Common G-code commands (G0, G1, G28, M104, M106) in 3D Printing - Time & Space Complexity

Time Complexity: Common G-code commands (G0, G1, G28, M104, M106)

O(n)

Understanding Time Complexity

When using common G-code commands in 3D printing, it's helpful to understand how the time to execute these commands changes as the number of commands grows.

We want to know: how does the printer's work time increase when we add more commands?

Scenario Under Consideration

Analyze the time complexity of this sequence of G-code commands.

G28 ; Home all axes
M104 S200 ; Set extruder temperature
G0 X10 Y10 Z0.3 ; Move quickly to position
M106 S255 ; Turn on fan at full speed
G1 X50 Y50 E10 ; Move while extruding
    

This snippet shows common commands for moving, heating, and controlling the printer.

Identify Repeating Operations

Look at what repeats when many commands run.

• Primary operation: Each command executes one after another.
• How many times: The number of commands determines how many steps the printer takes.

How Execution Grows With Input

As you add more commands, the printer does more work, roughly one step per command.

Input Size (n)	Approx. Operations
10	10 commands executed
100	100 commands executed
1000	1000 commands executed

Pattern observation: The work grows directly with the number of commands; doubling commands doubles work.

Final Time Complexity

Time Complexity: O(n)

This means the time to run all commands grows in a straight line with how many commands you have.

Common Mistake

[X] Wrong: "Adding more commands won't affect total time much because some commands are fast."

[OK] Correct: Even if some commands are quick, each command adds to total time, so more commands always mean more time overall.

Interview Connect

Understanding how the number of commands affects printing time helps you think clearly about efficiency and scaling, a useful skill in many technical roles.

Self-Check

"What if we combined multiple moves into one command? How would the time complexity change?"

Practice

1. What does the G-code command G28 do in 3D printing?

easy

A. Sets the extruder temperature

B. Homes all axes to their origin positions

C. Moves the print head quickly without extruding

D. Turns on the cooling fan

Solution

1. Step 1: Understand the purpose of G28

   The G28 command is used to move the printer's axes to their home or origin positions, ensuring the printer knows where the starting point is.

2. Step 2: Compare with other commands

   Other commands like G0 move quickly without printing, M104 sets temperature, and M106 controls the fan, so they do not home the axes.

3. Final Answer:

   Homes all axes to their origin positions -> Option B

4. Quick Check:

   G28 = Home axes [OK]

Hint: G28 always means 'go home' for all axes [OK]

Common Mistakes:

• Confusing G28 with G0 or G1 which move the head
• Thinking M104 or M106 control movement instead of temperature or fan
• Assuming G28 sets temperature or fan speed

2. Which of the following is the correct syntax to set the extruder temperature to 200°C using G-code?

easy

A. G28 S200

B. M106 S200

C. G1 S200

D. M104 S200

Solution

1. Step 1: Identify the command for setting extruder temperature

   M104 is the G-code command used to set the extruder temperature to a specified value.

2. Step 2: Check the syntax

   The correct syntax is M104 followed by S and the temperature value, so M104 S200 sets the extruder to 200°C.

3. Final Answer:

   M104 S200 -> Option D

4. Quick Check:

   M104 sets extruder temp = M104 S200 [OK]

Hint: M104 sets extruder temp; M106 controls fan [OK]

Common Mistakes:

• Using M106 which controls the fan instead of temperature
• Using G1 or G28 which are for movement, not temperature
• Omitting the S parameter for temperature value

3. What will happen when the following G-code commands are executed?

G0 X50 Y50
G1 X100 Y100 E10

medium

A. The print head homes all axes, then sets extruder temperature to 10°C

B. The print head moves slowly to (50,50) while extruding, then quickly to (100,100) without extruding

C. The print head moves quickly to (50,50) without extruding, then moves to (100,100) while extruding filament

D. The print head turns on the fan and moves to (100,100)

Solution

1. Step 1: Understand G0 and G1 commands

   G0 moves the print head quickly without extruding filament. G1 moves the print head while extruding filament as specified by the E parameter.

2. Step 2: Analyze the commands given

   First, G0 moves the head to X50 Y50 quickly without extrusion. Then, G1 moves the head to X100 Y100 while extruding 10 units of filament.

3. Final Answer:

   The print head moves quickly to (50,50) without extruding, then moves to (100,100) while extruding filament -> Option C

4. Quick Check:

   G0 = fast move no extrusion, G1 = move with extrusion [OK]

Hint: G0 = fast move no extrusion; G1 = move with extrusion [OK]

Common Mistakes:

• Mixing up G0 and G1 commands
• Assuming extrusion happens during G0
• Confusing E parameter as fan speed or temperature

4. A user writes the following G-code to turn on the cooling fan at half speed:

M106 S128

But the fan does not turn on. What is the likely error?

medium

A. The printer firmware might require a different command or fan pin setup

B. The S value should be between 0 and 255, 128 is invalid

C. The command should be M104 to control the fan

D. The G28 command is missing before M106

Solution

1. Step 1: Understand M106 command and S parameter

   M106 controls the cooling fan speed with S value from 0 (off) to 255 (full speed). S128 is a valid half speed.

2. Step 2: Consider why fan might not turn on

   If the fan does not turn on, it is likely due to printer firmware settings or hardware configuration, such as fan pin assignment or disabled fan control.

3. Final Answer:

   The printer firmware might require a different command or fan pin setup -> Option A

4. Quick Check:

   M106 S128 valid but hardware/firmware may block fan [OK]

Hint: Check firmware and hardware if M106 S128 doesn't work [OK]

Common Mistakes:

• Thinking S128 is out of range (it's valid)
• Using M104 instead of M106 for fan control
• Assuming G28 is needed before fan commands

5. You want to start a print by homing all axes, setting the extruder temperature to 210°C, waiting for it to reach temperature, then moving the print head to X10 Y10 quickly without extruding. Which sequence of G-code commands is correct?

hard

A. G28M104 S210M109 S210G0 X10 Y10

B. M104 S210G28M109 S210G1 X10 Y10 E0

C. G28M109 S210M104 S210G0 X10 Y10

D. M106 S210G28M109 S210G0 X10 Y10

Solution

1. Step 1: Identify commands for each action

   G28 homes all axes. M104 sets extruder temperature without waiting. M109 sets temperature and waits until reached. G0 moves quickly without extruding.

2. Step 2: Check command order for correct sequence

   First home with G28, then set temp with M104, wait with M109, finally move with G0 to X10 Y10 without extrusion.

3. Final Answer:

   G28
   M104 S210
   M109 S210
   G0 X10 Y10 -> Option A

4. Quick Check:

   Home, set temp, wait, then fast move = G28
   M104 S210
   M109 S210
   G0 X10 Y10 [OK]

Hint: Use M109 to wait for temp after M104, then move with G0 [OK]

Common Mistakes:

• Using M106 instead of temperature commands
• Moving with G1 and extruding when not needed
• Setting temperature after moving the head