First off, the picture I showed in my last post didn't really represent a defective part at all. The missing piece of plastic didn't really have anything to do with whether the nuts would stay in place or not. I disassembled the extruder assembly, put in the thicker nuts, and that seemed to do the trick. Leveling the two heads was still a difficult proposition, though. I had to alternate tightening the horizontal bolts going through the fan with the vertical ones holding the assembly onto the cart, but eventually I managed to get the thing pretty even. Here's a photo of my first test print:
Came out pretty nicely, I thought. One of the things the manual said to look for were gaps in the layers, and I did see some of those (more visible with the black filament I switched to later):
The solution to this was to tighten the tension on the extruder. Counterintuitively, you have to turn the tension bolt counterclockwise to tighten the tension. Not catching on to that may have been the source of my initial extrusion problems.
I had some issues with adhesion in a few of the early prints, but using a raft seemed to help with that. Here are some photos of me printing out the accessories:
Notice that the piece on the left has a lot of support material. I had trouble getting that off. I tried using a Dremel tool to cut it away, but all it ended up doing was melting the plastic, which made getting the support material off much more difficult. I did get it off eventually, and the part -while not pretty any more - did function. Those parts are for the spool support, which assembles like this
The two bearings are supplied with the kit and press into the printed parts. Here's a video of the support arm (the bottom piece) printing:
Here's what it's supposed to look like when assembled:
Another printed part holds a couple of felt pads. The filament goes through these pads in order to clean off any dust stuck to the fiber so that it can't get into the extruder and cause a clog. You can see it in this picture of the fully assembled printer, complete with accessories mounted.
However, you may notice that there's only one spool in the picture. When I tried to run the second extruder, I couldn't get it to heat up. At first I thought it was a problem with the thermistor, but some resistance measurements with a multimeter make it look more like the heater is what's not working. I've posted to the support forum to get suggestions on what to do about that.
The display is also not working. It lights up, but only with a blank blue screen. We'll see what the forum has to say about that as well. I'm wondering a bit if these could be my fault: ESD damage due to lack of a proper ground while handling, or maybe from moving the X axis too rapidly by hand while demonstrating the motion to my daughter. But I don't think either of those scenarios is super-likely, as everything else is working fine.
You may also notice the can of hair spray in the background of the photo. I was having some adhesion problems, so I did some googling to see what solutions were out there. The two most often recommended solutions were hair spray and painter's tape. The hair spray seems to work pretty well for me, creating a tacky film on the kapton tape that I can easily clean off later with a denatured alcohol solution.
I had another adhesion problem resulting from the second extruder. It was pushing up the layers that the first extruder had laid down. After a couple failed prints I rechecked the distance between the extruder nozzle and the print bed, and found that the second extruder was no longer level with the first. It was a bit lower, which explained why it was contacting the filament laid down by the first extruder. After releveling the two, everything worked fine and I was able to print out my own copy of the toolbox I had designed with OpenSCAD a while back. Looks like I'll have to periodically check the leveling to make sure it doesn't slip again.