Anycubic Kobra-2 FDM Printer

A few years ago I bought a 3D resin printer so the kids and I could learn a little bit more about modeling and fabricating 3D objects. While it's been a great experience, we haven't printed much in the last year because of all the headaches of dealing with resin. Every time we do a print we have to deal with temperatures, level the plate, put on all the safety gear, and then clean up everything at the end. It's a lot of overhead and dangerous enough I don't want my kids doing it when I'm not home. I've been thinking it would be nice to have a traditional FDM printer on hand to lower the barrier for printing simple things so that printing will be more accessible to my kids. After a lot of internet wandering, I decided to get the new Anycubic Kobra-2. It's new, works with Linux, and shipped from Amazon with a 1KG spool of filament for $300.

Setup

The kids and I setup the Kobra-2 on my desk in the garage. The assembly wasn't too difficult, although it took us a while to figure out how to hold the frame so we could get some of the machined screws lined up properly. It was also a little unclear how the feeder tube was supposed to go in the header (does this go any farther in?). Once it was setup we ran the auto calibration tool to probe the height of the build place. Auto calibration was a required feature for me, and one of the reasons why I'm happy to be buying a printer after the technology has had a chance to mature. We then preheated the filament and had it print the famous 3DBenchy boat design. The kids and I watched with wonder as the extruder spun around the plate with robot brrrrr noises. FDM printing is so much more exciting to watch than resin because you really see it happen. With resin the plate moves up and down every few seconds, with an upside-down design that's coated in excess resin. While you add a whole layer at a time, it takes a long time to get through all the pads and supports before you get to your actual design.

Sample Prints

3D Benchy only took 30 minutes to print out. One of the other selling points of this printer is that it can do higher speed prints (150mm/s to 250mm/s, compared to the 60mm/s of the stock Ender printers). I was really tempted to get one of the $600 Bambu printers, which can do up to 500mm/s, but decided we should start with a basic printer and see how much we like it first. Benchy came out looking pretty good, though you can see some pixelation in the windows that I don't think you'd have in resin. That's fine though- I think I'm more interested in building functional widgets with this printer than detailed figures.

The next thing we printed was a small mesh cup I pulled from thingiverse. This design came as a plain STL object so I had to load it into a slicer to render to gcode. Anycubic says to use PrusaSlicer, which is a powerful slicer built for Prusa printers. It's free and has a Linux version that worked on my Chromebook's Linux container. I had to download the settings from the Anycubic support site, but they came up fine. For this design I just loaded the cup, hit slice, and saved the gcode. Prusa had a lot of detailed info about how it built the object. I liked that it recognized the interior and autofilled it with a grid to save on material. The scaled down version of the print took about an hour to build (correctly predicted by Prusa). I was impressed that the printer was able to build a thin mesh and have it come out ok (though later I broke it trying to trim some of the base).

Next up was a micro-sd card holder. I found a clever design someone had made that had a radial container with a screw-on lid. The threading is really interesting to me because it gives you a way to connect parts together (someone also modified the design so you could screw together multiple micro-sd containers, though I doubt I'll ever fill this one). The parts I printed screwed together just fine. Two of the slots weren't deep enough, but that's ok. I should have added an up label though, as the slots don't have enough friction to keep cards in place if you open it upside down.

Finally, I printed a baby guardian dragon dice holder from Thingiverse for my niece. This design has a spot for you to put a die. It's a cute design, though the FDM version resulted in a bunch of lines on the angled surfaces.

Issues

We have had a few issues with the Kobra-2 during our first week of use. My son had a few failed prints that we're trying to figure out. The printer would get partway through the base of the design, get stuck, and then go into an endless calibration loop. It's possible this is because we installed a newer version of the slicer than we were previously using. When I went back and sliced the design with my chromebook it printed fine. Again, it's nice that the setup/cleanup for a print is so easy. The other main issue has been quality. The FDM prints look good, but they're not as detailed as the resin prints. Below are some zoom-ins that show how this results in the FDM prints coming out jagged in certain spots.

Power

One thing I've noticed about the FDM printer is that it the motors really get a beating, zig zagging back and forth all the time. Our house doesn't have great wiring, so the lights in the garage (and bathroom) flicker slightly when the printer is bouncing. Also, there's a spike in power when you start up because it needs to warm up the build plate and nozzle. Maybe I'll look into getting a battery or power conditioner for the plug to smooth out the signal.

Overall

Overall, I'm pretty happy with the Kobra-2 so far. After dealing with all the resin printing pains it's been a breeze to get FDM working. I don't think we'll print a ton of things, but it's nice to have the option to design and build stuff when we want.