Reading G-code for troubleshooting 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 what actions to perform during printing.

intermediate

What does the command G1 X50 Y25.3 E22.4 mean?

It tells the printer to move the print head to position X=50, Y=25.3 while extruding 22.4 units of filament.

beginner

Why is reading G-code important for troubleshooting?

Reading G-code helps identify where the printer might be making mistakes, such as wrong movements, missing extrusion, or incorrect temperatures.

intermediate

What does the command M104 S200 do?

It sets the extruder temperature to 200°C without waiting for it to reach that temperature before continuing.

intermediate

How can you spot a problem with filament extrusion by reading G-code?

Look for E values in movement commands. If E values don’t increase when the print head moves, filament may not be extruding.

What does the G-code command G28 usually do?

A Home all axes

B Set extruder temperature

C Pause the print

D Move to X=0 Y=0

G28 tells the printer to move all axes to their home positions, usually the origin point.

If the printer is not extruding filament but moving correctly, which G-code part should you check?

A X and Y coordinates

B M104 temperature settings

C E values in movement commands

D G28 homing commands

The E values control filament extrusion. If they don’t increase, no filament is pushed out.

What does M140 S60 command do in G-code?

A Set extruder temperature to 60°C

B Set bed temperature to 60°C

C Move print head to Y=60

D Pause the print for 60 seconds

M140 sets the heated bed temperature, here to 60°C.

Which G-code command waits for the extruder to reach the target temperature before continuing?

A M109

B M104

C G1

D M140

M109 sets extruder temperature and waits until it is reached before moving on.

If you see G1 X100 Y100 E0 repeatedly without increasing E, what might be wrong?

A The printer is paused

B The print head is not moving

C The bed temperature is too low

D The filament is not extruding

Since E is not increasing, filament is not being pushed out during moves.

Explain how reading G-code can help you find why a 3D print is failing.

Think about what each part of the G-code controls in the printer.

Describe what the E value in a G1 command represents and why it matters.

Focus on the role of extrusion in printing.