Take the filament all out of your AMS2 and put it in dry mode with the silica gel still in there and let it get to temperature. Note the AMS2 humidity measurement.
Take the silica gel out and let the RH restabilize and quit changing and read the humidity again with the AMS totally empty of desiccant and filament. This number is important. Air is the easiest thing for the AMS2 to dry.
The empty humidity is as good as it gets for the AMS2. I don’t know what RH you should expect, though. I don’t have an AMS2. But with the AMS empty the only water it needs to remove is what is in the air.
Air holds very little water even at high humidity compared to filament. Desiccant can hold much more water than filament. These are important to keep in mind when thinking about moisture and drying.
Putting desiccant in an AMS can really help or it can really hurt because it holds so much more water than filament or air. If your desiccant is more dry than the empty RH your AMS2 can hit, then it will help. More than that, it will do the lion’s share of the drying so why even bother with an AMS2?
On the other hand, let the desiccant get wetter than the AMS2 can hit when empty and you cripple the AMS2. Since desiccant can hold so much more water than filament, if your desiccant is too wet, that’s the water the AMS2 will be removing. Yep, it will dry the desiccant but it takes a long time and meanwhile your filament just sits in there taking a sauna.
Putting desiccant in an active dryer can help with drying but again, why bother with an active dryer if you’re just going to load it up with desiccant? And you have to keep the desiccant dry if you’re going to do that. Ignore the desiccant moisture content and you waste the whole point of an active dryer. You are literally paying to get bad results.
About the color change on silica gel, it is generally at too high of RH for our purposes. Use the actual relative humidity number instead. You can see where your desiccant is by just putting it in a sealing plastic cereal box or even a ziplock bag with a hygrometer and read the humidity when it stabilizes. If the number is higher than the totally empty AMS2 when in drying mode, it is compromising your drying.
Also, plastic bags are unsuitable for long-term bead/desiccant storage because they are permeable to water vapor. They are good enough for a quick measurement but will let desiccant soak up as much water as it wants if left.
As to what the RH ought to be in an active dryer when drying filament - there is no answer anyone can give you. Here’s why. In an active dryer you have filament giving up moisture at some rate depending on its moisture content, formulation, and type of plastic. On the drying end you have some process removing the water that will see the rate of removal dependent on the humidity both inside and outside the dryer. All of those are variable.
The humidity inside the dryer will be a superposition of everything affecting the water flow from filament to air to being moved outside.
The easy answer is the humidity in the dryer should be as low as the empty dryer relative humidity when drying and stable but you never really get there because as soon as you put filament in there, the way most people dry (or don’t) you’ve added a water source which increases the humidity in the box.
Probably clear as mud but the details are all there. Desiccant in an active dryer is either a waste of an active dryer or actively reducing the effectiveness of the active dryer depending on it the operator keeps it dry or not - at least more dry than the active dryer can hit empty.
