Any thoughts about this broken prints?
Hello there!
I am working with a friend of mine on a surfboard and he designed the fins in order to 3d print them. I used PETG from Moebyus, 0,05mm, 25% infill (gyroid) (stock PrusaSlicer configuration, nothing else was modified) and they were really strong on hand, we tried to break one but it was really difficult. Today, he tried the board, it was a good surfing day, you could easily reach high speeds, and this happened:
They broke perpendicularly to the print layers, something really weird, and on a almost perfect line.
They were designed in SolidWorks, and on the program, the design could handle the requirements of the forces applied, so we really don't know why they broke.
Any thoughts about this issue?
We are printing them right now at 50% infill, I hope this will help.
Also, the PETG has no moisture and before printing it is cleaned with a dust filter (a thingiverse clamp style filter).
I can upload the STL files if needed.
Thank you very much for your help!
Best Answer by bobstro:
It's hard to see from the pics, but it doesn't look like the part split along layer lines. Proper orientation when printing helps, but it look like you had it laying flat already.
- As @vintagepc noted, extra perimeters do far more for part strength than infill.
- I wouldn't give up on gyroid infill so quickly. It has good strength from all sides. Some patterns only help with compression from the top of the print. In any case, infill isn't going to give you the real strength.
- You will likely get a much stronger part using a larger nozzle. Infill lines will be thicker and stronger, and you can use higher layer heights (if desired) to both print faster and strengthen the part.
- I'd use higher layer heights, and certainly not 0.05mm! There are a http://westkustsurf.nl/?page_id=1915 3" target="true">lot of surf fin articles out there with more detail, so see what the experts recommend!
- PETG is more flexible than PLA, but with high density, also tends to shatter when it fails. I was surprised when I took some PETG parts and gave them a good smack with a hammer. (Wear eye protection and put them in a bag to catch the debris if you try this.) Quite a few sharp shards exploded out from the impact. You might want to look into using nylon for this purpose, as it'll bend quite a bit more. I've just dabbled using Taulman Bridge, but found it wasn't nearly as scary as I expected.
A guy from MatterHackers has released a video and article on this very topic. He's using CF Nylon.
RE: Any thoughts about this broken prints?
Just an observation the infill does not look like 50%; and it looks to me like the fins hit something solid like a sharp edge of some rocks.
RE: Any thoughts about this broken prints?
Hi!
The ones that broke (on the pics) have a 20% infill, right now I am printing them on 50% (I will update the post once we try them, we think that doubling the infill will provide extra strength, correct me if I am wrong please).
Also, they broke on the water, with is really strange, it was on a part of the beach with no rocks 🤔
RE: Any thoughts about this broken prints?
Hello there!
I am working with a friend of mine on a surfboard and he designed the fins in order to 3d print them. I used PETG from Moebyus, 0,05mm, 25% infill (gyroid) (stock PrusaSlicer configuration, nothing else was modified) and they were really strong on hand, we tried to break one but it was really difficult. Today, he tried the board, it was a good surfing day, you could easily reach high speeds, and this happened:
They broke perpendicularly to the print layers, something really weird, and on a almost perfect line.
They were designed in SolidWorks, and on the program, the design could handle the requirements of the forces applied, so we really don't know why they broke.
Any thoughts about this issue?
We are printing them right now at 50% infill, I hope this will help.
Also, the PETG has no moisture and before printing it is cleaned with a dust filter (a thingiverse clamp style filter).
I can upload the STL files if needed.
Thank you very much for your help!
Attachment removed
Update: The attached screenshot is the actual fin in Prusa Slicer with the actual print setting (we are printing them right now at 50%, doubling the infill)
RE: Any thoughts about this broken prints?
What type of infill? Gyroid would not be my first choice. Cubic, or maybe 3D Honeycomb would be better to add strength.
RE: Any thoughts about this broken prints?
More perimiters are likely to do more for strength (especially shear strength) than infill changes. Infill really is best at offering strength to prevent crushing of parts; not so much straight up snapping or shearing. That's when you want to thicken the walls to prevent the break from starting and propagating.
RE: Any thoughts about this broken prints?
Ok! I'll use Cubic instead! Thanks for the advice, Tim!
RE: Any thoughts about this broken prints?
Hi @vintagepc , Do you think 2 more perimeters will work? Thank you in advance!
RE: Any thoughts about this broken prints?
If you're using the default of 2, definitely. Maybe even 5 or 6 total. Also, consider upping your filament temperature by 5-10 degrees; it'll help the layers fuse better and make a stronger part. (Forgot to mention this - printing too cold will work but result in parts that shear easily at layer lines)
RE: Any thoughts about this broken prints?
Ok! I am printing right now at 0.05mm, 40% infill (cubic) and 5 perimeters! I will ad another 5ºC to the print! Thank you very much!
I will let you know if this new config works better 😉
RE: Any thoughts about this broken prints?
Good luck!
RE: Any thoughts about this broken prints?
It's hard to see from the pics, but it doesn't look like the part split along layer lines. Proper orientation when printing helps, but it look like you had it laying flat already.
- As @vintagepc noted, extra perimeters do far more for part strength than infill.
- I wouldn't give up on gyroid infill so quickly. It has good strength from all sides. Some patterns only help with compression from the top of the print. In any case, infill isn't going to give you the real strength.
- You will likely get a much stronger part using a larger nozzle. Infill lines will be thicker and stronger, and you can use higher layer heights (if desired) to both print faster and strengthen the part.
- I'd use higher layer heights, and certainly not 0.05mm! There are a http://westkustsurf.nl/?page_id=1915 3" target="true">lot of surf fin articles out there with more detail, so see what the experts recommend!
- PETG is more flexible than PLA, but with high density, also tends to shatter when it fails. I was surprised when I took some PETG parts and gave them a good smack with a hammer. (Wear eye protection and put them in a bag to catch the debris if you try this.) Quite a few sharp shards exploded out from the impact. You might want to look into using nylon for this purpose, as it'll bend quite a bit more. I've just dabbled using Taulman Bridge, but found it wasn't nearly as scary as I expected.
A guy from MatterHackers has released a video and article on this very topic. He's using CF Nylon.
RE: Any thoughts about this broken prints?
My issue with Gyroid is that it has open channels that run the length of the part, so any flex can twist the part, and then all the loads are on the perimeters and become a shearing force. Any infill that closes those channels will be better in this application. More perimeters will help impact strengths, but probably not help with the twist problem - and looking that the breaks, it was twisting that caused the damage. Just an opinion...
RE: Any thoughts about this broken prints?
oh wow, bobstro, thanks for the info! We will consider printing a new pair on nylon.
Also, thanks for the links!
RE: Any thoughts about this broken prints?
On YouTube I saw a movie, that higher perimeters is better for strength.
Infill only a little , by 30 - 40 % is de maximum, higher is never(almost) better.
Search for the german guy, he always makes movies about strength testing.
https://www.youtube.com/channel/UCiczXOhGpvoQGhOL16EZiTg
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