So I printed a support for my GoPro 6 today and this happened: https://imgur.com/a/FynXv4Y

Any idea of what im doing wrong? TPU is supossed to be so strong and hard to break and this looks so bad

The 3d model: https://www.thingiverse.com/thing:4143216

Something definitely isn't right there. Your print settings look reasonable. I print TPU at 230°C with an 80% fan speed but that is on a direct drive printer so if you are using a bowden setup it might require different settings. I have no experience of printing with a bowden setup so someone much more experienced on here at 3D printing and who also has a bowden printer (such as kafie1980) might be ale to offer some better advice on print settings to tweak.

I checked the STL file and there are no mesh errors in them so it must be something to do with the way your printer ins printing the item or a problem with the TPU.

How old is the spool of TPU and how are you storing it? It almost looks like you have moisture in the filament which is bubbling as it prints thus causing air pockets in the print layers which can result in gaps in the print, rough looking layers, and weak layer adhesion.

Looks like moisure to me, too, causing bubbling.

Try warmimg the reel (obviously keep well below melt point!!) for a couple of days slowly to drive any moisture out and then try again.

In the winter I store my TPU in an old bureau with under cupboard that is up against a radiator. In the summer that furniture top is in sunshine, reels are in bottom.

And 215 is low for Flex TPU, I run 230, too.

TPU does NOT like remote bowden drive printers. I have one of each type, the direct does, the indirect does not! (No matter what I have tried)

First question I will ask is which printer, which TPU filament and temperatures you are printing at?

Your prints appear to be under-extruded and suffers from layer adhesion. Try bumping up the extrusion multiplier in increments of 0.1.

You can print certain TPU designs on a bowden setup and my way to identify those prints are the ones where the layers keep stacking on top of each other with slight overhang.

Here are some of my junk prints and they were printed in the orientation they are currently placed:



In a nutshell: use 95A Shore hardness TPU, use dry TPU filament, ensure the 3d design is nice and smooth, ensure your retraction is dialed in, experiment with nozzle temperatures, ensure the flow rate via the extrusion multiplier and ensure extruder steps are dialed in, slow down the print for the first few layers, experiment with object orientation and placement to work around overhand and avoid supports, always use a brim for thin walled prints, ensure couplings/fittings between the extruder and hot end are nice and tight, ensure bowden tubes are not chewed off at the ends that are inserted in the press couplings as this causes excessive play and affects filament retraction.

All metal hot ends require 5-10 degrees centigrade extra (on my MicroSwiss hotend I am at 250 degrees).

Bowden requires around 6-8mm retraction with TPU.

A glass heated bed requires 5-10 degrees more temperature depending on the thickness of the glass. And its best preheat this to temperature so by the time the nozzle is at print temperature the bed is nice and warm. Clean glass beds with IPA and never touch it with your hands/fingers.

kafie1980 - How much retraction are you using with the direct drive extruder? I'm just starting to experiment printing Overture TPU and trying to dial in my settings. I can get some decent prints but there is a bit of stringing id like to work on. Right now I have the retraction off, my next step was to try and print a retraction tower to see what I can get away with.

On my printer (Ender3 with MicroSwiss direct drive extruder) here is what has worked for me to print the TPU mentioned above:

Extruder temp: 230*
Bed temp: 50*
Print speed: 15mm/s
Fan cooling: off

I level the bed the traditional way with a piece of paper. For PLA I let the paper slightly drag but for TPU I adjust until there is no drag. I find the TPU doesn't need to "squish" on the the first layer nearly as much as PLA does. I dry the material in my oven for 4 hours at 50*C prior to printing if it has sat out for any length of time.

-Ryan

I am running a MicroSwiss hot end but still on the bowden setup and my retraction settings for TPU are 6mm retraction length at 40mm/s retraction speed.

If you are using a direct drive then even 2mm should be sufficient. TPU needs retraction else it will be very stringy.

