiMaker’s Bowden machines. Several third-party definitions in the Cura repository override combing and Z-hop but not the distance, so a direct-drive printer can end up running it unchanged. On direct drive, start around 1 mm and tune from there.

Is there a coasting setting in PrusaSlicer?

No. Coasting is a Cura feature, off by default with a volume of 0.064 mm³. PrusaSlicer relieves end-of-line pressure another way, through Wipe while retracting together with Retract amount before wipe, which Prusa’s own profiles enable at 70-80%. Tuning the wipe is the equivalent step.

How much retraction is too much?

Once the tower stops improving, more distance only costs you. Bambu Lab recommends keeping the length at or below 2 mm on its direct-drive machines, because longer pulls draw melt towards the cold zone and cause clogs. The warning signs: a clog right after a settings change, ground filament, thin or missing starts after travel moves.

Should I raise retraction for PETG?

Slightly, and not as the first move. Prusa’s PETG filament profile raises the retraction length from 0.8 mm to 1 mm and adds a 0.2 mm lift on the same printers, which is a small change next to getting the filament dry and the temperature down. PETG takes up moisture readily, and damp PETG strings no matter what the extruder does.

Sources

• UltiMaker Cura: fdmprinter settings definition with retraction defaults
• PrusaSlicer: PrintConfig source, setting labels and built-in defaults
• Prusa Research: PrusaSlicer printer and filament profile bundle
• OrcaSlicer wiki: retraction test tower
• Prusa Knowledge Base: stringing and oozing
• Bambu Lab wiki: stringing and oozing