Sunlu S2 VS Creality Space PI Bake-Off Review

Too Lazy; Didn’t Read Version :

While neither one of these two were perfect by any stretch of the imagination, just don’t buy the S2 even if it is discounted and you have to pay full price for the Creality Space PI. The difference in performance vs value is huge.

Disclaimer: Both of these devices dried filament.

What follows is my opinion based on measurements and a table of what I found to be important to me personally. YMMV


Background: make versus buy and out of box impressions


I wasn’t a big fan to start with of the idea of having yet another bulky item on my desk. Plus, one can build a very effective dryer just using the box the filament came in and the heatbed, as noted in this recent post. However, I got tired of tying up my printer bed and wanted more convenience where I could set it and forget it. Last but not least, if I am going to buy something purpose-built, it had better be better performing and cheaper than what I can build myself. What was disappointing is that nobody bothered to measure actual temperatures of these filament dryers. :dizzy_face:

The high cost of many dryers in 2023, exceeding $100, deterred me from purchasing one. That’s more than the cost of 6 spools of PLA and 1/6th the cost of my P1P. Additionally, it wasn’t until recent experiments that I became convinced that I had a personal use-case justifying the investment in a dedicated dryer. PC filament changed my mind as I showed side by side results in this post.

When researching dryers, I encountered a plethora of truly awful advice on YouTube—misleading gimmicks and a lack of scientific rigor. So, as usual, I had to verify things for myself.

My philosophy on most electronic appliance purchases is simple: function over form. I’m not swayed by aesthetics; I want practicality. In fact, gimmicks are a turn-off for me; they feel patronizing and insulting to my intelligence. That’s why I was initially drawn to the original Sunlu S1 design. It had a straightforward button interface, a clear lid, and a simple rectangular shape. If only Sunlu had updated that design with improved temperature control, better air circulation, and a clearer display, they would have had a winner in my eyes. But no! They had to prioritize aesthetics over functionality.

On March 1st, when comparing prices on Amazon, there was a $16 or 25% price difference between the new Creality Space PI and the Sunlu S2. So, I opted for the S2. Despite its slightly lower(-5c) maximum temperature, I couldn’t justify the higher cost of the Creality model even though my principle justification was for filaments such as PC and ABS drying where the higher operating temp would have been an advantage.

Upon setting up the S2, I immediately noticed issues. Firstly, it was very unstable, with a high center of gravity that worsened with a full spool inside. Finding multiple stand solutions on confirmed that I wasn’t alone in recognizing this design flaw. It also tipped over when my printer was shaking my already unstable table, not a good start.

On-screen Temp reporting


As I set up the device and attached thermocouples to a sample spool, things quickly went downhill. Temperatures fluctuated wildly, varying by as much as 15°C throughout the chamber. However, the final blow came when none of the temperature readings came close to the advertised 65°C or what was displayed on-screen, not even with my sensors placed next to the chamber’s sensor input. I gave the dryer every advantage but I could not measure a single spot that hit the advertised or displayed temps. This discrepancy led me to believe that Sunlu falsifies their specs and temperature readings, as there’s no other explanation for such a drastic difference. Despite using six different thermometers and repositioning the sensors over two weeks of testing, the measurements remained consistently off.

Feeling thoroughly cheated, I attempted to contact Sunlu tech support about a possible defective unit, but received no response.

By this point, my buyer’s remorse was simply too deep and unrecoverable and I had already resolved to return the S2 through Amazon. However, just before doing so, I stumbled upon a deal that significantly reduced the price of the Creality PI, narrowing the cost difference to less than 10%. This made the Creality PI seem more worthwhile, but I remained skeptical given Sunlu’s misrepresentation and the common practice among Chinese manufacturers of misleading consumers. In short, would Creality be any better?

Product Review Using Personal Preferences

Before I shipped the S2 back and uncertain whether my emotions were clouding my judgment, I compiled a list of criteria important to me and scored each category from -2 to +2. For a +2 rating, the product had to exceed my expectations, while a -2 rating indicated misrepresentation or truly poor performance. I then did a thorough bake-off based on my personal preferences.


Score Personal Subjective Meaning
2 Exceeded expectations
1 Met expectations
0 Neither good or bad
-1 Disappointing
-2 Awful


Category Sunlu S2 S2 Comments Creality Space PI Creality Comments
Max Temp Advertised 65c 70c
Max Temp Reached 60c 70c
Price Advertised on Amazon $70 $86
Price Paid on Amazon $60 $66
Display -2 Very hard to see, backlight does not stay on 1 Great contrast and color, would be better if it had antiglare surface
Controls -1 Not responsive touch screen must hit multiple times -1 Not responsive touch screen must hit multiple times
What’s wrong with just simple buttons
Clear View of Spool? -2 Blocked in top-down view, Unnecessary Smoked glass -1 Unnecessary smoked glass
Temp reached advertised levels? -2 Really far off and uneven 1 Performed as advertised
Temp Accuracy -2 Totally inaccurate 2 Very Accurate
Evenness of Drying/Heating 0 Very Uneven ±15c throughout the chamber 2 No significant or measure hot spots
Humidity Sensor Accuracy -1 Off by 15% -1 Off by 10%
Internal Humidity Regulation -2 Must lift cover periodically to release moisture 2 Even temps throughout cycle
Lid Spool Accessibility 1 Good access -1 What were they thinking?
Power Supply -2 Wall-wart, horrible waste of space and dangly cord 2 Integrated- 2 wire power cord- excellent.
Drying 0 Must lift cover periodically to release moisture 1 Does the job well
Spool Path 1 2 Paths top only 0 1 path top only
Overall Size on Table 1 Just the right size -2 Hinged lid makes it unwieldy
Stability on Table -2 Tips over during heavy printer vibration 0 Stable
=========== ==== ====
Total Score -13 5


