Sunlu T3 Firmware Update May 2026

Update only if you have a specific problem (thermal runaway, ABL not saving). Otherwise, keep the stock firmware. If you want better features, skip official updates and go straight to Marlin custom builds (e.g., from Insanity Automation or TH3D) – they’re more reliable and add advanced options like linear advance.

Rating: 2.5/5 – It works, but Sunlu’s poor documentation and two-step (mainboard + screen) process make it frustrating for beginners.

Sunlu T3 Firmware Update: A Comprehensive Guide

The Sunlu T3 is a popular 3D printer known for its high-quality prints, ease of use, and affordability. Like any other electronic device, the Sunlu T3 requires periodic firmware updates to ensure optimal performance, fix bugs, and add new features. In this write-up, we will guide you through the process of updating the firmware on your Sunlu T3 3D printer.

Why Update the Firmware?

Updating the firmware on your Sunlu T3 3D printer is essential to:

Preparation

Before updating the firmware on your Sunlu T3, make sure you:

Downloading the Firmware Update

To download the firmware update for your Sunlu T3:

Updating the Firmware

To update the firmware on your Sunlu T3: Sunlu T3 Firmware Update

Using the Sunlu Firmware Update Tool

If you are using the Sunlu-provided firmware update tool:

Using Arduino IDE

If you are using Arduino IDE:

Post-Update Checklist

After updating the firmware:

Troubleshooting

If you encounter any issues during the firmware update process:

To update the firmware on a Sunlu T3 3D printer, you typically use a microSD card to flash a .bin file directly to the motherboard. The Sunlu T3 is widely recognized as an Ender 3 clone that uses a modified 32-bit BTT SKR Mini E3 V2 controller board.  Update Procedure  Obtain the Firmware:

Official: Download the T3 32-bit firmware from the official Sunlu website.

Custom (Marlin): Community members have archived the official firmware on GitHub and created custom Marlin versions that fix issues like fan mapping or bed leveling. Prepare the microSD Card: Update only if you have a specific problem

Format a low-capacity microSD card (ideally 32GB or less) to FAT32.

Copy the firmware file onto the card and rename it exactly to firmware.bin. Flash the Printer: Turn off the printer. Insert the microSD card into the printer's slot.

Power the printer on. The screen may remain blank for 10–30 seconds while the update installs.

Once the main menu appears, the update is complete. You can verify the version in the Settings or About menu. 

Updating the firmware on a Sunlu T3 (also known as the "Terminator 3") is often a necessary step for enthusiasts because the stock firmware has several known limitations, including fan mapping errors and disabled PID tuning for the bed. The T3 is essentially a modified Ender 3 clone using a 32-bit board similar to the BTT SKR Mini E3 V2. Available Firmware Options

Depending on your comfort level with tinkering, you have three primary paths:

Official Sunlu Firmware: Official updates are hosted on the Sunlu Website or shared via their Official Facebook Page. Version 3.40 is a common stable target for official users.

Community Custom Firmware: Developers have released optimized Marlin versions that fix bugs found in the original code, such as incorrect extruder fan mapping where the fan only ran when motors were active rather than when the hotend was hot. You can find these on GitHub and Printables.

Self-Compiled Marlin: Since the T3 uses a standard architecture, you can compile your own firmware using the Marlin Configurations repository for the Sunlu T3, allowing for features like 5x5 grid bed leveling and higher hotend temperatures (up to 285°C) if you have an all-metal hotend. Installation Procedure

The T3 updates via a microSD card inserted directly into the motherboard slot at the front of the printer.

Format the Card: Use a microSD card formatted to FAT32 with an allocation unit size of 4096. Preparation Before updating the firmware on your Sunlu

Prepare the File: Copy the .bin firmware file to the root directory of the card. Ensure it is the only .bin file present. Flash the Printer: Turn off the printer. Insert the microSD card. Power on the printer.

The screen will remain blank for several seconds while the light on the motherboard flashes. Once the main menu appears, the update is complete.

Post-Update Reset: It is highly recommended to select "Restore Defaults" and then "Store Settings" (EEPROM) after flashing to ensure old settings do not conflict with the new firmware. Key Improvements in Updated/Custom Firmware

Fixed Fan Control: Corrects the error where the hotend cooling fan fails to turn on during stationary heating.

PID Bed Tuning: Enables more stable bed temperatures, which Sunlu curiously left disabled in many stock versions.

Enhanced Leveling: Expands the Automatic Bed Leveling (ABL) to a more precise 5x5 grid.

Thermal Safety: Custom versions often include refined thermal runaway protection and higher temperature limits for upgraded hardware. Troubleshooting Common Issues sunlu 3d - Facebook

If you attempted a screen update that failed, the printer might be stuck on a logo screen. A fresh firmware flash is the only cure.

The official Sunlu firmware is often months behind the mainline Marlin branch. For experts, compiling your own firmware allows for custom boot screens, advanced power loss recovery, and Input Shaping.

If you want to compile your own:

Turn off the printer and remove the bottom panel (usually 4 screws). Look for the version printed on the circuit board:

| Problem | Likely Cause | Solution | |--------|--------------|----------| | Nothing happens when powering on | Wrong firmware version (e.g., V1.4 file on V1.3 board) | Double-check board version. Revert to older known-good firmware. | | Screen stays blue indefinitely | SD card not formatted correctly | Reformat FAT32, 4096 bytes. Use a smaller card (≤16GB). | | Printer shows “No printer attached” | LCD firmware mismatch | Update LCD firmware separately, matching the main board update. | | Filament sensor stopped working | New firmware has different pin assignment | Check Sunlu T3 community config files (e.g., from Team Fugu or official GitHub). | | Update “bricked” the printer | Bad flash or power loss during update | Use an ST-Link programmer (V2) to recover the MKS Robin Nano board. |