3D Printing Weight of 3D Printed Body Tubes

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BigMacDaddy

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In one of the other threads the conversation turned to (touched on) fully 3D printed rockets. I have always avoided printing body tubes whenever possible and instead prefer to print parts that fit on standard Estes cardboard body tubes. Someone posted that they have 3D printed lots of complete rockets and that "I do not think that they are that much heavier" so I was curious about what the difference in weight is.

Quick table below -- for the purpose of this quick analysis I basically selected the stock Estes body tube and trusted the thickness and weight that was presented in OpenRocket for the stock Estes cardboard tube (with the exception of the BT-80 which is obviously incorrect so I weighed a couple of those). Then I switched the material to "Printed PLA" and changed the Wall Thickness to either .8mm or 1.2mm (representing 2x or 3x .4mm layers). Obviously weighing everything would be more accurate but I was just trying to get a rough approximation for the increased weight. These are all 18" long tubes except the BT-80 which is the stock 14.25". The weights listed are in grams with the multiplier indicating the ratio of the 3D printed weight to the cardboard tube weight.

1650117901154.png

So the printed body tubes range from 2.4x to 7.1x as heavy as the cardboard tubes with total weight increases of a range of 20g to 80g. Obviously, whether the 3D printed body tube is "too heavy" is going to depend on your design, purpose, how large an engine you want to use, etc... I would also point out (for anyone that happens to come across this that is new to rockets) that often increasing weight in the rear of the rocket forces us to offset that with more weight in the nose to create similar stability. Generally speaking a fully 3D printed rocket shifts weight backward as compared to a rocket with a plastic nose cone, cardboard body tube, balsa fins, and cardboard engine mount. Given this, some designs will see the increased weight being further compounded if nose weight is needed to stabilize the rocket.

What the heck I will look at the weight of fins also... This analysis is simply looking at 4x flat fins that are 5cmx5cm in size (obviously the real benefit in 3D printed fins is in the cool shapes you can print but I was just curious about weight). This also assumes a solid print which would be the case if you just printed a flat fin that is not too thick.

1650116096792.png

Not as much of an increase as I would have guessed (at least not over plywood that I usually use). Balsa is still the king when it comes to light fins but I still think that 1.5-2mm plywood is a good balance of strength, finishing, weight, etc...
 

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cwbullet

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Great info. I think the key with 3D printing is similar to using metal or fiberglass. If you plan to fly light, use as little as possible.
 

Kelly

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It would be interesting to see such a comparison done using paper (or any other material) vs printed plastic on an equal strength basis. That is, compare a paper body tube to a PLA body tube that is printed with whatever thickness assures that the two are equivalent in strength. Or, if we're comparing fins, look at parts with equivalent stiffness.
 

BigMacDaddy

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It would be interesting to see such a comparison done using paper (or any other material) vs printed plastic on an equal strength basis. That is, compare a paper body tube to a PLA body tube that is printed with whatever thickness assures that the two are equivalent in strength. Or, if we're comparing fins, look at parts with equivalent stiffness.

I agree -- I have often thought about this with fins...

However, the idea of "strength" is actually pretty complicated (especially w/ 3D printed parts and designs). For example, a 3D printed body tube is relatively strong to vertical compression but not particularly strong along Z-axis for sideways stress (especially w/ only 2 perimeters).
 

lowga

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This is a great thread on a number of levels. My preference is to use 3D printed parts with cardboard tubes...but sometimes I will "kit bash" to achieve the desired result. For instance, I am currently working on an Estes 7240 Honest John. The fin can is 3D printed from Boyce Aerospace, the nose cone is plastic from the 7240 kit. the body tube is Mach 1 BT-60 thin-wall fiberglass.

The specs for the build are to create a park-flyer version of the Honest John variant called "Father John." Boyce Aerospace was nice enough to design and print the air brakes, which will be fly away on launch but look great on display.

I wanted something that would be rugged, easy to fly, and be large enough to use a Jolly Logic Chute Release to keep the rocket close to the pad. The other option is a nose cone deploy altimeter.

Waiting for a warm day to spray primer, and then on to finishing. Certainly the thin wall fiberglass it heavier than cardboard, but not so much as a 3-D printed tube would be--and much stronger in all axis.

I may try a go at having the motor band and some (prototype) launch lugs made for the rocket. That would add more scale realism.

HoJo 7240 Kitbash 2.jpg HoJo 7240 KitBash Fin Can.jpg HoJo 7240 Kitbase tube.jpg HoJo 7240 Kitbash 2.jpg HoJo 7240 KitBash Fin Can.jpg HoJo 7240 Kitbase tube.jpg
 

dr wogz

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That has always been one of my argument. 3D printing isn't a replacement, it's an alternative. And I feel a few (a lot?!) seem to think the strength / robustness is equal to or only slightly inferior to the traditional materials; paper, wood, etc.. it's not. (And we've all seen how susceptible it it to heat & UV..) Many will also print to make it easy / quick to print, and that can create a weak part (3D printed parts are weakest parallel to the layers, as with the wood grain) Or try to print the part in one shot.. Breaking the part into multiple pieces, orienting them accordingly on the bed, then making an assembly will yield a stronger part. but that takes time & effort. 3D printing is supposed to be quick.. (or so it's believed..)

