My 2 cents: I’ve been building my own circuits for a while now, and controling a two-wire-DC fan usually is through PWM and a power transistor. If the transistor is rated 2A, I’d say that’s the safe limit. With an inductive load like a motor you may have need for a flywheel diode to cut magnetic field breakdown, which may reach its limit - so if one is there, one might want to check. If it’s not there, the transistor might wear out at some point, under the bombardment of high voltage spikes, but this will happen also with the smaller fan. And regarding the overall power consumption, the additional one-digit-watt’s should really make no difference.
That’s of course to be taken with a grain of salt, not knowing if Snapmaker really implemented the circuit as I said.
I’ll just say I did get it working last night, it works great, and I redid the calculations for transistor loading, PCB trace width ampacity, and cable ampacity. There’s a ton of headroom and like @Hauke said you could put about 10 fans on this circuit and be fine. Which is convenient because I’m thinking about adding a second one.
@Franky, thanks for the numbers on the hot end fan, I’m referring to the part cooling fan though, the tiny 2510. I haven’t experienced any issues with the hot end not having sufficient cooling.
The control circuit is going to be a pin output from the MCU directly driving the transistor. The transistor output goes directly to the fan ground and switches ground.
There is no flyback circuit.
To limit how off topic this post got, I moved my measurements into here:
@brent113, the numbers and picture are from the 2510 part cooling fan 
, look carefully 
the fan for the hotend heatsink is a 4010 blower in the side. Sorry if I mislead you saying hotend fan, I meant part cooling fan.
BTW, do you think that the RC circuit is a low pass filter to control the fan via PWM?
Did you also get to measure if the 5015 has enough current to go full blown and get the maximum rpm ?
that’s a really nice job 
!
OK, I somewhat gave up on my problematic green PLA. I redid extruder calibration, and it improves results, but I am not close to the results of my other printer. I played a bit around with flow rates and printing speeds, but in the end nothing is satisfying. I suppose in the end it is the print cooling, wich seems to be better on my other printer. I could now verify by temporarily adding a fan, but I decided to go the more pragmatic way: When I need something printed in green, use my other printer 
As long as I don’t reach that printer’s build volume (cosiderably smaller), that’s OK. Other PLA works nice enough on SM2, and I suppose with the improved extruder calibration I may be just fine. At some point I may follow the example of others here and upgrade my print cooling.
What thermal paste would you use? Most of what I find at Amazon has working temps much lower than 200 degrees C. Thanks in advance for the help.
@00coday I believe the best would be Boron Nitride thermal paste. It’s relatively inexpensive, available on Amazon and many other places, rated to 1000C, and is electrically non-conductive so you won’t short anything out.
I used this one: https://www.thermal-grizzly.com/produkte/4-hydronaut - ratet up to 350°C. However, Boron Nitride is more common, but since I try to support local dealers and could only find the other paste, I went for that one. Not sure if I really would recommend it - it was surprisingly difficult to get into the cavity.
EDIT: Thermal Grizzly is not smelling nice when hot… no recommendation at all!
Thanks for the info - I appreciate it.
Hi there,
A thermal paste is a right thing to use but just boron nitride alone is not the wide answer: You have to look for one stable at least until 300 deg C (max temperature the Snapmaker Hotend can achieve in a really good day) and also that has the highest thermal conductivity. That it’s expressed in W/mK (Watts/milliKelvin ) the higher the better. In that sense, Thermal Grizzly Kryonaut has 12.5 W/mK , Hydronaut 11.8 W/mK an stable until 350 C. The Boron Nitride thermal paste can go from 1.8 W/mK ( the one from CircuitWorks, only stable until 200 C ) until the one from Slice Engineering with reaches 31.4 W/mK at 100 °C ( seems to have some dependency on temperature) and stable until 850 C (according to their website ). I think that @brent113 is referring to this one, which is an excellent one and designed for 3D printing.
Thanks, I wasn’t aware there were other manufacturers than the one I saw on Amazon, which was Slice.
OK, I think it’s “offcial” for me - it is the badly designed print cooling that causes my PLA trouble. I could not get it out of my head, so I did another temperature tower with a fan just stuck to the print bed close to the print head:
And the result is much better, close to what I get from my other printer. Here’s the comparison - left: temp tower with stock cooling - middle: temp tower with fan on the print bed (stopped the print - no need to waste filament…) - right: from my other printer (which knoecked the tower ower mid print)
So I suppose I’ll mod my printer for better cooling. I already printed myself an adapter to fit in a 30x30 fan I had lying around instead of the stock 25x25 fan. From the datasheets it should have double air throughput. Still, the effect was neglegible. I suppose it is also a problem that the fan blows air that is already warm from the heatsink of the extruder. Also, my impression is that the air blows a bit too low, too far away from the printing point of the nozzle. All this adds up to the poor part cooling.
