March 27, 2011
It’s been a busy couple of months on this project, and I have lots more to say, but here’s a quick summary of what ended up happening with the bot:
Where I last left off, I had physically assembled the Makerbot as well as the extruder. I ended up trying it the next day…
And it just didn’t work. I tried lots of different experiments - different software on my computer and the various hardware boards on the bot, disassembling things and reassembling them, testing circuits, etc. etc. Nothing. The platform moved, but I couldn’t communicate with the machine via my computer.
One thing that quickly became apparent was that the extruder board (which controls the part that actually melts the plastic) was defective or otherwise busted. This was sort of a shame, but I was eventually able to get a replacement board from the sellers, Makerbot (more on that later).
I ended up shipping it back to myself in Philadelphia to keep working on it. Right away, I replaced my defective extruder board with the new one. Should work, right? Well… sort of. The extruder wouldn’t extrude for more than a minute or so, if that. When it did, it was globby and slow. The build platform would also skip steps, meaning that it would not move as far as it should one at least one of the axes as it was building.
(What does this mean? Since the motor has no idea whether it was successful in moving the platform, this meant that you’d get something built a little bit, and then the next step up would be shifted a little bit - imagine if you were constructing a building, and the second floor started ten feet over to the right of the first, you’d have an overhang, the building wouldn’t look right, or be stable, etc.)
Fortunately, I’m a member of Hive76, which is a local Philly community of makers and 3D printer people. Several people there spent literally hours with me troubleshooting these problems. Here’s what we found:
I made a mistake in putting the extruder together - the toothed wheel that grips the filament as it comes into the extruder wasn’t put on tightly enough, so it was slipping. The rod that Makerbot ships (shipped) with each machine to help you get this distance right is actually not helpful for fixing this problem! It just needs to be quite close, so it gets a strong grip on the filament.
Applying lubricant to all of the axes - particularly the z-axis - basically fixed the skipping problems.
As for simply getting the machine connected to my laptop so I could control it - the key was to keep trying different versions of the extruder firmware and motherboard firmware. I wonder if the fluorescent lights in my fiancee’s Dad’s workshop also may have caused some interference with the electronics.
And that was pretty much it… Oh, except for the very, very long process of calibrating the machine. There are dozens and dozens of settings with completely inscrutable names (“feed rate” controls the movement of the build platform, the setting for the ratio of filament length to width is on the “Carve” menu, etc.). This took me another few weeks of detailed work to get right.
So I got the bot working pretty well, as you can see in the video. The bot is printing a small plastic part that can be used to build another, different, 3D printer. The printer isn’t at all perfect, but it’s also not bad for this level of technology and for my level of skill. I’ve also been thinking a lot about whether it’s possible to build a more reliable kit, and how this could be done, and working on that. I’ll probably have some more posts about that later.