Bambu PET-CF BambuStudio Settings

MrSteve

Hey all, I'm going to run an annealing test for the Bambu PET-CF (it recommends doing so) with a test cube and have a few questions regarding the print settings. The orca docs say to run this with the same print settings as the parts to see how much shrinkage happens on each axis. Onto the questions:
1) before anything, I am using Bambu Studio for the slicer, should I continue with this slicer or should I just switch over to something like Cura?
2) all of the parts have infill modifiers, so does that mean I have to import those modifiers for each part and print separate cubes for them, or will one cube test be enough with no modifiers?
3) will I need to worry about switching anything for the Mask?
4) Are there any other weird advanced settings I need to worry about other than the things listed in the doc?
5) should I bother using another filament for supports?

Separate question: Do I need to anneal right after the print finishes or could I wait a few days to anneal everything all at once?

Thank you very much

hoffmantactical

MrSteve Cool! Will be interesting to see the results, as I've not tried annealing any PET-CF yet. To try and address your questions:

I'd stick with Bambu if you are using a Bambu printer, otherwise just use Prusa.
With lowers the outer perimeters is what effects the shrinkage. Infill only makes an impact if it's pretty thick or has large flat sections.
So I'd not worry about the masked areas.
Annealing is pretty much just a scaling issue, though warping could be an issue, and there is little on the slicing end of things that will fix this.
Probably not worth the trouble, but could be fun.

I think it's best to anneal quickly to eliminate any effects water might have, but with PET-CF this is probably a non issue. Definitely leave the supports on.

To address number two from above a bit better, you need to look at how the part shrinks. There are two types of shrinkage. The first is absolute shrinkage, the actual print lines becoming shorter. The other is line to line shrinkage, the layers and lines shrinking together. Generally the line to line shrinkage is the significant one, though absolute shrinkage can be high with some unfilled Nylons and PLA.

Print a long sample with aligned infill and use that to determine absolute shrinkage. If you make the sample wide enough you can also use it for line to line shrinkage on the horizontal axis. If you measure it in the middle the perimeters at the ends will have no effect. I'd print a second sample for the Z axis.

An interesting part of these two modes of shrinkage is that many infills below 100% will shrink at the absolute level, possibly very little. Mostly it's the Z axis and parallel lines compacting.

Would be interesting to get some theories on why the line to line is typically greater then the absolute.

kjufer

hoffmantactical Do you use the .6 nozzle while using the pet-cf and how does that affect the orca prints?

MrSteve

Thanks for the response!
In my opinion, the line to line shrinkage could be greater due to the forces keeping the layers together playing a greater role in that specific scenario rather than just thermal expansion and contraction. When the part cools after annealing and impurities are "heated out" of the crystalline structure, the overall size of the individual lines all shrink somewhat at the same time, causing a temporary large strain between the layer lines. These lines then contract toward each other more forcefully and with greater impact vs the mass and size loss from the impurity loss alone, which is probably why warping becomes even more of an issue as well.
This is just my 2 cents though and not that detailed, I only have taken an introductory materials science class (and didn't really pay that much attention)
I will get some calipers and heat the test parts tomorrow in an oven according to the Bambu guidelines, and post the shrinkage results here. I'll do a small test cube as well as some longer and taller prints to fine tune the shrinkage measurements.

hoffmantactical

kjufer I try to use a 0.5 or 0.6 with the Bambu to prevent clogging. 0.4 works with others. 0.6 will produce a rougher finish, but works.