<p>What would cause this effect, and how can it be avoided?  </p>

<p>This is a PLA print, and it should look like <a href="http://www.thingiverse.com/thing:1560347" rel="noreferrer">this</a>. I tried 215 and 225°C and both had the same effect. An earlier similar print at 220°C was not as bad but it still had some catching- it seems hit and miss and not strongly related to extrusion temperature. </p>

<p>Outside: </p>

<p><a href="https://i.stack.imgur.com/nlRb8.jpg" rel="noreferrer"><img src="https://i.stack.imgur.com/nlRb8.jpg" alt="enter image description here"></a></p>

<p>Inside: </p>

<p><a href="https://i.stack.imgur.com/PQtTj.jpg" rel="noreferrer"><img src="https://i.stack.imgur.com/PQtTj.jpg" alt="enter image description here"></a></p>

<p>I'm using a QIDI dual extruder printer with Makerware 2.2.2.89 software and these parameters: </p>

<p><a href="https://i.stack.imgur.com/6FJLL.png" rel="noreferrer"><img src="https://i.stack.imgur.com/6FJLL.png" alt="enter image description here"></a></p>

<p><a href="https://i.stack.imgur.com/Ge9ZK.png" rel="noreferrer"><img src="https://i.stack.imgur.com/Ge9ZK.png" alt="enter image description here"></a></p>

<p>Speed is 60/80mm/s. </p>

[{'answer_id': 3104, 'author': 'Tormod Haugene', 'author_id': 115, 'author_profile': 'https://3dprinting.stackexchange.com/users/115', 'pm_score': 2, 'selected': False, 'text': '<p>As pointed out in the comments, what you are seeing could very well be related to <em>lack of cooling</em>: </p>\n\n<p>You may notice that the irregularity in the print become more and more pronounced the further up you see. I believe this happens because <em>the area that is printed is reduced gradually closer to the top</em>, which in turn will give each printed layer <em>less time to cool</em>. (The frequent revisits of the hot nozzle will not allow the top layer to cool naturally.)</p>\n\n<p>This problem is very common when printing models with small cross-sections, and are typically solved by:</p>\n\n<ul>\n<li>Installing additional print cooling fans (cooling the actual print, not the hotend/heat sink)</li>\n<li>Printing several items at the same time (to increase the cross-section)</li>\n<li>Reducing print speed (gives more time to cool, but might not work for very small models)</li>\n<li>Reduce printing temperature</li>\n</ul>\n\n<p>If you can, installing additional fans and/or printing multiple objects at the same time are probably the most efficient solutions - in my opinion. However, either method would be worth exploring. </p>\n\n<p><strong>PS:</strong> When printing PLA, set your fans to full. ABS, on the other hand, does not like cooling.</p>\n'}, {'answer_id': 3105, 'author': 'tbm0115', 'author_id': 98, 'author_profile': 'https://3dprinting.stackexchange.com/users/98', 'pm_score': 3, 'selected': True, 'text': '<p>I think that you should first verify that you have the latest firmware and a newer version of MakerWare. I experienced similar issues around that version of MakerWare and remember a lot of print errors came with it.</p>\n\n<p>I believe the MakerBot Dual firmware is somewhere around 7.? and is no longer in development.</p>\n\n<p>MakerWare is also no longer in development as a standalone application and seems to have been ported over to the MakerBot Desktop. However I\'ve personally found v2.4.1 to be substantially more stable than v2.2.</p>\n\n<p>I have not tested it, but supposedly the new MakerBot Desktop (v3.10) is compatible with the Replicator Dual "Original". I had tried an earlier version of MakerBot Desktop and reverted back to MakerWare 2.4 because I ran into issues with connectivity. However, I\'m not certain it was an issue with software so much as the exploding voltage regulator...</p>\n\n<p>It might be best to give the new software a shot and/or try v2.4 of MakerWare, if you can find it.</p>\n\n<p>Here\'s the link to the latest <a href="https://www.makerbot.com/download-desktop/" rel="nofollow noreferrer">MakerBot Desktop</a></p>\n\n<p>Here\'s the release notes for <a href="https://support.makerbot.com/learn/makerbot-desktop-software/release-notes/makerbot-desktop-release-notes_13520" rel="nofollow noreferrer">MakerWare/MakerBot Desktop</a> v1.0-latest (v3.10+)</p>\n'}]
['https://3dprinting.stackexchange.com/questions/3084', 'https://3dprinting.stackexchange.com', 'https://3dprinting.stackexchange.com/users/3992/']