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When I load filament through the nozzle, it wants curl up and stick to the nozzles face. if I pull it off and get a straight piece that has cooled before it makes it to the plate and measure it, it isn't round but rectangle, measuring .54 x .67 mm. My Replicator has a .4 nozzle and squirts round, no curl up and dries to .34

When I was first tuning my machine the nozzle swept across and downward, ( bad setting in firmware ) crashing into my lexan build surface.
I'm thinking this must have distorted the tip. I did order a new one. I just can't believe how much smaller the .4 replicator nozzle puts out..

I have had alot of issues printing, especially infill. And I wounder if the nozzle could be a lot of it. I even wounder if I got the .7 nozzle by accident. I read someone else did..

Bill

I would run a 0.5mm drill through the existing nozzle you can do it with the drill in your fingers.
The odds are something is jamming the tip, possibly the lexan you ran it onto or something in the filament ...
In general free air extrusion will be greater than nozzle size because of die swell, you could easily see a free air extrusion in the 0.6mm to 0.9mm range from a 0.5mm tip, depending on the plastic and other factors, it should however be round.

Here is an update for you guys, I confirmed that my Rostock was shipped with a .7 nozzle, instead of the .5..

I think that has caused a lot of my issues...

Bill