TABLE OF CONTENTS
PETG (Glycol-modified Polyethylene Terephthalate) is a popular variant in the PET family of plastics, known for its excellent printability and toughness compared to other PET copolyesters. While it’s the go-to choice for 3D printing, pure PET is rarely used due to the advantages of PETG.
This material offers superior mechanical and thermal properties when compared to PLA, making it a great alternative for users who encounter issues with ABS like warping or cracking, while also needing enhanced strength over PLA with excellent dimensional stability. However, PETG has low chemical resistance and moderate temperature resistance, softening at approximately 80°C (Glass Transition and Vicat temperature).
Printer Setup Requirements
- Extruder Temperature: Minimum of 230°C (±15°C) is required, with 245°C recommended for standard prints. Use lower temperatures for bridging applications.
- Heated Bed: Required heated bed temperature is between 75°C - 85°C.
- Enclosure: Not necessary, but beneficial for print quality.
- Part Cooling Fan: OFF for functional parts (to enhance layer adhesion), or set to LOW for improved bridging and surface appearance.
- Feeding / Spooling: No specific requirements, but ensure smooth feeding to avoid jams.
Some slicers come with pre-configured PETG or CPE profiles. If not available, you can start with a PLA or ABS profile and make necessary adjustments.
Bed Surface Recommendations
Proper bed surface choice is crucial for successful PETG printing. Here are the recommended surfaces:
- Glass Bed: Print directly on a glass bed with a thin layer of Magigoo Original or glue stick (do not print directly onto the glass).
- Flex Plate: Textured/Frosted PEI sheet is ideal, but remember to wait for the bed to cool for easier part removal.
Bed Leveling & Nozzle Height
To ensure an effective first layer, both bed leveling and nozzle height are essential:
- Level the bed properly.
- Set the nozzle height correctly, ideally 0.1 mm (the thickness of two pieces of standard paper).
Preheat the bed to 75°C - 85°C before calibrating the nozzle height or levelling. Given PETG's strong adhesion, consider a slightly larger gap than usual to prevent sticking to the nozzle.
Filament Storage
Store PETG away from sunlight in a resealable bag with desiccant.
Being hygroscopic, PETG can absorb moisture, leading to bubbles in extrusion and poor layer adhesion. While it usually absorbs moisture over months, high humidity can accelerate this process significantly.
Preventing Moisture Absorption
Store and print PETG at humidity levels below 20% to prevent moisture uptake. Using a filament dry box during printing and resealable bags with desiccants when not in use is highly recommended.
Printer Settings
Printer Settings
Nozzle Temperature
PETG typically prints at 230°C - 250°C, with 245°C recommended for functional parts.
This filament is prone to oozing, which can be mitigated by adjusting the nozzle temperature. Higher temperatures improve flow and layer adhesion, particularly beneficial for mechanical parts, while lower temperatures are better for overhangs and support removal.
Start near the middle of the manufacturer's recommended range. If they suggest 230°C - 240°C, try 235°C. If your extruder can’t reach top temperatures, stick to the lower end. Adjust temperatures in increments of ±5°C based on print quality.
Bed Temperature
The heated bed should maintain a temperature of 75°C - 85°C. Avoid exceeding 80°C, which is near the glass transition temperature for PETG.
Cooling
When printing PETG, you can either set the part cooling fan ON or OFF.
- For maximum layer adhesion and strength, keep the fan OFF.
- For better overhangs and surface quality, use the fan at LOW speed, around 20% if possible.
Troubleshooting
Poor Surface Quality
Achieving a clean and smooth surface finish with PETG is essential. If you encounter rough or textured surfaces, consider the following solutions:
Improving Surface Quality
Check Filament Moisture: Ensure your spool of PETG is dry. To test for moisture, extrude the filament; a popping sound indicates moisture absorption, leading to rough extrusion. Use a dry box and preventive measures to maintain optimal printing results.
Extruder Temperature and Flow Rate: If these are too low, PETG won't extrude correctly, resulting in gaps. Adjust the nozzle temperature to the recommended range to resolve this.
Filament Feeding Friction: Excessive friction can lead to under-extrusion. Move the spool holder closer to the printer and ensure the filament guide tube isn’t too tight.
High Extruder Temperature: If the temperature is set too high, the filament may sag during steep overhangs. Keep the cooling fan on LOW for better underside quality, and consider reducing the nozzle temperature.
Nozzle Blockage: A partially blocked nozzle impedes extrusion. Regularly clean the nozzle to prevent this issue.
Print Speed Adjustments: Lowering print speeds can reduce vibration, leading to better quality. A recommended maximum speed for Bowden systems is about 45 mm/s, with 60 mm/s for infill.
Retractor Settings: Incorrect retraction settings can negatively impact print quality. If retraction distance is too high or speed too slow, it may not prime properly for the next layer, causing gaps. Temporarily disabling retraction can help identify if it’s the cause. If needed, adjust both retraction distance and speed. Too high a retraction speed might grind the filament, causing jams.