Power Cords and Power Supply

Sunlu, Wall-Wart??? Really? in 2024? This also limits where one can place the device since the power plug is inconveniently placed on the side.

Creality, internal power supply with power switch(NICE!!!) :+1:

The Lids? WTF??? Creality Space PI means it takes up more space!!!

The Creality lid is awful, :-1:there is no justification for this swinging back so far increasing the overall depth to 23". It forces one to reach 2 feet back to grab the lid and takes up unnecessary space. They almost had it right if they had just made a lid stop, a real missed opportunity.

While the S2 Lid completely was obscured by the second heating element and the filament spool was blocked so you wouldn’t know what was in there without opening it up. As if the smoked glass wasn’t enough.

Why can’t these companies just use clear acrylic?

Display quality


Creality emerges as the clear winner when it comes to the display. Adding to that, Sunlu’s failure to allow the backlight to remain on creates a frustrating experience, requiring users to manually activate the panel to view the display again. In contrast, Creality keeps the display illuminated after the cycle ends. Additionally, the S2 features a seemingly pointless LED ring, which, in my opinion, is merely a gimmick and an annoyance I quickly disabled. It would be more valuable if it, for example, changed color or pattern to indicate certain statuses, but it’s evident that it serves no practical purpose and is simply a light show.

Actual temps versus what was on the display

Air Circulation and recorded temps using a calibrated thermometer

Both of these were taken at the same time and only provide a visual representation of where the heat was distributed. Both had empty cardboard spools inside and both were allowed to reach temps after 20 minutes. The only conclusion one might draw is that perhaps the smoked glass on both minimizes the escape of radiant heat. That is the only justification I could find for using smoked glass.



Both Side by Side

The S2 says it now has air circulation and you can indeed hear “a fan” working, but however they implemented it, it simply does not even out the temp circulation which is a concern given that a low temp filament or spool could be easily warped or the filament fused if unevenly baked.

The Creality on the other hand was the clear winner in this category. It has a well placed circulating fan and their ads make a big deal about this. I will say that the Creality feature lives up to the hype. For me, this was the clincher because after all, if a dryer can’t meet the temps, what’s the whole point?

Here they are side by side using a Type K plug thermistor thermometer. The thermistor probe was placed inside the filament hole near the spool hub. Both had cardboard spools and were allowed to reach temp

As a final sanity check I used a food thermometer. Why? Because this thermometer can be trusted for two reasons, it can be calibrated and it can be verified by simply measuring boiling water and/or melting ice.



Relative Humidity measurements a wasted effort

Relative Humidity measurements a wasted effort

As with many experiments, I delved into a rabbit hole trying to ascertain how to accurately measure temperature and RH. I gained valuable insights, and since this post is already lengthy, I’ll mention that there are only two designs for RH sensors, both of which are inherently inaccurate without calibration. Moreover, both sensors eventually oxidize and degrade over time, explaining why most of my hygrometers fail after only 6-18 months of use.

However, I also learned how to calibrate humidity and utilized the Salt Brine method to demonstrate the inaccuracy of all my hygrometers, as well as to measure the discrepancy in reporting relative humidity (RH) between both dryers. Yet, ultimately, I realized that without the ability to control RH, as would have been beneficial in the S2, there’s little point in displaying it if it cannot be calibrated either. In my opinion, this renders it a mere waste of display and components. Furthermore, it became evident that both dryers were based on the exact same design and likely shared components, given the similarities in display and controls. They either mimicked each other or another source.

Conclusion - Either one will dry your filament


While both companies get failing grades for putting form over function with respect to case designs(smoked glass that obscure viewing what filament is inside as well as foolish stylish shapes), both will dry filament. So if you already have an S2, the Creality is not worth upgrading to. Creality does get bonus points for “truth in advertising

However, Sunlu gets real negative marks in my view, they had an opportunity to address my concerns when I emailed them two weeks ago but they made a choice not to respond. They also made a choice when they posted false information on their site and product literature. So on those two items alone, I have some real bias against buying anything they make that is hardware related. If you lied to me once, how can I possibly trust anything you say?

If you didn’t figure it out yet, the S2 was shipped back to Amazon for full credit.


First of all, thank you for your interesting write-up. It’s way better than practically all the other reviews I’ve seen.

