I will spend this evening dismantling half of my 3D printer in order to remove some stuck filament from the stepper motor. As I already did this once before, it isn't as scary any more. I did have to buy a special torque screwdriver to do it the first time. But by now I'm pretty familiar with the various moving parts of my printer, I understand where the different problems come from, and I can fix the thing most of the time. It turns out that the 3D printer is a relatively simple machine, especially if like in my model the stepper motor that pushes the filament is well separate from the heated extruder / nozzle part of the machine.

I don't know how my color laser printer works half as well as I now know how my 3D printer works. But then I owned that laser printer for years and have printed over 5,000 pages with it with rarely a problem. The only time something really went wrong was when I tried to print on something which wasn't suitable for printing on, and it stuck to the roll of the toner cassette. I had to change to toner cassette to fix the problem, but that wasn't any more difficult than a regular toner replacement. In comparison to that the 3D printer is very problematic. After running okay for about a month, he developed problems. For some time I couldn't get a single print to succeed, in spite of having repeatedly cleaned the stepper motor and the nozzle. Now I reached a point where with some tinkering I can get some prints to succeed, until then there is suddenly a failed print and I need to tinker again to fix things.

I believe that the fundamental problem is the printing bed of the XYZ Da Vinci Jr. 1.0w not being 100% stable in height: If I calibrate the nozzle height to a good value, and check after a print again, the gap between the nozzle and the print bed has changed. And printing only works in a narrow range of gaps: Too close and the plastic doesn't flow out of the nozzle well, too far and the plastic cools down too much before reaching the print bed or the previous layer, and doesn't stick to it well enough. Sometimes it appears as if the bed height moves during the print. So the print starts okay, and then after a number of layers something moves, and the next layers go bad. Right now I don't know how to fix it. We are talking of tenths of millimeters here, so it isn't as if something was visibly lose and could be easily fixed.

In short, a 3D printer is still a technology for home tinkerers, and not yet a consumer technology.