Issues Using Stainless Steel Nozzle

Because I plan on printing with filled filaments soon, I decided to go to ebay and get some cheap stainless steel nozzles for my hotend in order to reduce wear. I figured they could also be used for normal plastics as well, mainly so I don't need to swap nozzles all the time. I tested out the extruder with a temperature calibration print (different temperatures at different layers) that went from 220 to 175C in 5 degree increments. I printed it before with a brass nozzle, and to my surprise, I could barely tell the difference between 220 and 175. When I printed it with the stainless nozzle, it failed after 200C with, what looked like, severe under extrusion. The layers, even at 220, were very weakly held together; I could easily pry the print apart with my hands, and it was even weaker than a print at 170C with a brass nozzle. The filament wasn't grinding, and it seemed like the stepper motor was still extruding filament, but maybe it wasn't extruding enough filament. I'm not sure what was happening, as there are no signs of clogging, and apart from the print's results, it didn't seem like the extruder was under-extruding; I had it pretty well tuned before with the brass nozzle.

I did notice that when the plastic was extruded into mid-air, the lines of filament were a little bit thicker, which suggests a wider opening in the nozzle, but I don't think this would be the issue, as the first few layers of the print went down flawlessly.

Anyway, is this typical of stainless steel nozzles? I know they have poor thermal conduction when compared to brass, but I didn't think it would equate to a ~50C difference in print temperature.

Info about printer and nozzle:
Stock MK10 extruder
0.4mm (supposedly) stainless nozzle from HERE
Folger Tech FT-5 3d printer
BAM!Tack silver (not filled, just color) PLA filament from HERE (Great results with brass nozzle)

Stainless steel transports heat a lot worse than brass. If the thermal sensor isn''t extremely close to the opening of the nozzle you will get wrong temperatures and the actual temperature of the nozzle can be a lot lower than shown.
The swelling of the filament is completely normal when extruding free into air.

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Quote
Srek
Stainless steel transports heat a lot worse than brass. If the thermal sensor isn''t extremely close to the opening of the nozzle you will get wrong temperatures and the actual temperature of the nozzle can be a lot lower than shown.

So should I just increase the temperatures to make up for the difference, or would that not be a good idea due to the PTFE lining in the hotend? The 14C ambient temperature where I print probably doesn't help things very much, but it seems like my MK10 extruder would just be incapable of using a low-conduction nozzle like this. At this point, it just seems like using brass nozzles and replacing them every so often is the only way for me to go if I don't want to replace my entire hotend. Honestly, I probably won't even print with filled materials very often, and the only one I have is bronze-filled, so it should be fine.

Oh, and here's the hotend so you can look at it. The thermister is highlighted in red, and yeah, it's pretty far away from the actual nozzle.

From that picture, you have the nozzle too far out, that will make things worse, you need to screw in the nozzle all the way in and I would recommend you to cover the heater block with fiberglass or ceramic fiber.

SS nozzles will take longer to heat up, but once heated will be more stable than the brass ones, don't raise the temperature but rather let it heat a little longer before start printing.

Edited 1 time(s). Last edit at 12/13/2016 05:47PM by ggherbaz.

Quote
ggherbaz
From that picture, you have the nozzle too far out, that will make things worse, you need to screw in the nozzle all the way in and I would recommend you to cover the heater block with fiberglass or ceramic fiber.

SS nozzles will take longer to heat up, but once heated will be more stable than the brass ones, don't raise the temperature but rather let it heat a little longer before start printing.

Well, my problem is that the way this extruder block is designed, the PTFE-lined threaded rod (melting chamber?) has to thread into that aluminum block along with the nozzle (It's the same hole). If I did screw in the stainless nozzle all the way in without the melting chamber attached, there would be no more threads in the aluminum heater block left for the threads on the melting chamber. This nozzle was designed for E3D hotends, so this would likely be less of an issue for those, but with my current configuration, I can't really thread the nozzle in any farther.

Perhaps if I do the "volcano mod" (I've heard a lot about it with the FT-5, I don't know much about it) I'll have enough thread space to screw in the nozzle all the way, but for now, I think I'll have to stick with brass.

Usually nozzles have about 5 to 6 mm threaded section, heater blocks are usually 12 mm tall which allows for a 6 and 6 mm connection. You might have a 10mm block and maybe a volcano style nozzle?

You can get a thicker block or as you mention a volcano block on Aliexpress for few bucks.

Yeah, I'll probably go with that. I actually think that my heater block is less than 1cm thick, so that could be the issue right there. It looks like the standard MK10 extruders that some makerbots have, but it could definitely use an upgrade. Thanks for your help!