My RepRap is working! Over the Thanksgiving weekend I had a solid chunk of time to address the problems I’d been having. After a full day of tweaking I was able to print a nice looking single walled box and a very ugly looking minimug.
The minimug was ugly because I hadn’t set the feed diameter in Skeinforge and it had defaulted to 1.75 mm and I’m using 3 mm PLA. So the printer was extruding a lot more plastic than it thought it was. After I fixed that I printed another minimug and it came out much nicer, although it was neither water nor alcohol tight.
I’ve since printed a bunch of stuff and have experimented a bit with some of the 3D design software. I’m still a RepRap n00b but at least I have a working printer! It’s pretty exciting. I’m very impressed with the quality of the prints I’ve done, and this isn’t bragging because the quality of the prints has very little to do with my efforts and a lot more to do with the all the work that’s been put into the RepRap project.
The rest of this post is a collection of notes for other people who are really new. These are places where I really stumbled, so this list might be valuable to someone else.
- After I assembled my printer I was tempted to just jump in and try printing something but was immediately disappointed. I didn’t realize how much careful hardware and software calibration was required. Eventually, this guide is what got me from a totally non-functioning printer to a working machine:
I disovered that leveling the print bed is really crucial. This is stressed a few times on the wiki and in other documentation, including the guide above, but it’s easy to underestimate. I think this is especially true if you’re printing on cold blue tape (without a heated bed). I gather that a heated bed is more reliable, but I think a lot of novices will opt for printing PLA on blue tape as I did, simply because it cuts down a little bit on cost and complexity. (That being said I think I’m going to get a heated bed very soon and would recommend anyone else just skip cold blue tape because it poses some ugly problems like prints getting totally stuck.)
In my case, the level of the bed can be the difference between perfect print and total garbage. When I started, total garbage was the extruder’s nozzle dragging a growing tangle of plastic around the bed, with nothing sticking to the bed at all. After I carefully leveled the bed so that the nozzle at Z=0 was only one sheet of paper above the bed, I got pretty decent prints right away.
While I was calibrating the machine, my Z-axis started making a horrible metallic grinding noise. I was lucky to have some bicycle grease handy and smeared a dab on each of the Z-axis threaded rods which silenced them. Perhaps this is obvious, but I would recommend getting some machine oil or grease if you don’t have any, just in case.
As I was assembling my printer, I made a few mistakes that weren’t deadly but damaged some printed parts slightly. When I was putting the extruder together, the small gear needed to be reamed out to fit on the spindle. Since it was such a tight fit, I didn’t think I needed to use the set screw to hold it in place, especially since I would need to file out the nut trap to fit a nut in. Over time, the gear loosened and I ended up having to use a set screw. This was fine, until I needed to disassemble the extruder to clean out the hobbed bolt. After I did, I realized that the nut trap was no longer able to hold the nut in place, and I couldn’t screw the set screw into place. This meant the motor would just spin its shaft inside the gear, and the extruder wouldn’t work at all. Eventually, I was able to force the set screw into place to hold the gear on, but if I hadn’t I would have been in trouble.
The lesson I learned was this: if you realize that a printable part might fail, print it as soon as possible, unless you have access to another machine that works. I’m sure that if you’re hacking on your RepRap all the time, this is obvious, but it’s easy to get carried away and put this off if you’re a novice. Right now I’m printing a few other parts that were weakened when I was building the printer (for example: one of those “h” shaped endstop holders), since the printer is working now I don’t want to take any chances.
I initially bought a Makergear hot end kit because it seemed to be recommended by a lot of people and was available in the US. I had some issues when I first started printing which could be attributed to the hot end, but it’s certainly possible (and even very likely) that it was an error on my part. I eventually gave up and bought a J-Head hot end from RepRap-USA.com, and that has worked really well for me. The J-Head hot end is also much, much simpler to use, as it involves almost no any assembly. Frankly, the Makergear hot end is quite fiddly to assemble.
This follows from the last note. Since I had two hot ends, I also had two thermistors, that happened to be identical. When I received the J-Head in the mail, I decided to use the thermistor that came with the Makergear kit and put the new one aside. A few nights and a few assemble/disassemble cycles later, one of the thermistor’s leads broke.
Since I had a spare, all I had to do was swap it out, but if I hadn’t I would have had to order a new one. Thermistors are super cheap, so it wouldn’t have been a big deal, but it would have been a bit of a pain in the ass. In the future, I’ll be sure to have several spares of parts like these, those that are cheap but essential. If you’re going order something from McMaster or another online supplier, and the part you’re ordering is around a dollar or two, save yourself the hassle and buy two or three even if you only need one.