As we all know, wet 3D filament may cause printing failures. These include nozzle clogging, finished product warping, and a rough surface. So when we judge that the filament humidity is high, we usually choose to dry the filament before printing. There are many common ways to dry filament, such as using a heat gun or a food dehydrator, etc. One of them is to use an oven.
Is using an oven a simple and practical way to dry filament? Next, we will analyze this issue in depth from four aspects.
1.Filament Drying Temperatures Explained
The purpose of drying filaments is to remove the moisture in them, not to heat them to the "melted chocolate" state. Therefore, you must pay attention to the temperature when drying. In fact, there is a critical temperature between the material maintaining its original form and becoming liquid - the glass transition temperature(Tg).
The glass transition temperature is the key temperature where a material changes. It goes from a hard and brittle glass state to a soft rubber state. This is the temperature where the material starts to become soft and elastic.
PLA and ABS may restore their hardness after overheating (exceeding Tg), but may deform or warp after cooling. TPU and nylon may become softer or more hygroscopic, and are prone to adhesion or strength loss after cooling. Therefore, the drying temperature of most materials needs to be controlled below the glass transition temperature while evaporating the moisture.
| Meterial | Drying Temp | Drying Time | Tg (Glass transition temperature) |
|---|---|---|---|
| PLA | 45-50℃ | 4-6 hours | 55℃ |
| ABS | 80-90℃ | 4-6 hours | 105℃ |
| NYLON | 60-70℃ | 8-12 hours | 50-70℃ |
| PETG | 65-75℃ | 4-6 hours | 80-85℃ |
| TPU | 40-60℃ | 4-6 hours | ≈-50℃ |
The drying temperature of TPU is close to its Tg, but due to proper time control, it will not cause large-scale movement of molecular chains and cause damage; the drying temperature of NYLON is slightly higher than Tg, but the heating process is controlled and will not damage the material.
2.Temperature control
Since the temperature control of the oven depends on the sensing of the thermostat. The heating element will continue to heat the air until the thermostat senses the set temperature and turns off the heating element.
The heating element will keep releasing heat even after it is turned off. This will cause the temperature to keep rising.In addition, the sensing of the thermostat has a certain delay. This means that when the thermostat reacts, the temperature inside the oven is usually higher than the set value. The temperature error is usually between ±5°C and ±10°C.Even if the temperature is set to the required level for drying, this is why the filament may still be overheated and baked.
Solution:
- Low temperature drying. Select the lowest temperature setting for drying, and keep the temperature between 40°C and 60°C.
- Install a thermostat. Check the internal temperature in real time and adjust the heating intensity of the oven in time.
3.Moisture removal effect
The oven heats the air inside the space, which can evaporate the moisture on the surface and inside of the filament to be dried, thereby drying the filament. The fan inside the oven can enhance the convection of the internal air, thereby achieving the purpose of uniform heating. In addition, most ovens have vents, which are helpful for removing water vapor. These functions basically meet the conditions for using the oven as a filament drying box.
However, the design of the oven will consider a certain airtightness to avoid heat loss. This may cause the water vapor to not be completely removed and remain inside the oven. As the moisture generated by evaporation gradually accumulates, the relative humidity inside the oven will increase. The moisture may be reabsorbed by the filament, affecting the drying effect of the filament.
Solution:
- Slightly open the oven door: During the drying process, keeping the oven door open a small gap (about 1-2 cm) can help water vapor escape
- Place desiccant: Place some desiccant (such as silica gel desiccant) inside the oven to effectively absorb water vapor. Avoid choosing desiccant containing harmful ingredients, which may release harmful gases when heated.
4.Residual odor
When you put different filaments at their drying temperature, they usually do not give off bad or harmful smells. At normal drying temperatures (such as 60°C), common filament materials such as PLA, PETG, and TPU usually have a slight plastic smell or sweet aroma.
For ABS and nylon, a slight odor and the volatilization of organic compounds may be emitted. As a relatively closed space, the oven may have a certain odor remaining inside. If food and other ingredients need to be dried later, they need to be ventilated.
If the heating time is too long or the temperature is higher than the normal drying temperature, 3D printing materials usually emit irritating gases. Plastic materials like ABS, nylon, and TPU can release harmful gases. These gases may harm the human body.
Solution:
- Maintain ventilation: Maintain a good ventilation environment when drying the filament and after drying to give the smell a chance to dissipate.
- Clean the oven: Remove the residue inside the oven to prevent the odor from continuing to evaporate
Conclusion
Using an oven as 3d printing dry box is feasible to some extent. However, it is necessary to pay attention to the real-time control of temperature, humidity control and subsequent processing of drying. In contrast, professional filament dryers can provide precise temperature and humidity control to ensure filament quality and drying efficiency. This way, you can avoid the risk of damaging your oven due to a failed filament drying attempt.