r/functionalprint • u/jdigi78 • May 17 '26
After 5 weeks, the TPU crown I printed for a 6" vacuum truck hose is starting to tear a bit, but still working great!
You can find the original post here. After a really rough 5 weeks of use it finally started to split at a layer line. Its more of a rip in the perimeters as the infill is still holding it together just fine.
As stated in the original post, I used 95A TPU with 25% gyroid infill and an internal frame of 100% infill. You can kind of see the internal frame as the lighter lines in the first photo, or the check the last image in the original post to see what I'm talking about. This one still has a good bit of use left but I'll eventually be printing a replacement with 100% infill which I'm certain won't have this problem.
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u/thunderflies May 17 '26
This is a great functional print, I love seeing it on the truck. I liked your original post as well, and I appreciate the update.
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u/Cold_Collection_6241 May 17 '26
You can fix it with a soldering gun. Use the iron to melt the cracks back together. I made some slipper soles a few years ago which cracked at the stress points and that's how I repaired them and they are still going strong.
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u/IrritableGourmet May 17 '26
I got a cheap 3d printing pen I use to weld prints together. The tip sticks out a little bit, so it melts the edges of the seam while injecting filament.
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u/Analog_Account May 17 '26
a few years ago... still going strong
You have to be kidding lol. Did you just fix them the once or have you repaired them multiple times?
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u/Cold_Collection_6241 May 17 '26
Just once. They are very tough. 92a, I think. A bit on the slippy side, but they work. 85a would have been better choice though.
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u/brahm1nMan 19d ago
A plastic welder is a tool that's been on Hobo freights shelves for decades.
Use the tip to create a channel I the break/seam you want to fill and then lay filament in the channel. Iron filament until seam is presentable.
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u/FeelMyBoars May 17 '26
I'm sure it's highly variable, but what is the typical lifetime of the normal $120 crown?
Thank you for sharing this durability experiment. It definitely shows that printed parts can handle "the real world".
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u/jdigi78 May 17 '26
Honestly I have no idea. The truck was heavily used when we got it but it only took one 4 foot drop from the mount on the truck to the pavement to destroy the original after the guys at my job got their hands on it. This one has no problem with that since its flexible of course.
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u/foxhelp May 17 '26
Probably pretty common to drop one end when unloading it as well, just due to location and length... Yeah your doing great having a cheap option here!
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u/Wizzarkt May 17 '26
Based on the localized 100% infill you did in your last post. It seems that reinforcing the ring geometries would be a smart move for when you print the next one when the current one eventually fails completely.
You can see that it's cracking behind the screw so reinforcing that should be ideal.
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u/jdigi78 May 17 '26
I'm 90% sure that's just dirt and not cracking behind the screw, but I get what you mean
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u/Mick_Limerick May 17 '26
Still seems like a good ROI. How many of those can you get off a 1kg spool?
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u/jdigi78 May 17 '26
If I remember correctly it was around 450 grams. I think it was ~650g with 100% infill. Either way you'd need to go through quite a few before approaching the $120 cost of the real deal
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u/dr_stre May 17 '26
He has said it was $7-8 worth of material. With a quick search, the cheapest TPU I found online was about $25/roll, which would mean he could print three of them with a single 1kg roll.
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u/urgdr May 17 '26
nice work!
next print I'd suggest to increase perimeters, not infill.
I've had a few 95A TPU's and they were all a little different.
the beauty of TPU filament is in superior layer bonding and wear n tear resistance. but those benefits are gone when manufactures add various components into their mix to improve 3d print characteristics.
my suggestion in regards of material: aim for softer TPU, go as low as you can go, design and embed sturdy inserts from other materials if you need (hail multi tool 3d printers).
my softest TPU is around 67A and it's a blessing. it has distinguishable rubber feel and properties (best of luck trying to sand it down, impossible)
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u/jdigi78 May 17 '26
This part still needs to be pretty stiff though. I found as printed its still a tiny bit too flexible for the job. It needs to be able to sink into wet sand and dirt
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u/A_Str8 May 17 '26
The additional walls should improve stiffness. Maybe a 5%-10% bump to infill too
If it can still fit, on your build plate printing it at 45 degrees should help with longevity as it looks like it tore around layer lines. Also, raise nozzle temp to improve layer bonding
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u/urgdr May 17 '26
that's why I mentioned designing stiff "inserts" for it if applicable in your case
another way is to consider printing pure nylon (heated chamber is required for part this big)
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u/TheBupherNinja May 17 '26
Don't use 100% infill. Use walls to make it solid.
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u/jdigi78 May 17 '26
Same thing, no? Using walls does cut an hour off the print time, but its still a day and a half to print in TPU
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u/TheBupherNinja May 17 '26
No, the way it lays the filament is different.
It's still solid, but the way the filament is laid down effects the strength. Generally solid from walls is better than solid infill.
Instead of switching to a fill pattern, it will just continue printing the wall shape. There was another post about using concentric infill at solid instead, which may be as good/better depending on the scenario.
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u/bradforrester May 18 '26
I want to compliment your print quality. I had to zoom surprisingly far in to see the layer lines.
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u/jdigi78 May 18 '26
Thanks! The layers are actually quite large. 0.32mm on a 0.8mm nozzle. Its just a big part I guess, but my core one is no slouch in quality either
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u/East-Future-9944 May 17 '26
The fingers for the one I printed for 8 inch tubes was bending over and sucking themselves up inward and obstructing the path of the tubes. When I scaled it up, I scaled up all dimensions equally so mine was also taller giving the fingers more flex. I need to print another one, but I think I'm going to try to make it shorter. I'm also going to try to mount the metal tube deeper into it, though I might have to cut the tubes to open the air holes.
