How Much Desiccant Does a Bambu Lab AMS / 2 Pro Need?
Share
By Lee Zhong, GrandCube3D
For the GC3D configurations discussed here, five front square desiccant boxes hold approximately 160 g of beads. Adding four spool-core canisters provides roughly another 360 g, bringing the combined fill to about 520 g—3.25 times the front-box-only amount.
About 160 g can be a useful starting point. The reason to move towards 520 g is to give the enclosure a larger moisture reserve, particularly when you want to maintain low humidity with fewer refill interruptions.
These figures come from our product-use experience and customer feedback. They are approximate filling amounts for these configurations, rather than Bambu Lab's required quantities for every AMS.
From five front boxes to a 520 g combined setup
When we first offered our five front square desiccant boxes, the typical combined bead fill was around 160 g. Customers used them with orange indicating silica gel or molecular sieve.
We later developed our spool-core desiccant canisters. Using four canisters alongside the front boxes added approximately 360 g of filling capacity in the customer setups discussed here.
| Configuration | Approximate bead fill | Practical reference |
|---|---|---|
| Five front square boxes | 160 g total | 1× |
| Four spool-core canisters | 360 g total additional fill | About 90 g per canister |
| Front boxes plus four canisters | 520 g combined | 3.25× |
The increase is 360 g of additional desiccant, not a final total of 360 g. The combined setup carries a little more than three times the original bead mass.
Actual fill weight varies with the desiccant's bulk density, bead size, holder version and filling level. Weigh your own refill: tare the empty holder, add the beads, and record their net weight. Use the same desiccant when comparing configurations, and close each holder without forcing or compressing the contents.
What customers have reported
The change was noticeable in the feedback we received after customers combined the two types of holder.
| Desiccant | Front boxes alone, around 160 g | Front boxes plus spool-core canisters, around 520 g |
|---|---|---|
| Molecular sieve | Reported RH readings below 10% | Reported readings around 0–5%, including best-case displays of 0% |
| Orange indicating silica gel | Reported readings around 15% | Reported readings around 5–10% |
These are customer-reported readings, not results from a controlled comparison. We do not have standardized records of room temperature, ambient RH, filament load, sensor calibration or maintenance intervals for these reports. They show what customers have experienced; they do not promise the same percentage in every room.
The measurement source also matters. Bambu Lab's current guidance distinguishes the original AMS's humidity-level indicator from the percentage display used by the AMS 2 Pro. A level or status icon cannot simply be read as an RH percentage. Bambu Lab: humidity detection and display differences.
A reported 0% display does not establish completely moisture-free air or a dry spool. Check the meter's specified range and accuracy before interpreting very low readings. For everyday use, the more valuable result is a storage environment that remains suitable for your filament.
Why combine front boxes with spool-core canisters?
The two positions let us use the available space in complementary ways.
Our front square boxes offer broad vented surfaces that expose the contained beads to chamber air. In our customer-use experience, this is a practical arrangement for bringing humidity down after loading the enclosure.
The spool-core canisters add a larger quantity of desiccant within the centres of compatible spools. Their value is the extra reserve available as moisture continues to enter through normal use.
Both groups adsorb moisture at the same time. The front boxes do not switch off once the air becomes dry, and the canisters do not wait to begin working. Our design approach combines accessible, vented front holders with additional storage capacity inside the spool cores.
That same arrangement underlies our desiccant kits for the original AMS and the AMS 2 Pro. Choose the correct front-box version for your machine and check spool-core compatibility; sharing a layout principle does not make every part interchangeable.
The additional mass can provide more working reserve under comparable conditions. 3.25 times the bead mass does not establish 3.25 times the drying speed or service life. Air access, desiccant condition, moisture entering the enclosure and the chosen humidity target all affect the result.
Why molecular sieve and orange silica gel give different results
The amount of desiccant and the type of desiccant answer different questions.
More material provides additional capacity. Its useful capacity at your target humidity depends on the adsorbent. Supplier equilibrium data show molecular sieve retaining greater water uptake than silica gel at low RH under the stated test conditions. This helps explain its suitability for very low-humidity storage; it does not predict an exact AMS reading. IMPAK/Sorbent Systems: equilibrium water-capacity table.
Orange silica gel remains a convenient option when you value an indicator you can inspect. Follow the colour-change instructions for the particular beads you buy.
The 5–10% readings in our customer feedback are not a universal lower limit for orange silica gel. Grade, starting condition, temperature, enclosure and measurement all matter. For a fuller comparison, read Orange Silica Gel vs. 4A Molecular Sieve for 3D Printing.
