If you have ambient air that has a high relative humidity, it can affect the drying process of your filament negatively: the drying process may take an unnecessarily long time and you may never get as good (in terms of dry) results as someone who lives in a place that has pretty dry ambient air.
Using this gadget you can generate dry air that you can feed to your filament dryer to dry your filament more effectively. If you have a Sunlu S2 dryer you can use my custom Sunlu S2 Base to connect the air dryer to your S2.
This model is kind of the small low-budget brother of MZips Air Dryer. The general idea is to pump air through a container filled with silica gel beads to generate dry air.
Noticeable differences:
- MZip's model uses a big container holding around 800g of desiccant which allows to dry 20-30 spools of filament. This was way too much for me. The container of my model holds around 100g of dessicant. I can pump air through the dryer for around 24h before the outcoming air becomes more humid.
- MZip's model uses a glass container for the desiccant. This is nice if you use desiccant that has a color indicator. My silica gel is just white and does not change color. So I was able to print my desiccant container und save money. Moreover, I can adjust the size of the container to my needs.
- MZip's model uses cheap humidity sensors, which can measure down to 10% RH. Once the sensor is mounted in the fixture, you don't have access to it's batteries. Thus, you need to mount cables on it and connect it to a separate battery holder.
My model is designed for a Xiaomi humidity sensor that can measure even below 10% RH. And once the sensor is glued in to the fixture, you are still able to change the battery.
What you need:
- Xiaomi - Mi Temperature and Humidity Monitor 2
- Glue to mount the Xiaomi into the fixture and seal the gaps. I used silicon glue used in aquaristics.
- Silica Gel Beads
- An aquarium pump for 4/6mm (ID: 4mm, OD: 6mm) PVC hose. I use a cheap (around 10€) JEBO 6700. It has an adjustable (!) flow rate of up to 4l/min and an air pressure of 22 Kpa. I set the flow rate to the minimum, because otherwise the desiccant gets used up much faster.
- 4/6mm PVC hose
Instructions:
- Print all three parts. I used PLA+:
- 0,2mm layer height
- 4 walls/perimeters
- 20% Gyroid infill
- The bottom part must be printed with supports. The other do not need supports.
- Use silicon glue to mount the Xiaomi in the fixture. Note that no glue should hit the sensors! I would also protect the sensor area while the glue is drying. Maybe with some tape. ***
- The gaps on the outside should also be sealed with silicon.
- Mount PVC hose on the bottom part and on the top part/lid.
- The pump must be connected to the top part. So air is flowing down through the silica gel container.
- Let the glue dry for multiple hours, maybe 1-2 days. It is probably a good idea to pump air through the fixture while the glue is drying. ***
Usage:
- Fill silica gel beads into the middle part, the container.
- Screw all three parts together.
- Connect the lid to your pump.
- Connect the bottom part (the exit) to your filament dryer.
- Start pump and filament dryer.
- Once the Xiaomi shows too high humidity numbers, exchange the silica gel.
*** Important:
I did not protect the sensor area with tape while drying and I also did not do the last step of the instructions above, i.e. I did not pump air through the system but instead led the silicon glue dry “on its own”. But I noticed a strange thing: The Xiaomi showed way too high humidity numbers, 20-30 %RH. First, I was thinking that the air dryer just does not work. But then I measured the humidity at the exit of the system using a different Xiaomi, which showed a value of 5%.
I guess the acid fumes of the silicon glue somehow affected the Xiaomi. So be aware, that your Xiaomi could also be affected negatively.
Luckily, after days/hours of usage, the measurement of the Xiaomi improved. Now the shown value is only 2-3% off. It can now show a value down to 9%. And that is sufficient to know when the silica gel get's used up.
Results:
In my case the ambient air usually has a relative humidity around 60-70%. When drying PETG at 65°C in my Sunlu S2, the S2 never showed a value below 28% RH, even after 12+ hours. But feeding it with dry air, it came down to 14%, even much faster. And it seems 14% is the lowest value my S2 can show. I guess the real value is even lower.