One thing with the MicroSwiss or any other all metal hot end is that you do not want too much retraction that results in a clogged hot end as a result of the molten filament pulled above the heatbreak and rapidly cooled.

I used to have auto bed leveling but my sensor developed a fault and I reverted back to manual bed leveling which to me is not that big a deal since I learned the hard way spending hours taming my metal working milling machine.

I do not change the bed leveling for different filaments but instead use the Z-offset for the extruder. PLA is 0 while TPU is -0.1 just to avoid any squish.

I have a crappy roll of Sunlu TPU at the moment and waiting to place an order for my favourite which is what one of the local store's sells here and comes from the same factory as SainSmart TPU and its AUD 10 cheaper: https://www.nextfpv.com.au/products/next...8kg-1-75mm

I never dried filament (I do not have an electric oven but a gas one which can't maintain a consistent temperature) but instead keep it in zip lock bags. I have thought of buying a filament dryer but there are mixed opinions about them.

(17-Jun-2022, 04:16 PM)kafie1980 Wrote: I am running a MicroSwiss hot end but still on the bowden setup and my retraction settings for TPU are 6mm retraction length at 40mm/s retraction speed.

If you are using a direct drive then even 2mm should be sufficient. TPU needs retraction else it will be very stringy.

One thing with the MicroSwiss or any other all metal hot end is that you do not want too much retraction that results in a clogged hot end as a result of the molten filament pulled above the heatbreak and rapidly cooled.

I used to have auto bed leveling but my sensor developed a fault and I reverted back to manual bed leveling which to me is not that big a deal since I learned the hard way spending hours taming my metal working milling machine.  

I do not change the bed leveling for different filaments but instead use the Z-offset for the extruder. PLA is 0 while TPU is -0.1 just to avoid any squish.

I have a crappy roll of Sunlu TPU at the moment and waiting to place an order for my favourite which is what one of the local store's sells here and comes from the same factory as SainSmart TPU and its AUD 10 cheaper: https://www.nextfpv.com.au/products/next...8kg-1-75mm

I never dried filament (I do not have an electric oven but a gas one which can't maintain a consistent temperature) but instead keep it in zip lock bags. I have thought of buying a filament dryer but there are mixed opinions about them.

Ok thanks, ill give a few retraction settings a try and see where I end up.  I do have the MS direct drive all metal hot end, so ill start safe and work my way up.  

I have a Sunlu filament dryer and I can say its pretty much useless.  It doesn't get hot enough to really dry material, nor is it sealed well enough IMO.  I throw my TPU in the oven every once and a while and never have to deal with moisture problems.  I also keep it in a sealed bag with descant when i'm not using it.  

-Ryan

The Sunlu S1 dryer only heats up to 30-40 degrees celcius and doesn't evenly heat the top part of the enclosure which is why it's next to useless, but Sunlu have just released a new S2 version which goes up to 70 degrees celcius (~160 fahrenheit) and has heating elements in the lid. People who have used it are saying it's much better than the S1 so I'm considering possibly getting one.

I currently just use zip-lock vacuum bags with silica gel packs in them which seem to work well and I haven't yet needed to dry any spools. They just go straight back in their vacuum bags as soon as the print has completed.

Did you hear any popping or fizzing during the print? That's another way to tell if it's moisture issue.

TPU is very hygroscopic. You can get dryers that are purpose 'made' for drying filament, or get a food dehydrator and mod it to fit your needs. As kafie1980 mentions, there are mixed opinions regarding dryers so do some research first.

Summers are humid where I live. I used to have issues with wet filament before I bought the Westinghouse WFD101W. Since then I have not had issues with wet filament. YMMV

This is an example of a company selling basically a food dehydrator as a filament dryer and charging a markup.

https://www.printdry.com/product/printdr...ent-dryer/

There are lots of STLs on Thingie that you can use to extend the height for multiple spools. Make a spindle (or multiple) to dry as you print.