PETG is an easy-to-work-with 3D printing filament, but that doesn’t mean it’s trouble-free.
One of the most common issues is poor bed adhesion, which can lead to warping and failed prints.
The most common reason why PETG is not sticking to bed is a dirty printing surface. PETG may also fail to stick to an uneven bed or if the bed temperature is wrong. Other common culprits include wrong nozzle selection or the wrong temperature of the hot end.
Common Culprits Of PETG Bed Adhesion Issues
PETG is fast emerging as a popular 3D printing filament choice. It presents stable dimensions, it doesn’t shrink after printing, and is even food safe.
However, printing bed adhesion issues can lead to problems like curling corners and even layer separation. Luckily, most of the issues have an easy fix.
1. Dirty Print Bed
Dust, fingerprints, and residues left after printing can all reduce adhesion and affect the quality of your PETG project.
The easiest way to determine whether the bed needs to be cleaned is by performing a streak test.
To do this, wash your hands and wipe them with alcohol. This helps remove natural skin oils that could get onto the bed. Alternatively, wear powder-free latex gloves.
Soak a paper towel in isopropyl alcohol (at least 91% alcohol concentration) and wipe the bed side to side to cover the entire surface. If there are streaks once the alcohol evaporates, the bed is dirty and needs proper cleaning.
How To Clean A Dirty Bed
Conflicting advice online could make it hard to pick the right cleaning method for the printing surface. For instance, you may think that wiping the bed with acetone might suffice.
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However, acetone could damage the bed and is only seldom used. Hot water and soap and isopropyl alcohol are more effective cleaning agents.
To clean the bed:
- Handling the bed only from the edges, follow the steps in your 3D printer’s manual and remove it from its place.
- Mix a few drops of unscented dishwashing liquid with hot water.
- Use a soft paper towel as a sponge to wash the bed with hot, soapy water.
- Rinse thoroughly with clean hot water.
- Dry out the bed with paper towels and place it back on the printer.
Follow this procedure as often as necessary.
To maintain the bed clean, you should rinse it with alcohol after every few prints.
Wear gloves to prevent skin oils from getting onto the bed – alcohol isn’t very effective in removing these stains. Pour a small quantity of alcohol in the middle of the bed and scrub with a fresh paper towel. Wash with hot water and soap when you’re done. This procedure can help you remove PLA residues.
If instead you want to clean PEI oxides, follow the same steps but replace alcohol with acetone.
2. Unleveled Print Bed
Another reason why PETG may adhere unevenly to the bed is a bed that hasn’t been properly leveled to begin with.
When this happens, the printer can’t respect the distance parameters between the nozzle and printing surface. This results in material extrusion closer to the bed surface in some spots and farther away in others. Your piece can warp, its corners may lift, or the bottom layer could even separate completely.
How To Level 3D Printer Bed
Many 3D printing newbies believe that it’s enough to level the bed after assembling and calibrating the printer. However, the bed should be leveled every time after changing the nozzle and at least once a week – even the best printers can fall out of calibration.
To level the bed:
- Clean the bed as described above. If you’ve cleaned it after the last print, wipe it with isopropyl alcohol to remove any dust.
- Preheat the nozzle and bed to their normal operating temperatures (around 210°C to 250°C for the extruder and 80°C to 100°C for the building plate).
- Home the printer to take it to the 0,0,0 position.
- Check the printer settings for Bed Leveling, Bed Tramming, or Level Corners. The setting name can change from brand to brand.
- Slide the printer nozzle to one corner and slip a sheet of paper under it. Adjust the nozzle height until it barely touches the paper. Repeat for all other corners and the center of the plate.
- Run a print test to see if it worked.
3. Damaged Build Plate
An incorrect nozzle setting that has it grinding against the bed or a moment of distraction when removing a printed model could result in a damaged build plate.
Most 3D printer beds are designed to withstand wear and tear, and a few scratches won’t affect adhesion. However, the damage could sometimes be extensive.
Deep scratches or portions where the bed’s coating has peeled off could prevent the filament from adhering properly.
How To Fix A Damaged Build Plate
Most 3D printers have glass or resin (acrylic) beds. The general consensus is that surface scratches on both materials don’t affect adhesion.
Deep scratches on glass beds often lead to cracks and can’t be repaired. The only way to fix the problem is by installing a new bed.
Deep scratches and burrs in resin beds can sometimes be fixed through sanding.
- Put on a pair of powder-free latex gloves and run your hands over the build plate. Mark the spots where the gloves catch on the plate – these are the spots that need fixing.
- Sand down the burrs with 120-grit sandpaper and clean with a Scotch Brite pad.
- Clean the bed with hot water and soap to remove the dust.
Follow the same steps to sand a metal bed. If the damage is extensive, sand the entire build plate rather than just some spots. You may have to replace the bed if sanding didn’t improve adhesion.
4. Wrong Nozzle
PETG’s popularity is closely linked to the ease of use of this material. However, this doesn’t mean that you can print it with any kind of nozzle.
If all you know is that you need an all-metal hot end, you might think that using a hardened steel nozzle is fine.
However, hardened steel doesn’t have an internal surface as smooth as other metal nozzles and it could lead to lower-quality prints and even prevent adhesion.
The diameter of the nozzle is another thing to consider.
How To Fix Printing Issues
If the PETG doesn’t stick due to an incorrect nozzle selection, all you have to do is change the nozzle.
Brass nozzles with a diameter of 0.4mm are the best for this material.
5. Wrong Nozzle Temperature
If you have used the right type of nozzle but the PETG doesn’t stick, the problem could be that you’re printing at a too-low or too-high temperature.
