Prusa XL – Troubleshooting Guide

Like any other 3D printer, problems can also arise with the Prusa XL. Here I’ll list the most common errors and how to easily fix them.

First of all, you should know that Prusa offers its own troubleshooting guide for the Prusa XL. However, to provide a simple overview, we will list the most common problems here.

Stringing and Oozing

Of course, you can adjust the print temperature, cooling, and filament retraction, but that doesn’t solve the problem in most cases. Stringing can lead to hairy prints, especially with multi-material prints. However, this is very easily fixed by drying the filament. It doesn’t matter what material: PLA, PETG, ABS, ASA, TPU, PC, NYLON, PVA, etc. I’ve never dried PLA or PETG for my MK3s. It always worked well. But with the Prusa XL, it’s different. Drying is simply necessary. The differences can be enormous.

Moisture in the filament

Prusa emphasizes that in multi-tool configurations, even PLA can release moisture absorbed by heat in the hot tool, which increases stringing.

Prusa also has a guide on this. There are different ways to actively dry the filament. However, it simply makes sense to purchase one or more special filament dryers.

In my opinion, the brands Sunlu and Creality offer the best dryers on the market. I originally had a Sunlu S4, but now I’ve switched to a Creality Space Pi X4. While it’s a bit more expensive, it offers several advantages, such as two separate heating chambers and active dehumidification. It can also be heated up to 85 degrees Celsius, whereas the Sunlu S4 only goes up to 70 degrees Celsius.

However, these only accommodate up to four spools. Therefore, I also have a Sunlu S2, which also works very well. This way, all five tools are supplied with dried filament. I also connected them directly to the extruders with PTFE tubing.

I recommend appliances with active dehumidification and temperature control; make sure that the appliance reaches the temperature required for your material (e.g. nylon ≈ 80 °C). Brands like Sunlu/Creality are common – check recent tests/reviews and the max temperature before you buy.

I can recommend these filament dryers:

• Creality Space Pi x4 (For 4 Rolls – Costs around 200€)
• Creality Space Pi Plus (For 2 Rolls – Costs around 90€)
• Sunlu S2 (For 1 Roll – Costs around 50€)
• Sunlu S4 (For 4 Rolls – Costs around 140€)

These are the drying temperatures and times provided by Prusa:

Material	Temperature	Time
PLA	45 ºC	6 hours
PVB	45 ºC	8 hours
PETG	55 ºC	6 hours
ASA	80 ºC	4 hours
PC	85 ºC	5 hours
PCCF	95 ºC	4 hours
PA11CF	90 ºC	6 hours
TPU	60 °C	4 hours
PEI	150 °C	8 hours

Further options

Since the Prusa XL has a tool changer, there’s another possible cause for stringing: the nozzle seals. The nozzle seals must be correctly adjusted. Prusa describes this well here: https://help.prusa3d.com/guide/5-first-run_482742#663410

When printing with multiple print heads, the prime tower should be enabled and placed as close as possible to the tool docks and between the print object. This minimizes the extruder travel distance.

Also make sure that the “Oozing Prevention” function is activated in the slicer. Because if too much material collects at the tip of the nozzle, this can lead to a layer shift.

Excessive oozing can cause material build-up at critical points, which subsequently leads to collisions and thus to layer shifts – especially in multi-tool setups. Therefore, first check the humidity, temperature, retract settings and activated oozing prevention in the slicer.

Layer Shift

Hardware Check

There are a variety of hardware problems that can and will lead to a layer shift. Basically, anything that has to do with XY movement. Therefore, check the following parts:

1. Check the belt tension
2. Check the XY-Carriage is correctly aligned
3. Check the CoreXY movement and the belt alignment for friction or grinding
4. Check for loose or poorly secured Drive Pulleys
5. Check the tool docks for correct alignment
6. Greasing the Tool-Changer
7. Check the belt end locks

1. & 2. It’s important that the belt tension is correctly adjusted and equal on both sides, and the Y-carriage must sit flush and parallel at the front on both sides without any gaps. I’ve already written a detailed guide for this: https://investegate.de/prusa-xl-belt-tension-alignment-calibration-guide

3. Move the X and Y axes back and forth and check if everything runs smoothly without issues. After 1-2 years, the linear rails should be lubricated. https://investegate.de/maintaining-the-prusa-xl/#Lubricating_the_Linear_Rails

4. The drive pulleys on the XY motors must be mounted at the correct height so that the belt can run parallel. And very importantly, they must be tight. Both screws must be tightened gently but firmly. It’s a good idea to use Loctite here.

