RogerBW's Blog

How can I tell when the 3D printer has finished a job, without going down to the cave where it lives and checking it?

I'm using an Ultimaker 2+, which does not have a direct Internet connection. I regard this as a selling point - it means that the only digital interaction it has with the outside world is when I stick the SD card in the front and tell it to print something, so I don't have to worry about a compromised IP stack. But that also means I can't log into the thing and see how it's going.

OK, it does have a USB socket, so I could just plug in a machine running octoprint. And I probably will eventually. But this was the quick and dirty approach.

First, I wanted a proper camera looking over the print bed, and (one 3D-printed plastic clip later) that's what I have. The other end of its USB cable goes into a computer that sits next to the machine. This is mostly so that I can see if the print process has gone wrong, for example a layer that's not sticking to the previous one and instead is turning into "clown hair"; that happened a few times when I was getting the hang of the printer.

So I have video of the thing; actually it takes one shot per minute, on a cron job, since that's fast enough for my purposes. Could I do some sort of image analysis to find out when a print is complete? Or... hang on a minute, when the print bed drops at the end of the process, the camera can see out of the front opening of the machine, which I've covered with cardboard in the current slightly chilly weather. So I can actually control what the camera sees at that point.

Just throw the captured images at the zbar library, and when analysis of the latest image reports the right QR-code, the print is complete!

At that point the cron job sends a notification via SIP TEXT to my VoIP handset, as well as popping up a message via Jabber on whatever desktop or laptop I'm using at the time. Yes, yes, the octoprint thing will happen eventually, but this is pleasingly Heath Robinson.