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  1. #81
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    Nice stuff. Let us know if the premium price-tag is deserved... here

  2. #82
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    Hi TommyDee,
    This is a really, really good design. I have one suggestion to help some of us avoid pushing smaller tube into a larger tube. This remedies the cost of the native 4mm to 3mm Festo adapter (QSM-4-3 153326). Was trying to PM you the idea, but PM doesn't allow attachments (only links). BTW, there are a few competing designs and most could benefit equally from a similar concept. Just an idea I thought I'd throw out.
    Thanks,
    Tim

    Tubing Adapter built into Design.JPG

  3. #83
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    Hello Tim and thank you for the suggestion. Early on I tried using 3mm tubing and adapter and quickly learned that the grip area was too small to be reliable with true Teflon tubing. Teflon tube is not "qualified" for use in push-to-connect fittings, but it works with 4mm tubing with mixed results for longevity. I had my 3mm fitting just scrape off Teflon while printing and pushing the tube right out there.

    I tried some different tubes that were other versions of Teflon, like TFE, and found that the material had too much stiction, meaning it wasn't as slick to the filament going through it. This made the filament motors work harder.

    Also note that the stock tubing actually measure 2.8mm rather than 3mm. That would be 7/64" which is a strange size. The saving grace is the feed-tube in the cartridge itself. Early development used a printed splice with the barrel-nuts that worked quite well... save the headache of using the barrel nuts.

    My go-to solution today is a short length of stock tubing inside the nozzle housing which has minimal clearance (enough to maintain actuation of the spring). The 4mm fitting feeds the filament directly. If things are properly lined up, and the gaps are managed, you can actually feed the filament into this 2.8mm diameter length of tubing when you plug the 4mm tube into the fitting.

    I do like the idea of having a mid-ship fitting that could split the feed tubes, but you have to know you can pull the old filament through the nozzle's fittings without binding. Removing the tube with the hot-end fully hot is the key to making simple filament changes. This is the reason I don't like the barrel nut in the nozzle housing. This is the first restriction that the "bulb" in the nozzle clears everything, removing the most old filament possible. checking the ID of the hole at the threaded end of the fitting is part of this. And this is a balance... you need a 2mm hole but aligned well enough with the tube in the hot end to make sure you do not deform the 2.8mm tube when feeding in the new filament.4

    Overall, I think we are nearly there for trouble free filament changes. The only real issue I still deal with is the wear of the 4mm tubes from plugging in and unplugging the tube. The worst thing that happens, and it happens more often than not, is that the tube is rasped by the fitting grippers causing it to hold no matter what, and that forcefully removing the tube will break the little gripper part inside the fitting.

    People do realize that rotating the tube inside the push-to-connect fitting will cause this issue of not releasing the tube reliable, right?

    For the latest hub solutions, a 19" tube can be trimmed from time to time until it reaches 17". Then, if you need to, you can splice the tube with a 4mm-to-4mm fitting... of even a printed splice to put 2 4mm fittings into.

    Some more expensive fittings are better about their release... they may have stronger metal grippers... and the release sleeve is longer for more positive release... and most have a lot more free-play than the common Chinese versions. And they are a whole lot more expensive in most cases. Free-play being how much the tube moves in and out between pressure and retract. I have evaluated many common high quality fittings, and even $5 fittings are prone to failure using Teflon (again, as Teflon is not supported by OEMs in PTC fittings).

    I know there is a lot of words here. This is pretty much the culmination of what I have learned to date. If you would like an expanded explanation of any of these thoughts, please feel free to request elaboration on specifics.

  4. #84
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    Quote Originally Posted by TommyDee View Post
    I tried some different tubes that were other versions of Teflon, like TFE, and found that the material had too much stiction, meaning it wasn't as slick to the filament going through it. This made the filament motors work harder.

    Also note that the stock tubing actually measure 2.8mm rather than 3mm. That would be 7/64" which is a strange size. The saving grace is the feed-tube in the cartridge itself. Early development used a printed splice with the barrel-nuts that worked quite well... save the headache of using the barrel nuts.

    My go-to solution today is a short length of stock tubing inside the nozzle housing which has minimal clearance (enough to maintain actuation of the spring). The 4mm fitting feeds the filament directly. If things are properly lined up, and the gaps are managed, you can actually feed the filament into this 2.8mm diameter length of tubing when you plug the 4mm tube into the fitting.
    I was thinking of this at the extruder side, because you must use 3mm OD tubing with the threaded barrel to hold it in place.

    Quote Originally Posted by TommyDee View Post
    Overall, I think we are nearly there for trouble free filament changes. The only real issue I still deal with is the wear of the 4mm tubes from plugging in and unplugging the tube. The worst thing that happens, and it happens more often than not, is that the tube is rasped by the fitting grippers causing it to hold no matter what, and that forcefully removing the tube will break the little gripper part inside the fitting.
    Is the unplugging of the tube needed if everything is working as expected. I did not realize that there was a need for a lot of disconnecting and reconnecting?

