How to Prevent 3d print stringing: a Step by Step Guide

Stringing, also known as "oozing," is a common issue in 3D printing where small strands of filament are left behind as the print head moves across open spaces. These unwanted strings can diminish the aesthetic quality of your prints and sometimes interfere with the functionality of the final model. Fortunately, stringing is preventable with the right settings and techniques. In this tutorial, we’ll explore the causes of stringing and provide a step-by-step guide to eliminate it.

What Causes Stringing in 3D Printing?

Stringing occurs when molten filament leaks out of the nozzle during non-print moves. Several factors contribute to this problem:

1. Improper Retraction Settings: Retraction refers to the process of pulling the filament back into the nozzle during travel moves to prevent oozing.

2. High Printing Temperature: Excessive heat can make the filament too fluid, increasing the likelihood of oozing.

3. Travel Speed: Slow travel speeds give the filament more time to ooze out.

4. Filament Quality: Poor-quality or moisture-laden filament can exacerbate stringing.

Step-by-Step Guide to Prevent Stringing

Step 1: Calibrate Retraction Settings

Retraction is a critical factor in combating stringing. Adjusting retraction settings involves tweaking the following parameters:

● Retraction Distance: This determines how much filament is pulled back into the nozzle during travel moves. Start with a 5-7mm distance for Bowden extruders and 0.5-2mm for direct drive extruders. Test and adjust incrementally.

● Retraction Speed: A speed of 20-60mm/s works well for most printers. Faster speeds reduce oozing but may cause filament grinding if set too high.

How to Adjust Retraction Settings

1. Open your slicing software (e.g., Cura, PrusaSlicer).

2. Locate the retraction settings under the printer settings or material settings menu.

3. Print a "stringing test" model (e.g., a calibration tower) to evaluate the changes.

Step 2: Optimize Printing Temperature

Temperature Tower

Filament behaves differently at various temperatures. Printing at too high a temperature can cause the material to become overly liquid, increasing the chances of stringing.

Steps to Optimize Temperature

1. Check the recommended temperature range for your filament (usually printed on the spool).

2. Print a temperature tower to identify the lowest temperature that maintains good layer adhesion and minimizes stringing.

3. Adjust the nozzle temperature in your slicer and re-test if necessary.

Step 3: Adjust Travel Speed

Increasing travel speed reduces the time the nozzle spends moving over open spaces, giving the filament less time to ooze.

1. Navigate to the travel speed settings in your slicer.

2. Increase the travel speed to 150-200mm/s and observe the effect on stringing.

3. Test with a small print to confirm the settings are optimal.

Step 4: Enable "Combing" Mode

Most slicers offer a "combing" or "avoid crossing perimeters" feature. When enabled, the nozzle stays within the bounds of the print, reducing the need for long travel moves across open spaces.

How to Enable Combing

1. In your slicer, search for the combing mode setting.

2. Set it to "Within Infill" or a similar option, depending on the slicer.

3. Re-slice your model and print to evaluate the result.

Step 5: Use High-Quality Filament

Poor-quality or moisture-laden filament is more prone to stringing. Moist filament absorbs water from the air, which vaporizes during printing, causing bubbles and strings.

How to Handle Filament

1. Store filament in an airtight container with desiccant packets.

2. Dry filament before printing using a filament dryer or an oven at a low temperature (e.g., 40-50°C for PLA).

3. Use trusted brands known for consistent quality.

Step 6: Drying Filament in a Filament Dryer

Using a filament dryer is an effective way to remove moisture from filament, ensuring consistent quality and reducing stringing.

How to Use a Filament Dryer

1. Choose the Right Dryer: Invest in a dedicated filament dryer designed for 3D printing materials.

2. Set the Correct Temperature: Refer to the filament manufacturer's guidelines for drying temperatures. For example:

○ PLA: 40-50°C

○ ABS: 70-80°C

○ Nylon: 70-90°C

3. Load the Filament: Place the filament spool inside the dryer and start the drying cycle.

4. Drying Time: Typically, 4-6 hours of drying is sufficient for most filaments, but heavily moisture-laden spools may require longer.

