Manual G-code modifications in 3D Printing - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is G-code in 3D printing?

G-code is a set of instructions that tells a 3D printer how to move, where to move, and how fast to move. It controls the printing process step-by-step.

beginner

Why would you manually modify G-code?

You might change G-code manually to fix printing errors, adjust print speed, change temperatures, or customize specific movements for better print quality.

beginner

What does the G1 command do in G-code?

G1 tells the printer to move in a straight line to a specified position at a set speed. It is used for controlled movements during printing.

intermediate

How can you safely edit G-code without causing print failures?

Always back up the original file, make small changes, understand what each command does, and test the modified code on a small print before a full print.

intermediate

What is the effect of changing the temperature commands (M104, M109) in G-code?

M104 sets the extruder temperature without waiting, while M109 sets the temperature and waits until it is reached before continuing. Changing these affects how the filament melts and prints.

What does the G28 command do in G-code?

A Moves the print head to a specific coordinate

B Starts the print

C Sets the extruder temperature

D Homes all axes to their origin

G28 moves all printer axes to their home position, usually the origin point.

Which command sets the extruder temperature and waits until it is reached?

A M104

B M140

C M109

D G1

M109 sets the extruder temperature and pauses the print until the temperature is reached.

Why should you back up your original G-code file before editing?

A To prevent losing the original if edits cause errors

B To share it with friends

C To speed up printing

D To reduce file size

Backing up ensures you can restore the original if your changes cause problems.

What is a common reason to manually edit G-code?

A To adjust print speed or fix errors

B To change the color of the filament

C To change the printer brand

D To increase the file size

Manual edits often fix errors or customize print speed and movements.

What does the G1 command control?

A Temperature settings

B Straight line movement

C Fan speed

D Pause the print

G1 commands the printer to move in a straight line to a specified position.

Explain why and how you would manually modify a G-code file for a 3D print.

Think about improving print quality or fixing issues.

Describe the difference between M104 and M109 commands in G-code.

Focus on how the printer handles temperature changes.

Practice

1. What is the main purpose of manually editing G-code in 3D printing?

easy

A. To increase the printer's physical size

B. To change the filament color automatically

C. To customize printer actions beyond slicer settings

D. To update the printer's firmware

Solution

1. Step 1: Understand what G-code controls

   G-code commands tell the printer how to move, heat, and print.

2. Step 2: Identify the effect of manual edits

   Editing G-code manually lets you change these commands beyond what slicer software sets.

3. Final Answer:

   To customize printer actions beyond slicer settings -> Option C

4. Quick Check:

   Manual G-code editing = Customizing printer actions [OK]

Hint: Manual edits change printer commands directly [OK]

Common Mistakes:

• Thinking it changes physical printer parts
• Confusing G-code editing with firmware updates
• Assuming it changes filament color automatically

2. Which of the following is a correct G-code command to pause a print?

easy

A. M104 S0

B. G28

C. G1 X10 Y10

D. M25

Solution

1. Step 1: Identify pause commands in G-code

   M25 is commonly used to pause SD card printing.

2. Step 2: Check other commands

   M104 S0 sets temperature to 0, G28 homes axes, G1 moves the nozzle.

3. Final Answer:

   M25 -> Option D

4. Quick Check:

   Pause command = M25 [OK]

Hint: Pause print with M25 command [OK]

Common Mistakes:

• Confusing M104 (temperature) with pause
• Thinking G28 (home) pauses print
• Using movement commands to pause

3. Given this G-code snippet:

G1 X50 Y50 F1500
M104 S210
G4 P2000

What does the command G4 P2000 do?

medium

A. Moves the nozzle to X=2000

B. Pauses the print for 2 seconds

C. Sets the temperature to 2000°C

D. Homes all axes

Solution

1. Step 1: Understand G4 command

   G4 is a dwell command that pauses the printer for a set time.

2. Step 2: Interpret parameter P2000

   P2000 means pause for 2000 milliseconds, which equals 2 seconds.

3. Final Answer:

   Pauses the print for 2 seconds -> Option B

4. Quick Check:

   G4 P2000 = 2-second pause [OK]

Hint: G4 with P value pauses in milliseconds [OK]

Common Mistakes:

• Thinking G4 moves the nozzle
• Confusing temperature commands with G4
• Assuming G4 homes axes

4. You want to slow down the print speed by editing the G-code. Which line correctly changes the feedrate to 1200 mm/min?

medium

A. G1 F1200

B. M220 S1200

C. G28 F1200

D. M104 F1200

Solution

1. Step 1: Identify feedrate command

   G1 with F sets the feedrate (speed) for moves.

2. Step 2: Check other commands

   M220 changes speed multiplier, G28 homes axes (no feedrate), M104 sets temperature.

3. Final Answer:

   G1 F1200 -> Option A

4. Quick Check:

   Feedrate set by G1 F value [OK]

Hint: Use G1 F to set move speed directly [OK]

Common Mistakes:

• Using M220 which is a speed multiplier, not direct feedrate
• Trying to set feedrate with G28 or M104
• Confusing feedrate with temperature commands

5. You want to add a pause at layer 5 in your print by inserting a manual G-code command. Which approach is best?

hard

A. Insert M25 after the layer 5 start comment in the G-code file

B. Replace all G1 commands with M25 in layer 5

C. Add M104 S0 at the start of layer 5

D. Delete the commands for layer 5 to pause printing

Solution

1. Step 1: Identify how to pause at a specific layer

   Layer changes are usually marked by comments; inserting M25 pauses the print.

2. Step 2: Evaluate other options

   Replacing all G1 commands breaks movement, M104 S0 turns off temperature, deleting commands stops printing.

3. Final Answer:

   Insert M25 after the layer 5 start comment in the G-code file -> Option A

4. Quick Check:

   Pause at layer = Insert M25 at layer start [OK]

Hint: Insert M25 at layer start comment to pause [OK]

Common Mistakes:

• Replacing movement commands with pause command
• Turning off temperature instead of pausing
• Deleting commands which stops print instead of pausing