    Please take my comments as just clarification and thinking through the steps needed. Frankly I haven't done the conversion (tubing and fittings are on their way). I was thinking that there may be an option that people haven't explored yet to make the conversion a little easier. You and others have basically resolved the fatal flaws of this printer, and I am a beneficiary of that work.... I'm just tweaking. I'll let you know if I catch a snag during the conversion.

    Thanks,
    Tim

  5. #85
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    I love the fact that people provide the input to fine tune the current successes of this group.
    For that I certainly thank you for keeping the process alive.

    Your first question, considering the extruder side is correct if you pull the 3mm (2.8mm) tubing through the top of the stock nozzle (extruder) housing. There is no other way to hold the tube completely inside the small metal tube inside the nozzle housing. I have tried over and over again to actually make a barrel nut fit on true 3mm tubing. It simply crimps the tube too small inside to not jam the filament at some point and making removal difficult or incomplete (long stringy remainder). You will also find that true 3mm tubing doesn't fit well inside the metal tube in the nozzle itself. But again, with a length of the stock tubing found inside the cartridge, you can splice that easily if you have some spare parts. The trick is to not damage the tubing while threading the barrel nut in place. A length of coat-hanger wire in the tube will help to "stuff" the tube so it doesn't twist or collapse. A small cordless drill will help install the nut with a consistent slow speed. Be sure it has enough depth in the chuck.

    Question two involves the process for changing filament. This is an area we still seem to have some level of disagreement on, or maybe just some confusion. Once you get rolling, I would love to see others' options on how to best achieve this including the pro's and con's.

    I have a method that has become nearly foolproof. I know I need to video this process to make it perfectly clear but I simple haven't had the time in the last quarter to get there.

    But I will outline my process quickly and the achievable goals by doing so. Please know that I could easily be overlooking required comments for this process. This also requires me to clarify why I use the hardware I use to achieve this.

    My hardware does not use barrel nuts!
    My hardware is using only a short length of stock tubing inside either a printed nozzle housing or a modified stock nozzle housing. This depends on your level of capability to modify parts. However, I have had great luck with both. Right now, the housing that Bo sells is probably the most robust if you have limitations to modify the stock plastics. This reply is associated with this in mind. Barrel nuts in the nozzle housing will not apply to this discussion as they rarely allows you to remove nearly all the filament in the melt area due to the slightly reduce inside diameter at the barrel nut.

    On the filament driver side, a fixed tube would work just as well as a push-to-connect fitting. Having a quick connect here only helps in that you have a second place to pull the tube from. I suspect a simple barb fitting is quite sufficient on the driver side. Also know that the barb fitting will be stretching the Teflon tube significantly and I have not tested this yet.

    Process for removing and replacing the filament; I know I've posted this elsewhere but lets see how consistent this off the cuff reply compares;

    1) start a test print. (purge does not get the filament hot enough... my observations)
    2) cancel the test print when it is done purging prior to laying down filament. This is known as the Hershey process.
    3) pull the hot-end tube immediately after cancelling the test print! You will get most of the filament out of the nozzle this way.
    4) snip the little bulb of semi-melt from the exposed end of the filament.
    5) remove the hub and back-drive the filament out. It is your choice to keep it or just snip this part that was already "tractor'd" through the system. I re-use it if storage isn't an issue. It does drive easier if you re-align the score marks when you reload the filament.
    6) drive in the new filament until it gets to the end of the tube. Be careful again to not allow the tube to twist in the process. No rasping allowed if you want to ever remove the tube from the cold end again.
    7a) choice: either plug in the tube in the hot-end fitting and drive the filament all the way into the nozzle... (your hot-end needs great alignment for this)
    7b) or protrude the filament ~3/4" (18-20mm) enough for you to start the filament into the small tubing inside the nozzle housing. This is the safer method as long as you know you got the melt out completely. There is about 40mm of tubing inside the nozzle and all this is doing is getting it started before finally seating the tube in the fitting.
    8) drive the filament all the way into the nozzle tip from the hub until it stops.
    9) replace the hub and organize your filament spool with whatever system you are using.

    That's it. You can now either purge out the old color, or better yet, start your print; let the system make the Hershey pile in the waste tray and immediately "Pause" the print. When you "Resume" the print, it will do another Hershey operation and by then, your new color should be pure. Repeat if needed (rarely do I have to). If what I wrote here is your experience in color purging, you've duplicated my experience with filament changes. Note that I never removed the nozzle housing; I do a lot of work with the hub in hand which is what others have tried to eliminate. I can only recommend the Black&Decker drill-driver to ease the 1/2 meter filament feed by hand. A number 2 square tipped hex bit fits the filament driver perfectly.

