---
title: Tutorial 30 Time as a First-Class Parameter
description: Controlling the 4th dimension of printing.
---

Tutorial 30 Time as a First-Class Parameter

1. Lesson Header

Lesson Number: 30
Level: Advanced
Title: Time as a First-Class Parameter
Estimated Duration: 30 Minutes
Prerequisites: Lesson 10 (Speed), Lesson 25 (State)
What You Will Build: A "Timelapse Trigger" and a "Cooling Tower".

2. Concept Introduction

The Clock is Ticking.
Usually, we think of G-code as spatial (X, Y, Z).
But time is critical for:
- Cooling: Plastic needs time to solidify.
- Photography: Cameras need time to focus.
- Chemical Reactions: Some materials (foaming filaments) expand over time.

We can control time explicitly using Dwell (G4).

3. Machine State Explanation

G4 (Dwell).
Pause the machine buffer.
- G4 P1000: Wait 1000 milliseconds (1 second).
- G4 S1: Wait 1 second (Standard G-code, but Marlin prefers P).

The Buffer:
Normally, the printer reads ahead. G4 forces it to empty the buffer and wait. This ensures synchronization.

4. Command Breakdown

G4 P[Milliseconds]: Wait.
M400: Wait for moves to finish (implicit in G4, but useful on its own).

5. Minimal Working Example

The Pause.
Move, Wait, Move.

G1 X10
G4 P2000 ; Wait 2 seconds
G1 X20

6. Visual Representation

Interactive preview is available in the interactive reader.

7. Build Exercise

Task: Create a "Minimum Layer Time" script.
If a layer is too small (e.g., the tip of a cone), the plastic doesn't cool.
We must slow down or wait.
Method:
1. Print Layer.
2. Move Nozzle Away (Park).
3. Wait (G4 P5000).
4. Return and Print Next Layer.

This is better than just slowing down F because it moves the hot nozzle away from the part.

8. Deep Insight Section

Timelapse Triggers.
"Octolapse" works by inserting G-code at every layer change:
1. Retract.
2. Move to specific X/Y (Park).
3. Wait for stability (G4 P500).
4. Trigger Camera (M240 or external pin).
5. Wait for shutter (G4 P200).
6. Return and Resume.

9. Common Failure Modes

Oozing: While waiting (G4), the nozzle is hot. Gravity pulls plastic out. You MUST retract before a G4.
Blobs: When returning after a wait, the nozzle might need a "Prime" (un-retract) or it might have a blob on the tip.

10. Real-World Application

Foaming Filament.
"ColorFabb LW-PLA" foams when heated.
The longer it stays in the nozzle, the more it expands.
You can vary the density by changing speed (Time in nozzle).
Slow = More foam (Lighter).
Fast = Less foam (Heavier).

11. Final Clean Version

The Timelapse Script:

; Lesson 30 - Timelapse Trigger
G21
G90
M83
G28

; --- Layer 1 ---
G1 X100 Y100 E5 ; Print...
G1 X110 Y100 E5 ; Print...

; --- SNAPSHOT ---
G1 E-5 F3000 ; Retract 5mm
G0 X0 Y200 F9000 ; Park Head
M400 ; Wait for move to finish
G4 P500 ; Stabilize (500ms)
M240 ; Trigger Camera (or M42 P5 S255 if using pins)
G4 P200 ; Wait for photo
G0 X110 Y100 F9000 ; Return to last position
G1 E5 F3000 ; Un-retract
; ----------------

; --- Layer 2 ---
G1 Z0.4
G1 X100 Y100 E5
; ... Repeat Snapshot ...

12. Stretch Challenge

Challenge: Write a script that pauses for a different duration based on layer height.
Layer 1: Wait 1s.
Layer 10: Wait 10s.
This simulates a "variable cooling" requirement for a material that gets hotter as it builds up.