MakerBot Print is our newest print-prepration software, which supports native CAD files and STL assemblies,
allows you to interact with all your printers via the Cloud, and many other exciting new features.
Hey CharmPeddler! This is probably more detail than you wanted, but here goes:
There are a few things that can cause the threads to be too tight, but usually screwing the top on and off a few times clearances things well and they work more smoothly. Here are some things to check if that doesn't do it for you:
Make sure your extrusion settings are correct for the particular roll of filament you are using. If the filament is out of spec a bit (just a bit on the thick side, for example) the result will be over extrusion. If you can, get a good pair of digital calipers and sample about 20 points along about a meter length of the filament you are using and average them together. In Cura, you can update the process and edit your filament diameter to reflect its real-world diameter. It is a pain in the butt, but it really can make a difference. I've printed tons of these things in all sorts of filaments, and any time I have a fitment issue, it almost always turns out I have an over extrusion problem that needs to be adjusted out.
Does the cap snap on well? If the cap is way too tight too, there is definitely a print setting issue - probably over extrusion. For the cap, you should be able to snap it on and off without having to sand anything. If the cap fits ok, it is probably a problem other than over extrusion.
Make sure you aren't using supports. The model is designed so that it can print without supports. If supports are left on, sometimes it will put a few artifacts inside the thread area which can cause issues. If you are using PLA and your part cooling settings are working on other prints, it should give you no trouble.
Check the very base of the top (the part that screws down onto the collet to grip the blade) Make sure there is no flange or boogers right on that edge as sometimes that will cause issues. This can happen especially if you have your first layer squished a lot.
The shell thickness is a good call - if you have it bumped up to 5 or above, you can get away with a lot less infill (I need to update my instructions to reflect that). That shell increase shouldn't cause any thread issues.
I don't know for sure if Cura has the setting (probably) but check if there is a "inside-out" vs. "outside-in" setting for your outer perimeters. You want to be printing "inside-out". This allows more accurate overhangs without using supports. It can sometimes cause some surface defects, but they won't impact this print. If you are trying to print outside-in on this model, it may cause some sagging on some of the thread overhangs and cause you some issues.
Let me know how it goes! I'd love to see one come off a legit MK3!