PETG How to Improve Bed Adhesion

PETG, or glycol-modified polyethylene terephthalate, is a commonly used thermoplastic filament in 3d Printing, especially for functional parts. It offers advantages such as improved flexibility compared to PLA and reduced susceptibility to warping compared to ABS, making it ideal for designs requiring compliance and durability in high-stress applications.

Although PETG is generally considered easier to print with, achieving optimal print settings for PETG can be a challenge. Fine-tuning the print settings, especially for the first layer, can be more difficult compared to PLA.

Poor bed adhesion can result in various issues when printing with PETG. In the best-case scenario, you may encounter slight warping or minor shifts in layer alignment. However, in more severe cases, the prints can detach from the build surface, leading to filament pooling and significant print failures. Before making adjustments to print settings, it’s essential to ensure that the bed is level and the Z offset is properly calibrated.

If calibration issues have been ruled out, and you’re still facing adhesion problems, PETG itself may be the culprit. Let’s explore effective strategies to tackle the challenges associated with this finicky filament

Increase Hot Bed Temperatures

To evaluate the hot end temperature for optimal adhesion, you can print only the first layer of a test file multiple times. Begin with a temperature at the lower end of the manufacturer’s recommended range (typically between 220 and 250 °C), and gradually increase the temperature by 2 to 5 °C for each subsequent print. While any file can be used, a simple option is the XYZ calibration cube, stopping the print after completing the first layer.

The goal is to find the lowest temperature that still provides good adhesion while minimizing stringing and warping issues. If the temperature is too high, the extruded filament may appear overly wet and runny. The ideal hot end temperature is when the filament adheres to the build plate and cools down sufficiently before the next layer is applied.

Keep in mind that the temperature required for the first layer may differ significantly from that needed for subsequent layers. Ensure that if you adjust the first layer temperature, the remaining layers still print at an appropriate temperature, whether it is the same as the first layer or not. Complete the printing of the calibration cube to gather the necessary information for temperature optimization.

Increase Hot End Temperatures

Low bed temperatures can also contribute to warping issues with PETG. Insufficient bed temperature can cause the printed PETG to cool too quickly, resulting in shrinkage and curling along the edges.

However, tuning the bed temperature can be challenging. If you observe warping, try increasing the bed temperature. The recommended range for PETG bed temperature is typically around 60 to 90 °C. It’s crucial to raise the temperature gradually and perform test prints, as PETG can adhere too strongly at higher temperatures.

If you notice a reduction in warping or no warping at all after making temperature adjustments, but the print is still not perfect, it might be necessary to slow down the print speed.

Reduce Print Speed

Insufficient cooling time between layers can contribute to warping in PETG prints. Slowing down the print speed for initial layers allows more time for each layer to cool and reach the temperature of the bed, reducing the likelihood of warping.

Many slicing software options include a dedicated setting for initial layer speed, so you don’t have to compromise on overall printing speed. PrusaSlicer, for example, allows you to set the initial layer speed as a percentage of the normal print speed, while Cura uses defined values. Both can be adjusted to fit your requirements, with the recommended range falling between 30 and 45% of the regular print speed.

Even with a slower print speed, you may still encounter issues with parts cooling too rapidly and lifting off the bed. In such cases, the culprit might be the parts cooling fan. As you may have noticed, PETG printing is highly dependent on proper cooling.

Consider adjusting the cooling settings for the parts cooling fan. You can reduce the fan speed or delay its activation for the initial layers to limit the cooling effect during that critical phase. Experimenting with different cooling settings can help find the right balance between cooling and adhesion for successful PETG prints.

Switch Off the Fan

PETG prints can often benefit from minimal or no parts cooling fan. This is because controlling the cooling rate is crucial for PETG to cool properly and reduce the risk of warping. Using the parts cooling fan on the first layers can lead to rapid cooling and potential warping issues. Disabling or reducing parts cooling can be an effective solution when printing with PETG.

While some users completely avoid using the parts cooling fan for PETG, you may find it necessary to achieve sharp overhangs or specific print features. Fortunately, most slicing software provides a dedicated fan setting for the initial layers. It is generally safe to turn off the fan entirely for the initial layers, or it may already be disabled by default.

By fine-tuning the hot end and bed temperatures, reducing the print speed, and adjusting the parts cooling fan, you can create the optimal printing conditions for PETG. With these adjustments, you can ensure the filament cools at the right rate, leading to successful prints with reduced warping. However, if persistent warping issues persist despite these efforts, seeking additional assistance and guidance may be necessary.

Apply a Raft or Brim

Finally, one of the easiest solutions for improving adhesion with PETG is to use a raft or a brim.

A brim is a set of filament lines printed around the model, creating additional contact area with the build plate. This helps enhance adhesion by increasing the surface area in contact with the bed. On the other hand, a raft is a platform printed directly on the build plate, with the actual part printed on top of it. This not only increases the contact area but also facilitates easy removal of the initial layers from the model.

While increasing surface area can aid in improving adhesion, it’s important to note that it can also potentially lead to more warping. It’s best to address any existing warping issues by evaluating and adjusting temperature settings before resorting to the use of rafts or brims.

In addition to improving bed adhesion, rafts and brims offer other benefits as well. When combined with the previously mentioned solutions, they can be particularly useful for purging the nozzle and ensuring cleaner finishes on your prints.

By considering the use of rafts or brims along with other strategies discussed, you can enhance adhesion and achieve cleaner prints with PETG.