<p>This is a continuation of <a href="https://3dprinting.stackexchange.com/questions/19523/filament-not-being-extruded">this question</a> where comments and answers were extremely helpful in diagnosing the issue, which I am still unable to solve.</p>
<p>I determined I have the problem shown in figure 3 on <a href="https://3dprinting.stackexchange.com/questions/15629/what-are-ways-to-avoid-heat-creep">this question</a>. How I confirmed that is I started a print and monitored it closely. As soon as the filament stopped coming out I paused the print and pulled out the filament - it looked like this:</p>
<p><a href="https://i.stack.imgur.com/OO4oZ.png" rel="nofollow noreferrer" title="Photo of filament with different sized diameter after being pulled from hotend"><img src="https://i.stack.imgur.com/OO4oZ.png" alt="Photo of filament with different sized diameter after being pulled from hotend" title="Photo of filament with different sized diameter after being pulled from hotend" /></a></p>
<p>I snipped the expanded part off and re-inserted the filament back in, hit resume print and it continued printing normally, except it had skipped a layer or two.</p>
<p>What I understand is there can be a few reasons for this problem:</p>
<ol>
<li>Filament moving too fast and not being able to melt at the nozzle</li>
<li>Too much heat in the radiator block causes the filament to soften up and unable to be pushed by the incoming filament.</li>
</ol>
<p>To combat case 1 I reduced the speed of the print using the knob down to 80 % which already felt like it is too slow, but that didn't seem to make a difference. I also tried printing at speeds of 85 %, 90 %, and 95 % as well and the problem occurred in all of them. So this leads me to believe that speed is probably not the issue.</p>
<p>I read that there could also be another thing causing case 1 and that is over-extrusion. To verify this I did the 100 mm extrusion test where I marked 0 mm and 100 mm and extruded 100 mm manually in steps of 0.1 mm. It took a while but eventually in the end I determined that it is under-extruding at 95 mm actual filament extruded which means there is less filament being pushed which should actually be working against the jam. I pulled the filament out after the test to see what it looks like and this was it:</p>
<p><a href="https://i.stack.imgur.com/bCDQp.png" rel="nofollow noreferrer" title="Photo of filament with significantly different sized diameter"><img src="https://i.stack.imgur.com/bCDQp.png" alt="Photo of filament with significantly different sized diameter" title="Photo of filament with significantly different sized diameter" /></a></p>
<p>Nevertheless, I adjusted my E-steps from 93 to 99 and repeated the 100 mm test again which this time was about 1 mm off (99 mm actual filament extruded) but I guess my markings could be off too so it should be good enough. I again checked the filament and it still had an expansion on the end.</p>
<p>At this point, I'm assuming that there is no issue with my extruder and print speed, so I'm on to case 2.</p>
<p>I tried printing at 180 °C but that had no effect.</p>
<p>I also tried printing without heating the bed as I read that could affect the cooling of the radiator as the fan will be blowing hot air, but that also didn't help and the filament seized.</p>
<p>I took the fan cover off and set the nozzle to 200 °C. After a few minutes, I measured the surface temperatures on the cooling block/radiator using a multimeter which showed 47 °C on the top-most fin and 65 °C on the bottom-most. I also tried reducing the nozzle to 180 °C and took measurements again which were pretty much the same with about a degree or 2 off. Ok so maybe something is fishy here because in <a href="https://youtu.be/ItJTrTX6HJw?t=308" rel="nofollow noreferrer">this video</a> you can see the temperatures he's reading are in the 35-40s range.</p>
<p>Just to confirm this was the problem I took quite a large home fan and directed it such that the stream is hitting the radiator from about 5 cm (this is while the hot end fan is not mounted with the screws but hanging on the side, which was also blowing at the radiator). I waited a couple of minutes and measured the temperatures again which this time showed 35 °C on the top and 50 °C on the bottom. That was as low as I could get it and the house fan was pretty strong. I extruded another 100 mm manually and this is what the filament looked like afterward:</p>
