3D Printing Weight of 3D Printed Body Tubes

[Rustie0125]

When comparing the strength of printed components it's tricky. With 3D printing, you get the option to create significant strength from structure. If I was printing a centering ring, it wouldn't just be a disc. It would have structure. Might also have some threaded insert pads. This also holds for tubes. It would be double walled with a honeycomb spacer if printed, not just extruded as a coil of hot plastic on top of the next stacked up ring of plastic. That would be a bad design for that construction methodology. Might even have a super light glass epoxy cover. So comparing a badly designed bit of wood that was used simply because it exists as a poorly laminated sheet to a disc of plastic printed to look like the badly designed disc, is irrelevant. ish....
View attachment 581630

So funny enough forcing a structure into a double wall for me has turned out bad. I'm not saying double walls are bad. They are good. But what I found was when I try add structure to the internal walls the surface is horrible, see images attached. But when you design the wall as solid 3mm width and get good at the slicer. You are able to get smooth clean walls. While printing 1layer thinkess. I assume cura is just better at figuring out what settings it needs to get the best surface finish and its lighter. So that's the method om testing at the moment. Here is Pic of the same tube but I let cura figure out what settings was needed.

 

[cwbullet]

So funny enough forcing a structure into a double wall for me has turned out bad. I'm not saying double walls are bad. They are good. But what I found was when I try add structure to the internal walls the surface is horrible, see images attached. But when you design the wall as solid 3mm width and get good at the slicer. You are able to get smooth clean walls. While printing 1layer thinkess. I assume cura is just better at figuring out what settings it needs to get the best surface finish and its lighter. So that's the method om testing at the moment. Here is Pic of the same tube but I let cura figure out what settings was needed.

You have an issue with under extrusion.

 

[Rustie0125]

You have an issue with under extrusion.

The images probably not clear this is not an under extrution problem. It's actually the opposite. The surface issues are material that should not be there as the retraction rate vs the start of the next print is so close together it forms a loop on the outside of the surface rather then just a square between the walls

 

[Rustie0125]

The images probably not clear this is not an under extrution problem. It's actually the opposite. The surface issues are material that should not be there as the retraction rate vs the start of the next print is so close together it forms a loop on the outside of the surface rather then just a square between the walls

Remember this is not normal PLA it's active foaming

 

[Rustie0125]

Apologies; I did not consider cost (just time and mechanical properties). To be fair, the OP is listed as being in the US (New Jersey).

That I can understand fully! It'll be interesting to see what comes of these tests.

Well interestingly enough even the cost aspect of conventional tubes can be more expensive then 3D printed ones, Im based in Canada so one would think i can get cheap ground shipping but no.. due to the size and shape they only use couriers. here is the math.

So while im on this mission to design all 3D printed rockets, iv been printing 40mm diameter body tubes so that would be BT60 1.64" OD. And iv finally been able to get the weight done below that of BT60 tube for a linear foot. To prove this I ordered two lengths of BT60 tubes from my local online store which is 2 hours away(GTA).
So shipping is my only option. Due to the shape of the tubes 18" lenghts I would need x2 for a 30+ inch rocket. They cost me $CA4.10 per tube with tax. That's $8.20 for both. Plus shipping of $18 because of their shape.
That's $26.20 two get a single rocket worth of tube here. A roll of LW-PLA cost me CA $34 on Amazon(prime) and I can print 260" inches of linear tube from a single roll of filament.
I could drive to local hobby shop spend the fuel and buy bulk to get the cost down but I could also just get the roll of filament delivered to my door..
Food for thought

 

[cwbullet]

Post an STL, and I will try to print it. I am pretty sure I can.

 

[OzHybrid]

So funny enough forcing a structure into a double wall for me has turned out bad. I'm not saying double walls are bad. They are good. But what I found was when I try add structure to the internal walls the surface is horrible, see images attached. But when you design the wall as solid 3mm width and get good at the slicer. You are able to get smooth clean walls. While printing 1layer thinkess. I assume cura is just better at figuring out what settings it needs to get the best surface finish and its lighter. So that's the method om testing at the moment. Here is Pic of the same tube but I let cura figure out what settings was needed.