How much makes sense in your environment?
Use the 160 g and 520 g configurations as starting references, then assess how well your enclosure holds the conditions your filament requires.
| Your storage conditions | Practical starting approach |
|---|---|
| A relatively dry room, infrequent lid opening and prepared filament | Try the front-box setup first. If it maintains the required conditions for a convenient interval, that may be enough. |
| Humid surroundings or frequent spool changes | Consider the combined setup for additional reserve. Record how the chamber recovers after openings and how long the refill remains effective. |
| Front boxes lower RH successfully, but require servicing too often | This is a useful reason to add spool-core capacity, after checking closure and refill condition. |
| RH stays high even with fresh desiccant | Check sealing, bead exposure, the reading and the filament load before assuming the quantity is the only problem. |
| A spool may already contain absorbed moisture | Follow its material-specific drying procedure, then protect it during storage. |
Room RH alone is not a complete description of the workload: record room temperature too. The number of openings, time spent open and condition of incoming spools also matter.
For comparisons after heated drying, let the chamber return to a similar, stable storage temperature. Cooling can raise RH even without additional water entering. Bambu Lab: temperature and humidity readings.
How often should you replace or regenerate the fill?
Our feedback supports the practical benefit of a larger reserve, but it does not establish a fixed number of days between services. We therefore recommend building a maintenance interval around your own humidity trend.
- Start with an effective charge. Use fresh beads or material regenerated according to its supplier's instructions. Record the desiccant type, net fill weight and refill date.
- Establish your baseline. Close the lid properly and note the chamber reading once temperature and humidity have settled. Record room conditions, filament load and the sensor used.
- Check more closely after a change. As a starting monitoring routine, check daily during the first week after installing a new configuration. Check again after substantial spool changes or unusually humid conditions.
- Adjust the inspection interval to the trend. If the system remains stable, weekly checks may suit your routine. If readings rise quickly, inspect more often. These are suggested check frequencies, not measured refill lifetimes.
- Service before storage becomes unsuitable. Follow the filament's storage requirement and the desiccant's indicator instructions. A sustained rise under comparable, closed conditions is a reason to inspect the seal and refill.
When you compare 160 g with 520 g, the useful result is how long each effective charge maintains your chosen storage conditions under similar use. Do not treat a brief rise immediately after opening as a complete service-life measurement.
If both front and core holders contain spent material, refresh the charge serving that enclosure. Keep a prepared refill sealed so maintenance can be a quick exchange. Our AMS desiccant replacement guide covers the condition checks in more detail.
Does the AMS 2 Pro heater change the recommendation?
The heater gives the AMS 2 Pro an active drying function; effective desiccant supports the storage period around those cycles. Bambu Lab recommends sealed storage with effective desiccant after drying moisture-sensitive filament. Bambu Lab: filament drying and storage recommendations.
Do not assume a filament-drying preset fully regenerates your refill. Follow the desiccant supplier's process, and check the heat limits of the complete holder separately.
Keep the installed boxes and canisters clear of spool movement, rollers, feeders and air passages. The AMS 2 Pro uses controlled intake and exhaust during drying, so additional capacity must leave that airflow working normally. Bambu Lab: AMS 2 Pro drying function.
If humidity stays high after a cycle, our guide to AMS 2 Pro humidity stuck around 30% walks through the next checks.
Frequently asked questions
Is 160 g enough for an AMS?
It can be, if an effective refill maintains the conditions your filament needs for an interval that suits you. Treat 160 g as an approximate front-box configuration, not a universal minimum or maximum.
Should every AMS owner use 520 g?
The combined configuration is useful when you want additional reserve and less frequent servicing. If your current setup already maintains suitable storage conditions with manageable maintenance, extra capacity is optional.
Will 520 g guarantee 0% RH?
No. The 0–5% molecular-sieve readings are customer feedback, including best-case display values. They are not a guaranteed outcome or a measurement of moisture inside the filament.
Do I need all four spool-core canisters?
The approximate 520 g total includes four. With fewer compatible, occupied spool cores, your available fill is lower. Weigh the configuration you actually use instead of assuming every installation carries 520 g.
At GrandCube3D, the reason for combining front boxes with spool-core canisters is practical: make more effective desiccant available within the enclosure and make low-humidity storage easier to maintain. Start with a known refill, watch the trend, and add capacity when the maintenance interval tells you it would help.