Today, I printed a new version of the dry box base—this time using PETG, a material with a higher heat deflection temperature than PLA. I also upgraded the fan to a much more powerful model: a high-speed centrifugal blower rated at 10,000 RPM, with nearly 5 times the power of the previous one. For safety and stability, I also switched the PTC heater back to the 100W version.
To monitor the internal temperature behavior, I placed two SNZB-02LD sensors inside the sealed box. One sensor’s probe was positioned right at the PTC airflow outlet, in the bottom-left corner of the container – where the temperature is expected to be highest. The second probe was placed at the top of the filament spool, to measure how heat rises and accumulates near the ceiling.
As for the TH Elite system, I placed its sensor in the bottom-right corner of the container – the expected endpoint of the airflow circulation path.
This positioning should give a clear view of whether warm air effectively reaches the far side of the enclosure.
Once everything was set up, I started the test. As expected, the bottom-left corner near the PTC outlet showed the fastest temperature rise – confirmed by the SNZB-02LD sensor connected to the metal probe at that location, which corresponds to the SNZB-02LD display shown on the right side in the picture.
Meanwhile, the sensor at the top of the filament spool showed a much slower temperature increase, and the TH Elite sensor in the bottom-right corner responded the slowest of all. At one point, when the PTC outlet temperature had already reached 90°C, the bottom-right corner was still reading below 40°C. This clearly shows that the hot air isn’t completing its circulation loop effectively – it’s pooling near the heat source and not reaching the far end of the box.
To improve the airflow loop, I added an additional fan at the top-right corner of the container – right above the TH Elite sensor. This fan is configured to push the upper-layer air downward, in hopes of reinforcing the circulation loop and reducing the internal temperature gradient. Aside from this change, all other conditions were kept the same.
This setup should help determine whether forced downward airflow at the far end
can make the internal temperature more balanced and improve the overall drying effectiveness.
I then proceeded with the second round of testing using the updated setup.
With the newly added circulation fan in place, I observed that the temperature difference between the top sensor and the bottom-right sensor had noticeably decreased – dropping to around 10°C, compared to over 20°C in the previous test.
However, the temperature gap between the PTC outlet and the top of the enclosure was still quite significant – remaining at over 30°C. This indicates that while airflow at the far end has improved, heat is still accumulating too much near the source, and the upward convection from the PTC is still insufficient.
It seems that I still need to add another fan directly at the PTC outlet – this time to push the hot air upward immediately, in order to reduce temperature buildup in that corner and balance the airflow path more effectively.
After ending the test, I found that the support structure near the PTC outlet,
including parts of the filament roller, had already started to deform from heat exposure. This confirmed that hot air is still pooling in the lower corner,
causing localized overheating that damages printed components.
Despite all the tweaks, this round of testing reminded me that airflow design is never just about adding more power—it’s about guiding heat to where it needs to go, and away from where it shouldn’t stay. There’s still work to do, but at least now I know where the real problems lie. One step closer.
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