is_extruder_used is a logical-filament-slot indexed bool array — start-gcode
templates use it as `is_extruder_used[N]` where N is a logical filament slot
(matches how the rest of the codebase consumes per-filament arrays like
filament_settings_id, nozzle_temperature_initial_layer, etc.).
`tool_ordering.all_extruders()` returns LOGICAL slots and was correctly
marking those. But the IMEX-secondary marking added in 5aa624b025 was
writing PHYSICAL extruder indices straight into the logical array, mixing
index spaces. On any printer with physical_extruder_map size > 1 (MMU/AFC),
this marks the wrong slots and misses the right ones.
Symptom on the user's Neo XP 0.6 (pem [0,0,0,0,1,2,3,3]) in copy mode
[0:P,1:C] with object on slot 2 (PLA):
- tool_ordering marks slot 2 (correct: object's filament).
- IMEX active = [0, 1] (physical T0, T1) → mistakenly marks logical
slots 0 (ABS) and 1 (ASA), neither of which is used.
- Slot 4 (PLA on physical T1, the actual filament that loads on the
secondary in copy mode) is NOT marked.
- Start-gcode template emits EXTRUDER=ABS_temp EXTRUDER1=ASA_temp
EXTRUDER2=PLA_temp; no EXTRUDER4.
- PRINT_START macro reads t4=0, skips heating extruder1 — T1 stays
cold during the print.
Translate physical → logical via resolve_filament_for_head before marking
(per-plate imex_head_filament_map override consulted, with first-routed
fallback when no override is set). This matches what the firmware actually
loads on each carriage during the parallel-mode print, and what the rest
of the IMEX hot path (PA emission, layer-change temperature) already does.
Result on the user's setup post-fix:
- is_extruder_used[2]=true (object), is_extruder_used[4]=true (T1 in copy).
- Start-gcode emits 2 temps for the actually-used filaments.
- extruder1 heats correctly to slot 4's temp before the print begins.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
OrcaSlicer: an open source Next-Gen Slicing Software for Precision 3D Prints.
Optimize your prints with ultra-fast slicing, intelligent support generation, and seamless printer compatibility—engineered for perfection.
Official links and community
Official Website:
Github Repository:
Follow us:
Join our Discord community:
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Main features
- Advanced Calibration Tools
Comprehensive suite: temperature towers, flow rate, retraction & more for optimal performance. - Precise Wall and Seam Control
Adjust outer wall spacing and apply scarf seams to enhance print accuracy. - Sandwich Mode and Polyholes Support
Use varied infill patterns and accurate hole shapes for improved clarity. - Overhang and Support Optimization
Modify geometry for printable overhangs with precise support placement. - Granular Controls and Customization
Fine-tune print speed, layer height, pressure, and temperature with precision. - Network Printer Support
Seamless integration with Klipper, PrusaLink, and OctoPrint for remote control. - Mouse Ear Brims & Adaptive Bed Mesh
Automatic brims and adaptive mesh calibration ensure consistent adhesion. - User-Friendly Interface
Intuitive drag-and-drop design with pre-made profiles for popular printers. - Open-Source & Community Driven
Regular updates fueled by continuous community contributions. - Wide Printer Compatibility
Supports a broad range of printers: Bambu Lab, Prusa, Creality, Voron, and more. - Additional features can be found in the change notes.
Wiki
The wiki aims to provide a detailed explanation of the slicer settings, including how to maximize their use and how to calibrate and set up your printer.
Download
Stable Release
📥 Download the Latest Stable Release
Visit our GitHub Releases page for the latest stable version of OrcaSlicer, recommended for most users.
Nightly Builds
🌙 Download the Latest Nightly Build
Explore the latest developments in OrcaSlicer with our nightly builds. Feedback on these versions is highly appreciated.
How to install
Windows
Download the Windows Installer exe for your preferred version from the releases page.
-
For convenience there is also a portable build available.
Troubleshooting
- If you have troubles to run the build, you might need to install following runtimes:
- MicrosoftEdgeWebView2RuntimeInstallerX64
- vcredist2019_x64
- Alternative Download Link Hosted by Microsoft
- This file may already be available on your computer if you've installed visual studio. Check the following location:
%VCINSTALLDIR%Redist\MSVC\v142
Windows Package Manager
winget install --id=SoftFever.OrcaSlicer -e
Mac
-
Download the DMG for your computer:
arm64version for Apple Silicon andx86_64for Intel CPU. -
Drag OrcaSlicer.app to Application folder.
-
If you want to run a build from a PR, you also need to follow the instructions below:
Quarantine
-
Option 1 (You only need to do this once. After that the app can be opened normally.):
- Step 1: Hold cmd and right click the app, from the context menu choose Open.
- Step 2: A warning window will pop up, click Open
-
Option 2: Execute this command in terminal:
xattr -dr com.apple.quarantine /Applications/OrcaSlicer.app -
Option 3:
-
Linux (Ubuntu)
- If you run into trouble executing it, try this command in the terminal:
chmod +x /path_to_appimage/OrcaSlicer_Linux.AppImage
How to Compile
All updated build instructions for Windows, macOS, and Linux are now available on the official OrcaSlicer Wiki - How to build page.
Please refer to the wiki to ensure you're following the latest and most accurate steps for your platform.
Klipper Note
If you're running Klipper, it's recommended to add the following configuration to your printer.cfg file.
# Enable object exclusion
[exclude_object]
# Enable arcs support
[gcode_arcs]
resolution: 0.1
Supports
OrcaSlicer is an open-source project and I'm deeply grateful to all my sponsors and backers.
Their generous support enables me to purchase filaments and other essential 3D printing materials for the project.
Thank you! :)
Sponsors:
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Backers:
Ko-fi supporters ☕: Backers list
Support me
Some Background
Open-source slicing has always been built on a tradition of collaboration and attribution. Slic3r, created by Alessandro Ranellucci and the RepRap community, laid the foundation. PrusaSlicer by Prusa Research built on Slic3r and acknowledged that heritage. Bambu Studio in turn forked from PrusaSlicer, and SuperSlicer by @supermerill extended PrusaSlicer with community-driven enhancements. Each project carried the work of its predecessors forward, crediting those who came before.
OrcaSlicer began in that same spirit, drawing from BambuStudio, PrusaSlicer, and ideas inspired by CuraSlicer and SuperSlicer. But it has since grown far beyond its origins. Through relentless innovation — introducing advanced calibration tools, precise wall and seam control, tree supports, adaptive slicing, and hundreds of other features — OrcaSlicer has become the most widely used and actively developed open-source slicer in the 3D printing community. Many of its innovations have been adopted by other slicers, making it a driving force for the entire industry.
The OrcaSlicer logo was designed by community member Justin Levine (@freejstnalxndr).
License
- OrcaSlicer is licensed under the GNU Affero General Public License, version 3.
- The GNU Affero General Public License, version 3 ensures that if you use any part of this software in any way (even behind a web server), your software must be released under the same license.
- OrcaSlicer includes a pressure advance calibration pattern test adapted from Andrew Ellis' generator, which is licensed under GNU General Public License, version 3. Ellis' generator is itself adapted from a generator developed by Sineos for Marlin, which is licensed under GNU General Public License, version 3.
- The Bambu networking plugin is based on non-free libraries from BambuLab. It is optional to the OrcaSlicer and provides extended functionalities for Bambulab printer users.