5. Monitor and Use: After drying, load the filament directly into your printer to maintain its low-moisture condition.

Step 7: How Often Should a Filament Dryer Be Used?

Regular use of a filament dryer can ensure consistent print quality and prevent moisture-related issues like stringing and poor layer adhesion.

Guidelines for Dryer Usage

1. Before Every Print: For filaments highly sensitive to moisture, such as Nylon or PVA, dry the filament before each print session.

2. After Extended Storage: If the filament has been stored for more than a week without a sealed container or desiccant, use the dryer before printing.

3. Environmental Factors: In high-humidity environments, frequent drying (e.g., every few days) may be necessary for all filament types.

4. Visible Signs of Moisture: If you observe bubbling, hissing, or inconsistent extrusion during printing, dry the filament immediately.

By establishing a regular drying schedule based on filament type and environmental conditions, you can maintain optimal filament performance.

Step 8: Fine-Tune Additional Settings

Other slicer settings can also help mitigate stringing:

● Z-Hop: When enabled, the nozzle lifts slightly during travel moves, reducing the chance of dragging filament across gaps.

● Coasting: Coasting stops extrusion slightly before the end of a travel move to relieve pressure in the nozzle.

● Wipe: Wiping moves the nozzle over the print area to clean off excess filament before travel moves.

Step 9: Clean the Nozzle

A clogged or partially blocked nozzle can disrupt extrusion and cause stringing. Regularly clean your nozzle to maintain smooth filament flow.

How to Clean the Nozzle

1. Heat the nozzle to the printing temperature.

2. Use a cleaning filament or a needle to clear any debris.

3. Perform a cold pull to remove stubborn residue.

Stringing Towers a Quick Guide

Stringing towers are calibration models designed to help minimize stringing in 3D printing. They consist of multiple vertical columns spaced apart, forcing the printer to perform non-print travel moves where stringing is most likely to occur.

What Are Stringing Towers?

Stringing towers test your printer’s performance during travel moves by highlighting stringing issues. They are easy-to-use models that visually display how different settings affect stringing.

How to Use Stringing Towers

Step 1: Obtain a Model

● Download: Search for "stringing test tower" on sites like Thingiverse.

● Create: Use CAD software to design columns spaced 10mm apart.

Step 2: Slice and Print

● Import the model into your slicer.

● Use your current settings and print a baseline model.

Step 3: Adjust Settings

1. Retraction: Test different distances and speeds.

2. Temperature: Lower in small increments to minimize stringing.

3. Travel Speed: Increase speed to reduce nozzle dwell time.

Step 4: Compare Results

Print multiple towers, changing one variable at a time, and compare to find the best settings.

Filament-Specific Stringing Tips

Different materials have unique properties that influence stringing. Here are some common materials and how to handle them:

● PLA: Low stringing potential but sensitive to high temperatures. Use lower temperatures (190-210°C) and moderate retraction settings.

● PETG: Prone to stringing due to its sticky nature. Use minimal retraction and lower travel speeds.

● ABS: Less prone to stringing but requires high temperatures (230-250°C). Ensure proper cooling to minimize issues.

● TPU: Highly flexible and prone to stringing. Slow print speeds and precise retraction settings are essential.

● Nylon: Absorbs moisture quickly, leading to stringing. Dry thoroughly and use high temperatures (240-270°C).

Adjust settings based on the material’s behavior to achieve optimal results

Environmental Humidity and Its Impact

Humidity can have a significant impact on stringing, especially for hygroscopic filaments like Nylon and PETG. Moisture absorbed by the filament can turn into steam during extrusion, increasing stringing and weakening prints. To mitigate this:

● Use a Dry Box: Store filament in a sealed container with desiccants.

● Dry Filament Regularly: Use a filament dryer if the material has been exposed to high humidity.

● Monitor Environment: Keep the printing area below 50% relative humidity if possible.

Post-Processing to Remove Stringing

If stringing occurs despite calibration, you can remove it post-print:

● Heat Gun: Gently apply heat to melt and eliminate fine strings.

● Brass Brush: Carefully sweep away strings without damaging the model.

● Sandpaper: Smooth the surface to remove residual imperfections.

Post-processing is a useful step for achieving a professional finish when stringing cannot be entirely avoided.