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Beware the Bowden Tube!

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  • Beware the Bowden Tube!

    I've had my Creality Ender 3 Pro printer for a bit more than a year now, and I've done a huge amount of printing in that time. For most of that time it has been a trooper, producing great finely-detailed parts for me. But of late I'd been having more and more trouble with print quality, primarily due to difficulty with the extruder feed. In the last week or so things finally got to the point where most of my jobs were failing due to extruder feed jams.

    Up until now I'd never checked out the condition of the Bowden tube -- the plastic tube that carries the filament from the extruder drive to the hot end. But today I decided it was worth a look, because unless I figured out what was going on I could no longer produce parts.

    Removing the Bowden tube from its tube fittings was a bit of a chore. I knew to depress the plastic collars on the fittings to release their grip on the tube, but that was easier said than done. I ended up unscrewing the fitting at the hot end so I could take the assembly to the bench to work on it.

    Once I got the Bowden tube out of the hot end fitting I could see there was an obvious problem. The end of the tube had been scorched. I suspected that was the cause of the feeding problem. I cut off the scorched end with an X-Acto knife and reassembled things. Once I got everything together and running again it was plain I had fixed the problem. The machine was printing just beautifully again -- like new.

    IMG_3031.JPG IMG_3032.JPG

    I do not know what material my Bowden tube is made of. I do know that there are aftermarket Bowden Tubes made of PTFE -- a Teflon product that has high lubricity and extreme temperature resistance. I need to get some of that.

    It looks like the Bowden tube may need periodic maintenance or replacement. Live and learn.

    I am very glad to have my machine running like new again. The extruder feed issues were causing me much grief.

    Ed Bianchi

  • #2
    Hi Ed, that'll be PTFE tube which is pretty good up to 240°C, the higher temp stuff is sold as 'Capricorn' tubing, that in itself is dubious, anyone can sell any old tubing called Capricorn but it's supposedly safer up to about 270°C

    I just found their spec page, the dark blue XS series Capricorn is good for 340°C
    Last edited by Kevan; 02-21-2021, 04:54 AM.


    • #3
      Interesting Kevan. Thank you for the link.

      I am debating whether to install a kit that mounts the extruder drive directly on top of the print head or simply upgrade my Bowden tube.

      At this very moment my machine is printing the largest piece I have even done and doing a bang-up job of it. It is such a relief seeing the machine working so well. It will take a full day to finish the part. It is about half done.

      My next job will probably be in TPU (ThermoPlastic Urethane), which is the most flexible filament I've used to date and the one that has given me the most grief. If that goes well I will probably stick with the remote extruder drive. The remote setup keeps the mass of the printer head to a minimum, which allows for faster printing without overshoot, oscillation, stepper motor skips and other undesirable dynamics.

      I'm coming to the conclusion that the entire filament transport system is the maintenance imperative of FFF (Fused Filament Fabrication) 3D printing. Bowden tubes, extruder drive sprockets and hot end nozzles are the key service parts that need to be replaced periodically. How often? My experience says at least once a year.

      It would be nice to find an "hour meter" to install on my printer -- a way to keep track of just how many hours the machine has been run since the last maintenance. That would be very helpful in setting up a routine preventive maintenance schedule. (One of those meters came standard on my John Deere lawn tractor.) All I would need is a clock that runs whenever the printer is powered up. Something I'll research and report on.

      Ed Bianchi


      • #4
        That shouldn't happen if you're printing at the right temperature for PLA. When you start getting hotter, that becomes an issue, especially if your hot end is getting hotter than it needs to be.

        If you're looking at upgrades, then a direct drive extruder is a great one to do. The other is an "all metal" hot end. This is where the PTFE stops earlier, and a heat break goes between the block and the sink. This keeps the PTFE well under it's temp limit, even when printing high temperature materials. If you go with a direct drive extruder, it'll be a good time to switch to an all metal hot end as well.

        These things are all worth consideration when looking at getting into 3D printing. This is also a great example of how starting with a budget printer (nothing wrong with that, Enders are great printers) can cost as much, or more, in the long run, as a more expensive printer (such as Prusa).


        • #5
          I have been routinely printing at 240C for PETG and Nylon, which is probably why my Bowden tube got toasted. At least 240C is what the info screen tells me. I still do not have a good way to gauge how hot my nozzle is. My experience over the last few months has been setting the nozzle temp higher has made things run better. And that may have been due to restriction in the Bowden tube, caused by overheating! Positive feedback to failure.

          I hear you Mr. Flippant about how you can spend as much upgrading a budget printer as buying a high-end printer. I've been working my way up that curve. I have invested in an all-metal hot end, a self-leveling kit, and yes, a direct drive extruder kit. That last was ordered just a day or two ago. I've held off installing any upgrades while I was trying to diagnose and fix the base machine.

