Start and end G-code customization in 3D Printing - Step-by-Step Execution

Concept Flow - Start and end G-code customization

Printer powers on

↓

Start G-code runs

↓

Print job executes

↓

End G-code runs

↓

Printer finishes and cools down

The printer runs start G-code before printing to prepare, then prints, then runs end G-code to finish and cool down.

Execution Sample

3D Printing

; Start G-code example
G28 ; Home all axes
G1 Z5 F5000 ; Lift nozzle
; End G-code example
M104 S0 ; Turn off nozzle heater
M140 S0 ; Turn off bed heater
G28 X0 Y0 ; Home X and Y axes

This code homes the printer and lifts the nozzle before printing, then turns off heaters and homes axes after printing.

Analysis Table

Step	G-code Command	Action	Printer State Change	Notes
1	G28	Home all axes	X=0, Y=0, Z=0	Start G-code: prepares printer position
2	G1 Z5 F5000	Lift nozzle 5mm	Z=5	Prevents nozzle from scratching bed
3	Print job runs	Print layers	Nozzle moves, extrudes filament	Main printing process
4	M104 S0	Turn off nozzle heater	Nozzle temp=0	End G-code: cool down nozzle
5	M140 S0	Turn off bed heater	Bed temp=0	End G-code: cool down bed
6	G28 X0 Y0	Home X and Y axes	X=0, Y=0	End G-code: park head
7	End	Print finished	Motors off, cool	Printer ready for next job

💡 All start and end commands executed, print job complete

State Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	After Step 4	After Step 5	After Step 6	Final
X position	unknown	0	0	varies	varies	varies	0	0
Y position	unknown	0	0	varies	varies	varies	0	0
Z position	unknown	0	5	varies	varies	varies	varies	varies
Nozzle temperature	off	off	off	printing temp	0	0	0	0
Bed temperature	off	off	off	printing temp	printing temp	0	0	0

Key Insights - 3 Insights

Why do we home all axes at the start (G28)?

Homing sets the printer's position to a known point (0,0,0). This ensures the printer knows where the nozzle is before printing, as shown in step 1 of the execution_table.

Why lift the nozzle before printing (G1 Z5)?

Lifting the nozzle prevents it from scratching the print bed or existing prints. This is shown in step 2 where Z moves to 5mm before printing starts.

Why turn off heaters at the end (M104 S0 and M140 S0)?

Turning off heaters cools the printer safely after printing, preventing damage or burns. Steps 4 and 5 in the execution_table show these commands.

Visual Quiz - 3 Questions

Look at the execution_table, what is the Z position after step 2?

A 5 mm

B 0 mm

C Unknown

D 10 mm

💡 Hint

Check the 'Printer State Change' column for step 2 in the execution_table.

At which step does the printer turn off the bed heater?

A Step 3

B Step 5

C Step 6

D Step 4

💡 Hint

Look for 'M140 S0' command in the execution_table.

If the start G-code did not include G28, what would likely happen?

A Printer would home axes anyway automatically

B Printer would skip heating

C Nozzle position might be unknown, causing print errors

D Print would finish immediately

💡 Hint

Refer to the key_moments about homing axes and step 1 in the execution_table.

Concept Snapshot

Start and end G-code run before and after printing.
Start G-code prepares printer (home axes, lift nozzle).
End G-code cools down (turn off heaters, home axes).
Customizing these codes controls printer setup and finish.
Proper start/end codes prevent print errors and damage.

Full Transcript

Start and end G-code customization controls what commands the 3D printer runs before and after a print job. The start G-code usually homes all axes to set the printer's position to zero, then lifts the nozzle to avoid scratching the bed. After the print job runs, the end G-code turns off the nozzle and bed heaters to cool down the printer and homes the X and Y axes to park the print head. This sequence ensures the printer is ready and safe before printing and properly finishes after printing. Missing or incorrect start/end G-code can cause print failures or damage. The execution table shows each step with commands and printer state changes, helping visualize the process. Variables like nozzle position and temperature change step-by-step. Key moments explain why homing and heating commands are important. The visual quiz tests understanding of these steps and their effects. Overall, customizing start and end G-code lets users control printer behavior for better prints and safety.

Practice

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