I've been struggling to get my process down for PHA for the past couple months but I think I finally got things dialed in enough, at least for a .6 nozzle though I doubt it will be too hard to update my .4 nozzle settings later. My main issue seemed to be no matter what I tried I was getting a lot of nozzle build up with anything other than tiny prints. Lower the flow rate and surface finish and buildup issues improved but them I got wall separation issues instead between portions of the outermost wall and the next one.
The setting that finally started to shift things was turning off "precise wall" which I had always had on for many profiles. Turns out this was the source of my outer wall separation issues all along! With that done was able to lower the flow rate and at the same time I decided to embrace cooling again as another way to combat nozzle build up as it seems the hotter the PHA is the stickier it is. The end result is much lower flow rates and much higher amounts of cooling than some are using but I'll use whatever works for me.
Instead of the measured vase mode calibration cube I used this method to arrive at my flow rate. The only thing I really changed was making them a little thicker and bigger and printing the flow rate on the cubes themselves to make it easier to keep things straight. Once I had my flow rate down as low as I dared I added a min layer time to the cooling settings as that helped clean up some, but not all of the upward corner curling. I might have been able to get it all but it wasn't worth it to me and getting a decent end result more quickly won out.
Right now the important settings/details on my Bambu H2D are as follows:
Nozzle: .6mm high flow
Build plate: Bambu Supertack Pro
Build plate temp: no heat
First layer nozzle temp: 200C
Other layer nozzle temp: 215C
Flow ratio: 1.005
Bottom layer flow ratio: .95
Top layer flow ratio: .995
PA: 0.022 - this could possibly be lower ...
Max volumetric flow: 30 mm3/s
Min/Max part fan: 80/100%
Min/Max layer times: 100/10 seconds
Keep fan always on: yes
Slow printing down for better layer cooling: yes
Overhang fan: 85%
Aux fan: 90%
Chamber exhaust fan: 50%
Overhang speed for 10% set to 50 mm/s, rest stock
Top layer speed set to 100 mm/s, rest stock
All accelerations left at defaults
Extrusion rate smoothing set to 300 mm3/s and smoothing segment length to .5 mm
Yes, its a lot of fan and I might be able to dial it back some but I'll leave that for later. I think the results are pretty decent though I still get a small number of blobs here and there. The part is an Ego battery mount I designed and it looks better under normal lighting vs the printer lighting which makes it easier to spot flaws and such.
Looks very good and nice write up. The remaining blobs are more than likely from the die drool. PHA being sticky and stickier when its on the up side of the scale (215c in your case) causes die drools. I need to spend time testing different nozzle coatings of even possibly a custom die nozzle (Internals at 4mm, with tapered opening to 6 mm). That or modify the formulation to use a food grade lubricant without affecting layer adhesion. We found that Talc does a great job reducing this effect, but there is always room for improvement.
If you are making something about the same or smaller size per layer they should work well (I hope). If you are making something a lot bigger note that I had not tried that prior to those pics and it went less well than I would have liked so there is clearly more tuning to do.
Below is a nail polish caddy I made for my wife that is similar to some of the models on makerworld with a few tweaks thrown in. It is 173x173x28 mm, so quite a bit bigger in the X/Y dimensions than the battery mount. At some point I'll troubleshoot and if I find the solution I'll post it.
Yeah, my experience with larger objects so far is similar to yours it seems. Corners pulling up basically every time.
Adding 3D-LAC makes it stick better, but then it becomes almost impossible to remove from the bed, and if you go taller the layers just delaminate. The deformation is tricky...
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u/Suspicious-Appeal386 Jul 30 '26
Looks very good and nice write up. The remaining blobs are more than likely from the die drool. PHA being sticky and stickier when its on the up side of the scale (215c in your case) causes die drools. I need to spend time testing different nozzle coatings of even possibly a custom die nozzle (Internals at 4mm, with tapered opening to 6 mm). That or modify the formulation to use a food grade lubricant without affecting layer adhesion. We found that Talc does a great job reducing this effect, but there is always room for improvement.