Introduction
In the realm of 3D printing, the aim of producing clean, high-quality prints is an incessant challenge that many hobbyists and professionals strive to achieve. One of the most common problems associated with Fused Deposition Modeling (FDM) 3D prints is stringing – strands of filament, resembling a spider web, that appear when a 3d printer moves between areas without extruding filament. Stringing occurs because the retraction settings are not proper, and the filament oozes out of the nozzle during moves without printing.
What is Orca Slicer?
Orca Slicer is sophisticated open source slicing software that can be used for FDM 3D printers. Orca Slicer is a fork of Bambu Studio – which was created using PrusaSlicer / Slic3r – and was developed by GitHub user SoftFever; with the goal of having more features and customization.
Why Perform a Retraction Test?
Retraction is the action of drawing filament back into the nozzle during non-printing moves to help reduce oozing and stringing. When retraction settings (retraction length, speed, etc) are not properly set/matched, you may experience stringing, blobs, and/or under-extrusion. The retraction test in Orca Slicer provides a retraction tower, which is a 3D model made up of multiple sections, which is printed using different retraction lengths for each section. By examining the tower,
Prerequisites
Before conducting the retraction test, ensure you have the following:
1. Orca Slicer Installed: Download the latest release from the Orca Slicer GitHub page or the official Orca Slicer website.
2. 3D Printer Ready: Your printer is fully built with all components (extruder, hotend, etc.) undamaged and operational to print quality. The nozzle should be clean without leaks.
3. Filament Loaded: Use the filament you will be using as different types of filament (PLA, PETG, ABS, etc.) require different retraction settings. If your filament is wet, make sure to dry it out so that you don't get stringing because of filament moisture.
4. Printer Profile and Filament Profile: Set your printer and filament profiles in Orca Slicer to your specific hardware and material variables.
Step-by-Step Guide to Running the Retraction Test
Step 1: Install and Set Up Orca Slicer
1. Download And Install: Go to the Orca Slicer GitHub releases page or the official website to download the most recent version for your OS - Windows, macOS, or Linux.
2. Set Up Printer Profile: In Orca Slicer, go to the Printer Settings tab and either select a profile for your printer or create a new profile. You should set the print volume, specify the type of extruder (direct drive or Bowden), and nozzle size.
3. Set Up Filament Profile: In the Filament Settings tab, select the filament type (e.g., PLA or PETG), and provide some basic parameters, like temperature and bed temperature. These will be the starting parameters for the retraction test.
Step 2: Access the Retraction Test
1. Create a New Project: In Orca Slicer, start a new project by going to File > New Project.
2. Open Calibration Menu: Navigate to the Calibration menu in the top toolbar. Select Retraction Test from the dropdown list. This will open a new window for configuring the retraction tower.
Step 3: Configure Retraction Tower Settings
The retraction test will create a tower that has multiple sections - one for each retraction length. You can vary the following settings on the retraction test panel:
● Start Retract Length: The retraction length for the first section of the tower. Default is 0 mm (no retraction). For direct drive extruders, I suggest the default is okay. For Bowden extruders, start with 1-2 mm.
● Stop Retract Length: The retraction length for the last section of the tower. Default value is 2 mm. In a Bowden setup, you may find that you will need to set the stop length at 5-6 mm.
● Step Increment: The increase in retraction length for each section. Default is 0.1 mm, I suggest you use 0.2 mm and move through the steps quicker.
● Retract Speed: The speed for retracting the filament. Orca Slicer only varies length for the retraction test, so please set a fixed speed (maybe 35-45 mm/s for direct drive and 50-60 mm/s for Bowden)
For example, for a direct drive extruder, you might set:
● Start: 0 mm
● End: 2 mm
● Step: 0.2 mm
● Speed: 40 mm/s
For a Bowden extruder, try:
● Start: 1 mm
● End: 6 mm
● Step: 0.2 mm
● Speed: 50 mm/s
Step 4: Slice and Print the Retraction Tower
● Generate G-Code: Once you have set your configurations and selected OK, the retraction tower model will be generated. The Orca Slicer will create the tower and label each section with a designated retraction length.
