3D Printing Printing single fins

[bad_idea]

For those of you who print single fins, what orientation and print settings do you use? It seems intuitive to me that a fin would be strongest if printed laying flat so that the infill would be transverse (at the cost of the time and mess of support structure when needed), but since I know some people print them with the root vertical (perhaps with some tilt), I'm wondering if my intuition is off.

Also curious how you've chosen infill percentage and pattern for your fins.

 

[Bravo52]

I print mine flat on the build plant. I've printed some resin and I would print those vertical. I don't recommend printing single fins in resin unless you are using a flexible type resin and I'd only use that for really small rockets.

 

[bad_idea]

I should have specified I'm working with an FDM printer (Prusa Mk. 4).

 

[Bravo52]

I should have specified I'm working with an FDM printer (Prusa Mk. 4).

No, I get it. I also have a Prusa and that is what I use. I print flat to the bed with smoothing. I mostly use it to make templates for cutting balsa fins. I just mentioned the "resin" because the orientation matters for that medium.

 

[frogglicker]

For those of you who print single fins, what orientation and print settings do you use? It seems intuitive to me that a fin would be strongest if printed laying flat so that the infill would be transverse (at the cost of the time and mess of support structure when needed), but since I know some people print them with the root vertical (perhaps with some tilt), I'm wondering if my intuition is off.

Also curious how you've chosen infill percentage and pattern for your fins.

I think your intuition is correct. Printing them flat would probably be the strongest. I print many of mine vertically, with some tilt so that the layers are not parallel with the root so that I can add airfoils to the leading/trailing edges. I am still experimenting with this and have not found the "secret sauce". Printing them vertically with a tilt (and supports) works pretty well with PLA+, but I'm generally struggling a bit with PETG.

I just started working with the PETG and found that fin and nose cone tips get mushed and gooped up. I think it's because the layer is not cooling off fast enough, so I am trying some testing by kicking up the fan speed once my layer time drops to a certain level.

However, for flat, square fins, I would print on the sides so the layers are going through the fin, then laminate with a thin coat of epoxy to lock it all together.

 

[cwbullet]

Orientation is key. It can be tough to get a great print no matter the printer.

 

[frogglicker]

Orientation is key. It can be tough to get a great print no matter the printer.

Amen

 

[thzero]

If it's a pure flat fin, then just printed flat

Otherwise I try and do the layers either perpendicular to the root or where the layers, as grain, align with the leading edge.

Both of these can be tricky with certain fin designs.

 

[SolarYellow]

I've seen some tests that support the hypothesis that the mechanical properties of resin prints are not significantly affected by the direction of the layers. I always figured that for a resin printer, just orienting the layers parallel to the root would be the easiest and probably involve the fewest/no supports. You could set up a whole garden of fins on a run and be pretty efficient with resin and post processing, once you had your settings dialed in.

Is there significant evidence to the contrary out there?

I might do some fin cans and/or fins in Blu-Tough Nylon Black at some point.

 

[frogglicker]

This question has been bugging me. How can I print my fins with airfoils so they are strong and do so in the fastest way possible? I know that my standard orientation (verticle) is not ideal. The SpiderMax rocket that I built earlier this year had a fin break along the layer lines and it's been bugging me ever since.

I decided to take a sample fin that I am working on and slice it with several different orientations. To get a sense of each.



The configurations are the same:

• Resolution: 0.08
• Infill: 15%
• Perimeters: 4
• Brim: 10mm
• Supports: Grid style with Recilinier Grid pattern - I found this allows for the cleanest separation for most models. YMMV

First up, Root Edge:

• Print Time: 5h23m
• Post Processing: Medium (with epoxy lamination)
• Strength: Probably the weakest orientation
• Overall: I would probably print this with 6 perimeters laminate with epoxy for larger prints

2nd print - Mild tilt

• Print Time: 6hs
• Post Processing: Medium - more support clean up but it is all on the edges that are not seen
• Strength: Better - "grain" is not parallel with the body tube.
• Overall: This has been my default PETG orientation. I still get rough edges on my airfoils but the tips are flat so no globbing. Since the grain is not parallel, it falls in line with the "balsa" rule of "Grain flows toward the body".

3rd Print - Extreme tilt

• Print time: 6h23m
• Post Processing: probably the same as the 2nd print. For PETG, steps need to be taken to prevent globbing at the tip of the trailing edge
• Strength: Very Good - probably the best for the vertical orientation prints
• Overall: If you can prevent globbing on the edge tip, this would probably be the best for strength and post-processing. Also, this orientation has some danger of failing unless the printer is well-tuned and the print is positively stuck to the bed.

