spongy prints with 0.35mm nozzle from SeeMeCNC

[knightwolf313]

I had just made a couple of small upgrades to my RMaxV2, I upgraded to the injection mold cheapskates and the spring arms, I added 2 more blower fans for print cooling, and I also put a smaller nozzle on the Hotend. All from SeeMeCNC. The printer seems to be going through the motions of printing correctly, but with longer prints it leave a 'spongy' print when printing at 40mm/s at 210C in PLA. any thoughts or suggestions?

[Glacian22]

It looks like your extruder motor is skipping for sections of the print. Are you using the stock EZstruder? If so, the increase in pressure needed for the smaller nozzle could be maxing out the available torque. Upgrading to a geared extruder would fix it if that is in fact the issue.

[geneb]

You're printing too fast with the .35 nozzle. The smaller the nozzle, the slower the print. Back it down to 30mm/sec or less until the "layer rot" goes away.

g.

[knightwolf313]

dropped speed down to 15mm/s and doing a test print now

[Eaglezsoar]

Please let us know if Geneb's idea works.

[teoman]

When i had results like that with my 0.5 nozzle I ignorantly concluded that i was going too fast (for my case) and as i needed speed over quality at the time, i switched to a 0.7mm nozzle, which did not help much.

After some time I discovered that i had charred the ptfe tube inside the hotend which was causing a restriction.

Cut a piece off my bowden tube which was probably too long to begin with and replaced the ptfe tube in the hotend with that.

Might be worth inspecting if slowing down does not cure your problems. The ptfe tube can pe bushed out of the hotend by removing the bowden adapter and the nozzle and pushing it with a screwdriver from either end.

[U.S. Water Rockets]

When I had results like that I found that increasing the extruder temp 5 to 10 degrees made the filament less viscous, and the prints came out a lot nicer.

[geneb]

Different solution to the same problem, BUT with a .35 nozzle there's physical limits as to how much material you can shove through that tiny hole at a time. Increasing the temperature will improve things up to a point - until you hit the flow rate restriction of the nozzle diameter.

Layer "rot" boils down to one or more of these things:

1. Speed too fast for current temperature
2. Speed too fast for the nozzle diameter
3. Temperature too low for the current speed
4. Artificial restriction in the filament path:
This could be one of these things:
a. PTFE tube has been over-temped and has a constricted diameter that's "grabbing" the filament.
b. Carbonzied chunk of filament that's partially blocking the nozzle
c. Oversized filament - I've run into filament that had 2mm bulges!
5. Hobbed gear teeth at the EZStruder are filled with plastic and thus greatly reducing it's "grip" on the filament. This can result in inconsistent feed rates that will
appear to be one of the first four issues.

So what did I miss? What else can cause layer rot? (and yes, this is going to end up in the manual. )

g.