I think I may be looking at this topic from a different perspective. The things I’m trying to understand about any given filament dryer are:

  1. Will using it as designed damage the filament? If yes, then it’s a flat-out reject. On this question, i seems you found that the Sunlu might pose a risk to the filament.

  2. How well does it dry? If a good drying in a blast oven drives off n grams of moisture, what percentage of n does the filament dryer achieve, and in what time frame?

This is where it generally all falls apart, because the people who have access to a blast oven will naturally default to that and thus have no reason to evaluate a $60 filament dryer. An exception might exist for someone who has access to a blast oven at work but may nometheless want to dry filament at home for their 3D printing hobby. Such a person would have the means, the motive, and the opportunity.

The next closest thing would be someone who chucks a sample of filament in their kitchen oven and dries it that way. As long as they can weigh it before and after, at least it’s some kind of yardstick. IIRC, cncKitchen did this in one of his videos.

Or maybe you have a few different filament dryers, and you try drying 100g from the same spool in each of them, and see which one comes out the driest by weighing them and compoaring. If nothing else it would establish a pecking order, but if, in the worst case, i.e. none of them is close to the ideal, then it might be a source of false confidence.

  1. How good is good enough? If moisture was causing stringing and after drying it no longer does, then I guess by definition that’s good enough. Is 50% as good as a blast oven good enough? I have no idea. Arguably, the answer to #3 matters more than the answer to #2, so maybe skip #2 altogether?

Hmmm… More questions than answers. I think I may just get a blast oven and be done with it. It would presumably be the tool of choice for annealing as well.

I will have to try the Creality when one of my Filadryer units die.

There is a cliché regarding cameras that fits here. When a professional photographer was once asked, ‘What’s the best camera?’ he answered, ‘The one that’s with you.’ The obvious point is that a big and bulky camera is often inconvenient to take everywhere but everyone usually has a cell phone and cell phone camera technology has gotten so good, it’s good enough.

So, keeping with that notion, what’s the best dryer? The one that dries your filament. That’s why I pointed out early in my post that I was totally satisfied using my oven and a cardboard box… until I wasn’t.

At this point it comes down to choices where does one spend one’s money? I’ll admit to the feeling the thrill of finding a bargain, it can be addictive. Consequently, I hate the feeling of the opposite when I feel I was cheated or that I missed out on a deal.

That seems way too fast. As a point of comparison, in its datasheet Silicon Labs estimates the RH drift on their si7021 sensor to be 0.25% per year. Their datasheet says it can develop a kind of “memory” if it’s exposed to too high of a humidity, which is why it has a built-in heater that’s under programmatic control to avoid that condition. Nonetheless, their datasheet also gives a method for restoring a sensor by baking it dry again if it were to happen severely. Perhaps your sensors can be restored also? I know how you hate waste, and it would be a pity to have to junk them after such a brief life.

We’re talking about very different products. The one your referring to is an active piece of electronics. Let’s hope that’s not what these dryers are using because then they have zero excuse for not calibrating it. They may be using the DHT11 variant which everything I read since you pointed it out to me a week ago indicates that is notoriously inaccurate. Everyone is recommending skipping over that and moving to the DHT21 or greater

What I am talking about is a passive component that is essentially a hygrometer version of a thermistor. They are ubiquitous in just about every cigar humidor or pet reptile container hygrometer. They work fin until you leave them in your car or in a damp basement, then they fail quickly.

Here are some examples from my collection and I can tell you that’ve taken enough of these apart to say that they are ubiquitous, just not very robust:

Here’s the HS202L variant on Amazon

I wanted to tear down the S2 just to see what’s inside it but it’s all glued together like a child’s toy, not a serious piece of electronics(yet another annoyance I didn’t mention, can’t be repaired). There was a teardown done on YouTube showing this.

In the photograph of the PCB, they show a two wire sensor which is common to what I’ve seen with the Amphenol HS30P class of sensor. It’s also located right where the air intake is for the inside of the dryer which further supports that this is the hygrometer. A thermistor is much smaller and wouldn’t need a protective shroud.

This image was from YouTube

This image I took from the inside of unit I had in my hands before I returned it to Amazon.

Here’s an example of that sensor mounted on a PCB available on Amazon. Note the two wires and similar shroud.

Ah, OK, mystery solved. BigClive gives a reason for why they may be going bad so quickly then: using DC rather AC to read those sensor elements progressively destroys them:

Maybe/Kinda similar to why you don’t want to use DC to drive an LCD display, even thought you can get away with it in the short term. Eventually it destroys it.


Wow, what a great review! Thank you for also taking the time to present your results in detail, that was probably as much work as preparing and performing the test!

I have read praises for food dehydrators, especially the Graef DA 2042. It was said to have great temperature accuracy and distribution, has a 300W heating, 80°C max temp, isolation, active convection, outlet for damp air and fits 2 spools. 24h timer seems to round it off. All at a price close to the dedicated filament dryers.
My only problem is the notorious lack of space, so I still use the X1C drying feature.

Has anybody that in use and can comment on it? If it lives up to the claimes, it seems like a no-brainer maybe except compared to the Sunlu S4 if you need the capacity.