Thanks for writing this note, Pavel - you are making good points/ asking good questions.
OK, so we do have a service contract - BUT it doesn’t cover “consumables” and the heads are considered consumables. A tech came out a year ago and swapped heads (model-support) and that bought us more time. Thing is, they didn’t really give us great detailed instructions about how to clean the heads. We/ I thought I was following the directions but without proper training, the interpretation is wide. Plus, starting 6-mo after we got this printer, we used Durus material and it appears that Durus is harder on the heads (aka it gunks up faster) compared with Vero. The service contract NOW contains a once-per-year training and maintenance visit. That would have been great to have gotten last year.
The two main reasons why I think the heads are the problem are: (1) the July-service contract tech says so and (2) because the prints are bad (even on things that used to print fine). From knowing what the stl and solidworks model looked like, I can see where the support was meant to print and instead the model material above it has sunken down in the spot above it. I used to be able to print a whole bed of these small knobs and then a few months ago, I saw them “sinking” - the support not showing up most of the time and the model material blobbing down as if it were deposited but fell to the lower height since the support wasn’t there. One time this spring, I printed a whole bed and the parts were basically glued-down - no support, just model material straight on the print bed. I chipped them off and I’m very impressed that I didn’t scratch the print bed (which I believe is only aluminum) with my steel scraping tool! The tech that was here did a load cell calibration in July and said that the heads are bad but that he’s tried to get as much as he can out of them - I take that to mean he’s increased the voltage to the drivers/actuators that push the material thru and he said if we keep doing this, it will become erratic. I haven’t done a load cell cal yet myself - it’s been a month and we did a soak in alcohol since the last one. It’s on my list of things to do but I’m not looking forward to “erratic” behavior.
I took some photos and I’m due to post another note with “before” and “after” for the model/stl and then the real thing. It’s bad - you might want to get some tissues ready!