Add a rod so blob triggers crash detection?
I'm not sure if this is brilliant or dumb as I'm not around my printer to have a closer look at. My idea would be to attach a short metal rod to one side of the x-axis that would just barely go under the heat block next to the nozzle. By either adding some custom g-code or by printing a small tower on that side so the nozzle would pass over this rod. If a blob is stuck to the hot end it would hit the rod and possibly trigger crash detection and stop the print.
Y'all think this would work? If I can force a blob to form by extruding against the bed in one spot I may just try it because it should be pretty easy.
RE: Add a rod so blob triggers crash detection?
You need to have the code select the correct height at the correct time. I would use a switch or sensor to detect the blob. Of course, the blob could be on a different side of the nozzle and still be an issue.
It could be part of the initial Z level calibration routine. I use the warm-up time to clean the print head with a brass brush.
RE:
I'd rather mount camera pointing at the nozzle and se image processing tools (machine-learning model) to detect the blobs.
This should be doable by modifying for example https://github.com/TheSpaghettiDetective/obico-server or just doing some basic code from scratch.
You could do thins with pretty low camera such as basic cameras with RaspbberyPi or ESP32 - for example 640x480 is just way enough to make it work.
Assuming you want to take picture once per second and do inference that can be done pretty easily on RPi (even Rpi Zero would probably handle it).
And for example if the blob is detected over 5 times in a row then trigger an alarm (to avoid short term false positives).
Hm.... I guess I could try to do that in free time 😎
What would I need would be some photos from camera with labels as 'good' and 'bad' state of the printing end nozzle.
See my GitHub and printables.com for some 3d stuff that you may like.
RE: Add a rod so blob triggers crash detection?
Will have to look it but there are probably easy ways to test for blobs without getting to fancy and requiring lots of computer power. Capacitance or thermal measurement may be able to tell if the print nozzle is getting covered.