Hey all, hope you are having fun over the holidays printing. I’m currently having a good time with Simplify3D and just like many other slicers I’m still seeing these fine web-like strings. If you guys have any suggestions I’d appreciate some ideas to try.
My basic current settings are PLA at 190C on the first layer with cooling fan off, then 185C for all remaining laters with cooling fan on. I’ve seen recommendations to reduce the heat, but I feel like I’m already pretty low.
Retraction settings are 30mm/s and 1mm distance. I’m trying a print now at 2mm distance to see if that helps. Will post the results when it’s done.
EDIT: Looks a bit less stringy… but maybe now every other layer. I’ll keep digging and iterating.
My experience was that its a mix of temperature and retraction.
I use 3mm retraction with 40mm/s speed and have no stringing any more.
Those strings at that specific location look like another setting located on the advanced page of S3D.
I would guess its the setting “Only retract when crossing open spaces.” or “Minimum travel for retraction.”
Play with all those settings on the right upper side and see if that improves anything.
To further test retraction and temperature and speed and stringing use this one: http://www.thingiverse.com/thing:909901
Thanks for the reply @3DPrintEvangelist. I actually had only bumped it up to 2mm distance. I’m going to try 3mm @ 40mm/s now on the illuminati piece, and then I’ll switch to the retraction test model 
It’s definitely everywhere the extruder is moving at 80mm/s if that affects things as well. See here:
So after switching to 3mm retraction @ 40mm/s I’m getting the exact same results as 2mm @ 30mm/s. I’ll try the retraction test model now and lower the non-printing move speed to 60mm/s from 80mm/s. I also disabled cooling for the first 10 layers.
EDIT: And here are those results
It’s hard to tell, but I think disabling cooling has helped in the first 10 layers for the strings. I’m going to try to disable it completely. On certain parts though, cooling is required or the parts look all melty and start to have blobs.
With cooling disabled and my end script fixed so the nozzle moves away from the last printed position quickly, things are looking a lot better. Weird though… I wouldn’t expect cooling the filament would create strings. You’d think the opposite would be true and help it snap off the string as it was cooling. Because cooling helps overhangs and reducing blobs, I’ll have to keep experimenting with ways to reduce those if I turn cooling off. Or ultimately fix the string issue with cooling enabled still.
Here’s retraction at 4mm @ 50mm/s and cooling enabled again after layer 10. I’d say this is about as bad as the first one (and cooling seems to have a big impact on creating these strings).
It matches my experience mostly. Temperature is the biggest factor in stringing for me as well.
The second to last print looks perfect to me.
Regarding cooling, I guess it is because of the bad air flow / cooling design. The extruder is not completely shielded from the airflow and the air is blown in a very broad area and not precisely where the filament was extruded. Other printers have better designs with a funnel and a very precise and close airflow. That is why a few months ago I tried to motivate someone to design a better cooling solution. Sadly I am not capable to do something complicated like that.
My experience is that when I use cooling, the extruder has to counter the cooling, thus heating up and with higher temperature = more stringing. If you watch the temperature curve closely you can see the temperature drop once you enable cooling and the extruder having to heat up. And I am using the original head cover with silicone tip and additionally my heat(cooling)shield that I bent from a metal shield. And I closed all gaps in the plastic parts with blue tape. But still an effect once I turn on cooling.
But beware with changing cooling during printing. At least with me it creates heavy warping. Here is a cube where I changed cooling from 50 to 100% (at about 20% print time) and a few minutes later back again to 50%:
Your prints look much cleaner than mine 
Here is my stringing test print:
Wow, thanks for the replies @3DPrintEvangelist … it really helps me keep thinking about things. I’m actually running my printer with the extruder cover off (ever since I had to take it off every couple prints when it would jam all of the time). Now it sounds like I should put it back on to help to shield the nozzles from the cooling air. I do notice that they usually don’t even reach 185C, but tend to stay just below. It didn’t occur to me that the actual temperature of the filament is much higher than what’s reported because of the extreme cooling without the cover (the thermistors must sense the outer mass of the aluminum more than the heated center of the nozzle). Let me reinstall that and see how bad the strings are then with cooling on.
Your cube doesn’t look like it should have changed that much at the cooling levels you describe. That’s some serious shrinkage. Would it do that with black or white zeepro PLA?
Up until now I’ve been using Zeepro filament, but I just converted my machine to direct feed into the top from a 1KG spool of black Radioshack PLA hanging on the back of the machine. I kind of half expected this new Radioshack PLA to be terrible, but it’s actually really nice so far (no complaints).
Are you running your printer with the top cover off? I noticed that any slight amount of drag on the gantry seriously affects the accuracy. I run it with the top cover off and that little black angle deflector removed.
Second extruder tube removed temporarily while I only have one spool holder and one 1KG spool of filament.
