3D printing nose cones: assorted questions

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neil_w

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I've had some 3D printing done before (using commercial service, don't have my own printer), but not nose cones. And so I have some questions. The nose cone I am considering printing is BT55 and very short and stubby (like 1").

Material:
1) I assumed I'd either use ABS or PETG. PETG sounds like a good material but I haven't used it before. Is it possible (using normal techniques, no crazy chemical baths) to get a good smooth finish to it?
2) Would ABS layer adhesion be something I would need to worry about for a small nose like that?

Dimensions:
3) What sort of wall thickness would I need? I don't care about minimizing weight in this instance, since I'll be needing nose weight anyway.
4) Given typical printing characteristics, should I size the shoulder true, or slightly over or undersized?

Any other tips?
 
I've had some 3D printing done before (using commercial service, don't have my own printer), but not nose cones. And so I have some questions. The nose cone I am considering printing is BT55 and very short and stubby (like 1").

Material:
1) I assumed I'd either use ABS or PETG. PETG sounds like a good material but I haven't used it before. Is it possible (using normal techniques, no crazy chemical baths) to get a good smooth finish to it?
2) Would ABS layer adhesion be something I would need to worry about for a small nose like that?

Dimensions:
3) What sort of wall thickness would I need? I don't care about minimizing weight in this instance, since I'll be needing nose weight anyway.
4) Given typical printing characteristics, should I size the shoulder true, or slightly over or undersized?

Any other tips?

For PETG:
1) Not much dissolves PETG. It is difficult to solvent weld (haven't tried THF yet though), and doesn't bond with epoxy very well. However, it is sand able, and I would imagine someone with some skills as yourself could get a good smooth finish with a little work.
2) Don't know on ABS, but PETG layer adhesion is excellent. I would mount your anchor point in your nose weight though...why stress it.
3) I would do 2-3 mm think for a really robust cone. You could do thinner, but if you aren't worried on weight, why try. Some bumps printed on the inside of the nosecone will help with nose weight addition later.
4) I would print PETG true to size. It shrinks very little. I don't think I have had a part come out more than 1% off the model. In fact, most are within 0.2 mm. As I said, it is sandable, so if you wanted to be sure you could always go over by 0.2 mm and be sure.

If you have a CAD model already I offer print service in PETG. email me if you are interested: info at labratrocketry dot com
 
For PETG:
1) Not much dissolves PETG. It is difficult to solvent weld (haven't tried THF yet though), and doesn't bond with epoxy very well. However, it is sand able, and I would imagine someone with some skills as yourself could get a good smooth finish with a little work.
2) Don't know on ABS, but PETG layer adhesion is excellent. I would mount your anchor point in your nose weight though...why stress it.
3) I would do 2-3 mm think for a really robust cone. You could do thinner, but if you aren't worried on weight, why try. Some bumps printed on the inside of the nosecone will help with nose weight addition later.
4) I would print PETG true to size. It shrinks very little. I don't think I have had a part come out more than 1% off the model. In fact, most are within 0.2 mm. As I said, it is sandable, so if you wanted to be sure you could always go over by 0.2 mm and be sure.

If you have a CAD model already I offer print service in PETG. email me if you are interested: info at labratrocketry dot com

Thanks, good info. Once I have an STL file I'll send it over for you to look at.
 
Subscribed! I recently received one made by Shapways of a PNC 55SP. Beautiful work, very light, but it will require some resurfacing. Feels like 250 grit sandpaper on the surface and I'll want to hear what anyone else has to say about that. Mine came with a coupler which fits a little snug, but that will change once I begin to sand it to fit. Feels pretty durable and I have no idea what kind of plastic it is. But it's not as thick as commercial nose cones can be.