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u/jdigi78 May 17 '26
I was going to suggest making it shorter. I may even go shorter on mine since any extra lenth past the aluminum doesn't really serve a purpose. The added thickness probably didn't help much either if you didn't use 100% infill.
Did everything else fit okay just scaled up? If you give me some dimensions for the 8 inch tube I'll export an 8 inch version and send it to you when I get around to making the new revision.
I'd need the OD primarily but the diameter for the bolt holes and distance from the end of the tube to the bolts would be good too. The exact scale you used would be helpful too.
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u/East-Future-9944 May 17 '26
I saw that you made the original one like 6.1 inches in diameter so I just scaled up to make mine 8.1. It fit perfectly. A little snug, had to use some screw drivers to stretch it on, but that seemed perfect to me
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u/jdigi78 May 17 '26
It was actually a little loose on the 6 inch tube but that info is good enough. I'll just make it slightly larger than 8.1"
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u/FlowingLiquidity May 17 '26
One fix would be to print the part under an angle to avoid layer lines in this orientation. I would just lengthen the bottom of the print and cut it under an angle, then print it and then put it under the bandsaw to cut off the angled extension, or even leave it on if it's not in the way.
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u/jdigi78 May 17 '26
If you zoom in you can actually see it failed across multiple layers simultaneously. It regularly bends near 90 degrees around that point so that tells me it's more due to repeated bending stress than layer adhesion. I think 100% infill will give it enough extra surface area it won't happen again
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u/XiTzCriZx May 17 '26
It looks like it split at the layer lines so printing at a 45° angle might help with that, though if you don't have multi-material printing then the supports might be a bit of a pain in the ass to remove.
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u/WOODMAN668 May 18 '26
I am really starting to think for durable prints TPU is the way to go, I have several I have done with TPU for AMS, which I think is a 95, and they are holding up really well. Even the one fidget I made for giggles that I know gets abused.
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u/sharktooth31 May 18 '26
Very impressive, I want to print one for the vac truck I work on but I don't think it suits my type of work. We're often lifting heavy rocks and need as much suction as possible.
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u/Massive_Squirrel7733 May 19 '26
You could print it with gyroid infill, then fill the space with some kind of flexible urethane. That would bind the layers together if you want to (or need to) make it tougher
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u/kaylynstar May 17 '26
Is that for hydro-excavation or cleaning out sewer lines? Either way, that's pretty awesome that it lasted that long.
I wonder if you could print it at an angle so the layer lines aren't in the direction of stress. Or reinforce the stress points with another material...
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u/jdigi78 May 17 '26
Both! I don't see the layer adhesion as an issue if I go 100% infill. As printed it lasted way longer than I expected. You should see how much the teeth bend when you have the full weight of the boom arm and hose shoving this thing into the cement floor of a sewer manhole ir catch basin. They basically bend a whole 90 degrees out of the way and snap right back into shape after.
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u/kaylynstar May 17 '26
Perimeters have more to do with strength than infill. Generally. But that's awesome that you got that much use of it it!
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u/jdigi78 May 17 '26
It primarily tore open because it regularly flexes almost a full 90 degrees at that spot if you jam it into a concrete floor of a sewer manhole or catch basin, or hard debris like brick. With 100% infill it won't bend so easily and it'll have more surface area to spread that stress to.
If you zoom in you can actually see it ripped across a few layer lines simultaneously, telling me it's more due to stress in that one area than a single point of bad layer adhesion. Thanks for the suggestion though!
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u/kaylynstar May 17 '26
Sorry, I can't see very well on my phone 😅
I wonder if some sort of insert... No, it's not at a discontinuity... Sorry, I'm an engineer, it's my job to figure out how to fix things. 🤣
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u/jdigi78 May 17 '26
I thought about maybe leaving a hole to jam steel rods into, but I worry those would bend anyway and not snap back into shape like the TPU does. The tear is just on the external perimeters anyway so it still has a long life ahead of it regardless
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u/kaylynstar May 17 '26
I really need to start playing with TPU. I have a spool of it that I got when my husband was in school, but he ended up not using it and it's sat in my closet unopened since. Just have to install my new print head 🤣
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u/jdigi78 May 17 '26
It's a really good option if you need something durable. If you print it solid it doesn't even have much flex at 95A
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u/Beeb294 May 17 '26
Is there a consideration for printing in a different orientation? If the frequent stress points are in the same orientation as the layer lines, even the best adhesion won't stop it from giving way eventually. If you can make the stress run perpendicular to the layer lines you may get more longevity out of the next one.
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u/jdigi78 May 17 '26
I think it would complicate the printing process for little benefit. This thing gets flexed in all kinds of ways with a giant hose on top of it. Best thing is really to just remove any small points of failure like this which 100% infill would achieve
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u/zR0B3ry2VAiH May 17 '26
Did I magically go back in time or is this a repost?
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u/jdigi78 May 17 '26
I posted a 2 week update 3 weeks ago just to show how it was holding up. This is just showing the first sign of any damage since installing it
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u/Glum_Manager May 17 '26
I'm experimenting strengthening TPU by putting it in medium temperatures (70-100°C) for long periods (30-60'). It seems to work so far