Under-extrusion and over-extrusion in 3D Printing - Mini Project: Build & Apply

Understanding Under-extrusion and Over-extrusion in 3D Printing

📖 Scenario: You are learning how to identify and fix common 3D printing problems related to extrusion. Extrusion means how much plastic the printer pushes out to make the object. Sometimes the printer pushes out too little plastic (under-extrusion) or too much plastic (over-extrusion), which affects the print quality.

🎯 Goal: Build a simple checklist that helps you understand and spot under-extrusion and over-extrusion issues in 3D prints. You will create a list of symptoms, causes, and fixes for each problem.

📋 What You'll Learn

Create a dictionary with keys 'under_extrusion' and 'over_extrusion' each holding a list of symptoms

Add a variable for the common cause of extrusion problems

Write nested loops to iterate over each problem type and its symptoms

Add a final summary statement about extrusion issues

💡 Why This Matters

🌍 Real World

3D printing hobbyists and professionals often face extrusion problems that affect print quality. Understanding symptoms helps in troubleshooting and improving prints.

💼 Career

Technicians and engineers working with 3D printers need to identify extrusion issues quickly to maintain efficient production and reduce material waste.

1

Create the extrusion problems dictionary

Create a dictionary called extrusion_problems with two keys: 'under_extrusion' and 'over_extrusion'. Assign to 'under_extrusion' the list ['gaps in layers', 'thin or missing lines', 'weak prints'] and to 'over_extrusion' the list ['blobs on surface', 'stringing', 'thick lines'].

3D Printing

# Create the extrusion_problems dictionary with symptoms lists
# Your code here

Hint

Use curly braces {} to create a dictionary. Use square brackets [] for the lists of symptoms.

2

Add the common cause variable

Create a variable called common_cause and set it to the string 'incorrect extrusion multiplier', which is a frequent reason for both under-extrusion and over-extrusion.

3D Printing

extrusion_problems = {
    'under_extrusion': ['gaps in layers', 'thin or missing lines', 'weak prints'],
    'over_extrusion': ['blobs on surface', 'stringing', 'thick lines']
}
# Create the common_cause variable
# Your code here

Hint

Assign the exact string to the variable common_cause.

3

Loop through problems and symptoms

Write a for loop using variables problem and symptoms to iterate over extrusion_problems.items(). Inside the loop, write another for loop with variable symptom to go through each symptom in symptoms. (You do not need to print or return anything.)

3D Printing

extrusion_problems = {
    'under_extrusion': ['gaps in layers', 'thin or missing lines', 'weak prints'],
    'over_extrusion': ['blobs on surface', 'stringing', 'thick lines']
}
common_cause = 'incorrect extrusion multiplier'

# Loop through extrusion_problems and symptoms
# Your code here

Hint

Use extrusion_problems.items() to get both keys and values. Then loop over each symptom in the list.

4

Add the final summary statement

Add a variable called summary and set it to the string 'Adjusting the extrusion multiplier helps fix both under-extrusion and over-extrusion issues.' to complete the checklist.

3D Printing

extrusion_problems = {
    'under_extrusion': ['gaps in layers', 'thin or missing lines', 'weak prints'],
    'over_extrusion': ['blobs on surface', 'stringing', 'thick lines']
}
common_cause = 'incorrect extrusion multiplier'

for problem, symptoms in extrusion_problems.items():
    for symptom in symptoms:
        pass

# Add the summary variable
# Your code here

Hint

Use the exact string and variable name summary.

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