I must say that this is quite a disappointment - the campaign video made me think that cosiderable engineering has gone into designing the print cooling. That’s hard to believe. @Edwin, @JKC20: I’d strongly suggest that your team rethinks this for coming upgrades of the print head.
Are you sure that’s PLA? They didn’t send you something else?
My absolute worst print when I accidentally had PETG temps for PLA never looked that bad. There’s something else going on there. Maybe it’s bad filament. Bad nozzle?
Whatever it is there’s something else going on with either the filament or the machine or your settings because I’ve done plenty of perfect prints on mine with 3 different brands and 4 colors of PLA.
-S
@sdj544 I ordered this one:
Box & Spool both are in agreement with that, and optically it matches expectations. During my tests I printed it with as low as 175°C, which I suppose would not work with PETG. On my Fabtotum printer it prints OK. The temp towers might be misleading: They start at 225°C, which certainly is too much for PLA. With the Fabtotum temp tower you can see it gets better with lower temp’s, And if you look on my post from September 8th, the seal printed decent enough on Fabtotum with PLA settings - the not so nice parts are just stringing. I tend not to use retraction but to cut away strings later, since retraction sometimes leaves scars from the nozzle sitting still for the time the retraction happens.
Still, for PLA the green stuff has a surprisingly strong tendency for warping.
I have other PLA, which behaves better on Snapmaker 2, even on overhangs. But I recently did a very filigree print with well-behaved PLA, and while the effects were less pronounced, I could still see that Snapmaker 2 is not as good as my Fabtotum. I tried on SM", but then decided to use the Fabtotum again because of the problems with SM2. And after my experiment with putting a fan in front of the printhead, I’m 99.9% sure it’s cooling. While the Fabtotum is not blowing so much stronger as far as I can judge by feel, a difference is that Fabtotum really blows cold air, while Snapmaker recycles the air that already passed the heatsink of the extruder, and is warm already.
When I print the temp tower and watch, I can see that the first lines of the overhangs are actually neat and straight. But when the nozzle passes over them again for the next layer, they wobble and sag under gravitiy - you can see that the hot nozzle makes the cooled down PLA hot again so that it deforms. Under the pressure and weight of the layers above then the lower layers sag. With the added fan, this does not happen, the lower layers stay cool enough not to sag.
Oh, while I write this: Quick remark, and this actually is a key element I think: The most problematic prints are at layer height 0.08 mm! I did a temp tower with 0.2 mm layer height, and while that also is not really good, it’s much better. The flimsy 0.08 mm layers are of course much more prone to melt again when the nozzle comes by for the next layer.
On the prints you did, @sdj544, did they have thin, extended parts? My first prints with SM2 were kind of boxes, mainly right angles, walls, larger, rectangular protrusions, nothing too tiny, and I was really pleased with those prints, including the overhangs. The problems occur mainly on thin, long parts that stand out from the body.
On nozzle, thermistor, heater: I already exchanged the hotend, to no avail, and used thermal paste on the thermistor to have more accurate temperatures. no effect.
If you have any suggestions on what to test in terms of settings, let me know!
Strange. PRUSA has a reputation for great filaments. (At least I hope so, since I just ordered a couple rolls from them).
Different colors definitely react differently and need different nozzle temp, but not much more than 10º.
I printed pretty much the same temp tower. .2mm layers. Had a hard time really telling difference between temps. Slight differences. Ended up doing a second and watching nozzle temps because I wasn’t sure my gcode was right.
Right now I’m running a temp tower for some new filament:
I have been running with doors open and fan running on my enclosure with PLA lately, but originally I was running with 60º bed and doors closed with no problems.
I attached my g-code for my temp tower:
SmartTemperatureTower_PLA_180to225_SJ.gcode (3.8 MB)
-S
Thanks for sharing this!
There is another thing I have not explicitly stated which may also be misleading: The temp towers I show are scaled down by 50% and with layer height 0.08 mm, so the imperfections look even more horrible if you are used to the 100% ones. Here’s a picture of the 100% 0.2 mm temp tower I also did, which looks less crazy, but still not really good. The other is for comparison:
Especially the overhangs are not good:
If you add a second fan I’d like to see the duct you create/use! I’m feeling like I’m getting uneven/insufficient cooling to the rear on my overhangs even with the 5015 blower mod.
I think the answer is optimizing the shape, location, and orientation of the duct - it blows a bit to the right.
The F360 file is posted on thingiverse, it’s quite easy to manipulate if you want to try different locations. In the 5015 replacement main thread I posted a modification for someone here. That version might not fix your issue, but you could play with the left/right position of the outlet and adjust the angle, maybe more backwards.
Oh snap the 360 file is there?
Nice, I wanted to play with that a bit.
I was kinda thinking about dove tailing it into a side plate.
ok… printing them that small id also suggest your at the limits of PLA cooling fast enough for before the next layer, upgraded fan or not. Try printing 3 of those towers all at once so that each layer has time to cool while the same layer on the other towers is being printed
I also posted all my 360 files in this thread… if you need them again let me know