Under-extrusion and over-extrusion in 3D Printing - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is under-extrusion in 3D printing?

Under-extrusion happens when the 3D printer does not push out enough plastic filament. This causes gaps, weak layers, or missing parts in the printed object.

beginner

What causes over-extrusion in 3D printing?

Over-extrusion occurs when the printer pushes out too much filament. This can make the print look messy with blobs, stringing, or thick layers.

beginner

Name two common signs of under-extrusion.

Common signs include thin or missing layers and gaps between lines of filament.

intermediate

How can you fix over-extrusion?

You can fix over-extrusion by lowering the extrusion multiplier or flow rate in the printer settings, or by checking if the filament diameter is set correctly.

beginner

Why is correct extrusion important in 3D printing?

Correct extrusion ensures the printed object is strong, smooth, and accurate. Too little or too much filament causes weak or ugly prints.

What happens when a 3D printer under-extrudes?

A The print has gaps and weak layers

B The print has blobs and thick layers

C The printer stops working

D The filament melts too fast

Under-extrusion means not enough filament is pushed out, causing gaps and weak layers.

Which setting can help fix over-extrusion?

A Increase print speed

B Use thicker filament

C Lower extrusion multiplier

D Raise bed temperature

Lowering the extrusion multiplier reduces the amount of filament pushed out, fixing over-extrusion.

What is a sign of over-extrusion?

A Gaps in the print

B Blobs and stringing

C Thin layers

D Missing parts

Blobs and stringing happen when too much filament is extruded.

Under-extrusion can be caused by:

A Clogged nozzle

B Too much filament

C High extrusion multiplier

D Low bed temperature

A clogged nozzle blocks filament flow, causing under-extrusion.

Why should filament diameter be set correctly?

A To control print speed

B To adjust bed temperature

C To change layer height

D To ensure correct extrusion amount

Correct filament diameter helps the printer push the right amount of filament.

Explain what under-extrusion and over-extrusion are in 3D printing and how they affect print quality.

Think about how too little or too much filament changes the printed object.

Describe two ways to troubleshoot and fix extrusion problems in 3D printing.

Focus on printer settings and physical checks.

Practice

1. What does under-extrusion in 3D printing cause?

easy

A. Gaps or holes in the printed object

B. Blobs or excess plastic on the print

C. The print bed not heating properly

D. The nozzle clogging completely

Solution

1. Step 1: Understand extrusion basics

   Extrusion controls how much plastic the printer pushes out through the nozzle.

2. Step 2: Identify under-extrusion effects

   Under-extrusion means too little plastic is pushed out, causing gaps or holes in the print.

3. Final Answer:

   Gaps or holes in the printed object -> Option A

4. Quick Check:

   Under-extrusion = gaps [OK]

Hint: Under-extrusion = too little plastic = gaps [OK]

Common Mistakes:

• Confusing under-extrusion with over-extrusion
• Thinking under-extrusion causes blobs
• Mixing extrusion issues with bed heating problems

2. Which adjustment is commonly used to fix over-extrusion in 3D printing?

easy

A. Decrease the flow rate

B. Increase the print speed

C. Lower the nozzle temperature

D. Increase the bed temperature

Solution

1. Step 1: Understand over-extrusion causes

   Over-extrusion happens when too much plastic is pushed out, causing blobs or excess material.

2. Step 2: Identify correct adjustment

   Decreasing the flow rate reduces the amount of plastic extruded, fixing over-extrusion.

3. Final Answer:

   Decrease the flow rate -> Option A

4. Quick Check:

   Over-extrusion fix = lower flow rate [OK]

Hint: Lower flow rate to fix over-extrusion blobs [OK]

Common Mistakes:

• Increasing flow rate instead of decreasing
• Changing bed temperature which doesn't affect extrusion
• Confusing print speed with flow rate

3. A 3D print shows gaps between layers and weak bonding. Which code adjustment would most likely fix this?

flow_rate = 0.8  # current flow rate
print_speed = 60  # mm/s
# What should be changed?

medium

A. Increase print_speed to 90

B. Decrease print_speed to 30

C. Decrease flow_rate to 0.5

D. Increase flow_rate to 1.0

Solution

1. Step 1: Analyze print problem

   Gaps and weak bonding indicate under-extrusion, meaning not enough plastic is extruded.

2. Step 2: Choose correct parameter change

   Increasing flow_rate from 0.8 to 1.0 increases plastic output, fixing under-extrusion.

3. Final Answer:

   Increase flow_rate to 1.0 -> Option D

4. Quick Check:

   Under-extrusion fix = increase flow rate [OK]

Hint: Fix gaps by increasing flow rate, not speed [OK]

Common Mistakes:

• Decreasing flow rate worsens under-extrusion
• Changing print speed alone doesn't fix extrusion amount
• Increasing print speed can worsen gaps

4. A 3D print has blobs and stringing. The flow rate is set to 1.2 and print speed is 40 mm/s. What is the most likely error?

medium

A. Nozzle temperature is too low causing clogging

B. Print speed is too high causing under-extrusion

C. Flow rate is too high causing over-extrusion

D. Bed temperature is too high causing warping

Solution

1. Step 1: Identify symptoms

   Blobs and stringing usually mean too much plastic is extruded, called over-extrusion.

2. Step 2: Match symptoms to settings

   Flow rate of 1.2 is high, likely causing excess plastic output and blobs.

3. Final Answer:

   Flow rate is too high causing over-extrusion -> Option C

4. Quick Check:

   Blobs = over-extrusion = high flow rate [OK]

Hint: Blobs? Check if flow rate is too high [OK]

Common Mistakes:

• Blaming print speed instead of flow rate
• Confusing under-extrusion symptoms with over-extrusion
• Assuming temperature issues without evidence

5. You notice your 3D print has thin layers with gaps but increasing flow rate causes blobs. What combined adjustment can fix this?

hard

A. Decrease flow rate and increase nozzle temperature

B. Increase flow rate slightly and reduce print speed

C. Increase print speed and decrease bed temperature

D. Keep flow rate same and increase print speed

Solution

1. Step 1: Analyze problem symptoms

   Thin layers with gaps indicate under-extrusion, but increasing flow rate alone causes blobs (over-extrusion).

2. Step 2: Find balanced solution

   Increasing flow rate slightly adds needed plastic, while reducing print speed allows better layer bonding without blobs.

3. Final Answer:

   Increase flow rate slightly and reduce print speed -> Option B

4. Quick Check:

   Balance flow and speed to fix extrusion issues [OK]

Hint: Balance flow rate and speed to fix gaps and blobs [OK]

Common Mistakes:

• Changing only flow rate causing new problems
• Ignoring print speed effects on extrusion quality
• Assuming temperature fixes extrusion amount