Between print good practices/nozzle maintenance

sr1329 · August 14, 2020

(TL;DR: last paragraph only)

I’m still a noob been doing this for about a month. It’s been fun.

I suppose I’ll start a little off topic and this may end up being a nozzle/clog thread instead. So I’ve noticed that as a print proceeds it seems to tend towards underextrusion over time. Which is fine in terms of my models. They come out just fine and strong. This is PETG at 245C.

The issue is excitement to start the next print and last night this happened. I didn’t even clean the nozzle properly (Bed was cleaned properly though) and started another print.

What I noticed was the first layer was super thin and since i’m printing at 0.12mm I got excited about how thin and translucent it prints and how much resolution that would yield in the final model. It was also uneven in thickness and opacity. It had cool lines though.

Turns out I was wrong. That was gross underextrusion happening in front my eyes and I didn’t even realize what was wrong. In any case first layer is set to 0.2mm so it should look the same as a 0.2mm print in the first layer.

This morning I woke up to the print partially torn off the bed with spaghetti stuck to the nozzle getting pushed around. I cleaned the nozzle properly and the bed and restarted. The new print had a beautiful first layer that was thick enough to be opaque with a nice clean matte finish that looks like it will adhere subsequent layers like a champ.

So I got a nice lesson in what a first layer should look like and a reminder that first layer is 0.2mm anyway.

My question is what am I doing wrong? Actually I know but what can I do to prevent this?

My suspicion is that just sitting there extruding into a blob of melted plastic primed the extruder really well and cleared any clogs. The flow was perfect and the first layer, well I wish I took a picture of it, it was so even and prefect.

So getting the point should I be extruding a certain length before I start a new print? Should I use my cleaning filament each time? Or maybe it’s because I haven’t used a cleaning filament since the last roll? I think about 500g have gone through without a cleaning filament run at least.

What are best practices for nozzle maintenance? Both between prints and at certain intervals.

Edited August 14, 2020 by sr1329

geert_2 · August 15, 2020

The best practice is always to be very gentle with nozzles. No brute force, to avoid damaging brass nozzles, print head, and rods. Even if a rod is bent only 0.05mm, that is a complete layer-height of 0.1mm upon one rotation.

I do very gentle cold pulls ("atomic pulls") very week, or every time I change filament color or type, or as necessity requires when there is accumulation of dirt in the nozzle. After each print, I immediately wipe the nozzle's outside, before it cools down.

See my old (non-official) manual here:

https://www.uantwerpen.be/nl/personeel/geert-keteleer/manuals/