Print Failure Analysis - Diagnosing What Went Wrong

Failed prints are frustrating. But they’re also data. Every failure tells you exactly what to fix.

This guide teaches you to read failure patterns like a detective: What happened, why it happened, and how to prevent it next time.

The Five Most Common Failures

1. First Layer Adhesion Failure (40% of all failures)

What it looks like:

Nozzle approaches bed
Filament comes out but doesn’t stick
Plastic bunches up around nozzle
Print fails before completing first layer

Root causes (in order of probability):

Bed not hot enough (50%)
Bed not level (30%)
Bed surface dirty (15%)
Nozzle too high (5%)

How to fix:

Increase bed temp +5°C, try again
If that fails, re-level bed (0.1mm gap)
Clean bed with isopropyl alcohol
If still failing, nozzle might be clogged or damaged

Prevention:

Always level bed before printing
Always heat bed to target temp before starting
Clean bed monthly
Replace nozzle if damaged

2. Mid-Print Failure - Extrusion Stop (20% of failures)

What it looks like:

Print runs fine for first hour
Suddenly nozzle stops extruding
Nozzle keeps moving but no plastic
Print continues as empty structure (obvious failure)

Root causes:

Nozzle jam (clog prevents flow) - 60%
Filament runout (ran out of material) - 20%
Extruder skip (filament slips in feeder) - 15%
Mechanical failure - 5%

How to identify which:

After failure, check filament spool: Is there material left? (No = runout)
Check nozzle: Is it dark/burnt-looking? (Yes = jam)
Does filament have bite marks from feeder? (Yes = extruder skip)

How to fix:

Filament runout: Add spool, resume print (spool on top of failed print)
Nozzle jam: Stop print, do cold pull, re-level bed, start over
Extruder skip: Check tension on filament feeder, reload filament
Mechanical failure: Inspect extruder gears for cracks

Prevention:

Check filament weight before printing (avoid runouts)
Use quality filament (cheap filament clogs more)
Maintain nozzle temperature (don’t overheat, don’t under-cool)
Clean nozzle regularly (cold pulls weekly)

3. Warping Failure (15% of failures)

What it looks like:

Print runs fine for first hour
Corners start lifting/curling upward
Eventually corner peels off bed
Print continues but compromised

Root causes:

Bed too cold (doesn’t keep part warm) - 50%
No enclosure (ambient air cools too fast) - 30%
Print design (thin walls, no brims) - 20%

How to fix immediately:

Pause print
Increase bed temp +5°C
Spray adhesion promoter around curling area (risky but sometimes works)
Resume

How to prevent future warping:

Increase bed temp by 5-10°C
Add 5-10mm brim (creates extra adhesion)
Build DIY enclosure (cardboard box, $0)
Slow first 10 layers (reduce thermal shock)

Material-specific prevention:

PLA warps rarely (65°C bed sufficient)
PETG warps often (need 85°C bed + enclosure)
ABS warps severely (need 100°C bed + mandatory enclosure)

4. Model Quality Failure - Wrong Settings (15% of failures)

What it looks like:

Print completes successfully
But model looks terrible:
- Horrible layer lines (too thick)
- Stringing everywhere (wispy lines between parts)
- Model is fragile/weak (layers don’t bond)
- Unsupported bridges collapsed

Root causes:

Print speed too fast (50%)
Layer height wrong (30%)
Retraction settings bad (15%)
Missing supports (5%)

How to identify which:

Visible thick layer lines = layer height too high (try 0.15mm instead of 0.2mm)
Wispy stringing = retraction not working (increase retraction 1-2mm)
Weak/brittle model = print speed too fast or temp too low
Collapsed bridges = missing supports

How to fix:

Reprint at slower speed (80mm/s instead of 120mm/s)
Lower layer height (0.15mm instead of 0.2mm)
Increase retraction (5-6mm instead of 4mm)
Enable supports for this model

Prevention:

Use proven slicer profiles (don’t use “fast” profile for quality prints)
Preview sliced model before printing (check supports, layer count)
Start at conservative settings, only speed up after success
Print test cubes with new materials before committing to real projects

