3d printed materials

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MikeyDSlagle

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Not sure where to put this, so here seems like a good spot that will see some traffic.

I've been learning some 3d modeling with FreeCAD and have had a few pieces printed up using 3d hubs, mostly A/V bay stuff and some fin alignment devices.

These most recent items were made with PLA and the stuff seems a bit brittle. I have a Missileworks sled and seems much more robust. I understand the infill has some to do with it as well.

You folks know the kind of shock loads and what not our sleds go through and I know folks on here 3d print all kinds of neat little things for their birds. So what (affordable) material would be better for sleds, battery boxes and stuff like that?

ABS
PLA
PETG

And...
I had some centering rings printed with grooves to aid in aligning my fins. Worked like a charm, and made an easy to build fin can. I was going to get some CNC'ed but must be a really busy summer for Wingarcher and our correspondence was taking forever.

I used these skeletonized rings to align the fins on my Little John. Then I used the plywood rings outside the printed ones anyway, sandwiching them to the fin tabs.

fin rings 1.jpg 3d prints.jpg

The sleds were made to replace the plywood inside my Cowabunga nosecone. I had a few problems with it losing power and, with the way I had it built, it needed a complete overhaul anyway; and I am standardizing everything to RRC2+ so I don't have to remember all the different startup sequences. But now I am a bit concerned with the PLA being a bit brittle.

Thanks folks
Mikey D
 

djkingsley

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I tend to use PETG for my rocket parts that will be permenantly installed in the rocket. It has a higher melting point than PLA and while sitting in the sun on the pad I have had some brands of PLA soften and deform. For jigs and fixtures I use PLA pretty extensively.

For parts subject to extreme loads, I print with *** 910 Nylon, can't think of the brand name off hand. It requires an all metal hot end capable of hitting 260c, and I have better prints with a chamber around the printer. My chamber is not heated and is made out of paste board like those used in science fair displays.

I have tried ABS several times but was never happy with the results and have not spent nearly as much time tweaking settings as the other materials due to the smell.
 

Landru

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PLA will work fine. All my sleds and shrouds are PLA or PLA-PHA. The fin-cans I used to make are PLA as well.

I suggest 3 perimeters and 25% infill for strong light parts. Make sure your extrusion settings are good and the perimeter lines are in complete contact with each other or you are going to lose a lot of strength.

Also get your extrusion temperatures as high as you can while still printing well. Helps bonding a lot.


PET is also a nice tough material, but is heavier than PLA and hasn't glued as well for me.

Avoid ABS unless you really need the high temp material.
 

ttabbal

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PETG is used for the electronics sled in my L3 bird. Held up just great to a Loki M900.

As mentioned, PETG doesn't glue well. There are a couple things that work on it though. I'm using some solvent welding stuff from Weld-On that seems to work well on it. I can get the number when I get home. I also work around it by using heat-set inserts to run screws into. Which works great for battery holders, altimeter mounts, etc..

PETG has very good layer bonding, better than most materials. It's also almost as easy to print as PLA.
 

MikeyDSlagle

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PETG is used for the electronics sled in my L3 bird. Held up just great to a Loki M900.

As mentioned, PETG doesn't glue well. There are a couple things that work on it though. I'm using some solvent welding stuff from Weld-On that seems to work well on it. I can get the number when I get home. I also work around it by using heat-set inserts to run screws into. Which works great for battery holders, altimeter mounts, etc..

PETG has very good layer bonding, better than most materials. It's also almost as easy to print as PLA.
I don't intend to do much gluing to the parts but the solvent welding stuff will be good to have on hand JIC. Push comes to shove I can use larger holes and weld some threaded inserts into I will be using screws though. Either plastic thread cutting screws (something like this - https://www.mcmaster.com/#tapping-screws/=1973dcq) . Or tapping the holes to use nylon machine screws, which I would prefer. Never heard of heat set inserts. May be something for me to look at.
 

djkingsley

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If its going in a rocket I will go the extra effort to put holes for self tapping screws, the vibrations from launching have broken several welded PETG parts that I flew early in my 3d printing experience. For some of my daughters projects we use solvent to weld PLA parts with great success.
 

MikeyDSlagle

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So far everything I have come up with I have integrated standoffs with holes.

I don't have a 3d printer myself, yet, so everything goes through 3d hubs. I don't have to worry with setting up the machine and all the settings, but thanks for all the advice.
 

Cl(VII)

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Hatchbox PETG for me.

Also, PETG doesn't weld for crap...ever.
 

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