5. The tool docks must be installed correctly. Check that all docks are firmly seated and correctly aligned. Someone has already explained this clearly on Reddit.

6. There are three docking pins on the tool changer on the tool heads. These should also be lightly greased. There’s also a printable part available for this that can be screwed onto the Prusa Tube. This also works with your finger. Just follow this official Prusa guide.

7. Make sure the top and bottom screws are tight on the back of the tool changer, underneath the Prusa XL Cap.

Software Check

There are a few settings in the slicer that can cause a layer shift. In most cases, the nozzle collides with the print object, causing a layer shift. Here’s how to avoid this:

1. Filament accumulates at the nozzle tip
2. Warping
3. Infill Pattern
4. Z-Hop
5. Faulty Gcode
6. Multi Material Printing Problem

1. The most common cause of layer shift is filament accumulating at the nozzle tip. This can cause material build-up at critical points, which subsequently leads to collisions and thus to layer shifts. This is promoted by wet filament or too high printing temperatures. So, dry your filament with a filament dryer and try lowering the nozzle temperature. If necessary, print a temperature calibration tower. A brush mod can also help keep the nozzle clean. You can also try adjusting the filament retraction and flow. You can also print a calibration test for this.

2. Some materials tend to warp off of the print bed. This can cause a collision between the nozzle and the printed object, which in turn can lead to layer shift. Try increasing the print adhesion with a brim, for example.

3. There are a few infill patterns that can lead to nozzle-to-print collision. Prusa describes the individual infill patterns in detail here. So, make sure you choose an infill pattern that doesn’t cross itself in the same layer.

4. A Z-hop that’s too small or ramping can also lead to a collision. If necessary, disable the ramping function in the slicer and ensure the Z-hop is 0.4-0.8 mm. These parameters may be overridden by the filament settings in the slicer… So check these too.

5. Incorrectly generated Gcode can also lead to such a problem, although this very rarely occurs.

6. When combining different materials, especially when using PLA with PETG supports or vice versa, it can happen that they don’t bond together. This causes material to accumulate at the nozzle tip. And you now know what happens next. So check beforehand that your materials are bonded together in such a way that the two materials can adhere somewhat to each other.

Extrusion Fails

Extruder Motor is Not Spinning

This Error occurs due to increased resistance between the Dwarf and the cable connector, caused by the cable and connector being held too firmly in position. 

It is recommended to install the new screwable “main cable connector covers.” This will firmly secure the cable connection to the Dwarf board. However, if the problem persists, the Nextruder cable must be replaced. This is covered under the Prusa warranty.

You can find the required printable parts here under the heading “Nextruder” You also need some M3x10mm screws and nuts.

Filament Stuck Detection

The “Filament Stuck Detection” sometimes triggers even if there is no blockage. Many people have deactivated this function completely. I’ve played around with it a lot, too. And now I always leave it on. From my own experience, two factors played a big role: A nozzle temperature that was too low and a partially clogged or crushed nozzle.

The standard temperatures defined by Prusa are too high in my opinion. A temperature of 210-215 degrees Celsius is recommended for PLA and 230-240 degrees Celsius for PETG. However, if you want to print faster, you should increase the temperature.

I’m writing this because I initially printed PLA at 200°C. This frequently triggered the filament stuck detection. At 210°C, however, it works perfectly. It can also be triggered if the filament is too heavy to pass through the PTFE tube, or if the filament spool is blocked. If you still have the old PTFE tubes with a 2mm inner diameter, it’s worth switching to the 2.5mm inner diameter. New Prusa XLs already ship with 2.5mm.