Last Print - horizontal

• Print Time: 3hrs
• Post Processing: significant - leading and trailing edges on one side Also PEI texture on one side unless you print on a smooth surface
• Strength: Probably the strongest as the only risk would be the delamination of the layers vertically (unlikely)
• Overall: While there would be some post-processing to deal with, this looks to be the strongest and quickest print orientation of the 4 shown. The likelihood of being able to successfully print multiples of this fin in this orientation is much higher than the others.

None of this is scientific. It is only based on my anecdotal observations with 3D Printing and there are others with much more experience and knowledge.

However, @bad_idea, you have forced me to confront issues I knew to be there. The discovery of laying the fin flat, even with airfoils, cuts the print time in half, allowing me to print multiples at once (print is more stable) and I can still have post-processing done with a stronger fin, faster than with the vertical orientations. I am printing #4 right now and I will let you know how it turns out.

Thanks for the question. I hope this was helpful.

 

[thzero]

This is one set of fins, used on some fully 3d printed rockets that are 66mm and under - this just happens to have been from a set of fins for a Pringles rocket. Probably will try it with some 78mm rocket at some point.



I did try printing the above flat, but ran into some of the same issues others mentioned with having to spend a lot of post-processing time on the leading edge.

This was how I printed a larger airfoil fin for a 5.5" LOC stubby named The Joker. But considering that this was a DD 5.5 with fiberglassed LOC tube, its pretty heavy so these fins had a couple of layers of fiberglass on them.

 

[thzero]

T

• Overall: While there would be some post-processing to deal with, this looks to be the strongest and quickest print orientation of the 4 shown. The likelihood of being able to successfully print multiples of this fin in this orientation is much higher than the others.

Guess it boils down to the fin design and can it be printed any other way than flat? And also on your printer. I've had no issues printing the flat fins vertically as I showed in batches.... probably have upwards of 8 or 9 3d printed or mostly 3d printed rockets done that way.

 

[kramer714]

just printing flat fins? would you want to add an 'attachment feature'? Print the fin vertical? just wondering..

 

[frogglicker]

I just pulled the test fin off and the results are pretty amazing. The supports popped right off with little trash left behind. The airfoil is a little wavy and will need some work but the strength is unquantifablely stronger! I could same a verticle print with no problem. The horizontal print will take tools! I am very happy with the result. 5 minutes with the file and a few more with some sandpaper will make this fin as good as it needs to be. The downsides that I am seeing now:

• post-processing - as expected, the leading/trailing edges need some attention but are not brittle or worrisome.
• printer bed real estate - I can barely get 6 fins on my current CR Ender 3V2 Neo (and it's really tight) in the horizontal orientation. Vertically, I can get 34!

So if strength isn't a concern then the verticle orientation will work for mass, though it seems like it takes 2x as long to print as with horizontal. For my smaller rockets, it's not a big deal but I have a few 4" kits to test this spring so I will probably be printing flat and sorting out the post-processing because, to me, the strength is worth the clean-up.

 

[bad_idea]

I just pulled the test fin off and the results are pretty amazing. The supports popped right off with little trash left behind. The airfoil is a little wavy and will need some work but the strength is unquantifablely stronger!

Glad to know the theory bears some fruit! What filiment/infill/pattern did you use?

 

[thzero]

I just pulled the test fin off and the results are pretty amazing. The supports popped right off with little trash left behind. The airfoil is a little wavy and will need some work but the strength is unquantifablely stronger! I could same a verticle print with no problem. The horizontal print will take tools! I am very happy with the result. 5 minutes with the file and a few more with some sandpaper will make this fin as good as it needs to be. The downsides that I am seeing now:

• post-processing - as expected, the leading/trailing edges need some attention but are not brittle or worrisome.
• printer bed real estate - I can barely get 6 fins on my current CR Ender 3V2 Neo (and it's really tight) in the horizontal orientation. Vertically, I can get 34!

So if strength isn't a concern then the verticle orientation will work for mass, though it seems like it takes 2x as long to print as with horizontal. For my smaller rockets, it's not a big deal but I have a few 4" kits to test this spring so I will probably be printing flat and sorting out the post-processing because, to me, the strength is worth the clean-up.

Strength? I'm not sure that is stronger flat or if the layers are perpendicular to the root. Certainly if the layers are parallel to the root that is a going to be the weakest.

There is an answer for the first two..... do a test by setting up a test jig and measure it.

 

[frogglicker]

For the horizontal print earlier, the print is 6mm thick thick. The filament is PLA+, infill 15%, 4 perimeters, 3d honeycomb.

Typically, I print vertical fins in PLA+, infill @ 30% with a 3D Honeycomb pattern and a resolution of 0.08mm layer height and 4-6 perimeters.