● Preview G-Code: Preview your tower in the Preview tab. Look for the tower being sliced correctly and check the retraction changes in the G-code preview.
● Print the Tower: Save your G-code to your SD card or send to your printer via Wi-Fi (if it supports that function). Start the print and keep an eye on it in case there are bed adhesion issues or any other problems.
Step 5: Analyze the Retraction Tower
After the print has finished, inspect the retraction tower and find the optimal retraction length:
1. Check for Stringing: Observe for anything like thin strings or wisps of filament draped between the posts or cones of the tower and then note which section has the lowest amount of stringing, as this will be your best retraction length.
2. Check for Under Extrusion: If the area of the retraction tower has gaps or incomplete walls, the retraction length is probably too high and it is causing your print to under-extrude.
3. Use Calipers: Each section of the tower correlates to a direct retraction length, and with every iteration step of retraction length, you will be increasing it by a step increment (in our example it was 0.2 mm every single mm of height.) To be definitive remove the height in mm of the lowest or cleanest adjacent section, and use that height as your retraction length.
Step 6: Apply the Optimal Settings
1. Update Filament Settings: Open Filament Settings > Settings Overrides > Retraction, and enter the most optimal retraction length and speed based on the test results.
2. Save the Profile: Save the new filament profile to use these settings for future prints with a similar filament.
3. Test a Real Print: Let's try a small print (a 3DBenchy will do) and confirm that the new settings address the stringing and provide clean prints.
Advanced Tips for Retraction Optimization
1. Consider Retraction Speed
While Orca Slicer’s retraction test focuses on length, retraction speed is equally important. If stringing persists, try running a custom retraction speed test by manually editing the G-code or using a separate model. Suggested ranges:
● Direct drive: 30–50 mm/s
● Bowden: 50–70 mm/s
2. Account for Filament Type
Different materials have different retraction settings as can be seen below:
● PLA: Usually shorter retraction distances (0.2-0.8 mm) and medium speeds (30-45 mm/s).
● PETG: More prone to stringing, usually needing (0.8-1.5mm (for a direct drive) or 3-5mm (for Bowden)), and lower speeds 20-40 mm/s.
● ABS: Works like PLA, although you may have to set slightly higher retraction distances (due to its viscosity).
3. Enable Z-Hop
Z-Hop elevates the nozzle upon traveling moves and reduces the chance of nozzle collisions and stringing. In Orca Slicer, enable Z-Hop by going to Filament Settings > Settings Overrides > Z- Hop. A Z-Hop height of 0.2-0.4 mm should be fine in most circumstances.
4. Check for Other Issues
If stringing persists after optimizing retraction:
● Dry the Filament: Moisture can lead to oozing. Dry the filament in either a dehydrator or an oven - whichever is the recommended temperature.
● Use Lower Temperature: Higher temperatures can cause oozing. Use a temperature tower to determine the best temperature to print at.
● Check Extruder Setup: Check that you have correctly configured the extruder (direct drive or Bowden) in Orca Slicer.
5. Use Firmware Retraction (Optional)
If you have a printer that runs either Klipper or Marlin, in Orca Slicer you can enable firmware retraction (Printer Settings > Extruder > Use Firmware Retraction) and allow your firmware to handle the retraction. You'll have to configure the retraction settings in your firmware
Troubleshooting Common Issues
● No Change in Stringing: Make sure you are using the retraction settings correctly. Check the G-code preview to ensure the retraction commands are different across the tower.
● Over-Extrusion or Blobs: Decrease the retraction length or check that your nozzle is not leaking.
● Under-Extrusion: Increase the retraction speed or reduce the amount of retraction length to prevent clogs.
● Inconsistent Results: Check the quality of your printer hardware (ex. extruder gear, Bowden tube) and ensure your filament is dry.