PNC 55SP.jpg
 
Last edited by a moderator:
Subscribed! I recently received one made by Shapways of a PNC 55SP. Beautiful work, very light, but it will require some resurfacing. Feels like 250 grit sandpaper on the surface and I'll want to hear what anyone else has to say about that. Mine came with a coupler which fits a little snug, but that will change once I begin to sand it to fit. Feels pretty durable and I have no idea what kind of plastic it is. But it's not as thick as commercial nose cones can be.

View attachment 339029

I've ordered several items through Shapeways. I think that their standard plastics are nylon, based on digging for info on their site. I can say that it definitely different than ABS, and different still from PLA. I have had good luck with it, though I haven't used it as a nose cone. I did, however, buy a complete fin/fin can unit for a BT60 Black Brant III, and it built quite well. Even though the fins are thin, they have some give to them while still seeming to have good toughness. That thing has survived a lot of flights with no apparent damage.
 
I've ordered several items through Shapeways. I think that their standard plastics are nylon, based on digging for info on their site.

With that, I discovered their use of nylon plastic on this nose cone also. Didn't see what was the best glue for it though. The shoulder will need to be mounted. Further research said the use of standard glue, epoxy and CA are not the best options for long term. In fact, a hot glue gun was considered the best option for nylon. Interesting, eh?
 
I print all my nose cones with PLA which is one of the nicer materials to work with on consumer grade printers, though it doesn’t stand up to heat well. When generating your gcode, you have to put some thought into the wall thicknesses and fill percentage as well at the print speed for the cosmetic surfaces. If you’re supplying an STL file to a third party to print, they should do this for you but the final result is highly dependent on that step. I’ve printed everything from bt-20 noses up to multi-piece nose cones with replaceable tips for 3” airframes. Printed parts are considerably stronger than you would think. The investment in the printer was $300 which pays for itself pretty quickly (though keeping the thing working well is a hobby on its own). I print motor mounts, centring rings, motor retainers, couplers, lugs... It one of my most useful tools for mid and low power builds.

That said, PLA is a pain to finish nicely. It requires copious hand sanding and filler for a nice finish. With ABS, you can use an acetone vapour bath to get a smooth finish with far less work but abs has challenges with shrinkage and fumes.


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PLA is a pain to finish nicely. It requires copious hand sanding and filler for a nice finish. With ABS, you can use an acetone vapour bath to get a smooth finish with far less work but abs has challenges with shrinkage and fumes.

Sorry here, but you guys use these acronyms like everybody knows them.
 
Sorry here, but you guys use these acronyms like everybody knows them.

PLA, ABS, HDPE, PET, PETG etc are just varieties of thermoplastic. Some varieties like Nylon have common trade names, but they’re typically referred to by their abbreviations.

I haven’t tried asking for Acrylonitrile Butadiene Styrene pipe at Home Depot but I suspect they’ll look at you kind of funny ;)
 
I print ABS (Acrylonitrile butadiene styrene, now you can see why we use TLAs :wink:) for my parts. There is a slight weakness in the z-axis compared to x and y, but you design accordingly. Your material does not need to be isotropic to make functional parts.

BTW, TLA is Three Letter Acronym.
 
PLA, ABS, HDPE, PET, PETG etc are just varieties of thermoplastic. Some varieties like Nylon have common trade names, but they’re typically referred to by their abbreviations.

I haven’t tried asking for Acrylonitrile Butadiene Styrene pipe at Home Depot but I suspect they’ll look at you kind of funny ;)

Duly noted. Thank you.
 
My rocket team 3D printed our nose cone for our high power entry in IREC 2017 last summer and got all kinds of trouble from the judges (with no problems in flight smh) Doing that again this year, and coating it with an epoxy layer to prevent any heat issues. Depending on what speed and altitude you're shooting for you may run into some issues with layers coming apart or melting which can be solved with internal supports.

For a smooth exterior finish, layer height is where it's at. ABS can't really be finished with a acetone, and sanding takes forever. Making the layer height something like 0.1 mm will make the print longer, but will turn out much nicer in the end.
 
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