There's a new slicing mode coming out which would improve double wall strength. It's an angled slice. So the inner wall would be higher than the outer . This would give a longer bonding length between layers and should significantly improve the strength.
It amazes me what massive improvements are still available with software changes still using the same hardware.
Norm

 

[Rustie0125]

There's a new slicing mode coming out which would improve double wall strength. It's an angled slice. So the inner wall would be higher than the outer . This would give a longer bonding length between layers and should significantly improve the strength.
It amazes me what massive improvements are still available with software changes still using the same hardware.
Norm

Sounds promising, when I'm worried about layer separation I generally tilt the entire print 5 or 10 degrees and print on support. This also makes so that load is spread across multiple layers. Only used it on fins so far so the layer lines are not parallel to the forces. Iv never had issues so not sure how needed it is in the first place. Rockets are a compressive load along the body and the tubes are the strongest in that direction.. iv only tried LPR however

 

[Rustie0125]

Best of both worlds? Here is PLA+ connectors on end total of 4g and the double wall LW-PLA single layer wall thickness. Total 23g.. so I'm back in single 0.8mm PLA only territory. So if 28g is my worst and 11g best I'm hoping to fall somewhere in the 14 to 18g gram range with strong method.

This version is more sturdy and stick then the PLA version which is impressive but the double wall is costing me the weight.

Going to try single outer wall but with corrugated inside and no inner wall. Maybe some horizontal rings spaced out to give structure.

 

[Rustie0125]

Post an STL, and I will try to print it. I am pretty sure I can.

You welcome to try, See attached, LW-PLA 0.4mm nozzle single wall, outside and inside. really challenging print, I managed to get it to work with PLA but active foaming stuff the retraction speed seems to be the biggest headache

 

[cwbullet]

You welcome to try, See attached, LW-PLA 0.4mm nozzle single wall, outside and inside. really challenging print, I managed to get it to work with PLA but active foaming stuff the retraction speed seems to be the biggest headache

I will give it a try tonight. I will try PLA, PLA+, PETG, Nylon, and PC blend. I have five printers loaded and ready to go.

 

[Rustie0125]

I will give it a try tonight. I will try PLA, PLA+, PETG, Nylon, and PC blend. I have five printers loaded and ready to go.

Cool. I don't think you will have any Issue with PLA blends, PC and PETG is going to be another story. but the weights will be interesting to see.

 

[cwbullet]

Cool. I don't think you will have any Issue with PLA blends, PC and PETG is going to be another story. but the weights will be interesting to see.

I have no issue printing PC, PC Blend, or PETG, Once you have them dialed in on your printer, they are easy.

 

[shockie]

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.

View attachment 514493

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.

View attachment 514490

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 It still think that 1.5-2mm plywood is a good balance of strength, finishing, weight, etc...

What infill percentage and infill pattern did you use in printing the body tubes.

It seems to me, those 2 settings would show some optimal results, ie a balance of strength and weight.

And of course the result would be different for each and every filament.

Also, could not the wall thickness be even thinner by using petg-cf but have perhaps greater strength?

Finally, why not .2mm for later level?

 

[BigMacDaddy]

What infill percentage and infill pattern did you use in printing the body tubes.

It seems to me, those 2 settings would show some optimal results, ie a balance of strength and weight.

And of course the result would be different for each and every filament.

Also, could not the wall thickness be even thinner by using petg-cf but have perhaps greater strength?

Finally, why not .2mm for later level?

The original examples were just based on a number of walls (so no infill).

As soon as you go thicker, beyond just 2-3 walls to the point where infill matters, you will get heavier (albeit possibly stronger).

I think people are doing some interesting work incorporating geometry to single or double wall tubes to create structure and thus strength.

This is not really the area I am focused on. I am happy using cardboard tubes and do not see much value in printing them (I am in the USA where tubes are readily available and cheap). I am doing some experiments with rockets that have more complex geometry but this is on a case by case basis so results are not really generalizable.

 

[shockie]

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.

https://www.thingiverse.com/thing:3056609

how thin were the fins and did they have an airfoil cross section? Or tapering from root to tip? otherwise, a great looking model.