What filament dryer to use?  

RE:

Sunlu S4 is nice and convenient. I’m pleased with it.

was considering a Chitu Systems FilaPartner E1 Filament Dryer, but didn’t go for it

RE: What filament dryer to use?

What makes you think you need a filament dryer in the first instance?

I have never used one, and do not have one, to this day - never felt the need. Then again, I primarily use PLA anyways which isn't as absorbent in the first instance. 

I would consider the type of materials you intend to print with, and take it from there. If its just PLA or PETG, you could get away with not having a dryer at all - I simply unpack a roll and place it into a plastic container with desiccant (the cereal containers) for use, and when I switch I just put the roll into a sealed air tight bag and suck out the air with a small USB pump. Hasn't failed me yet....

Of course if you're printing nylon etc, thats a different story altogether. If I were to purchase, I would most likely look at the Sunlu range......

RE:

Because I print 90% PETG, and 10% exotic stuff. PETG performs significantly better when it's dry.
My main two issues with quality 3d printers are wet PETG, and a dirty build plate. Else it runs smooth.

PETG definitively does not get away with no dryer, if quality matters. I think I'm at 30kg+ a year, so that's my experience on it.

RE:

I went for a pair of Polymaker Polydriers, with a couple of additional storage boxes. They've been good, but since you need a spare box for drying anything new I can see I'm going to keep feeding the beast which could become costly (though they are a very neat solution). I've ordered another 3 boxes now, which will give me a box for a new roll of TPU and 2 for drying anything else...  Next step will likely be wall-mounting those that have filament housed in them.

Meanwhile I keep my assorted PLA in 2 other larger dollar-store-style boxes with desiccant. I've put polyurethane tape around the top which squashes nicely to create an okay seal & taped a hygrometer to the inside so it can be read through the side to keep track of how that's storing. I also printed a desiccant container in clear to see any colour-change from outside and know to dry the silica.

RE:

It depends on the kind of  filaments that you intend to print.  Some of them (PA, PC, TPU ) need a drier that reaches 75-80C of temperature at least, else you won't be able to dry properly those filaments in a reasonable amount of time. Most of the driers in the market don't go past 70C.  That's fine for PLA, PETG. ABS, ASA or PP. Much less so for PC and specially nylon and TPU. AFAIK, the only affordable driers able to deal properly with those filamenta are the PrintDry Pro-III and the Sunlu E2. Apart from that, you can use food dehydrators  or professional drying machines, which are very expensive and probably not worthwhile the cost for an individual customer, like most of us in this forum.

RE: What filament dryer to use?

I also have the sunlu s4 and I can't complain. It's my first dryer so I can't compare it to others.

RE:

Having a dryer handy is definitely worth it. As mentioned, the necessity for one does depend though, if you primarily use PLA and live in a desert climate with average humidity <20%, then you likely dont need one. If like me you live in a damp climate which rarely, if ever, sees humidity drop below 60%, then I would say it's a must.

When it comes to what to pick, I would answer with "whatever your budget can afford". Polymakers offering was mentioned above, which is great but costly if you want to expand out with the containers. There are a number of much cheaper offerings but don't generally exhaust air or distribute heat as well. But if you build into your drying process to open occasionally when drying and rotate the spool, it'll do the trick. You'll likely find mods for these cheaper ones on Printables etc that you can print online to improve on the design.

Drier aside, I would recommend putting thought into how you plan to store your filament which if done right will reduce the amount of drying time, and overall energy cost associated. Cereal containers with desiccant was mentioned, polymakers boxes are a fancy version of that but the budget option is just vacuum pack bags.

My own set up has a Creatility Space Pi drier, with a couple printed mods to improve it. I also have the polymaker dryer and 2 filament containers. My process focuses on drying and storing. More hygroscopic and expensive filaments, such as PC-CF, TPU etc, end up in the polymaker containers, where they stay as I will always dry for a couple hours before printing. Everything else is dried for a couple hours in the Pi. I always make sure to vacuum pack my filament straight after use and/or drying to generally just mitigate against the filaments taking on water in the first place.

Stefan from CNC kitchen has a very good article/video on this. Worth a watch, https://www.cnckitchen.com/blog/cyo43tzz88uqge65xgwz0wv8yvv3rs  

RE:

I too have the Sunlu S4 and, so far, it has worked well.

For myself I print mostly in PETG and the drier has made a difference, particularly after a period of inactivity. For others as favours, presents etc. I also print in PLA, which is, almost by definition, less frequently (and I've got a larger collection of PLA in a range of colours which tend to be bought for the project and then left on the shelf - consequently some of it is ~5 yrs old). I store the filament in its ziplok bag with the original silica gel pouch which will get rejuvenated in the drier as I use it. I've also dabbled with PC & PP (facilitated by my newly acquired Core One). All of them have printed well with the drier, although as I always dry the filament for an hour or so before use (longer if I haven't used it for a while) I haven't compared the quality with non-dried filament ever since I initially noticed the difference. I used to have a single spool drier (eSUN) but, due to my promise to myself to justify the cost of the Core One 😁(previous printer was a mini), I've also started to dabble with multicolour prints - hence the investment in a multi spool drier.

One of the reasons for opting for the S4 was its ability to maintain a preset humidity level over an indefinite period of time, as opposed to simply heating the filament to a preset temp - I didn't see that functionality with other driers at this price point.

One drawback with the S4 is that the single compartment, although it fits 4 spools, has no way to differentiate between the spools so the temp/humidity level has to be set for the lowest temp filament (usually PLA - there always seems to be a roll of Prusament Galaxy Black or Sunlu black in there)

RE: What filament dryer to use?

Is 70c really warm enough for the PC and Nylons of the world?  A lot of threads say up to 110c for these. 

Then again, a lot of threads say 50c for PLA, and in my experience that will turn some PLA into blocks instead of filament. 

RE:

You'd need an oven to get anything above 70 degrees C really, as standard driers aren't built for high temps. At 110 degrees C I'd be concerned the spool would fall apart. Most filament manufacturers now either have totally cardboard spools or have a cardboard center with plastic outer rings (Prusa and bambu). Any adhesive holding the cardboard would soften at that temperature. The tension of the coiled filament then gives it good potential to become a filament spaghetti delight.

I believe that CNC Kitchen video I linked previously gets into the temp question and the principals around drying. But ultimately elevated temp and time will be your friend. The temperatures recommended to dry filaments at really are just the highest you can pick without the filament softening or turning into a puddle. As PC and Nylon can withstand higher temps, you therefore theoretically can dry at higher temps. It will quicken the process but ultimately increasing the time at lower temp (65-70oC) should be almost as good.