<p><a href="https://i.stack.imgur.com/g12ZN.png" rel="nofollow noreferrer" title="Photo of filament with a blob of filament a the end after being pulled from the hotend"><img src="https://i.stack.imgur.com/g12ZN.png" alt="Photo of filament with a blob of filament a the end after being pulled from the hotend" title="Photo of filament with a blob of filament a the end after being pulled from the hotend" /></a></p>
<p>It still had a blob on the end and I'm pretty confident given more time it would clog up again.</p>
<p>Honestly, at this point, I feel like I've put way too much time and effort into resolving this issue and that is frustrating me as I fail to see any results.</p>
<p>I'm even more confused by the fact that I have had a couple of 3h prints go flawless, then out of the blue, it starts doing this problem. Sometimes it doesn't happen, sometimes it happens 3-5 times per print. I had an 8h print which went very well until the last 30 min when it clogged, thankfully I was around and I did the snipping procedure so the print finished but it is visible where it skipped a bunch of layers and has a weak spot.</p>
<p>It is quite annoying to have to babysit the printer like that and I'm really reaching out to anyone who'd be able to help me.</p>

[{'answer_id': 19542, 'author': 'iblue', 'author_id': 34449, 'author_profile': 'https://3dprinting.stackexchange.com/users/34449', 'pm_score': 2, 'selected': False, 'text': '<p>Yes.</p>\n<p>The issue is, that there are small gaps between the layers. But you can coat the print in an airtight material. While epoxy and similar materials work very well, they are somewhat too viscous and take a long time to cure.</p>\n<p>My special recipe for coating PLA prints with a fast-curing airtight thin layer is:</p>\n<ol>\n<li>Dissolve 1 g Paraloid B-72 in 20 ml acetone.</li>\n<li>Dip or otherwise evenly coat the print and dry at room temperature for 10-20 minutes.</li>\n</ol>\n'}, {'answer_id': 19543, 'author': 'R.. GitHub STOP HELPING ICE', 'author_id': 11157, 'author_profile': 'https://3dprinting.stackexchange.com/users/11157', 'pm_score': 2, 'selected': False, 'text': "<p>In theory, yes you can without any additional materials. But it requires a very high level of perfection for your 3D printer's output.</p>\n<p>&quot;Gaps between layers&quot; are not the issue. There is no &quot;gap&quot; between the extrusion at layer N and an identical-path extrusion at layer N+1 if layer N+1 is extruded correctly and remelts the surface of layer N sufficiently to bond everywhere. There are <em>grooves</em> between layers from the extrusions not having perfectly rectangular cross-section and rather slighty rounded edges, but these are not &quot;gaps&quot;.</p>\n<p>Where gaps do come in to play is from inconsistent extrusion. If at any point the printer fails to resume extrusion where it's supposed to, or extrudes slightly less material than it's supposed to, there's a possibility that the complete remelt/bonding described above does not happen. It's also possible that grooves <em>turn into gaps</em> under high pressure, by providing a surface where the pressure can act like a wedge to separate weakly-bonded layers.</p>\n<p>Also involved here are issues with the filament quality. If the filament contains air pockets or has absorbed moisture, there will be tiny bubbles bursting in the extrusions, making a potential path for air to pass through.</p>\n<p>I have not succeeded in producing an air-tight container, especially not at high pressure, but I have made test containers for a vacuum that take several minutes to return to ambient atmospheric pressure after the pump is removed. This was using PLA with a non-high-temperature-capable hotend. I'm planning on revisiting this at some point with the temperature cranked way up (now with all-metal) with PLA and other materials to see if there's any practical viability to the theoretical possibility of getting it right.</p>\n<p>Short of that, iblue's answer to use an airtight coating is a great option if you can deal with the dimensional changes or compensate for them in designing your parts.</p>\n"}]
['https://3dprinting.stackexchange.com/questions/19547', 'https://3dprinting.stackexchange.com', 'https://3dprinting.stackexchange.com/users/34389/']