Crushed Nozzle

I’ve already covered this topic in detail. Some people, including myself, have simply overtightened the nozzle freehand. This happens quite quickly if you’re not very careful. I’ve designed a 3D-printable torque wrench for this purpose. This will prevent this from happening again.
And your squashed nozzle isn’t lost. It can be undone easily.

Clogged Nozzle

A nozzle can become partially or completely clogged. This is often caused by contaminants in the filament. However, residues from different filaments can also remain and accumulate in the nozzle over time. To properly clean the nozzle, it is recommended to perform a cold pull. This can also be useful if, for example, you are switching from black to white and you don’t want any contaminants in the print image.
This works best with natural nylon. Esun also offers a special cleaning filament at an affordable price, but this is probably just nylon. I have been using this for many years for cold pulls with success. To do this, I load the cleaning filament at 270°C and let about 10-20 cm of it extrude. Then I let it cool to 70°C. I then open the filament idler door and pull it out from the top using pliers. Usually one pass is enough to completely clean the inside of the nozzle.

Belt Tension & Alignment

Belt tension and alignment are essential for good prints. This can cause a variety of problems, but layer shifts and ghosting are the most common.

The guide provided by Prusa leaves a lot of room for improvement… which is why I’ve written my own very comprehensive belt tension guide for the Prusa XL. This should allow you to perfectly adjust your belt tension and simultaneously achieve a perfectly parallel X-axis alignment.

Loud Z-Axis Movement

The Prusa XL can produce loud noises, especially during longer Z movements.

In most cases, this issue is easy to resolve.

Start by cleaning both Z spindles with isopropyl alcohol (IPA) and a clean cloth. Simply hold the cloth against the spindle while moving the heatbed up and down to remove any dirt or residue.

Next, apply a small amount of lubricant such as Super Lube to the Z spindles. Prusa offers an optional nozzle attachment for their supplied lubricant tube, but it’s not necessary — applying the grease with your finger works just as well.

Tip: Less is more. Apply the lubricant to just a few spots along the spindle and then move the bed up and down several times to evenly distribute it.

If the problem persists after cleaning and lubrication, the cause may be mechanical misalignment or excessive tension in the Z-axis system.
Here are a few possible reasons:

• Misaligned trapezoidal nuts or bearing blocks
  → Can create resistance and lead to loud or uneven movement.
• Z-Wobble
  → If one or both Z-spindles are bent and therefore run unevenly, this can also lead to loud noises.

More on this in the Z-Wooble / Z-Banding tab.

Loud CoreXY Movement

With the Prusa XL, loud noises during XY movements can have various causes. Here are the most common reasons:

1. Improper or loose belt tension:
   If the belts are too loose or too tight, they can cause noise when moving the axes. Properly tensioned belts run quieter and more smoothly.
2. Lack of lubrication or dirt on linear rails or guides:
   The Prusa XL uses linear rails (MGN rails). If these aren’t lubricated properly or have dirt/debris, it can cause friction noises. Read more in my Prusa XL maintenance guide.
3. Wear of idler pulleys over time:
   The idler pulleys on the Prusa XL can wear out after about two years of use. This wear can cause noises like squeaking or rattling during XY movements, as the bearings inside the pulleys degrade and no longer run smoothly.
4. Mechanical misalignment or binding:
   If the axes aren’t perfectly aligned or if something is causing binding, it can make motors or mechanics noisy.
5. Wear or poor-quality parts:
   Over time or with low-quality replacements, parts can wear down and cause noise.
6. Unstable or poorly assembled frame:
   A frame that’s not rigid enough can amplify vibrations and noises.

The most common causes for loud noises in XY movements on the Prusa XL are incorrect belt tension, lack of lubrication on linear rails, and broken idler pulleys.

Z-Wooble & Z-Banding

Z-wobble refers to periodic surface artifacts or waves along the Z-axis, usually caused by inconsistencies in how the printer moves vertically. It’s most visible on smooth vertical walls and tends to follow a repeating pattern layer-by-layer.

To determine whether your printer is affected by Z-wobble, you can print a Z-wobble test tower and inspect the surface for repeating patterns or irregularities.

The Prusa XL uses high-quality trapezoidal lead screws to drive the Z-axis. These are critical for accurate vertical movement. However, even with Prusa’s precision, issues can still develop over time.

