Monoprice i3 Mini (Wanhao i3 Mini clone) sudden persistent under-extrusion (maybe)?

First off, I'm new here and thus is my second attempt at posting my issue to ask for help. The first attempt was made several days ago and, after getting a message saying it needed to be approved by a mod, nothing happened..

In short, I bought the printer mentioned in the subject for cheap. It's my first 3D printer and I'd always wanted one, so I thought it was fate telling me the time was now!

I initially had bed adhesion issues, but corrected them by changing the print surface, leveling it ~20 times in a row and before every print, and learned the importance of glue sticks ^_~

For the last 3 months, everything was fantastic. I love this little clunker, even though there are FAR better options available. As a hobbyist, I was very satisfied.

That all changed about 3 weeks ago, when I started getting severe warping on every print, and more recently a rather severe case of what appears to be under-extrusion. No change was made, as one day I was printing fine and the next day things started to separate between layers and are full of holes. I'll attach pics when I get home.

So far, I've tried 4 different filaments (2x petg and 2x pla) from two brands, adjusted the printing temperature, adjusted the layer height, adjusted print speed, and even completely disassembled the entire device to ensure its free from clogs and 'rough spots' with all the moving parts (including the filament feeder and filament tube).

I'm really at a loss for what to try next. I'm hesitant to replace the entire hot-end, as it looks like it'll cost almost as much as I paid for this entire printer. And if that's the case, I might as well replace the entire thing. Though I'm not entirely convinced that the issue will be corrected with that...

The filament looks like it's being extruded correctly when I use the "add filament" option in the printer's menu, so I'm thinking that the physical movement is somehow causing the filament to retract? I'm open to suggestions and feedback here, as I really REALLY love 3D printing and want to continue turning all sorts of ideas into real physical objects...

Apparently the mobile version of this site doesn't want me to edit pictures into this thread, so I'll post them below. As for the Cura settings, everything not mentioned below was left at the default/autocalculated value for "Fine" quality:

Temp: 220C
Speed:25mm/s
Initial layer height: 0.3mm
Layer Height: 0.06mm
Line Width (for all in it's section): 0.4mm
Infill: 50%

For the plate adhesion section, I typically use a "raft," whose width/margin is set as high as it can without exceeding the area of the print platform, but not to exceed 15mm. I use the raft in combination with frequent leveling and glue stick application to overcome the apparent "normal" bed adhesion issue with this printer, and it usually works wonderfully for me. Until the above issue started, anyway...

Attachment 15334Attachment 15335

These pics show my most recent print, made using the settings I outlined in my earlier post. for the record, I've incrementally changed the speed/temp/layer thickness and other settings to diagnose this problem, but so far everything comes out looking like the above pics.

Also, sorry for the double post...

Do you hear clicking from the extruder when this happens? It could be a clogged nozzle or some other source of friction in the filament path. Also, the layer height you mentioned, 0.3 mm, is too thick for a 0.4 mm nozzle. In general, layer height should be no more than half the nozzle width.

Thanks for the reply, Jamcultur!

I originally heard clicking from the filament feeder gear in the very beginning. It turned out to be related to a (very) dirty feed cog. I cleaned it, printed an upgrade for the filament feeder clamp, and had no clicking or feeding issue since.

Just to be sure it isn't the issue, I'll take it apart and examine/clean that mechanism again. I'll also change the layer height to 0.2mm, and again to 0.1 if the overall issue is unchanged.

If anything changes, I'll take more pictures and post them like last time.

Edit: I accidentally reversed the two layer height values in my original post. I'll edit that post to correct it, too.

have you changed the nozzle yet ?

Clogged nozzles can sometimnes be uncleanable and nozzles are dirt cheap.
It only takes a tiny bit of crap in a small piece of filament to permamently bugger a nozzle up.

I know :-)

Okay, here's a mid-project update.

I printed Benchy. Well, the bottom of Benchy, since everything above the hull detached and looked more like a ball of wool than a boat...

So, I spent most of the early afternoon taking apart the entire thing again. I ensured the nozzle was clean (it was), re-leveled the crappy printing arm (these are supported on only one side) to discover the whole thing was leaning by about 8 degrees, and examined the tube that brings the filament to the hotend. The tube seemed rough inside, so I replaced it. The feeder gear (sorry, I still don't know what its called lol) was coated with compressed filament powder, and I noticed that after that gear all filament was slightly rough.

At that discovery, I figured the feeder was putting too much pressure on the filament, which was deforming it, creating sharp snags. Those snags likely caught whenever the hotend moved, causing the filament to stop extruding.

After lowering the feeder tension (it's an upgraded one I printed a few months ago), I started Benchy again.

So far it looks back to normal. I'll add the pics to this post once it finishes. Might be worth adding what I found to an under-extrusion troubleshooting guide?

Final update: the issue I originally posted about returned while printing Benchy with *very* conservative settings. I ended up buying a new 0.4mm nozzle, capricorn tubing, and a few other things to replace what I thought might have been causing the issue.

And while waiting for delivery, I decided to splurge and bought the FLSUN QQ-S-PRO (a delta printer with a massive print area).

I absolutely LOVE my new printer, which has shown zero issues caused by anything other than my inexperience.

I think I'll eventually cannibalize my Monoprice to build a completely custom one that runs Marlin as a tinker/hobby project. Thoughts before this thread dies/closes?

I'm with you there - a good delta is a great printer - get the bed level make sure the belts are tight - and that's pretty much all you ever need to do :-)

And aren't they great to watch :-)

Turn the old one into a corexy - the only design that's faster than a delta :-)

Ah -
https://i.all3dp.com/cdn-cgi/image/f...pg_640x640.jpg

Okay one of those - hmm, not a helluva lot you can do with that. The frame can't really be reconfigured so all you've really got is a cheap board and a few stepper motors and an extruder and hotend - alll cheap as chips bits.
I'd be inclined to stick a 0.25 mm nozzle on it and use it for small high detailed prints.

Or - you can print some extrusion: https://www.thingiverse.com/thing:4334960 surprisingly strong.
And make anything you like :-)

I'm actually transforming it into a laser engraver instead, and building a cube frame from extruded aluminum. I'm fascinated by lithographs, and the ability to MAKE them is a concept I find rather pleasing. ;)

I know I got my MP cheaply, and that is normally IS a cheap device, but I thought at least the motors and board would be worth using, with a better power supply of course.