PETG requires a much higher temperature than PLA, for instance. The general range is between 210°C and 250°C. However, you may find that a temperature between 230°C and 245°C is optimal for most filament brands.
How To Adjust The Printing Temperature
While all PETG filaments have the same composition, there can be slight differences between products from various brands.
To gauge the correct nozzle temperature for your filament, set the highest temperature recommended by the manufacturer and watch the filament as it comes out from the nozzle.
If it is too burnt, or curled, or it still oozes after touching the plate, reduce the temperature by 5°C and try again until the extrusion is smooth.
6. Improper Bed Temperature
Similar to the nozzle temperature, the bed temperature can affect filament adhesion. You may see most enthusiasts recommend a bed temperature between 70 and 80°C. However, the actual temperature your bed should have for proper PETG adhesion and layering is between 80 and 100°C.
7. Incorrectly Calibrated Printer
One of the most common mistakes, especially when switching to PETG after using another filament type such as PLA, is printing the object before calibrating the machine.
Even though PLA and PETG have similar printer settings, there are some crucial differences that can determine the outcome of your project.
How To Calibrate 3D Printer for PETG
Calibrating (or recalibrating) a 3D printer could seem daunting if you’re a beginner. Follow the steps below to prevent adhesion issues:
- Set the hot end and bed temperature to the parameters mentioned above. Start from the lowest end of the range and work up in 5°C increments until the temperature is right.
- Set the retraction speed to 25 mm/s and the retraction distance to 3 to 7 mm, depending on the extruder type. Bowen extruders require a distance of 6 or 7 mm. Three to 4 mm is the ideal distance for direct drive extruders.
- Adjust the print speed to 25 mm/s for the first layer and outer walls. A speed of around 50 mm/s is fine for the internal layers.
- Set the travel moves as fast as possible to avoid oozing, preferably at a speed around 120 mm/s.
8. Wrong Print Bed Surface
PEI build plates are the best surfaces for printing with PETG.
However, you can still print on glass or metal plates as long as you improve bed adhesion.
How To Improve Bed Adhesion
If your 3D printer’s bed is made of a material other than PEI, the project’s success depends on how well you prepare the surface for printing.
Blue painter’s tape or Kapton tape are the best choices so that you don’t print directly on the metal or glass. You could also use a glue stick or hairspray as a release agent.
9. High Initial Printing Speed
Another frequent mistake when printing PETG is setting a too-fast extrusion speed. PETG adheres better if printed slowly.
As explained, the best speed for the bottom layer and outer walls is 25 mm/s. You can increase the speed up to 50 mm/s for the object’s core.
10. Incorrect Layer Height
Regardless of the filament you’re using, the layer height has a significant effect on print time, detail, and strength.
As a general rule, you should always maintain a bigger ratio between layer height and nozzle size. If using a 0.4mm nozzle, the ideal layer height for PETG is 0.28mm.
11. Wet PETG Filament
Beyond printer settings and bed or nozzle issues, the moisture level of the filament can also make or break the deal. For the best results, you should only use dry PETG filament.
How To Dry PETG Filament
The easiest way to make sure your PETG filament is ready to use is to treat it in a filament dryer (65°C to 70°C) for four to six hours.
Alternatively, you can dry the filament in an oven or food dehydrator.
The oven temperature and dry time should be similar to PETG (149°F to 158°F for 4 to 6 hours). Drying the filament in a food dehydrator is typically a longer process, the spool requiring around 15 hours at 158°F.
12. Poor Quality Filament
Quality filament can be expensive, so you may be tempted to use a cheaper version if you haven’t used PETG before and just want to run a trial.
However, you should keep in mind that poor-quality filament may not stick regardless of the settings and bed preparation.
PETG from Prusament or a filament with similar quality will rarely have trouble with adhesion. Low-end brands may require a sparkling clean bed and the use of a release agent, such as a glue stick, Windex, or a hairdryer.
Tips For Successful 3D Printing With PETG
PETG may fail to stick to the building plate for a variety of reasons, but there are a few ways to minimize those risks.
Ensure A Good First Layer
Getting the first layer right is crucial for your project’s success. Once the platform is calibrated properly, print a thin first layer then increase the layer height if necessary.
A thin layer cools down faster and can adhere to the bed properly.
Use A Fan
Using a cooling fan is not necessary with PETG, but it can help with retraction.
This will prevent stringing and bobbling, increasing the quality of your prints.
Keep The Nozzle Clean
Using a clean nozzle is important regardless of the material you’re using, but especially so when printing with PETG.
PETG filament can stick to a dirty nozzle, and blobs of it could be deposited in parts of the print where they don’t belong.
When the nozzle passes over to extrude in that place, it can bump into the hardened blob and cause a layer shift.
For this reason, it is crucial to start printing with a clean nozzle and pause to clean the nozzle for as many times as necessary during the process.
Ender 3 (Pro/V2) – PETG Not Sticking To Glass Bed
While the best surface to print PETG onto is PEI, most Ender 3 printers, including the Pro and V2, have glass beds.
You don’t have to buy a new bed to work with PETG. However, you should avoid printing directly on the glass surface.
To improve adhesion, you should cover the glass with blue painter’s tape or use a glue stick or hairspray or Windex.
You should also set a slightly lower bed temperature, between 70°C and 80°C, while the hot end temperature should be around 240°C.
If you’re using a cooling fan, you should also set the cooling speed on low.
Final Thoughts
The most common reasons why PETG doesn’t stick to the printing bed include an improperly calibrated printer and a damaged or uneven bed.
Wet filament may also fail to stick to the bed, and you should also consider the choice of nozzle and input the correct settings. If fixing these didn’t work, the problem could be the poor quality of the filament.