Common Symptoms

• Fine, repeating surface patterns or “waves” on the Z-axis of printed parts.
• Slight vertical inconsistencies that appear regularly every few millimeters.
• Squeaking, grinding, or resistance during Z movement (especially when powered off and moved manually).

Causes

• Dust and debris can accumulate on the threads over time, especially in open environments.
• Old or dried lubricant can turn sticky or gummy, causing inconsistent movement.
• Physical bending of a lead screw — even a slight bend — can create oscillations that transfer to the print.
• Misaligned installation: If the screw is mounted at an angle or under tension, it can introduce lateral forces with every turn.

Fixes and Maintenance

1. Inspect the lead screws visually:
   • Rotate them manually (with the printer off) and observe if they wobble or shift side-to-side.
   • Look for dirt, residue, or any visible thread damage.
2. Clean the lead screws:
   • Use a lint-free cloth and optionally a mild solvent (e.g., isopropyl alcohol) to wipe off old grease and debris.
   • Avoid excessive force to prevent bending.
3. Re-lubricate the threads:
   • Apply a small amount of PTFE grease, lithium grease, or other non-conductive, plastic-safe lubricant.
   • Rotate the Z axis to spread the grease evenly.
4. Check the screw straightness:
   • With motors disabled, slowly spin each screw by hand.
   • If one visibly “wobbles” side-to-side, it may be bent and require replacement.
5. Ensure the Z nut blocks are aligned:
   • If there’s stress between the lead screw and the nut, the movement may become uneven.
   • Make sure mounting brackets aren’t forcing the screw into a misaligned position.

How to check if a Z-spindle is bent

1. Raise the heatbed almost all the way to the top, leaving about 5 cm of space.
2. Remove the 3D-printed end stops at the top of the Z-axis.
3. Unscrew the four screws located at the corners of the heatbed.
4. Important: Do not pull out the linear carriage under any circumstances – the bearing balls will fall out!
5. Rotate the Z-spindles manually or via the printer menu to raise the bed fully, so it can be safely removed.
6. Carefully set the heatbed aside, ensuring it does not touch the Z-spindles. You can secure it using tape if needed.
7. Now move the Z-axis up or down using the printer menu. This will rotate the Z-spindles without any load.
8. Observe the spindles from directly above. If either spindle visibly wobbles and the deviation at the top exceeds 10 mm, it is considered bent and must be replaced.

Note: Bent spindles are typically covered under warranty.

How to Realign the Z-Axis on the Prusa XL

1. Move the heatbed all the way up using the printer menu.
2. Loosen (but do not remove) the screws of the Z motors, trapezoidal nuts, and Z-axis bearing housings — about 1–2 full turns each.
3. Lower the bed, leaving a gap of about 4–5 cm between the bed and the bottom of the frame.
4. Tighten the screws of the trapezoidal nuts and the Z motors. Use the holes in the heatbed frame to access the Z motor screws and tighten them in a crisscross pattern.
5. Move the bed up again.
6. Tighten the screws of the Z-axis bearing housings.
7. On the LCD, go to Control → Calibrations & Tests → Z Alignment Calibration and run the calibration.
8. Try printing a Z-Wooble Test Tower again and check for improvements.

MCU Maxtemp / Overheating Error

The “MCU Overheating” error on the Prusa XL means that the microcontroller (MCU) has reached a critical temperature. To prevent damage, the printer halts all operations.

This is a serious error and usually indicates issues with cooling, power supply, or internal electronics.

Common Causes of MCU Overheating

1. Insufficient cooling of the electronics
   • Unfortunately, the MCU isn’t actively cooled by default. However, it can be modded.
2. High ambient temperature
   • The printer is operating in an enclosed space or heated chamber, and the electronics can’t cool down properly.
3. Firmware bugs or sensor misreadings
   • Occasionally, incorrect readings can be caused by sensor faults or outdated firmware.

How to Fix the MCU Maxtemp / Overheating Error

If relocating the printer to a cooler environment isn’t an option, the problem can still be resolved relatively easily.

There are community-made mods available that add active cooling to the MCUs using small fans mounted directly over the mainboard components. This ensures continuous airflow and helps prevent thermal buildup during long prints.

