3D printed r-candy casing (possibly multi nozzle/core rocket)

[JMan]

Ok so I'm on a venture to 3D print my rocket casing, direct casting no grains.

1st has anyone done this if so any advice? And I've got mock-ups on sketchup I can put them on the 3D warehouse for viewing/download.

2nd what's the best material? I'm thinking abs plastic but if anyone has a better idea please let me know and would it be better to honey comb it or fill it full?

3rd if this does work I'm think multi nozzles such as 2-4 cores/nozzles that ignite sepretly but use the same cast of fuel, providing massive thrust to weight at the start and once they burn the center out they share 2-4 nozzles

 

My thinking: I've started with thick pvc, to contain pressure. But the only problems I've had were the bulk head and nozzle (friction fit and later screw on) seem to blow off or tear threads (if big enough) so I decided to make Fule the bulkhead/delay and it worked also tried nozzle less while they produced just enough thrust to get off he ground it wasn't enough to fly straight, I decided to cut weight it never seemed to blow the sides off thin wal pvc worked and so did 2 rolls of paper so the case really doesn't hold that much pressure it's the nozzle and bulk head I figured (until flamout occurs) so the 3d printing wouldn't need to be too strong. I can create as thick of a wall in the nozzle as o need or even drop a washer down there and drill holes if the nozzles get ate by the heat (I'm not worried for the side walls because the motors I've picked up don't seem to get hot untill shortly after landing I guess they get air cooled) the Fule is a good insulator so it shouldn't warp the printing untill after flameout.

 

Please correct anything that seems wrong or if you have tried it let me know how your experiments went.

Edited August 16, 2017 by JMan

[JMan]

update: printed my first rocket motor will fuel it tomorrow. made it honey combed to save fuel, but this caused it to not be airtight, making a slimmer, full version soon.

[Oinikis]

While 3D printed casing are concerning, and be carefull, but can you give us some photos?

[pyroman2498]

Why not just 3d print the grain mold ? The ABS most likely Wont hold up to the heat ... Edited August 18, 2017 by pyroman2498

[JMan]

I doubt it will pyroman but neither does pvc it warps and deforms but that's only way after the motors been fired, the only part I'm worried about deforming mid flight is the nozzle. 3d printings are too rough to make a mold, but this is an advantage to directly cast it as it grips the fuel better.

And pictures are on the way (I'm on an iPhone right now it won't let me insert pics)

[JMan]

Like I said I made it bigger than I wanted, I keep forgetting sketch up does radius not diameter. I can also upload it to sketup warehouse for any who want.

[JMan]

[JMan]

http://rocketry.mit.edu/2017/04/100-3d-printed-solid-rocket-motor/

 

well darn, guess I'm not the first but hey that's MIT. lets see if a high-schooler can do it. I'm going to try to track down their plans. I fueled the rocket today, squeezed it too hard and it got a dent in it (the hot fuel didn't melt the plastic but caused it to become malleable). The launch was more successful than I anticipated. rocket flew a couple hundred feet (remember I was expecting this thing to be half the diameter smaller throat less fuel) and I only filled it half full (100 g batch of kno2 su) despite the lack of air-tightness the motor didn't spew any (visible) exhaust out the sides, and stayed together until after flame out, upon which the nozzle separated from the combustion chamber.

 

anyone willing to try this it was pla plastic honey combed, duct taped to a 4ft x 1/4 in dowel rod.

[JMan]

next test is the half diameter rocket out of abs, not honey combed, and filled full of fuel.

[stix]

I don't understand why you would need to 3D print a casing for a rocket motor. There are many many other available and proven examples. In my view, the casing needs to be the strongest part of the the motor. Apart from that, I guess then we are taking about just "for the point of trying" - fair enough.

 

If someone came up with a method to 3D print a fuel geometry, ie. core burner, star shape or any others, using actual solid fuel, then THAT would be absolutely fantastic!

 

If you use some sort of plastic for 3D printing, then why not use a melt-able solid fuel for the layers?

 

I'm looking forward to hearing about future results. Think Big!! ie. outside the square.

Edited August 20, 2017 by stix

[MrB]

If you use some sort of plastic for 3D printing, then why not use a melt-able solid fuel for the layers?

 

Rocket candy should work fine for that purpose. You need a 3D printer that can either work with granules, rather then the regular spooled stuff, and either pause the print often (or work on multiple items at the same time) to let it cool and harden, or outright chill it once it's out of the nozzle.

It would, most likely be easier to just 3D print a mold, rather then print the darn thing, but sure. It should be possible.

 

On the other hand, if someone has the "other" kind of 3D printer, that works with layers of (plastic) powder and is laser-heated to melt specific parts of the layer to the structure below... As long as one can keep the powder from getting hot enough to start a fire, it should be good to go from the start. Not sure i would want to load something like that with rocket candy, but hey... Fire-hazards are fun.

[JMan]

Yah two problems you'd need duel etrduders and have one head print from powder. Not impossible but not in my price range. However pla plastics work as hybrid rockets (much more complicated than solid) but yes this is simply to experiment and to have done it, speaking of which I do believe I am the first person to have ever seccessfully launched a plastic 3d printed rocket. Theirs been metal rockets or teats but no one has actually launched a plastics 3d printed rocket that I've ever seen or found. If anyone finds one let me know cus I honestly think I'm the first.

[JMan]

And mrb I've had problems with nozzles and things blowing apart and not staying together so I'm expereminting with throats size mostly. My core burners don't get enough thrust and my nozzles build up too much pressure and rip the nozzle off (or bulk head) so I figure the ribbed part of the plastic grips the fuel and I don't have to compermise with nozzle sizes (I use washers usually) Edited August 21, 2017 by JMan

[Oinikis]

To be fair, these casings do not look really strong or heat resistant, they only look... nice. Knowing the cost of the equipment, I'd rather buy a lathe and turn metal motors.

[JMan]

I'm trying to do multiple nozzles though, school started and I'm taking act courses as well as getting my pilots livens so I have no time right now but I want to try the multiple cores/nozzles