Frequently Asked Questions / FAQs

The direction of moisture transport is given for each membrane in its Product Specification in the drawing ("Moisture Discharge Side" und "Dehumidifying Side").

Each membrane has a dark, almost black side and this is the "Dehumidifying Side", whereas the other side is lighter, grey structured and this is the "Moisture Discharge" side.

Discharging moisture from 3D-print filament in a reasonable time frame requires heat. Storage boxes with Rosahl membranes are suitable for dry storage of filament spools without the need for desiccant (Silica gel). Alternatively Rosahl membranes can be mounted to multi-material systems of 3D printers (e.g. Bambu Lan AMS) to keep filament spools dry. New filament spools from most manufacturers are sufficiently dry, so that they can be added into membrane based storage boxes or multi-material systems/AMS. If in doubt or in case the manufacturer recommends this, filament spools should be dried first.

A fan inside a storage box helps with circulating the air and hence also slightly helps with the dehumidifying. We investigated for the extent of the effect with a fan in a 50l storage box and a M-3M1R membrane.

The humidity drops slightly faster with the fan, but the effect is minor. We decided to not use a fan in storage boxes, since this makes the setup simpler (no fan power supply cable needed to the inside) and allows a fully silent operation.

Air density at sea level and 20°C is 1.204kg/m^3. Percentage of Oxygen is 20.94% so we have 252.1g Oxygen in 1m^3 of air.

A relative humidity of 60%RH at 20°C corresponds to an absolute humidity of 10.37g/m^3. When we reduced this down to 10%RH, which corresponds to 1.73g/m^3, we have split 8.64g of H2O into Hydrogen and Oxygen and transported the Hydrogen to the outside.

H2O is composed of 2x Hydrogen with a molecular mass of 1g/mol and 1x Oxygen with 16g/mol, so the Oxygen share of the above 8.64g H2O is 7.68g.

So, we have increased the overall Oxygen in 1m^3 from 252.1g to 259.8g and hence increased the percentage from 20.94% to 21.6%.

Given this minimal increase, there is no need to worry about any negative impact of Oxygen concentration inside a Rosahl membrane based storage box.

In principle yes. It should be taken into account that the maximum operating temperature of the Rosahl membranes is +50°C. Whenever the temperature within a dry box or AMS 2 Pro exceeds this value, the membrane should be switched off. In off-state higher temperatures are non-critical.

The VREG-2 power supply module is suitable for membranes up to size 3. Those are:

• Rosahl PD2 Dehumidifier Membrane
• Rosahl RD3 Dehumidifier Membrane
• Rosahl RD4 Dehumidifier Membrane
• Rosahl RS1 Dehumidifier Membrane
• Rosahl M-1J1R Dehumidifier Membrane
• Rosahl M-2J1R Dehumidifier Membrane
• Rosahl M-3M1R Dehumidifier Membrane
• Rosahl M-3J1R Dehumidifier Membrane
• Rosahl MDL-3 Dehumidifier Membrane

There exist two main situations resulting in a flashing LED on the VREG-2 module:

• Larger membranes can draw a high inrush current above the 3A, which the VREG-2 is capable of delivering. Reason for the high current is moisture discharge off the membrane after a longer period without operation. The VREG-2 tries to supply the high current and goes into thermal overcurrent shutdown and turns off the output voltage. After a moment the cycles starts again and can repeat multiple times until the membrane has discharged the moisture. The on-time of the LED gets longer with each cycle until being permanently on after some cycles.
• When using a USB power supply with insufficient current capability, it might happen that this also turns off the output voltage due to an overcurrent situation. This can also repeat until a continous operation is achieved. However, if the USB power supply turns off output voltage significantly quicker, then discharging moisture off the membrane might no work properly or can take significantly longer. In this case, as different higher power USB power supply should be used.

The VREG-2 module is no full USB-C PD sink device and just requests 5V/3A based on a resistor combination. USB-C power supplies with min. 15W should normally recognize this and be able to supply voltage and current accordingly. However, based on our own experience this is not the case for every model and some do not provide proper output voltage and current or even shut down the output after a short moment. There does not exist a universal solution and it's down to testing. Based on our experience, USB-A power supplies with a USB-A to USB-C usually work good because the voltage and current negotiation by USB-C PD protocol does not apply here and the power supply would always provide 5V with the maximum current it's capable of delivering.