<p>For a school project, my teacher gave me a brand new Longer 3D printer to create parts with. After one good job, the printer cannot get past the raft creation without air printing. The thickness of the printed filament tapers down until no filament is coming out. I do not believe there is a jam in the hot end because if I remove the filament and cut off about 4 inches, the printer extrudes as normal.</p>
<p>I am using 1.75 mm PLA on a Longer 3D LK4.</p>
<p>When the problem occurs, the extruder continues as normal but prints out very little filament. The extruder drive gear also ticks backward as if it cannot supply enough force to move the filament forward.</p>
<p>I have tried decreasing the speed, increasing the temperature, turning off retractions, but none of those options seemed to have any effect on the problem.</p>
<p>If videos or pictures could be helpful let me know what to include.</p>
<p>My working idea of what's wrong is that heat creep is causing the filament inside of the heat sink to soften causing the filament to thicken and Jam. I could be wrong.</p>
<p><a href="https://i.stack.imgur.com/T7Rxz.jpg" rel="nofollow noreferrer" title="Failed Raft"><img src="https://i.stack.imgur.com/T7Rxz.jpg" alt="Failed Raft" title="Failed Raft" /></a></p>
<p>Figure one highlighting how the filament thins over the course of the raft creation until no more filament is extruded.</p>
<p><a href="https://i.stack.imgur.com/7UhUH.jpg" rel="nofollow noreferrer" title="Thickened Filament"><img src="https://i.stack.imgur.com/7UhUH.jpg" alt="Thickened Filament" title="Thickened Filament" /></a></p>
<p>Figure two showing how random parts of the filament is thicker than others. The thickness is noticeable and once I cut this section off, filament flows freely through the Bowden tube without friction. With this section, the filament is difficult to remove and requires more force.</p>
<p>I have tried:</p>
<ul>
<li>increasing the interface thickness to 0.4 from 0.27 mm and from 0.4 to 1.0 mm</li>
<li>increasing the print speed from 50 mm/s to 90 mm/s
allowing the printer to cool off.
decreasing the temperature to 190 °C</li>
</ul>
<p>During the print, I have noticed that the heat sink is hot to the touch during the raft creation but cools off once the fan starts spinning.</p>
<p>The fan does not spin at all during the creation of the raft. But spins at full speed once the actual print has begun. Longer does not have a setting inside their software to change this.</p>
<p>I have gotten a few really small prints to work with print surfaces smaller than 2 cm wide</p>
<p>The prints themselves turn out great if they get past the raft stage (only for small prints). This additionally leads me to believe that heat creep is the problem and that the fan not being on is the cause.</p>
<p>Let me know if you have any ideas.</p>

[{'answer_id': 15692, 'author': 'Perry Webb', 'author_id': 15075, 'author_profile': 'https://3dprinting.stackexchange.com/users/15075', 'pm_score': 2, 'selected': False, 'text': "<p>If you use a build surface such as PEI, acetone frosts your surface, leaving a white film appearance.  If you have no additional surface on a glass or metal bed, it is incomplete cleaning.  If incomplete cleaning, you could try isopropyl alcohol (IPA) immediately after acetone, followed immediately by a water based cleaner or DI/distilled water. (IPA dissolves acetone and water dissolves IPA. Once the film dries the next step may not work.)</p>\n<p>You can't clean off a frosted surface.  The black surface of the hot bed in images of the CR-10S Pro appears to indicate that the steel bed has a build surface with a plastic material such as PEI.  Reviews of the build surface being difficult to remove prints also implies a plastic build surface on the steel.  Thus, it appears that the white film after cleaning with acetone is actually a frosted surface.</p>\n<p>If you use an Elmer's washable glue stick or one with PWP, it will form a barrier between your print and the build surface, that not only will protect your build surface, but will make it easier to clean your build surface with IPA or water based cleaners.</p>\n"}, {'answer_id': 15704, 'author': 'Snympi', 'author_id': 7470, 'author_profile': 'https://3dprinting.stackexchange.com/users/7470', 'pm_score': 2, 'selected': False, 'text': '<p>Acetone is quite an aggressive solvent, so white residue could be part of your heatbed print surface that is dissolved, and then when the acetone evaporates the dissolved part crystalise on the heatbed again.</p>\n<p>Acetone should only be used on PEI sparingly, not at all on powder coated surfaces. Use IPA (Isopropyl Alcohol) to clean of residue between prints. If you have problems with adhesion, you can also start by washing the build plate or surface with water and dish soap (with no other additives). The surfactant in the soap traps oils and other impurities and flush them away, instead of dissolving them temporarily and then depositing it on the build surface again when the solvent evaporates.</p>\n<p>Like mentioned in other comments, use IPA or water/dish soap to clean off any residue.</p>\n'}]
['https://3dprinting.stackexchange.com/questions/15732', 'https://3dprinting.stackexchange.com', 'https://3dprinting.stackexchange.com/users/27022/']