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A failed print is a clue, not a diagnosis. Missing or thin lines point toward under-extrusion; a sudden sideways step suggests a layer shift; fine threads between features are stringing; and corners lifting from the bed are often warping. Identify the shape and location of the defect, check what changed before it appeared, then test one likely cause at a time. The four patterns below are a practical diagnostic guide—not claims about four specific prints.
How to read a failed print before changing settings
Start with the visible pattern and where it begins. A defect confined to the first layer suggests a different investigation from one that appears throughout the part or starts suddenly at a particular height. Also note whether the problem is missing material, a displacement in the part’s geometry, loose strands, or an edge lifting from the build surface.
Write down what changed shortly before the failure: moving the printer, maintenance, a new filament, or a slicer-profile change can narrow the possibilities. Prusa notes that changes and maintenance history can help locate under-extrusion causes. Change one factor per test print where practical; changing several settings at once makes it harder to tell which mattered.
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- Check the printer manufacturer’s instructions for your exact model, hotend, build plate, and material before adjusting hardware or applying a surface treatment.
- Prefer low-risk checks—such as reviewing a profile or inspecting a pulley—before buying replacement parts.
- Do not treat a visual symptom as proof of a single failed component. Several different causes can produce similar-looking defects.
Missing or thin lines: check for under-extrusion
If printed layers have gaps or receive less material than intended, the symptom may be under-extrusion. The result can be weak: Prusa warns that “Printed objects with under extruded layers can be fragile and tend to break apart.” The gaps alone do not establish that the nozzle is clogged.
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Check likely causes in a sensible order
- Review the first layer. A nozzle set too close to the bed can restrict material flow. If the printer was moved or the hotend was serviced—such as after a nozzle change—run the model’s first-layer calibration. Do not compensate for poor adhesion by excessively squashing the first layer.
- Review slicer settings and the profile. Check whether the issue began after a profile or setting change. Confirm that the profile matches the printer and its installed hardware.
- Inspect the nozzle and extrusion path. A nozzle can be one cause, but inspect and follow the machine’s instructions before cleaning or replacing it.
- Check extruder gears and hotend cooling. Gear condition and insufficient hotend cooling are among the possible factors; use the manufacturer’s maintenance guidance for inspection.
- Consider the filament. If the problem began with a different spool or material, compare against a known suitable material and the printer’s recommended settings.
A temperature increase is not a guaranteed fix: higher temperature may also increase stringing. Test a modest, isolated change only when the material and profile guidance support it. Replace a nozzle only if inspection points to it, and verify that any replacement is compatible with the printer and hotend.
A sudden sideways step: investigate a layer shift
A layer shift occurs when the printed layers no longer align in their intended position, creating a sudden horizontal displacement. Note whether the shift is along the X or Y axis; that helps focus inspection on the relevant motion system.
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Inspect before adjusting or replacing parts
- Identify the axis and height where the part first shifts.
- With the printer’s maintenance instructions in hand, inspect belt tension and check that the relevant pulley is secure.
- Adjust only as the manufacturer specifies. Printer designs vary, so there is no universal belt-tension value to apply.
- Run a test print and see whether the displacement recurs before considering a replacement belt or pulley.
Prusa identifies incorrect belt tension and unsecured pulleys as common causes of layer shifts. Its guide says, “A loose or misaligned pulley is usually the main cause of staircase layer shifts”; that guidance is specific to the printer families covered by its support documentation, not every printer design. A shift is a reason to inspect these parts, not automatic proof that one must be replaced.
Fine threads between features: identify stringing
Small filament hairs or threads left between separate features are commonly called stringing or oozing. They are distinct from missing material in a layer or a sideways shift. Filament choice matters, and some materials can remain stringy even when settings are well adjusted; stringing by itself does not prove that a spool is wet, a nozzle is faulty, or one temperature setting is wrong.
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Check whether the strands appeared after a material or profile change. Confirm that the slicer profile is intended for the printer and filament, then consult the material and printer guidance before making incremental setting changes. Print a small test after each change so the result remains interpretable; there is no single correction established for all materials and machines.
Lifted corners: distinguish warping from first-layer trouble
When corners or edges pull up from the bed, the symptom is often called warping. UltiMaker’s UM3 manual attributes warping to material shrinkage during printing and describes a thin layer of glue as a possible measure for that model’s glass plate. That is a model- and surface-specific instruction, not a general recommendation for every printer or build plate.
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First check first-layer setup, the material, and the plate type, then follow the support instructions for the exact machine and surface. A treatment suitable for a glass plate may not be appropriate for another surface; do not transfer the UM3 remedy to a different printer without its manufacturer’s guidance.
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Not every rough or incomplete print fits one of these four patterns. Prusa’s troubleshooting index also distinguishes poor bridging, layer separation or splitting, ghosting, failing supports, first-layer issues, and surface problems above supports. These are different symptom categories, so identify the visible pattern before choosing a troubleshooting path. Detailed settings for those defects depend on the printer, material, and slicer profile; consult the relevant manufacturer documentation rather than assuming one fix applies across machines.
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