FDM Nozzle Sizes

Yes, it will print finer detail better, but with 3 big tradeoffs, IMO:

1. It takes, more or less, twice as long to print

2. The smaller nozzle is [exponentially] easier to clog

3. It loses strength

So combine the 2, and get a few days into printing something only to have it ruined by a clog and you have to weigh the risk vs. the reward.  For something with a lot of fine detail, the ability to print at .08mm layer lines instead of the .12 minimum with a .4 has its benefits, but just be aware that its not all roses.

The parts I'm considering printing with a smaller nozzle are tiny to begin with. This would be like doors and hand railings. It's really the stuff resin printers do better at. I figured the time would extend but I bet it won't be an issue on such small pieces. I'm very worried about clogs though. Especially since I have a bowden system and I've been lead to believe you have better extrusion control with a direct drive.

Spent 10+ years doing FDM. Simple rule, layer height and nozzle size should be withing a ratio. Yes, you can stray from that ratio and get results, but the "ideal" ratio is layer height = 3/4 to 1/2 nozzle diameter.

The "why"- The nozzle guides and squishes the round noodle of hot filament coming out into the previous layer causing it to oval and make more surface contact or bond for strength. Think of it like stacking round pencils in parallel. If fully round, minimal contact is made. If you flatten that, you get more ideal bonding.

VS

That said, as you go below 1/2 towards 1/4 layer height  to nozzle ratio, you are possibly beginning to shear and deform the polymer bonds in the filament (just because it's liquid- it's plastic so it's a polymer chain) especially when trying to go fast. At the same time, backpressure is causing the hotend dynamics to change and your filament melt cap (the liquid filament that squishes up beside the incoming rigid solid filament can push up to a point and cool causing hotend jamming.

Also my favorite nozzles were the 3DSolex nozzles. I was first introduced to them when Martin Bondéus first showed them to me up at Midwest RepRap Fest in 2017. The key to them was they are micro-drilled on a 5 axis CNC with multiple filament melting paths. This allows higher flow rates and lower nozzle temps. Most plain jane straight bore nozzles are run hotter than needed because of low thermal transfer to melting the filament- especially at higher flow rates.

VS typical straight bore

Also, at lower ratios, as somewhat seen in the first pictures above, the landing zone or tip of the nozzle has a huge effect on lower layer height ratios as the trailing edge is pushing and smoothing and forming that width of the resulting layer width of filament. A pointy nozzle with limited lip will not effectively shape or comb the layer making it look more like a plowed field than a smooth layer.

@Boilermaker1 posted:

Yes, it will print finer detail better, but with 3 big tradeoffs, IMO:

1. It takes, more or less, twice as long to print

2. The smaller nozzle is [exponentially] easier to clog

3. It loses strength

So combine the 2, and get a few days into printing something only to have it ruined by a clog and you have to weigh the risk vs. the reward.  For something with a lot of fine detail, the ability to print at .08mm layer lines instead of the .12 minimum with a .4 has its benefits, but just be aware that its not all roses.

Agree 100% with the above and sorry for my previous long winded detailed explanation.

In order to effectively and reliably use smaller nozzles, your feeder system (I consider the extruder to be a system of subsystems) and hotend must be the best they can be due to the longer print times, higher pressure rate inside the extruder, and slower raw incoming filament rate typically when using small layer heights and small nozzles.

I can teach and guide someone how to do it, what parts I typically used, how I tuned it, but in the end- today a resin printer and the resin formulations- let alone cost are much better than they were as I was getting out of the hobby.

Using the right tool for the right job- it got easier and cheaper.

This is some very helpful info @Vernon Barry. I'm printing at a 1/4 ratio now, if I understand you correctly. I print at 0.1mm layer height with my 0.4mm nozzle. My results have been great. I've printed that way for a while. I did clog a hot end this month and I couldn't seem to fix it.

Anyway, I appreciate the bit on the ratios. I wish I had that when I got started because it would have saved me a lot of trial and error.

I wouldn't mind trying the fancier nozzle. It makes sense that it would be better than a straight bore and I would be very happy to be happy to print a little bit faster.