However, as a simpler first step, you can try installing passive heatsinks on the stepper driver chips or other heat-sensitive components. These aluminum heatsinks help dissipate heat more efficiently and may already be enough to keep temperatures within a safe range — especially if the ambient temperature isn’t excessively high.

If you install the fan mods anyway, install the heatsinks as well. You can purchase a set of adhesive heatsinks in various sizes here on Aliexpress.

This modification is low-cost, easy to install, and completely reversible.

Manual Tool Calibration Offset

The Manual Tool Calibration Offset allows you to fine-tune the position of each tool head (extruder) relative to the others. This is especially important on multi-tool Prusa XL setups (e.g., with 2–5 tool heads), where slight deviations can occur over time.

When Should You Use It?

• After replacing or adjusting a tool head
• If you notice layer misalignment when changing tools mid-print

The process of manual tool calibration is well described in this article.

Filament Sensor Loud Squeaking

On the Prusa XL, the filament sensors can sometimes produce squeaking noises, especially when using materials like PETG.

This squeaking is caused by the mechanical pressure applied by the internal spring of the sensor, which presses against the filament to detect its presence. With stiffer filaments like PETG, the friction between the sensor lever and the filament increases, resulting in audible squeaking.

To reduce the pressure on the filament and eliminate the noise, you can replace the original spring-loaded mechanism inside the sensor with a magnet-based mod. These magnetic mods use opposing magnets instead of a physical spring, which:

• Reduces friction on the filament
• Minimizes squeaking
• Makes it much easier to load flexible filaments like TPU

You can find these mods here.

Tip: If you’re regularly printing with flexible or abrasive filaments, using a magnetic filament sensor mod is highly recommended for smoother feeding and quieter operation.

Firmware Hard-Reset

A firmware hard reset on the Prusa XL restores the printer to its factory default settings, including calibration data, tool offsets, and user configurations. This is useful when troubleshooting persistent issues or starting fresh after major hardware changes.

When Should You Perform a Hard Reset?

• After repeated firmware bugs or freezing
• When automatic calibrations consistently fail
• If you’ve installed hardware mods and want a clean setup

Some bugs or strange behavior may persist across firmware updates or downgrades, because user settings and calibration data are not fully erased during a standard update.

This means that corrupted configuration files, leftover calibration data, or incorrect tool offsets can carry over — even after installing a newer (or older) firmware version.

In such cases, performing a hard reset ensures that all user-modifiable data is wiped and the printer returns to a clean factory state.
It’s often the most effective way to eliminate stubborn issues that survive through multiple firmware changes.

How to perform a firmware hard reset is described here by Prusa.

Prusa Support

If you’ve tried everything and the issue still isn’t resolved, it’s time to reach out to Prusa Support.

PS: Prusa’s guides also have a comment function. In some cases, it’s worth reading these comments.

How to Contact Support

• Visit help.prusa3d.com
• Open the live chat (bottom-right corner) – available 24/7
• Have your printer serial number, firmware version, and a detailed description of the problem ready
• If possible, attach photos or videos to help the support team understand your issue faster

What to Expect

• Prusa’s support team is known for being knowledgeable and responsive
• They can assist with:
  • Hardware issues
  • Firmware bugs
  • Calibration problems
  • Warranty cases
• If the problem is complex, they may guide you through step-by-step diagnostics or escalate your case to an engineer

Tip

Before contacting support, gather the following:

• A clear description of the issue
• Steps you’ve already tried
• Photos/videos showing the problem
• Print files or logs if relevant (.gcode, .3mf, etc.)

Being well-prepared will save you time and help the support team assist you more effectively.

My Experience with Prusa Support

Even I personally encountered issues with my Prusa XL.
As one of the early adopters of the multi-toolhead version, I faced several problems that couldn’t be resolved on my own — despite extensive troubleshooting.

Eventually, my printer had to be replaced entirely by Prusa.
The process wasn’t completely smooth, but in the end, everything was resolved to my satisfaction.

I’ve documented the entire case, including symptoms, communication with support, and the replacement process, in a detailed blog post you can read here: