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  • TPU is easy and cool, so everyone should try it out.

    This is actually an answer I gave somewhere else in the forum, but it is not the first time I noticed people have a "fear" of using TPU, so I turned the answer into a little topic of its own.

    Sure TPU can be frustrating. This noodle kind of filament tends to escape at the extruder and even so, beside the actual failed print, nothing is lost and you can re-spool it, it can be a hassle.

    BUT: TPU is not that hard if you know the facts and rules. This is just my 50 cents of knowledge, which got me to a similar success rate than using PLA or ABS.

    Every 3D printer is able to print TPU. It may need a little modification, but this can stay when swapping back to other filaments.

    Price:

    TPU seems to be expensive at first glance, as the price per gram is higher than with other materials. But your are wrong here. Sure they usually sell 750g spools and they are a little more expensive than lets say PLA, but the main issue is the material density. TPU is lightweight. So even a spool only has 750g you may get the same amount of filament, when it comes to length.

    So the slightly higher price is coming from higher production costs and the lower sales rate. If I remember correctly the difference at my local filament store is around the same as for glow in the dark or other specialized stuff and about 4 euro or so.

    Also keep in mind that you (usually) don´t print giant objects. I have my spool for about 6 years now. Yes, just one spool. But I printed to many functional parts with it. Sure if I would print just dragons and statues it would run out as fast as other materials, but well I don't.

    TPU is absorbing water:

    TPU filament is absorbing moisture from the air. Well, this is true. I think. Fact is in all those years I own and use this single spool of TPU filament I never put it into a sealed box or dried it (even so I build a dryer for filament). It was stored in the opening like any other filament. (ABS/PLA). Even after about 6 years I have no issues with it.

    However. This is northern Germany and not Florida. Also the filament brand has probably a huge impact on that, so be prepared to need a dryer.

    I am noticing that the first few centimeters of PLA filament (10-15) are getting brittle in about a week, but the rest just prints fine. TPU does not get brittle, so maybe the first centimeters are moist and I simply don't noticed it yet, as it is used for the brim or so. The spools are stored in the open on a shelf next to my printers in a dry and (during the winter) minimal heated room inside my house. Maybe storing my stuff in the garage would result in a different result.

    Just be warned. If you hear noises like little bubbles bursting and the print has little gaps in it, your filament need to be dried.

    What else is required?

    You should have a direct extruder. Bowden is not a deal breaker, but creates more issues with retracts and requires a very narrow extruder outlet (see next point) or the filament will escape there as push forces fire back.

    Your extruder should also have next to zero space between the extruder gears and the inlet/outlet. If you look from the side onto your extruder gears there should only a minimum amount of filament being visible before and after the gears. You can print little triangular inserts to glue into those areas if needed, to fix the problem. Preferable in ABS/PETG as the extruder motor is getting hot during prints. They can stay installed, when printing other materials and should even make inserting any material much more easy.

    It is also useful if your extruder has a tensioning screw. If the gears are set to strong, TPU wants to go even sideways *between* the gears, when the pressure is to strong, while other materials grind. My TronxyX5s for example has an extruder spring utilizing a screw (basically the screw head insert) I need to remove. This results in giving the spring 4-5mm more room to expand and lowers therefor the tension. This extruder tension is probably more problematic than the gabs I mentioned before and after the outlet and inlet. TPU does not like to be squeezed. Like a stress ball it tends to find its way to escape the force.

    What are the most required print settings?

    Just set print speed to around 50% of your normal configuration (25-30mm/s), turn off supports and you are good to go.

    Speed and support wise you can go up later on. Start with the basics for maximum success.

    If you run into trouble also deactivate retraction.

    You can use supports, but be aware you need a sharp knife and therefor an opening to access the area to clean.

    A brim is possible increase layer adhesion, but the rule about cleaning applies here, too. I find the best way to cut of a brim is using scissors. TPU layers are bond like hell. If you print a timing belt, don´t be surprised if it actually works and cannot be ripped apart without massive force.

    A raft is a no go. It will impossible to be removed.

    Depending on the type of filament and the infill the squishiness is set. Use at least two or three walls. This makes the object robust. The less infill you use the more squishy the part gets. This is actually a good and probably the only situation calibration cubes can be handy to find your personal infill settings for different use cases. A more stiffer door bumper, but a less stiffer wallet print.

    Is bed adhesion a problem?

    When printing on glass or similar you need glue stick. I use cheap "UHU Stic". One layer of glue is enough for at least 5-10 prints.

    So if the print gets loose do that for your print surface, too.

    Some links for upgrading your printer.

    First a replacement of an extruder part with great images of where the TPU problem is: https://www.thingiverse.com/thing:3844646

    There is an image showing the filament path and a red line, where the gab is closed. Don´t get confused here. The bottom side is usually covered by the motor gear, when mounted and was removed as the before/after images where taken flat on a table. Keep in mind that extruder parts should never be printed with PLA due to the heat constantly radiating on the part. PLA will soften over time and very slowly. You don´t want to end up a 12 hour print because your extruder is melting.

    Second the insert I talked about above: (these are not the exact the ones I used for my GeitPrinter, but similar ones)
    Small filament guide for bowden extruder with screw thread. It can help with installing 'normal' filaments too. Sometimes I had some problems with this because of inside screw thread. Tested in JG Aurora A1 (I printed my Piggy with TPU), before that elastic filament was going out of the tube from time to time. INSTALLATION You need to unscrew the black metal plate (on photo: 1,2,3) and take it off. Drive in the guide up to some resistant (don't use too much force). Then, if the guide is not in the right position, slightly unscrew the tube holder (no. 4) and screw the guide in to position (if not just unscrew holder more), then screw back the tube holder and screw everything back to extruder. After that check if the guide is not too close to grinder (you can move it and listen if it grate with guide). If it is you will need to unscrew tube holder more or cut 1mm from the top of guide (where the screw thread is) and check again. If the part will break and stuck inside you will probably need to use left-handed screw (or right-handed from the side of tube holder after removing it) to pull it out. UPDATE: 21.III.2019 Updated model. Now it's without small holes on sides.

    Classic flexible filament guide for a direct extruder, model was built from scratch in Fusion360 by me


    You will probably find a matching part for your extruder when searching. Those are available for more or less every printer and/or extruder. Luckily my TronXY X5 has this little triangular guide build in. It could be a little bigger, but it works as it is.

    What to print?

    TPU is a great stuff to play with and there are so many things you can print with it. I created door bumpers, towel holders, hose adapters, protective dust inserts and there is so much more like: rubber feed, protective furniture corners, wallets, rubber washers .... The flex(ibility) is key here. If PLA or other stuff is breaking, try TPU.

    I hope I was able to shine a little light onto this cool and functional filament, so you give it a try.

    Happy 3D Printing
    Last edited by Geit; 05-24-2022, 05:27 PM.

  • #2
    Geit Very nice write up on how and why to use TPU. My 1st experience turned me off to it for a long time. I have 2 rolls of Inland TPU that I could not get to print, wouldn't stick to the bed, ball up on the nozzle, jamb. I was new to 3d printing and just gave up on TPU. Recently I had a need for a flexible part and tried TPU again this time it was a success and I have printed multiple things with TPU. Recently I needed something more pliable than TPU to I tried TPE and it prints well too. In fact as we speak I'm printing some tire foam replacements for some RC tires out of TPE.

    Thanks for sharing your knowledge on this topic and others

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    • #3
      I had fear of printing TPU. After reading your informative post, will try a seal for my tractor air cleaner to engine cover. Just what I needed.
      Click image for larger version

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      Thank you for sharing.
      Last edited by KitCarlson; 05-24-2022, 03:30 PM.

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      • #4
        Hmmmm, KitCarlson is there any heat in that area of your tractor? If so, I'm not sure TPU would be a good option.

