Z-banding and uneven layer lines: mechanical and settings checks

This guide is for anyone whose prints show stripes, ridges or rings on the side walls. It explains how to read the pattern, lists the causes printer, filament and slicer makers document, gives the checks Prusa, Bambu Lab and Creality publish for their own printers, and says when the fault is likely hardware.

What does the pattern tell you?

Simplify3D describes the defect as "lines or ridges on the sides of your part," and notes that many times "the defects will appear to be cyclical," for example "once every 15 layers." The pattern is the most useful clue you have.

Prusa's article on the "Benchy hull line" draws the line clearly: "If the problem is one thicker line or two thin lines at height of the Benchy's deck, it's most likely not a hardware problem with your printer. On the other hand, if you get uneven layers from top to bottom, it is most likely a hardware problem."

Two other defects can look similar. A sudden sideways step is a layer shift, not banding. Gappy, thin walls are usually under-extrusion.

Which lines aren't a hardware problem?

Start with these, because fixing them costs nothing.

Cross-section transitions

Bambu Lab's layer-lines article says obvious horizontal lines often appear at "cross-sectional transition areas (like the bottom of a box or places where the section changes)," in "flow rate change zones (like outer walls right after bridging)," and at toolhead or color switches. In its box and Benchy examples, it traces the line to shrinkage stress where bridging layers meet the outer wall.

Prusa reaches a similar conclusion. It believes the main culprit for the Benchy hull line is "the sudden transition from sparse infill into full top layers," which causes "an abrupt difference in the time a layer takes to print." It lists material, print cooling, the print environment, and filament dryness and composition as factors in how bad the line looks. Prusa also notes that the effect is more pronounced in a cool basement, and that the same G-code on the same printer with the same filament can show the line in one room and not in another.

What Bambu suggests, in its order:

• Change the model first. Add inner fillets or chamfers so bridging doesn't attach to the outer wall.
• Lower the overhang fan speed in the filament settings to reduce bridging shrinkage.
• Change the sparse infill pattern to Gyroid or Concentric and reduce infill/wall overlap.
• Print several parts at once to lengthen layer time and even out cooling.

Bambu notes these lines "are influenced by temperature, fan speed, geometry and more," so the fixes "help a lot but may not fully remove them." Our overhangs and bridging guide covers cooling and bridge settings in more detail.

Flow changes after bridges

When the outer wall goes from a low flow rate to a high one, such as right after a bridge, Bambu says "abnormal bulges or under-extrusion dents may occur." Its suggestions are to run Flow Dynamics Calibration, lower outer wall speed and acceleration, and enable "Smooth Speed for Discontinuity Area" in Bambu Studio. The most conservative option is to slow the outer wall to match the bridge speed.

Variable layer height

If the lines line up with the layer height changes in your slicer preview, Bambu says the cause is an abrupt jump between layer heights. It recommends turning on Smooth Mode for variable layer height in Bambu Studio. For complex models, it also suggests printing at a fixed layer height while you troubleshoot, to reduce the variables.

Z-hop on older single-lead-screw printers

Polymaker's layer-bulges page describes a case on older printers with a single lead screw. Its example is a Creality Ender 3 V2, where removing Z-hop made squished layers disappear. Its explanation is that the motor finds it harder to raise the axis than to lower it, so "when you have a Z-hop of 0.2mm, your printer may only raise 0.19mm, then drop back down 0.2mm." It suggests turning Z-hop off and enabling "Avoid printed parts when travelling" instead. Polymaker says layer bulges normally happen only on older single-lead-screw printers, though it doesn't rule out other machines.

Extrusion and temperature

Some banding isn't a Z problem at all. It comes from layers that are each extruded a little differently.

• Filament diameter. Simplify3D calls poor filament quality "the most common cause" of lines on the side of a print. It explains that a 5% variation in diameter could change the extruded width "by as much as 0.05mm." Bambu lists filament quality as a cause of random lines with local over- or under-extrusion. It suggests trying a different filament with consistent diameter and checking that the tolerance is 1.75 ± 0.02 mm.
• Wet filament. Prusa names filament dryness as a factor in how visible the Benchy hull line is. If the lines appear with only one spool, dry it before you touch the hardware. Our filament dryer vs dry box guide covers drying.
• Hotend temperature swings. Simplify3D says a poorly tuned PID controller lets the extruder temperature fluctuate, often in a cyclical pattern, which can create "visible ridges on the sides of your print." It says a properly tuned printer "should be able to maintain the extruder temperature within +/-2 degrees," and to consult your printer maker for how to recalibrate. Our guide to a fluctuating nozzle temperature covers how to spot and fix temperature swings.

Bed temperature. Many people suspect the heated bed cycling on and off. We didn't find printer- or slicer-maker documentation linking bed temperature swings to banding, so treat it as a theory, not an established cause. Simplify3D's documented temperature cause is the hotend.

Mechanical causes

If the lines repeat evenly up the whole print and survive the checks above, look at the machine.

Z lead screw, coupler and nut

• Alignment. Polymaker traces layer bulges on older single-lead-screw printers to "a leadscrew that isn't perfectly 90 degrees." Its check is to loosen the motor coupler, lift the screw out, raise the carriage, and see whether the screw drops straight into the coupler.
• A bent screw. Polymaker suggests rolling a removed lead screw on a flat table, where bends become noticeable. Creality's K1C guide for Z-axis noise starts with checking "if there are any bends or deformations in the three lead screws."
• Dirt and lubrication. Polymaker recommends cleaning the lead screw and lubricating it. Bambu Lab and Creality publish lead screw lubrication procedures for specific models, and Prusa's CORE One maintenance article names the lubricant for its leadscrews. These are covered below.
• Backlash. Simplify3D lists a Z-axis threaded rod "that is not being positioned properly," for example "due to backlash issues," among the mechanical causes. Polymaker suggests that if the screw is straight and aligned and bulges persist, an anti-backlash nut may help on printers that can take one.

Polymaker also notes that thin M5 or M6 threaded Z rods "can lead to rod wobbling or bending over time," and that anti-wobble couplings help but "are not a substitute for replacing bent rods."

Wobble from loose parts

Polymaker describes Z-axis wobble as "repeated minor layer shifts, sometimes with every single layer," and is blunt that "you can hone in all of the slicer settings properly, but it will not fix this issue." The causes it lists include:

1. A loose extruder carriage or hotend, which it calls "probably the most common cause." With the hotend at room temperature, give it a gentle rattle and look for free play.
2. Worn bearings or loose rollers. On printers with rollers, such as the Ender 3, Polymaker says to turn the nut on each roller until it holds tight to the aluminum extrusion.
3. A loose build plate on bed-slinger printers. It says this isn't an issue on CoreXY machines, where the bed only moves up and down.
4. Loose X and Y belts. It says they should have "zero-droop."
5. Tall, skinny parts on printers where the bed moves back and forth. Polymaker says these can wobble as the bed moves, leaving the top of the print wobbly while the bottom looks fine.

Microstepping and layer height

Prusa's online calculator includes a tool for choosing a layer height "in a way, that Z axis moves only by full step increments." It explains that if the Z axis is disabled partway through a microstep, the axis jumps to the closest full step, which introduces error, and that this happens to some extent even when the Z motors stay enabled. Prusa says this matters most for machines with imperial lead screws, "but also for unusual layer heights with metric leadscrews." Simplify3D likewise lists "poor motor controller micro-stepping settings" as a mechanical cause.

The arithmetic is simple: the distance the screw advances per turn, divided by the motor's full steps per turn. For example, a 1.8° motor (200 steps per revolution) on a lead screw that advances 8 mm per revolution moves 0.04 mm per full step. Layer heights that are whole multiples of that value land on full steps. Your printer's lead screw and motor may differ, so use your maker's specifications or Prusa's calculator rather than borrowing a number.

Checks by printer maker

Prusa

• Read the line first. Use Prusa's test: one line at a model transition is most likely not hardware, while uneven layers from top to bottom most likely are.
• Lubricate per the maintenance guide. Prusa's CORE One maintenance article says the Prusa Lubricant supplied with the printer is used to lubricate the Z-axis leadscrews, and warns not to use it on the linear rail. That article doesn't give a separate leadscrew procedure or interval, so check the maintenance article for your model.
• Choose full-step layer heights with Prusa's calculator if you print at unusual layer heights.

