All of sudden, I started having all sorts of problems with first layer adhesion. Since I’ve been using 3DLac on my glass build plate, this has never before been an issue. Try as I might, I just couldn’t get beyond the first layer which was a horrible stringy mess and refused to stick to the build plate. I won’t go into details of what I checked as it would be a long and boring read, but finally I decided to take a look at the nozzle itself. This is Diamond hot end, so it’s one great lump of brass. This is what I found.
That used to be a nice, round 0.4mm diameter hole. Here is another picture
That is a 0.8mm diameter drill bit inserted into what was once a 0.4mm diameter hole.
The nozzle has done many hundred of hours of printing but never with any abrasive filaments. Mostly just PLA. Of course, not every print has gone perfectly and there have been occasions when the nozzle has scraped across the previous layer.
I don’t really know what caused it, just general wear and tear I guess but the issues I had with printing were not a gradual process. One day all was well and the next day all was far from well.
I had a spare which I have fitted and now everything is back to normal. So I guess, if things go awry and you’ve checked all the obvious, take a look at your nozzle……….
Hot filament and cold Coffee 
Hi Ian,
you mentioned that you usually drill out your diamond nozzle to 0.5mm instead of 0.4mm.
Why is that? Faster printing? better flow? no clogging?
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Hi,
Yes I prefer 0.5mm nozzle diameter for all of the reasons you mention. Although 0.1mm may not sound a lot, the difference in area is huge. If you do the maths, the area of a 0.4mm nozzle is about 0.126mm^2 and the area of a 0.5mm nozzle is about 0.196mm^2 so it’s about 50% bigger. I use a layer height of 0.3 mm, the same as used with a 0.4mm nozzle but the width is 0.5 instead of 0.4mm. For the objects that I print, I don’t find the resolution to be a problem but the increased area makes it much easier to push the filament through. So there is less stress on the extruder, less chance of it grinding the filament, less chance of clogging, less pressure in the Bowden tubes so retraction can be reduced and more potential for printing at higher speeds.
Ian
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It would make sense to me that the cause of this is repeated z-homing. Glass is harder than brass, and since your nozzle acts as a probe tip, it’s getting “hammered” by the bed, bending/flattening/distorting it over time.
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Interesting thought but no way is that the cause. It takes the very lightest of pressure to lift the hot end so there is no “hammering” involved. I can lift the hot end off it’s seat easily with an extended finger. The replacement nozzle has done many hundreds of prints with no sign of flattening or distortion. Before I got the printer dialled in properly, I had a few problems getting the first layer right with the result that during the second layer, the nozzle was scarping across the previously printed part. I would think this was more likely the cause. Whatever the reason, it was a one off event which has not recurred.
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