For very unscientific testing, I chose an extra fin from my SpiderMax build as the control. The print is 6.35mm thick, with vertical orientation, 4 perimeters, and the parameters as above. With little effort, I was able to snap the fin across the layer lines. I was sadly surprised at how easy it was. It explains why SpiderMax's fin broke last summer. The horizontal test print is the same fin design, but on a smaller scale (except the width which is the same). I figured I would be able to at least get a delamination between the layers. Without tools, I was unable to do any damage to the fin.

Again, I mention that these are only anecdotal findings, with no quantitative results. However, it is my opinion from these findings that there is some evidence that printing them horizontally adds significantly more strength, and would be confident in them surviving a hard landing on rocky, mountainous soil where I fly.

The orientation should be based on what the result should be. For LPR, vertical is usually fine. I have printed multiple fins and fin cans over the past 9 months and I have had 2 failures: One where the fins were much too thin and the other was probably due to low resolution but I cannot be sure. This is a personal choice and I'm not saying any way is right or wrong. These are just my impressions.

Maybe more controlled testing by others would yield different results.

 

[thzero]

Why are you printing with PLA? PETG or ABS/ASA are better for structural, or into other stuff like PET-CF, PA*-CF, etc.

All my 3d printed rockets and components are all PETG right now, except for a few odd balls where either stiffness matters or high temp which is where some PET-CF/PA-CF come into the picture.

On rockets that are 3d printed and running on a G-64, the fins are 4 wall loops, 30% Gyroid (just my default) but with 4 wall loops it doesn't matter, in PETG and 3mm in width and printed with .16mm layer height.

Are you sure you are getting good layer adhension? That aside, I would expect to more easily snap a part at the layer lines in any vertical printed as opposed to a horizontal printing.

 

[frogglicker]

You make some excellent points.

When starting, like so many others, it was hit or miss on my prints. I had lots of spaghetti with frustration sauce. I picked up a roll of PLA+, got everything dialed in, and had great results. I stuck with that for months. Just this month, I picked up a roll of PETG and have been trying to get that dialed in. I think I have most of the kinks worked out and have printed a set of Red Max fins for a project that I am working on. I still struggle with some blobbing where the layers don't have much meat and I think that was b/c I shut the fans off. The print is spectacular except for the last few layers where everything comes to a point. I am working through kicking the fans where the lay has a smaller footprint and I'm getting closer. PETG is my next step. Having just updated the firmware, I opened up the temp ceiling for the bed and nozzle so I can go a little farther but I think I'm probably going to get something that is just designed to work with CF and ABS.

 

[vcp]

I haven't seen it mentioned... I've printed a lot of fins with the leading edge down. Yeah, just maybe two walls initially on the plate, and supports on the root or tip to keep it standing upright. It takes a little sanding/shaping to clean up the LE, but that's easy.

 

[bad_idea]

I've run a few test prints today, using PLA because it's cheap and good enough for A-B testing. I ran with relatively heavy infill (40%) and can't tell much of a difference in strength between flat and vertical. Running another set with 15% to see if I notice a bigger difference.

Regardless I'm already thinking I won't be printing flat for the application I'm working on now, since it's proving impossible to print a decent fillet on the side that's printed down. I'm currently inclined to print leading-edge down, just as @vcp suggests. (Edit: looking at the slicer output, I'm thinking trailing edge will require a lot less support material.) We'll see, I'll run some more test prints between now and printing the final fins (which will be PETG).

 

[kramer714]

Im always concerned when i hear about infill and strength.

Infill type - The way many (most?) slicers work will provide VERY different strength for different infills. 'Lines,' typically gives very poor strength since the nodes have gaps in them. Some slicers do better with honeycomb. The questions is what do the nodes look like. what does the continuity look like between layers.

'roof weakness' With a light infill depending on the geometry the roof can be considerably weaker than the side printed against the build plate. In buckling (from external load or flutter) the 'roof' is significantly weaker. than the 'floor'. This should be factored in when you are talking about strength of a fin.

'Modeled in ribs- spars' - If you are really trying to optimize the fin, strength and weight, the 'voids' can be modeled in. To ensure a good roof, do it Gaudi Style ( Sagrada Família ) The attached screenshots were from a 'day job project', the engineer needed to reduce some weight while keeping the bending strength high. The shape (not optimized but very buildable) was made to allow for printing in two diffenrent orintations, mainting a low overhang anagle while still tying the skins together.

'Solid'. For things like fins, I print them solid - calibrated for density. Beauty of 3D printing, push the button and walk away. I dont care how much time it takes plus PETG is $.016 per gram.

 

[frogglicker]

@kramer714, that is an interesting design. I'm going to try it out this weekend. Thank you!