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        • #5
          Click image for larger version

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          It is on air intake section, as a seal to upper sheet metal above fuel tank. It might be on the edge, but a good test.

          Original seal was rubber, it failed after 25 years of outdoor exposure.

          Print finished.

          Click image for larger version

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          Next print is a few tie rod joint dust covers. Have to design part.
          Last edited by KitCarlson; 05-24-2022, 08:41 PM. Reason: Add pics

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          • #6
            You're right, it is a good test, as long as it doesn't gum up the o-ring seat. Might be job to clean up if it does. And remember, manufacturers can use things like silicone rubber for seals, which can take a lot of heat.

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            • #7
              I found TPU did not easily enter extruder. I re-tried PLA to check for blockage, PLA easily fed. I heard that cooking oil as lubricant for TPU might help. Less than a drop of avocado oil, to lubricate about 1" of TPU worked great. The Odin-5 has a filament sensor switch at entry, oil help get past that.

              Printing went well.

              Glass build plate was removed and placed in water to remove glue stick adhesive, and part.

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              • #8
                Originally posted by KitCarlson View Post
                I found TPU did not easily enter extruder. I re-tried PLA to check for blockage, PLA easily fed.
                That is why the extruder space needs to be constrained. The noodle kind of filament bends sideways when pushed, which results in less energy to be used in normal filament direction. Also use the middle to upper range of temperature when printing. This is a reason why a bowden tube beside the friction should be a high quality tube with a matching diameter to avoid side bending within the tube.

                Also remember that the temperature range of filaments is dependent of print speeds. Mine states 200-230°C and I print at 215°C/25mm/s. If the temperature is to low compared to the speed, the extruder needs to push hard to get the filament through.


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                • #9
                  A few thoughts, observations. Please feel free comment, I have much to learn.

                  I used 220C, that seemed OK. Temperature well regulated. It is a volcano hotend, and recently did PID cal. I also verified temperature. Pleased by how TPU bonds.

                  The direct extruder did well. I have some concern about filament spool having unloading issues. I manually kept slack from time to time, to avoid tension. I think it might help to locate spool to far right. I have angled holder from XT-P S1 printer, now have an idea why it was angled.

                  My nozzle diameter is 0.4mm, but increased wall wall thickness to 0.5mm, as a way to speed print. I may get a 0.8 nozzle.

                  Travel speed was 30 mm/s, it seemed slow. Might try 40mm/s on next prints. Retaction and part cooling off. Noticed extra strings on travel, some loose fuzz in ID of part.

                  Using spiral top layer would improve appearance.

                  I hope to use tractor for mowing this weekend. I will report success or failure.

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                  • #10
                    Congrats. You know, some photos would be nice, to see exactly what you're doing.

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                    • #11
                      My SV04 had issues printing TPU was like yours KitCarlson was under extruding. I narrowed it down to the filament sensor. I bypassed it and the under extruding issues were gone. I'm printing at 30mm/s

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                      • #12
                        Some pics. Click image for larger version  Name:	20220525_103418.jpg Views:	0 Size:	277.1 KB ID:	15315 Back side, shows glue artifacts.
                        Click image for larger version  Name:	20220525_103518.jpg Views:	0 Size:	250.5 KB ID:	15316 Single layer test. It stays together when stretching.
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                        Top side up close.
                        Last edited by KitCarlson; 05-25-2022, 11:52 AM.

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                        • #13
                          Looking good KitCarlson. I'm sure you know a little water will remove the glue. It will be interesting to see how well it works. Look forward to seeing a photo of it installed.

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                          • #14
                            I used water, but texture is from variable glue thickness. I used 2 decade old glue stick. I purchased blue tape today. Will try that.

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                            • #15
                              Before picture in post number 5 above.

                              Here is after.
                              Click image for larger version  Name:	20220525_144933.jpg Views:	2 Size:	100.0 KB ID:	15322
                              Last edited by KitCarlson; 05-25-2022, 04:06 PM.

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