<p>This is printing PETG extruding at 250 °C, 1st layer bed at 80 °C then 60 °C on other layers.  Nozzle is 0.4 mm; printer is German Reprap X400.  The all metal extruder is clean with no oozing.  The print gets a blob when the wall width changes from 2 mm to 1 mm.  The extruder squishes the blob out the sides of the wall with subsequent layers.  Images below show both sides of wall.  I'm looking for the cause to come up with a fix.  I consistently get the same results in the same location when printing this file.  The reduced area of the layer does cause reduced speed to increase the print time for the layer (speed reduced when layer would print in less than 30 seconds; minimum speed 15 mm/s).</p>
<p>When I printed two, there was only one blob on one of two.  Below shows the speed settings.  The perimeters are three vertical shells, so the walls are all perimeters.  My understanding of the setting is the 2 mm wall printed at 20 mm/s and the 1 mm wall at 15 mm/s.</p>
<p>Printing similarly with 2 mm walls only and the same settings, the print is nearly perfect with only a few stringers.  Printing with only 1 mm walls does not have the blob, but does have stringers.</p>
<p>See solution at the end.</p>
<p></p>
<p><a href="https://i.stack.imgur.com/T0WBA.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/T0WBA.jpg" alt="enter image description here" /></a></p>
<p><a href="https://i.stack.imgur.com/xDyNO.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/xDyNO.jpg" alt="enter image description here" /></a></p>
<p><strong>Solution:</strong></p>
<p>Speeding up the print speeds and using thicker walls not only eliminated the blogs, but also completely eliminated stringers, and gave a near perfect print.  Apparently, the actual temperature that PETG extrudes is highly dependent on how fast it extrudes.  Printing too fast clogs the nozzle because the filament doesn't have time to melt.  Printing too slow causes the hotend to stop extruding from heat creep.  Here, the actual temperature of the extruded PETG was decreased by speeding up the extrusion.</p>
<p><a href="https://i.stack.imgur.com/7STxh.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/7STxh.png" alt="enter image description here" /></a>s://i.stack.imgur.com/Uhv61.png</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/15697', 'https://3dprinting.stackexchange.com', 'https://3dprinting.stackexchange.com/users/15075/']