Welcome to the SeeMeCNC Community

Printing on my new Rostock Max V2 and loving it, but my prints have this happening (see pic). Not sure what is causing it and would sure appreciate some help. My guesses are extrusion retraction rate or flow rate but would like to address it straight away rather than experiment to find a solution. Thanks for any help.

What filament are you using? I had similar problems with Colorfabb XT and couldn't solve it. Other filaments I have used didn't have the issue.
If you just extrude using the controls on MatterControl (not printing) does it come out smooth or are there little blobs occasionally?

Moisture could be. If it is abs.

Moisture could be. If it is abs. Do you hear any popping sounds?

I used up the last of my filament from MatterHackers and then started a fresh spool from Seemecnc. The MatterHackers print had a lot of the "bubbles" the Seemecnc print had only a few. No popping sound (as I am familiar with from printing Nylon with moisture). The spool from Seemecnc went from the vacuum sealed package with dessicant to printer and printed instantly, so I doubt moisture is the issue. One point: the bubbles on the Seemecnc print were only on the outside surface of the print whereas the MatterHacker print was inside and outside. I'm using Mattercontrol. When just extruding no bubbles.

What are your retraction settings?

O.K. I've figured it out, MOISTURE. After a lot of research I have determined moisture is the demon I'm dealing with. The popular solution seems to be a product called Eva-Dry, a silica based device that you put into the enclosed space and it draws out the moisture. I bought several and put one in my printing enclosure a 2' x 2' x 4' wooden box with a glass door that seals pretty well. Left it in for 10 hours and did not see my hygrometer drop 1% . Called the manufacturer the next morning to find out what was wrong and was told it takes 6-8 weeks for any appreciable moisture reduction! That's simply not going to work. Frustrated I tried something, I opened the door to the printing chamber and used my heat gun for about 1 minute. I watched as the hygrometer kept dropping a total of 7% in that time. My plan now is to devise a way to use a hair dryer, drilling 2 holes (one near the top and one near the bottom) and using a hair dryer to create a flow of warm dry air in the chamber. If anyone has seen this done or knows a link to someone who has pursued this avenue please enlighten me.

The humidity in the printing chamber isn't much of a concern. It's the moisture absorbed by the filament itself that really matters, since that is what gets shoved into the hotend.

Storing your filament in a sealed container with dessicant whenever it's not actually in use is probably sufficient in most cases. It takes time for filament to absorb or release moisture, so if it spends most of its time in a dry environment it's good enough.

Some people go further and create containers with a spool and feed hole so they can keep the filament dry even when it's actually being used. Here's one thread on that subject: http://forum.seemecnc.com/viewtopic.php?f=80&t=5826.

There are many kinds of dessicant, both disposible and rechargeable. The cheapest is probably a bag of rice.

This is mainly due to bad quality of filament in which air bubbles are trapped. You can just break the filament by hand and you will find these spaces at cross section.