          There is an upside to upgrading a 'budget' machine. You get to pop the hood, go in there with wrenches and zip ties, and learn the guts of the machine. You also add and pay for just the features you want, if and when you want them. Lotsa downsides too, no argument. But so far the cost of the upgrades has been quite reasonable.

          I've also ordered two meters of that Capricorn PTFE XS Bowden tubing -- thank you Kevan. I'll give that a try first. The other upgrades may wait a while. At least until I am comfortable enough that the base machine has been sorted and stable. Then I'll monkey with things when I feel motivated.

          I have ordered an hour meter. I'll install that soonest. I'll need to design and print a mounting bracket for it. Fun, fun, fun!

          Ed Bianchi
          Last edited by HO RacePro; 02-21-2021, 01:11 PM.


          • #6
            That's why I recommend getting a kit rather than a completed printer. Even the Enders aren't really kits so much as completed machines that were broken down into a couple parts. Prusa kits are literally just unassembled parts. The only thing that came in one piece was the hot end itself, with the heater and thermistor pre-installed. Otherwise, the entire printer is built by the end user, from the frame to the wiring. You learn a lot... and still have lots to learn.

            As for modding printers... it's a lot easier to take that on when you have a second printer. ;-) No fear that the printer will be out of commission if you forgot to print something you need, or break something in the process. My original Mk3 got a whole bunch of mods, pretty much all printed, and for convenience rather than quality or necessity improvements, AFTER I got my second one. ;-)


            • #7
              I've had 2 printers, the first was an Ender 3, yes it was a hair pulling out affair at times, then I sold it to buy a Qidi which has also been a hair pulling out affair at times but when I look back at what came off the Ender I'm amazed how good those prints were, with a 0.4mm nozzle I could print sharp lettering on my chassis, something the Qidi can't get close to for some strange reason.


              • #8
                I have designed parts with raised lettering on them. I have discovered that if the lettering is in the X/Y plane it can be difficult to get good results. Strangely enough if the lettering is in the X/Z or Y/Z plane (on the face of a vertical wall) I can get very good results even with relatively small fonts. Again, this is on my unmodified Creality Ender 3 Pro.

                An update on my Bowden tube research... At the moment I am printing a 6-pack of TPU parts with an indicated nozzle temperature of 240C and a bed temp of 50C. Running very nicely. TPU is the most flexible filament I have and the most likely to jam in the extruder drive. I am very close to declaring Victory over my recent struggles.

                That large PLA part I printed yesterday had a huge footprint, and I was worried I'd have trouble separating it from my glass bed. Nope. A light sideways tap with an assembly hammer broke it loose easily and cleanly. I've come to the conclusion that when the bed cools the differential shrinkage -- part versus bed -- stresses the glue bond to the point where it takes little force to break it.

                I do like printing on glass. It is extremely heat resistant and has a dead flat surface lacking any surface texture to suck up glue. As long as I can get the parts to separate easily I have no motivation to use anything else. This despite the fact I recently bought two of those magnetic flex sheets. Bought them to replace the one that came with my machine -- damaged due to overheating.

                I have considered buying a second machine. Not as a replacement for my Ender but to give me the ability to print more parts faster. If I establish a business selling printed parts it would make sense. At the moment I'd just buy another Ender 3 Pro. Overall I have had a good experience with the machine, and now it is the devil I know. I am pretty confident I can keep it productive, and It does everything I need it to do.

                Ed Bianchi
                Last edited by HO RacePro; 02-22-2021, 05:13 AM.


                • #9
                  "magnetic sheets" are not all made the same. From what I've seen of the "stuff" that Enders come with, I can understand why people prefer glass.

                  There are companies that make Prusa-style flexible steel sheets with a PEI coating of some kind. Wham-Bam is one of them. I have one for my Elegoo resin printer, and other than the fact that there's no PEI coating, since it's for resin, not filament printing, it's nearly identical. It's stiff, but flexible. It holds to the printer nicely, but pulls off easily by the tabs. Then a quick flex back and forth, and just about nothing will stay stuck. I've said it many times, but I have never, nor will I ever, use any kind of tool to remove a print from a printer. I gave the gift of a Wham-Bam flex sheet system for a friend for Christmas. He'd only printed straight on the steel bed of his printer prior to that, so it took him some getting used to, but he loves it.


                  • #10
                    I cringe when I see and read methods people use to get prints off, use a stanley blade...sharpen the edge of the scraper...use a scalpel...hammer & chisel...sadly all nominees for 'The Darwin Awards' some people aren't capable of thinking past the end of their fingers, blind to danger and often seen in A&E through stupidity.


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