5. Mechanical Failure - Hardware Issue (10% of failures)

What it looks like:

Print fails consistently in same way
Happens regardless of settings changes
Often accompanied by noise or grinding sound

Root causes:

Loose belt (skip in movement) - 40%
Clogged nozzle (permanent jam) - 30%
Bed leveling sensor broken - 15%
Extruder gears worn - 15%

How to identify:

Loosebelt: Watch nozzle during print, watch for stuttering or skipped movement
Clogged nozzle: Doesn’t extrude at all, nozzle feels hard when you push filament
Broken sensor: Bed leveling fails, error messages in printer display
Worn gears: Extruder makes clicking sound, can’t push filament through

How to fix:

Loosen belt: Tighten belt tension (check printer manual for adjustment)
Clogged nozzle: Do cold pull, if persistent, replace nozzle ($5)
Broken sensor: Contact manufacturer support (usually warranty repair)
Worn gears: Replace extruder gear ($10-30 depending on printer)

Prevention:

Check belt tension monthly (should have slight resistance when pressed)
Clean nozzle weekly (cold pull takes 5 minutes)
Maintain sensor (keep debris away)
Don’t force filament through feeder (stop if resistance > normal)

Failure Pattern Recognition

By the third failed print, patterns emerge. Use them:

Pattern: Always fails at same layer height → Likely temperature-related or mechanical issue at that point → Increase temps +5°C or inspect for mechanical stutter

Pattern: Always fails on first layer → Adhesion or bed leveling issue → Re-level bed, increase bed temp, clean surface

Pattern: Every print is successful but quality bad → Settings issue, not a failure → Slow down print speed, lower layer height, increase retraction

Pattern: Random failures (sometimes works, sometimes doesn’t) → Inconsistent settings or environmental factor → Check for temperature fluctuations, moisture in filament, loose mechanical components

Pattern: Large prints fail, small prints succeed → Usually warping (large surface area cools more) → Add enclosure, increase bed temp, add brim

The Failure Log (Track Your Learning)

Start keeping a record:

Date	Model	Material	Speed	Bed Temp	Result	Reason
1/28	Benchy	PLA	100mm/s	60°C	Failed adhesion	Bed too cold
1/29	Benchy	PLA	100mm/s	65°C	Success	Higher bed temp fixed it
2/1	Gear	PETG	100mm/s	80°C	Warped	Enclosure needed
2/2	Gear	PETG	80mm/s	85°C	Success	Slower + hotter bed

After 20 prints, you’ll see your printer’s patterns. Use this data to predict success.

The 90% Success Formula

Follow these 5 rules and your success rate hits 90%:

Always level bed before printing (eliminates 40% of failures)
Use proven printer profiles (eliminates 20% of failures)
Print at conservative speeds (eliminates 15% of failures)
Check and clean nozzle monthly (eliminates 10% of failures)
Check filament weight before printing (eliminates 5% of failures)

Together: Eliminates 90% of failures.

Learning from Failure

The good news: Every failure teaches you something specific.

The bad news: Learning requires analysis, not just frustration.

Instead of “ugh, another failed print,” ask:

Where did it fail? (First layer? Mid-print? Quality issue?)
What does that indicate? (Adhesion? Speed? Jam?)
What’s one thing I’ll change next time?

Then change ONE thing and reprint. If it works, you’ve identified the root cause.

Bad approach: Change 5 things at once, print succeeds → Don’t know which change fixed it

Good approach: Change 1 thing, print succeeds → Know exactly what fixed the problem

Failure Acceptance

Here’s the uncomfortable truth: You will fail again.

Even experienced users get 2-5% failure rate (varies by complexity and materials). Zero failures is impossible; 90%+ success is the realistic goal.

The goal isn’t perfection. The goal is: Learn why it failed, fix the cause, move forward.

Print failure is information. The best 3D printer operators are the ones who pay attention to failures, extract the lesson, and apply it.

Your next 10 prints will have fewer failures than your first 10 prints. That’s called learning. That’s progress.