Discovered an interesting fault with the use of steel nozzles in brass heat blocks.

Steel nozzles are recommended for abrasive materials FDM printing. There are also ruby and even diamond tip nozzles to “reduce wear”.

There are other benefits touted such as "food safe" and heat tolerant. But not in my scope here.

In my opinion, based on my knowledge of fluid flow dynamics and surface barrier effects and relative low flow rates of FDM extrusion, The concern of “hole enlargement” is a ruse. At worst there may may be an infinitesimal polishing of the bore but not an increase of diameter of say… 0.40mm to 0.50mm.  Even it there was, print performance change would be totally invisible over the time required. 

What does happen is the flat face of the tip will wear down much faster due to drag on the material. This is high speed rubbing with much more force in the wear direction. Part of the tip face is actually used to smooth and “polish” the adjacent row, depending on the width of the print line chosen.

So, wear is true, but more to the face of the nozzle than the bore.

But I discovered an issue with dissimilar materials. Steel nozzles in Brass heat blocks,

I assumed expansion rates are different between metal but with the amount involved, it would be quite infinitesimal. I am wrong about that assumption.

I have an IDEX printer, upon which I installed two steel nozzle extruder modules. All was well at first.

However, after several dozens of hours of print time, I noticed blobs contaminating  my prints. BLOBS !! ?  Where did that come from?

AH… around the nozzle base. The steel nozzle was a loose. I would say about a 10+ degree turn loose. Snug, but loose enough to leak.

Not just one, but both extruders suffered this fault. Maybe a one time event, but don’t know that yet. Will be paying close attention. May be a “thing” with steel in brass screw threads.

Just a “heads up” (or maybe down) if you notice blobs forming on your steel print nozzles.