But then again, I've never understood someone who prints a part such as a tube, when tubes are readily available (and stronger / lighter). 3D printing is great a really complex shapes & geometries.. Why use it as a substitute?
 

vcp

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The models I built for NARAM60 were wholly or largely 3D printed with the following considerations:
  • ABS printed single-layer vase mode, ~0.4mm walls.
  • print striations were not filled, but rather sanded smooth and wax-finished.
  • sanding reduced the single-layer weight by ~15 percent.
  • fin fillets were integrated, and perfect.
  • all shapes were blended aerodynamically.
  • fin alignment was 'perfect'.
  • bright plastic colors eliminated paint.
 

BigMacDaddy

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I had a few shipping and other heavier tubes so wanted to see how these compared to the equivalent 3D printed tubes. The results were surprising to me - at least for the heavier duty shipping tube.

I weighed three of the tubes I had (circled or with arrow pointing to them in picture below) and then modeled a tube with same OD and 1.2mm thick sides to see how much it would weigh (I just used Prusa Slicer estimates for grams of filament used).

1652040961061.png

Right Bottom Tube: 283x78.7mm (Cardboard: 57.3g / ABS Print: 86.04g 10h17m)
Middle White Tube: 483x80mm (Cardboard: 162g / ABS Print: 149.43 17h55m)
Partial Section of HiC Container: 112.5x103mm (Cardboard: 33g / ABS Print: 45g 5h20m)

So the white heavy duty shipping tube weighs 9% more than the 3D print would weigh. The other two cardboard tubes weigh less - 27% and 34%. I think that all these tubes are stronger than a 1.2mm printed tube -- at least against cracks on Z-direction but maybe not against dings. The white shipping tube is really heavy duty -- may need to make a static model out of that one. Big advantage in print speed and small cost savings since these tubes were all free.
 

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I print exclusively in ABS. This is because it can be dissolved in acetone and the slush can be used for bonding. Others like other filament choices, that's theirs, this is mine.
Recently fully printed a Minie Magg with GF cloth/ABS slush covering on the body tube and internally GF cloth lined nosecone.
Standard nosecone blown PVC 280gm, printed ABS GF reinforced190gm
Standard without motor 1500gm ..Printed, Finished with G64 1200gm. The disadvantage of printing is that it's layers. The GF reinforcement allows you to add a lot of strength and non layer dependant strength. You can add density adjustment blocks in CURA to increase the fill in local spots where you need additional strength. With normal construction, the material you are using would be homogeneous. More strength would be a tube that's stronger and heavier overall.
So short version is that for a MPR rocket, I reckon I can make something for the same purpose 25-30% lighter in ABS. That does take a bit of effort elsewhere.
 

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That has always been one of my argument. 3D printing isn't a replacement, it's an alternative. And I feel a few (a lot?!) seem to think the strength / robustness is equal to or only slightly inferior to the traditional materials; paper, wood, etc.. it's not. (And we've all seen how susceptible it it to heat & UV..) Many will also print to make it easy / quick to print, and that can create a weak part (3D printed parts are weakest parallel to the layers, as with the wood grain) Or try to print the part in one shot.. Breaking the part into multiple pieces, orienting them accordingly on the bed, then making an assembly will yield a stronger part. but that takes time & effort. 3D printing is supposed to be quick.. (or so it's believed..)

But then again, I've never understood someone who prints a part such as a tube, when tubes are readily available (and stronger / lighter). 3D printing is great a really complex shapes & geometries.. Why use it as a substitute?
Why print a tube?
I cannot even buy a full length of 29mm motor mount cardboard tube here in Australia. When I tried to buy some in US and ship here, it was 120 US$ for shipping alone. That forces me to look at alternatives. Including printing tubes. If I have to do that, I'll make the best tube I can. Once that methodology is done, I can create any tube I want. I'm nearly there.
Also as things change, the change accelerates.
Here's a link to the latest CURA profiles.
Wowsers is all I've got, having just tested it...... :)
Minie Magg nosecone was 24hr print before (and I was printing it quick) down to 13Hrs 35Mins

:)
 
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BigMacDaddy

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Why print a tube?
I cannot even buy a full length of 29mm motor mount cardboard tube here in Australia. When I tried to buy some in US and ship here, it was 120 US$ for shipping alone. That forces me to look at alternatives. Including printing tubes. If I have to do that, I'll make the best tube I can. Once that methodology is done, I can create any tube I want. I'm nearly there.
Also as things change, the change accelerates.
Here's a link to the latest CURA profiles.
Wowsers is all I've got, having just tested it...... :)
Minie Magg nosecone was 24hr print before (and I was printing it quick) down to 13Hrs 35Mins

:)


For sure if I lived in many other countries where parts are less available that would dramatically change the value proposition for fully 3D printed rockets. Although I would still see how much it was to ship a large shipment of body tubes, plywood sheets, Kevlar line, etc... before I shipped a bunch of kits.
 
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