3D printing for HPR

[JohnCoker]

What size nozzle are you using on your printers? I found 0.6 to be the best compromise between strength and quality.

I generally use 0.4mm nozzles, and for this test all FDM parts were printed with that size.

 

[OzHybrid]

Firstly, thanks for doing these tests. It's a lot of work.

An issue is comparing apples with apples. The results are the failure point of the component as the graphed parameter, but in changing what seems like a single variable, it's actually changing more than that. This gives a general indication, but not really a specific strength indication except for that specific part.
Take the number of walls as an example. As you increase the number of walls, the strength goes up. but the overall average density has increased despite maintaining the infill density at 50%, there is now less infill due to the increased walls. I'm going to assume that you increased the number of top and bottom layers too as they are effectively top and bottom walls, but I couldn't see that specified.
The same applies for the number of ribs. If you increase the number of ribs and decrease the thickness of the ribs to maintain the same volume, the effective density has increased because you have more "wall" printed at 100%density. You get a stronger part partly because more material has been printed. If you're not decreasing the rib thickness as you add more ribs then each rib added is potentially just more strength from more material.


I agree with your conclusions that from a strength viewpoint that printed is good enough. Especially if you're printing with a Bambu.....

I've been laminating fiberglass cloth between 2 fin halves and this is giving massive strength increases as well as joining the printed layers. So I think printed parts and what you can do with them has a long way to go. Have a look here

https://www.rocketryforum.com/threads/what-are-you-printing-today.150480/post-2600755

 

[JohnCoker]

I've been laminating fiberglass cloth between 2 fin halves and this is giving massive strength increases as well as joining the printed layers.

That's a great idea. I was thinking about printing a "pocket" for a piece of CF or G-10 plate, but two halves bonded to fiberglass cloth would be much easier to do.

 

[RGostowski_FiskAerospaceT]

Great data-based analysis of this 3-D part. Have you considered making couplers with the same internal spokes?

 

[OzHybrid]

Here's a test to do.
Number of walls/density. If you increase the average density to be what it would be by increasing the number of walls which effectively increase the average density. Is the average density increase better as an infill or as extra walls? Where's the sweet spot?

 

[JohnCoker]

Here's a test to do.
Number of walls/density. If you increase the average density to be what it would be by increasing the number of walls which effectively increase the average density. Is the average density increase better as an infill or as extra walls? Where's the sweet spot?

There are tests varying the number of wall loops (3-8), among other things. I tested various parameters in isolation (testing them in combination would make the number of samples explode). https://www.jcrocket.com/printed-components.shtml#hypothesis3settings

 

[OzHybrid]

There are tests varying the number of wall loops (3-8), among other things. I tested various parameters in isolation (testing them in combination would make the number of samples explode). https://www.jcrocket.com/printed-components.shtml#hypothesis3settings

In a few years, we've learned so much about 3d printing. Bambu prints ABS straight out of the box (with the aid of a filament dryer). This is in comparison to the months I spent tweaking settings on my Tronxy 400 cube where even looking at the print caused it to fail.
It's not possible to get perfect prints by tweaking 1 setting. They usually have to be tweaked in conjunction with others. And yet here we are today with a printer that will print a filament that wants to tear itself apart as it cools (ABS), out of the box..... Witchcraft.......
I see there's now a new filament "Easy ABS" where the A,B and S components have been varied and it has lower shrinkage. It also has less temperature resistance and strength, both comparable to PETG.
I'm ONLY printing with ABS as it's cheap, strong, has good temperature resistance for a rocket in the Australian sun and can be finished or glued ot laminated with fiberglass using an ABS/acetone slush which results in chemical bonding to the component.

cnc kitchen has done a lot of testing into strength.
Extrusion width is interesting. Creating more interlayer squish.

Arc overhangs for supportless overhangs.


I've also done some work with shaped components used as density modifiers at an overhang to easily create something similar.


Applying density modifiers in a component can give support or significantly increase strength where it's needed without an overall weight penalty if you can claim back a weight saving elsewhere.

 

[rharshberger]

In a few years, we've learned so much about 3d printing. Bambu prints ABS straight out of the box (with the aid of a filament dryer). This is in comparison to the months I spent tweaking settings on my Tronxy 400 cube where even looking at the print caused it to fail.
It's not possible to get perfect prints by tweaking 1 setting. They usually have to be tweaked in conjunction with others. And yet here we are today with a printer that will print a filament that wants to tear itself apart as it cools (ABS), out of the box..... Witchcraft.......
I see there's now a new filament "Easy ABS" where the A,B and S components have been varied and it has lower shrinkage. It also has less temperature resistance and strength, both comparable to PETG.
I'm ONLY printing with ABS as it's cheap, strong, has good temperature resistance for a rocket in the Australian sun and can be finished or glued ot laminated with fiberglass using an ABS/acetone slush which results in chemical bonding to the component.

cnc kitchen has done a lot of testing into strength.
Extrusion width is interesting. Creating more interlayer squish.

Arc overhangs for supportless overhangs.


I've also done some work with shaped components used as density modifiers at an overhang to easily create something similar.
View attachment 653383

Applying density modifiers in a component can give support or significantly increase strength where it's needed without an overall weight penalty if you can claim back a weight saving elsewhere.

Yes the printers have gotten better, but the Slicers are where the fiddly stuff gets done. My old version of CURA was okay, but it took a bit of tweaking, the newer 5.7.1 version I am using printed PETG with only minor temp adjustment straight out of the "box". I did not carry over my profiles from the old version specifically to see if the slicer had gotten any better or not.

 

[JohnCoker]

Applying density modifiers in a component can give support or significantly increase strength where it's needed without an overall weight penalty if you can claim back a weight saving elsewhere.

Agreed. Here I was trying to come up with a general set of parameters so people could get good results for structural parts. Of course you can tweak any individual component, but I believe I have posted good settings to start with, at least for ABS.