Bambu Lab

Bambu's layer-lines article covers the slicer causes above, then lists checks for "random, irregular" lines:

• H2, X2D, P2S and A1 series: remove the silicone sock and check that the hotend clip is fastened correctly and not bent, cracked or worn. Check that the magnet is intact. Then gently wiggle the nozzle assembly. Bambu says that if it "wobbles noticeably," the hotend isn't fully latched and the clip needs reinstalling.
• X1 and P1 series: Bambu says hotend loosening is "usually related to loosened nozzle fastening screws." Use an H2.0 screwdriver to check they're fully tightened.
• Lead screws (X1 series): Bambu's X1 maintenance guide says "the z-axis lead screws should be checked and greased every three months." Clean off dust and plastic first, then apply a thin coat with the bed at different heights. For other series, Bambu's lead-screw page links each model's own procedure.

Creality

Creality publishes model-specific pages. Several point to the toolhead, belts and bed as well as the Z axis:

• Ender-3 V3 SE ("Print Layer Texture"): causes include a wobbling print head, a loose belt, X-axis stuttering, a loose hotend kit, and changed parameters. Checks: adjust the X-axis eccentric nut, re-tension the belt, check the pulley and profile for damage and the X axis for jamming, and check the nozzle assembly screws. Creality also suggests testing the G-code files supplied on the printer's memory card if you've changed settings such as acceleration or outer wall speed.
• Ender-3 V3 KE ("Print Layer Lines"): causes include a loose gantry, a Z-axis V-wheel that sticks or is loose, loose extruder backplate screws, a loose belt, a loose nozzle assembly, and "severe wobbling" of the heated bed or slider plate.
• K1C (Z-axis noise): check the three lead screws for bends, clean them and apply lubricating oil, check for bed tilt, and check that the Z-axis motor screws are tight.
• K2 Plus: Creality's lead screw cleaning guide recommends lubricating once a week with frequent use, or every two weeks with infrequent use, using the procedure and lubricant it specifies.

For other models, search the Creality Wiki for your exact printer.

A sensible test order

1. Look at the pattern: periodic, one-off at a transition, or random.
2. Print a simple test with a fixed layer height, from your printer maker's profile.
3. If the lines match model transitions or bridges, try the slicer changes above.
4. Swap to a different, dry spool. If the lines change, look at the filament.
5. Check hotend temperature stability on the printer's display during a print.
6. Power off and check the nozzle assembly, toolhead, belts and bed for free play.
7. Clean and lubricate the Z lead screws following your maker's procedure.
8. Check lead screw straightness and coupler alignment where your maker documents it.

Change one thing per test print and write down what you changed.

When is it a job for support?

Contact the printer maker's support when:

• Uneven layers run from top to bottom after the slicer and filament checks. Prusa says that pattern is most likely a hardware problem.
• The maker's checks don't fix it. Bambu's article ends: "If the above methods are ineffective, it is recommended to perform maintenance on the device," and to submit a support ticket if that doesn't solve it.
• You find a bent lead screw, a damaged pulley, or a Z motor that won't hold. These are parts problems. Get the correct replacement for your exact model from the maker, rather than a generic part.
• The printer is under warranty. Ask support before taking apart anything the maker's guides don't cover.

When not to buy parts

Hold off on anti-wobble couplers, new lead screws or a new hotend if:

• The lines sit at one height where the model changes shape. That's a slicer and cooling problem, per both Prusa and Bambu.
• The lines change with the spool. Test the filament first.
• You haven't checked for loose screws. Polymaker calls a loose carriage or hotend the most common cause, and tightening costs nothing.
• The lead screws haven't been cleaned or lubricated on your maker's schedule.

If your printer maker's checks point to a worn or damaged nozzle assembly, our replacement nozzle guide explains how to match one to your exact hotend. Most of the mechanical checks above need only the tools your maker specifies.

Tools: what to check before you buy ↗