Trying to climb up the curve on my new mini. Can anyone offer an informed opinion on the relationship between nozzle temp and the diameter of the extruded HIPS plastic? I can’t quote exact measurements at the moment, but while trying to measure the diameter of what came out of the 0.5 mm nozzle, so that i could try to get better prints, I discovered that at 220 C the extrusion dia was more than 0.9 mm, and it decreased in diameter as the nozzle temp increased, but always larger than 0.5 mm all the way up to 280 C! I was afraid to go to 300. The relationships between print speed,and layer thickness, and layer width, and % extrusion, etc., is already pretty nebulous to me, without worrying about the temp… and it seems to me that some clever folks may have already come up with some curves or graphs or charts…or something to help out us newbies? I had assumed that for a 0.5 mm nozzle, what came out would also be 0.5 mm …but no such luck. Must be magic. Any help would be appreciated, thanks.
Dan
Much of the nebulous relationships should be taken care of by your slicer… 
I can’t say I’ve ever checked the extrusion diameter or come across a chart plotting the relationship. It should match your nozzle, but I believe you… since you’ve done the leg work. Are you measuring the diameter of the extrusion when extruded in midair? A +.4 difference seems odd… especially if its not being extruded into anything (ie. print bed). If you’re measuring the extrusion width on the bed or “vase” type wall, then it sounds like overextrusion (check your e-steps, or tweak the flow rate).
If anything I would think a higher temp would create a less viscous extrusion more subject to the effect of gravity… contributing to a phenomenon called “ooze”. Which brings us to cooling. Are you using the cooling fan? If at 100% the extrusion should cool / solidify pretty quickly… maintaining the diameter of the nozzle.
There’s also the factor of moisture absorbed by the filament. This could lead to extrusions with bubbles… usually leaving pit marks in your layers…
My final thought would be that the accuracy of the extrusion diameter probably isn’t as meaningful as the dimensional accuracy of the final project. Print a 20x20x20 calibration cube and check the accuracy of each axis. If they are off, try varying flow rate or calibrating e-steps to get better accuracy.
Anyway… don’t sweat the small stuff.
If you read about how the filaments are manufactured you will find out that to create a ~3 MM filament they use a nozzle size that is smaller than that(2.5 MM or so). The material expands after it is forced through the small hole in the nozzle and expands due to the pressure it was under to be forced through that said small hole. The same reason you are getting a extrude that is bigger than your nozzle size.
Or at least that is what I read while researching filament manufacturing.
Thanks guys, that makes sense. Shoving a “3 mm” dia filament through a 0.5 mm hole has got to require some pressure. I had assumed that it would be a laminar flow nozzle…and maybe it is, at temps around 300 C. Did the tests at Home Z with the extruder in the middle of the x range, extruding 10 mm into thin air with the fan off, did it 4 times each at 220, 240, 260 and 280 C getting an avg of 4 threads for an estimate of the dia. Im not smarter than the slicer program, but i do want to try to understand whats happening. What goes in has gotta come out. I’m having a really hard time getting my design to print…so i gotta dig deeper.
Good experiment… make sure the filament you’re extruding can handle the temps you’re proposing. Plastic can carbonize at high heats (at prolonged lengths). This can lead to clogging of the nozzle.
Probably best to stay within the filament manufacturer’s extrusion temp recommendations.
What you are referring to is Die Swell.
https://en.wikipedia.org/wiki/Die_swell
Thanks guys. For what it’s worth, here are the results from this test. For esun 3mm HIPS on a mini; Temp (oC):dia (mm). 220:0.8, 240:0.725, 260:0.644, 280:0.563. Looks pretty linear in this range.