If you are also using Simplify3D please add your profile here: Simplify3D Profiles
Sorry, I think I have misguided you.
I am running my printer from day 1 without any top or bottom covers. It never worked for me.
What I meant was that the left fan of the print head is the cooling fan and the air from that fan is leaking from several gaps in the plastic. If your original fan outlets have melted, which I expect for anyone that has ever printed ABS, it gets worse. Additionally the fan outlets will not protrude completely out of the print head cover and thus will blow partly inside the cover and cool down the heater from the extruder. That is why I and Jpod designed a cooling shield to minimize effects of the air from the cooling fan on the extruder. I even tried a version that eliminates the original cover. But then the cooling air is blocked by the cooling shield, so it was not a good design from me.
But as I mentioned earlier the original zeepro fan design is not good.
Wait. You are running the cooling fan without the head cover. Uh oh. Thats the worst combination. You directly blow cooling air over the heating element and nozzle. It tried that twice and using over 60% cooling fan, the extruder was not able to compensate and the temperature dropped until it clogged.
If you use cooling, you need the original head cover with the asbest plate and silicone bottom hole cover.
I am using a local german PLA brand. Its very cheap but I like the quality. I tested most brands out there and Verbatim or ColoFabb are better. But the difference is small and three times the price or even more is just ridiculous. So I stick with it 
But I am still a bit jealous of your retraction prints. They look so much cleaner than mine. I will have to test your S3D profile as well.
I sent you my Dual Extruder Profile via Email, as you mentioned in the post.
Did you not receive it?
That’s ok I think we are on the same page, I just tried to put my cover back on and noticed the fan ducts won’t stick out at all really. Not enough to be useful, so I’m just going to leave it off and leave cooling off. Then I think just adjusting the temperature to suit each print will hopefully be enough.
I think we could probably come up with a better way to do the insulating of the nozzles and cooling. How about just a silicone boot that goes over the heater blocks and lets the nozzles poke through. And extend the factory blower shield down about 0.050" or 1.25mm with a spacer block. How to form and hold the silicone in place though is a bit tricky. I could see 3D printing a mold, and then pouring the silicone in, then just bust the plastic mold to get the silicone out.
Sorry I haven’t been checking my email much while I’m on holiday break, but just posted my profile and your profile. Thanks!
I started using relative mode when I found that absolute mode was making horrible noises and generally worthless prints. I can only listen to my 3D printer make that dying animal sound for so long 
Maybe there’s a combination of absolute settings that I need to make that work correctly though?
Well, certain prints just don’t turn out right without the cooling fan. Overhangs are a challenge, blobs are more prevalent and layer to layer registration is bad around the outer edges.
So I took off my fan assembly and looked at it, then decided that there was no easy way to move the nozzle down lower. I also noticed it had melted already a little and there were two large holes on the inside corners that were probably blowing directly on the heater blocks. I taped over those with kapton tape, and also taped over the outside two blower vents, leaving just the one in the center open. The center one at least sticks down low enough to stick through the extruder cover. After putting this back together I ran a simple manual test to see if the extruder could quickly heat up to 190C with the cooling fan on… and it did, easily… and maintained temps right at 190C. So now I’m testing this new configuration on a difficult print that has overhangs. Usually when this part prints nice, it also has strings so hopefully it will now print nicely and do it without strings. I’ll let you know 
EDIT: It turned out great with just a couple visible strings… vs probably a couple hundred strings from before. This was a gear piece. Looks like this is the best setup I’ve had yet 
Nice, that you found an improvement.
One other interim solution could be that you use the original fan outlet design, that KingMartin was nice enough to cut in half and simply scale the bottom part a bit bigger in z axxis. Or put a self designed spacer in between. Than the fan outlets should protrude enough.
But in the end we need a better cooling airflow solution. Right now I don’t find my original thread.
I made a heat shield with metal and the original asbest plate. Silicone or another material should be easy as well I guess.
But making a funnel like cooling solution…no idea.
Something like this maybe, but modified for the Zim: http://www.thingiverse.com/thing:537918 or http://www.thingiverse.com/thing:16624
Here’s a test I did last night on the retraction test with this cooling solution. It seems to work great for the other gear part, but not so much the retraction test. Not really sure why though, and when I turn the temps up with cooling on, if the filament was hotter than the set temp, you’d think it would get worse with higher temps but it looks like it gets better!? After testing 180C, 190C, 200C with cooling ON, I tested at 190C with cooling OFF:
I like that flashforge cooling duct… I was thinking of making something like that. Something that’s removable would be good so it doesn’t melt when you’re not using it.
I am out of clues there.
For me its more temperature more stringing.
But what temperature to print I am still not sure either. My manufacturer tells 215 optimum with ±15 degrees.
But I print with 190. Higher gives me too much oozing and massive curling. 180 looks better but makes it very brittle.
And my other printer does 190 also with that filament.
Removable, exchangable sounds very good.
