OrcaSlicer: M600 G-Code Fix For Clean Color Changes

by Alex Johnson 52 views

This article addresses a common issue encountered by users of OrcaSlicer when performing multi-color 3D prints: the improper placement of the M600 filament change G-code command. Specifically, the problem arises where the filament change sequence occurs before the print head moves to the new color's starting location, leading to unwanted color bleeding or "zits" on the printed model. This guide will delve into the problem, explain the desired behavior, and propose a solution to achieve cleaner and more professional-looking multi-color prints. By understanding the intricacies of G-code and the OrcaSlicer's configuration options, users can optimize their printing process and overcome this frustrating issue.

The Problem: Color Bleeding and Zits

The core issue lies in the order of operations during a filament change. Currently, OrcaSlicer inserts the custom G-code defined in the "Change filament G-code" section before the printer moves to the starting coordinates of the next color layer. This sequence causes the following undesirable effects:

  1. Zits and Color Bleeding: After the new filament is loaded, the print head, still positioned at the previous color's endpoint, extrudes a small amount of the new color. This results in a noticeable blob or "zit" of the new color on the previous color's surface, which is particularly visible when using darker filaments on lighter backgrounds.
  2. Model Contact: The M600 command often includes retraction and z-hop movements. Because these occur at the previous color's location, the nozzle might still be close enough to the model to touch it, potentially causing slight imperfections or even dislodging small parts.
  3. Inconsistent Results: The severity of the problem varies depending on the specific model geometry, filament properties, and retraction settings. However, it consistently leads to a less-than-perfect finish, requiring post-processing to remove the unwanted color artifacts.

These color change imperfections significantly degrade the visual quality of multi-color prints and add extra steps to the 3D printing workflow. It also wastes material, even if it's just a little. Achieving pristine color transitions is a primary goal of multi-material 3D printing, and addressing this G-code placement issue is vital for optimal results.

Understanding the Current G-Code Sequence

To illustrate the problem, let's examine the problematic G-code sequence provided in the original issue:

G1 X187.104 Y69.78 E.03201 ; Last move of the previous color
;Color Change GCode START
M600 B5 E-0.1 L20 R205 T0 U50 X150.00 Y20.00 Z50.00 ; Filament change command
;Color Change GCode END
; stop printing object Assembly id:15 copy 0
; filament end gcode
G1 E-1.2 F960
G1 Z5.24 F3300
G1 X162.022 Y59.55 ; Move to the new color's starting position
G1 Z5.24
G1 Z4.12
G1 E1.2 F960

As you can see, the M600 command, containing the filament change parameters, is executed before the G1 X... Y... command that moves the print head to the new color's starting location. This means the filament change process, including any retraction or purging, occurs at the location where the previous color ended. This is the root cause of the "zit" and color bleeding issues.

This sequence also causes a potential issue as the Z height is adjusted before the move. This might cause the nozzle to drag across the previous color location.

The Desired G-Code Sequence: A Cleaner Approach

The ideal solution is to reposition the M600 command after the print head has moved to the new color's starting coordinates. This ensures that any filament oozing or purging during the filament change occurs at the correct location, minimizing the risk of color contamination. The desired G-code sequence should look like this:

;Color Change GCode START
G1 X187.104 Y69.78 E.03201 ; Last move of the previous color
; stop printing object Assembly id:15 copy 0
; filament end gcode
G1 E-1.2 F960
G1 Z5.24 F3300
G1 X162.022 Y59.55 ; Move to the new color's starting position
G1 Z5.24
G1 Z4.12
G1 E1.2 F960
M600 B5 E-0.1 L20 R205 T0 U50 X150.00 Y20.00 Z50.00 ; Filament change command
;Color Change GCode END

By placing the M600 command after the move to the new color's starting position, we ensure that any filament oozing or purging during the filament change occurs in the correct location. This effectively eliminates the "zit" issue and results in a much cleaner color transition. The result is a noticeably cleaner transition that reduces the need for post-processing. This approach aligns with best practices for multi-material 3D printing, ensuring optimal print quality and reducing material waste.

Implementing the Solution in OrcaSlicer

Unfortunately, OrcaSlicer (version 2.3.1 and earlier) doesn't offer a direct setting to control the exact placement of the custom filament change G-code. However, there are a few workarounds that can be implemented to achieve the desired result:

  1. Manual G-Code Editing (Not Recommended): The most straightforward but least efficient approach is to manually edit the generated G-code file. After slicing the model, open the G-code file in a text editor, search for the M600 command, and move it to the desired location as shown in the "Desired G-Code Sequence" example above. While this works, it's a tedious and error-prone process, especially for complex multi-color prints with numerous filament changes. It's also not a sustainable solution, as it needs to be repeated every time the model is sliced.

  2. Custom G-Code Scripting (Recommended): A more elegant solution involves using OrcaSlicer's custom G-code scripting capabilities. This allows you to automate the process of moving the M600 command. The exact implementation will depend on your specific needs and G-code knowledge, but the general idea is to:

    • Define a custom G-code macro that contains your desired M600 command and any associated retraction or purging commands.
    • Use a placeholder in the "Change filament G-code" section to trigger the macro at the correct location.
    • Implement a script that searches for the placeholder in the generated G-code and replaces it with the macro code.

This approach requires some scripting skills but provides a much more automated and reliable solution than manual G-code editing. There are various online resources and communities that can provide guidance and examples for implementing custom G-code scripting in OrcaSlicer.

  1. Feature Request and Future Updates: The most ideal solution would be for OrcaSlicer to provide a built-in setting that allows users to control the placement of the custom filament change G-code. This would eliminate the need for manual editing or complex scripting and make the process much more user-friendly. Users are encouraged to submit a feature request to the OrcaSlicer developers, highlighting the importance of this functionality for improving multi-color printing quality.

By using these techniques, users can improve the accuracy of color transitions in their 3D prints, lessening color mixing and decreasing the requirement for post-processing. The correct M600 G-code placement enhances print quality, making the printing process easier and producing superior results. With enhanced color purity and reduced material waste, prints will come out better.

Conclusion

The issue of incorrect M600 G-code placement in OrcaSlicer can lead to undesirable color bleeding and zits in multi-color 3D prints. While a direct solution isn't currently available within the slicer's settings, workarounds such as custom G-code scripting can be implemented to achieve the desired result. By understanding the problem, the desired G-code sequence, and the available solutions, users can significantly improve the quality of their multi-color prints. Furthermore, advocating for a built-in setting in future OrcaSlicer updates will contribute to a more user-friendly and efficient multi-color printing experience.

For more information on G-Code commands, you can check out this great resource.