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Why Start and end G-code customization in 3D Printing? - Purpose & Use Cases

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The Big Idea

What if your 3D printer could prepare itself perfectly every time without you lifting a finger?

The Scenario

Imagine you have to prepare your 3D printer for every print by manually setting temperatures, moving the print head, and cleaning the nozzle each time before starting and after finishing a print.

The Problem

Doing these steps manually is slow, easy to forget, and can cause print failures or damage if done incorrectly. It wastes time and can lead to inconsistent print quality.

The Solution

Start and end G-code customization lets you automate these setup and shutdown steps by adding commands that run automatically before and after every print. This ensures your printer is always ready and safely shut down without extra effort.

Before vs After
✗ Before
Heat nozzle to 200°C
Move print head to corner
Clean nozzle
Start print
✓ After
Start G-code:
M104 S200 ; set nozzle temp
G28 ; home axes
End G-code:
M104 S0 ; turn off nozzle
G1 X0 Y0 ; park head
What It Enables

It enables consistent, reliable prints by automating essential printer preparation and shutdown steps every time.

Real Life Example

A hobbyist customizes start G-code to always prime the nozzle and end G-code to cool down the printer and move the head away, saving time and preventing nozzle clogs.

Key Takeaways

Manual printer prep is slow and error-prone.

Custom start/end G-code automates setup and shutdown.

This leads to better print quality and less hassle.

Practice

(1/5)
1. What is the main purpose of the start G-code in 3D printing?
easy
A. To cool down the printer after printing is finished
B. To pause the print job temporarily
C. To prepare the printer by homing axes and heating before printing
D. To clean the print bed automatically

Solution

  1. Step 1: Understand start G-code role

    Start G-code runs before printing to prepare the printer, such as homing axes and heating.

  2. Step 2: Compare options

    Only To prepare the printer by homing axes and heating before printing describes preparation actions before printing; others describe after or unrelated actions.

  3. Final Answer:

    To prepare the printer by homing axes and heating before printing -> Option C

  4. Quick Check:

    Start G-code = Preparation before print [OK]
Hint: Start G-code sets up printer before printing starts [OK]
Common Mistakes:
  • Confusing start G-code with end G-code
  • Thinking start G-code cools the printer
  • Assuming start G-code pauses printing
2. Which of the following is a correct example of a command you might find in the end G-code?
easy
A. M104 S0 ; Turn off extruder heater
B. G1 Z0.2 F3000 ; Move nozzle close to bed
C. G28 ; Home all axes
D. M109 S200 ; Wait for extruder to reach 200°C

Solution

  1. Step 1: Identify end G-code commands

    End G-code usually turns off heaters and moves the print head safely away.

  2. Step 2: Analyze options

    M104 S0 ; Turn off extruder heater turns off the extruder heater, which is typical for end G-code. G28 ; Home all axes homes axes (start), C moves nozzle close (start), D waits for heat (start).

  3. Final Answer:

    M104 S0 ; Turn off extruder heater -> Option A

  4. Quick Check:

    End G-code = Turn off heaters [OK]
Hint: End G-code usually turns off heaters [OK]
Common Mistakes:
  • Choosing commands that heat or home axes as end G-code
  • Confusing waiting commands with end commands
  • Selecting movement commands that prepare printing
3. Given this start G-code snippet:
G28 ; Home all axes
M140 S60 ; Set bed temperature
M190 S60 ; Wait for bed temperature
M104 S200 ; Set extruder temperature
M109 S200 ; Wait for extruder temperature
G1 Z0.2 F3000 ; Move nozzle close to bed

What will the printer do first when starting a print?
medium
A. Home all axes
B. Heat the extruder to 200°C
C. Move nozzle close to bed
D. Wait for bed temperature to reach 60°C

Solution

  1. Step 1: Read the G-code commands in order

    The first command is G28, which homes all axes.

  2. Step 2: Understand command sequence

    Printer homes axes first, then sets and waits for bed and extruder temperatures, then moves nozzle.

  3. Final Answer:

    Home all axes -> Option A

  4. Quick Check:

    First command = G28 = Home axes [OK]
Hint: G28 always homes axes first in start G-code [OK]
Common Mistakes:
  • Assuming heating happens before homing
  • Confusing wait commands with first action
  • Thinking nozzle moves before homing
4. You added this line to your end G-code:
M104 S0
But the extruder heater does not turn off after printing. What is the likely problem?
medium
A. The command needs a G28 before it to work
B. The printer firmware does not support M104
C. The command should be M140 S0 to turn off the extruder
D. The command is correct but placed before the print finishes

Solution

  1. Step 1: Understand M104 S0 function

    This command turns off the extruder heater.

  2. Step 2: Check command placement

    If placed before print ends, heater stays on during printing. It must be after printing finishes.

  3. Final Answer:

    The command is correct but placed before the print finishes -> Option D

  4. Quick Check:

    Heater off command must run after print ends [OK]
Hint: Place heater-off commands after printing completes [OK]
Common Mistakes:
  • Using bed heater command instead of extruder heater
  • Assuming firmware lacks support without checking
  • Thinking homing is needed before heater off
5. You want to customize your start G-code to include a line that wipes the nozzle before printing. Which of these sequences correctly adds this action after homing and heating?
hard
A. G28 ; Home axes G1 E10 F300 ; Extrude filament to wipe M104 S200 ; Heat extruder G1 X10 Y10 ; Move to wipe position
B. G28 ; Home axes M104 S200 ; Heat extruder G1 X10 Y10 ; Move to wipe position G1 E10 F300 ; Extrude filament to wipe
C. G1 X10 Y10 ; Move to wipe position G28 ; Home axes M104 S200 ; Heat extruder G1 E10 F300 ; Extrude filament to wipe
D. M104 S200 ; Heat extruder G28 ; Home axes G1 E10 F300 ; Extrude filament to wipe G1 X10 Y10 ; Move to wipe position

Solution

  1. Step 1: Identify correct order of start G-code actions

    Start G-code should home axes first, then heat extruder, then move to wipe position and extrude filament.

  2. Step 2: Analyze options for correct sequence

    G28 ; Home axes M104 S200 ; Heat extruder G1 X10 Y10 ; Move to wipe position G1 E10 F300 ; Extrude filament to wipe follows this order: home, heat, move, extrude. Others mix heating and homing or move before heating.

  3. Final Answer:

    G28 ; Home axes M104 S200 ; Heat extruder G1 X10 Y10 ; Move to wipe position G1 E10 F300 ; Extrude filament to wipe -> Option B

  4. Quick Check:

    Home -> Heat -> Move -> Extrude = G28 ; Home axes M104 S200 ; Heat extruder G1 X10 Y10 ; Move to wipe position G1 E10 F300 ; Extrude filament to wipe [OK]
Hint: Home first, heat second, then wipe nozzle [OK]
Common Mistakes:
  • Moving nozzle before heating extruder
  • Extruding filament before heating
  • Heating after homing but before moving