2.7 Drying filament, and the two dryers

Module 2 · Lesson 7 of 10 · about 7 min

How drying works in this room

Filament that needs drying needs hours of it. Hours in an AMS means a printer nobody else can use. So real drying happens in the two dryers in the hallway, before you print.

When to dry. How fast filament gets damp depends on the brand and on the humidity, and many spools print fine after weeks in the open. Dry a spool when it shows the signs: bubbles, strings, weak layers, or popping and crackling at the nozzle (2.2 The materials).

• The AMS can dry filament while it prints. Every printer here runs firmware that supports this, and the AMS 2 Pro has a real drying system that heats up to 65 °C. While it prints, though, it automatically dries at a lower temperature, so that the filament does not soften in the AMS drive system. That makes it much slower than drying at the right temperature in a hallway dryer, and the filament it feeds early on has not had time to dry, so the first couple of hours of your print can come out damp. If a spool needs drying, dry it in a filament dryer before you print, and let the AMS keep it dry while you print.

• The AMS is not storage, and never was. Your filament lives in your own member box, ideally in a sealed bag (see "Storing filament" below). Bambu says that at normal indoor humidity, freshly dried filament can start printing worse within about 2 to 12 hours.

The two dryers

Royal dryer on the left and Sunlu S4 on the right on a shelf in the outer part of the 3D printing room

These are preferences, not rules. What matters is the temperature: if one dryer is busy and the other is free, use the free one, set to the right temperature for your filament. Anything that needs more than 70 °C has to go in the Royal dryer.

Temperatures and times. Use the drying temperature and time your filament's maker recommends, which you find in that filament's technical datasheet on the maker's website. For Bambu filament, use the table below, which is Bambu Lab's published guidance. If you have no figures for your filament, the S4's built-in presets are a safe fallback (see below). Each dryer's printed instructions tell you how to operate it.

Setting a dryer

Put your spools in, close the lid or door, then set the temperature and the time. Each dryer has its own printed instructions next to it. This is the short version.

Drying overnight? Set the time to end when you expect to be back. When the time runs out, the dryer switches off and your spools start taking up moisture again as they cool. A cycle that ends at 3 a.m. has undone some of its work by the time you collect your spools at 9.

Sunlu S4 (up to 70 °C)

Sunlu S4 control panel showing PV 49 °C, SV 50 °C, RH 21%, PLA, MO 1 and the SET, up, down and power buttons

1. Press the power button once to switch it on. (Press it twice quickly to switch it off.) It starts drying straight away with whatever settings it had last time, so set yours at once. Changes take effect while it runs.

2. Press SET to step through the settings. The one you are changing flashes. Use ▲ and ▼ to change it.

3. SV is the temperature it will heat to. Set it for your material.

4. Time is how long it will run. Set the drying time.

5. MO is the mode. Check that it shows 1, which means the dryer switches off when the time runs out.

6. Leave the other settings alone (°C/°F, the light bar and the filament type).

7. Check the display: SV and the time show your settings, and the time is counting down.

The S4 has built-in filament presets. They run cooler than Bambu's figures in the table above, so drying takes longer, but they are a safe fallback when you have no figures for your filament.

Royal dryer (Royal Catering RCDA-500/15S, up to 90 °C)

Royal dryer control panel showing 50 °C, light, time and temperature icons, up and down arrows, and the ON/OFF button

1. Hold the power button for about a second to switch it on. It beeps and the panel lights up. (Press it again to switch it off.)

2. Press the temperature button. The value flashes. Use ▲ and ▼ to set it. It changes in steps of 5 °C.

3. Press the time button. The value flashes. Use ▲ and ▼ to set it. Each press changes it by 30 minutes. Hold the button to change it by a whole hour. The longest setting is 24 hours.

4. Wait about 5 seconds. It starts by itself.

Sharing the dryers

• First come, first served.

• If there is space in a cycle that is already running, you may add your spools. You may never change the settings of a run in progress.

• If the temperature is wrong for your material, use the other dryer if it is free, or wait until that run has finished and its owner has collected their spools. Don't turn it down.

When you take filament out

• Let spools cool for 5–10 minutes before loading them into an AMS. Warm filament is soft and gets squashed in the feeder gears.

• Check the spool and filament: nothing warped or damaged, nothing stuck together, and the filament unwinds freely.

• Once it has cooled, seal it in a bag, or load it into a closed, latched AMS for your print.

• Drying the same spool over and over can make some filaments brittle. Dry it once, then keep it sealed.

Storing filament

Dried filament stays dry longer if it is sealed, so you need to dry it less often. A spool fits well in an IKEA ISTAD zip-lock bag, in the 4.5 L or 6 L size: squeeze the air out and close it. You can also buy vacuum storage bags made for filament. A desiccant pack in the bag helps keep it drier, but you don't have to use one. Either way, the bag goes in your member box.

Drying in the AMS during a print

You may turn on drying during a print for any filament the printer allows. If a filament or combination isn't supported, the printer won't start drying and tells you why, so you don't need to memorise a list. It can only decide correctly if it knows what is loaded, though: spools without an RFID tag must have their material type set by hand, which you have to do anyway.

• Keep the AMS vents clear. Don't stack things on top of the units.

• If you see water droplets inside the AMS HT, open the lid briefly to let the steam out, because water near electronics is a risk. It also means the spool was far too wet, so dry it in a dryer before using it again.