Pitting Issues: Gaps in the top surface (referred to as pitting) can occur due to low infill or improper temperature. This can be addressed by increasing the number of top layers to better support the top surfaces. For instance, using 6 top layers at 0.2 mm layer height achieves a 1.2 mm thickness, whereas the same layers at 0.1 mm yield only 0.6 mm. Increasing to 12 top layers with a 0.1 mm height reaches the desired 1.2 mm surface thickness.
Cleaning a PETG Nozzle Blockage
If you encounter a blockage in a PETG nozzle, one effective method is to feed a tougher material, such as Polycarbonate (PC), through the extruder. Due to the high extrusion temperature and toughness of PC, it can help clear the clogged PETG.
If the blockage persists and cannot be removed, replacing the nozzle with a spare is recommended.
Solutions to Prevent PETG Sticking to the Nozzle
PETG's viscosity during printing is similar to that of some adhesives, which can lead to filament accumulation on the nozzle and compromise print quality. Here are effective strategies to mitigate this issue:
Adjust First Layer Settings
- Increase Gap: Unlike some filaments that benefit from a 'squished' first layer, PETG should be printed with a larger gap between the nozzle and the bed to prevent sticking.
Control Material Flow
- Adjust Temperature and Cooling: Ensuring the right amount of material flows through involves tweaking the nozzle temperature and cooling fan settings.
Manage Retraction and Travel Speeds
- Increase Retraction: A higher retraction distance and speed can help reduce oozing. However, consider lowering the retraction speed specific to PETG to enhance performance.
- Monitor Z-Hop Settings: While Z-hop can prevent nozzle drag on delicate parts, it might cause the nozzle to pick up wisps of filament, so it's best to keep this feature turned off when possible.
Understanding Heat Creep
Heat creep refers to the phenomenon where heat travels up the extruder, causing the filament to soften prematurely. This can lead to jams, especially in lower temperature materials like PETG, which has a softening temperature of around 80°C. The problem is more pronounced in enclosed high-temperature printers or dual extruder setups where filament is idle for extended periods.
Solutions to Prevent Heat Creep
- Ensure Proper Cooling: Make sure the extruder fan operates correctly, and keep printer doors open for better airflow in enclosed setups.
- Adjust Temperature Settings: Printing at the lower end of the filament's extrusion temperature can help mitigate heat creep.
Heat creep-related jams are often exacerbated during retraction, as the filament passes the extruder gear multiple times. To minimize issues, consider printing simple parts with minimal retraction.
Minimising Stringing and Oozing
PETG materials can easily ooze, leaving unwanted strands during travel. Here are methods to tackle stringing:
Techniques to Reduce Stringing
- Cooler Nozzle Temperature: Lowering the nozzle temperature can help prevent excessive flow.
- Increase Retraction Settings: Lengthening the retraction distance or speed can retract filament effectively during movement.
- Boost Travel Speeds: This reduces the idle time of the nozzle, minimizing the risk of stringing.
- Utilize Advanced Slicer Options: Enabling coasting can also effectively reduce stringing occurrences.
- Avoid High Humidity: If your filament absorbs moisture, it can alter its viscosity, leading to stringing. Store your filament properly to prevent this.
Preventing Warping
While PETG typically has good dimensional stability, warping can still occur. Here are the causes and preventive measures:
Strategies to Avoid Warping
- Ensure Proper Adhesion: Incorrect nozzle height or bed adhesion can lead to warping. Make sure the nozzle is correctly leveled and that you're using suitable printing surfaces, such as textured or frosted PEI.
- Control Environmental Conditions: Drafts and cool air can increase internal stress in prints. Using an enclosure can help maintain optimal conditions.
- Preheat the Bed: Some heated beds may not deliver uniform temperature across the surface. Preheating can address this.
- Set Bed Temperature Appropriately: Keeping the heated bed at 80°C can improve both adhesion and print consistency.
Improving Layer Adhesion
Poor layer adhesion can stem from various issues, including the following:
Solutions for Better Layer Adhesion
- Calibration: Regularly calibrate your printer to avoid under-extrusion, which can lead to weak layer adhesion.
- Fan Settings: Running the cooling fan on a low setting or turning it off entirely can improve layer bonding.
- Avoid Moisture: Moisture-laden filament can lead to bubble formation during extrusion, compromising strength and adhesion. Ensure proper storage for your PETG.
Enhancing Bed Adhesion
PETG often requires specific conditions for optimal bed adhesion. Here are useful tips:
- Adjust Nozzle Height: Factor in an additional 0.02mm to 0.06mm margin to prevent gliding over freshly printed material.
- Consider Adhesion Aids: Products like Magigoo can aid in print removal by ensuring the part detaches when cooled.
Addressing Difficult Print Removal
While excellent adhesion is necessary for successful prints, overly strong bonding can make part removal challenging.
Methods to Improve Print Removal
- Use Magigoo: This product facilitates easy release upon cooling.
- Flex Build Plates: For textured or frosted PEI, allowing the bed to cool and then flexing it can help release parts.
- Adjust Heating and Nozzle Settings: If using glass without Magigoo, remove parts when the bed is hot
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