    With all honesty, I don't know how else to do this. If we could simply splice the next filament onto a tail of the current filament, nothing would need to come apart, no hub would be pulled, no drill driving would be required, no .cube3 file loader would be needed, and eventually the new color would show up. RARELY would I want to wait for a 1/2 meter of different color to be used up in a print before I see the color I switched to.

    The whole idea behind a filament change for me is to have a print where I can change colors at any time! The Hershey operation before resuming is longer than the initial one. If everything is working for you as mine does, you can "Pause" the print exactly where you want the color change; swap the filament; and "Resume" with the new color starting immediately on your print. Another fun trick is to load short lengths of different colors of filament in the Bowden tube and let them play out. If the unit is working properly, and the filaments don't hang up at the tube fitting, you can get an interesting print. And if you can do this, your feed system is pretty much optimized for anything.

    Don't let 9-step reading of the process put you off. This is a very natural process that once you do it, you'll only forget a step or two once or twice. Something like replacing your hub before you finish driving in that last 20mm or something silly like that where you would again remove the hub. Again, you see just how critical that tube alignment within the nozzle housing is for this to work smoothly. I now check every fitting to make sure the hole is 2mm clear; no chamfer on the threaded end if the tube is directly against it. A generous lead-in from the tube side would help. A 3+mm 135+ degree drill bit as apposed to a standard 118 degree bit would go a long way to provide that lead-in chamfer for successful feeding.

    I'm still playing with some of my own printed nozzle housing designs but my go-to is still the modified stock nozzle housings. One thing I want to achieve is that the nozzle housing can be removed from the printer without turning the fitting itself. Almost there! Todd knows what I am up to in this regard and I've posted some hints as to how I am working this elsewhere. Again, I just need time to finish this so I can share it. No priority at the moment.
    Last edited by TommyDee; 01-24-2018 at 03:08 AM.

  6. #86
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    I appreciate the detailed response. I've not had to go through a filament repair yet.

    This guy is using 2mm shrink wrap.
    https://www.youtube.com/watch?v=eJeU9lXiQPE


    Tim

  7. #87
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    This is how I change filament:
    http://www.print3dforum.com/showthre...ll=1#post42955

    Then I use the "Load Filament files" found here:
    http://www.print3dforum.com/showthre...ll=1#post41754

    I never remove the hub or the hot end. Only the tube from the hot end quick connect. I have not had an issue yet and I let the printer do most of the work. Keep in mind that the Load Filament files are designed to work with a 500 mm tube, but you can edit the included .bfb files to work with whatever length you have.

    It's just a matter of preference on how you do it.

    I also don't have any issues with alignment. It is handled internally by the printed parts of my hub and print head.

  8. #88
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    Very nice, I see what you're doing MegaloDon.

    TommyDee, I realize now that the mod has the 3mm OD tub fit into the threaded section of the 4mm OD fitting, so the fitting itself is doing the alignment of the 2 tubing sizes.

    As far as never had to change a filament, I spoke too soon. Neon Green out of the box was very brittle, especially the first section that had been stored in the skeleton tube and bent during storage. It actually poked a hole in the side of the skeleton tube and there were at least 3 breaks.

    Waiting on parts from Amazon tomorrow to do the mod. I'll disect the Neon green cartridge.

    Is there a preferred way to take the chip off of the cartridge. I'd think it would be easier with a little heating and a plastic pry thingy.

    Tim

  9. #89
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    Quote Originally Posted by tprothma View Post
    Is there a preferred way to take the chip off of the cartridge. I'd think it would be easier with a little heating and a plastic pry thingy.
    I used an X-acto knife and pried very slowly. If you do this, use an old blade as it will most likely break the tip. I'm sure there is a better way, but I wasn't worried about breaking an old dull tip. I've tried sharpening them and it works ok, but it's never as good as a new blade.

    The reason I used an X-acto knife is because there is almost no gap around the chip.

    The glue they use is a kind of gummy glue and it wants to drop back down. You need to get one side up and then pull it the rest of the way out. As you said, a little heat would probably help, but overall it's not that difficult.

  10. #90
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    Quote Originally Posted by tprothma View Post
    Very nice, I see what you're doing MegaloDon.

    TommyDee, I realize now that the mod has the 3mm OD tub fit into the threaded section of the 4mm OD fitting, so the fitting itself is doing the alignment of the 2 tubing sizes.

    As far as never had to change a filament, I spoke too soon. Neon Green out of the box was very brittle, especially the first section that had been stored in the skeleton tube and bent during storage. It actually poked a hole in the side of the skeleton tube and there were at least 3 breaks.

    Waiting on parts from Amazon tomorrow to do the mod. I'll disect the Neon green cartridge.

    Is there a preferred way to take the chip off of the cartridge. I'd think it would be easier with a little heating and a plastic pry thingy.

    Tim
    I would use the term "up to" the threaded end of the fitting. Note that the fittings I use only have a 2mm ID hole through the fitting.

    You will find that the green will print just fine once removed from the Cube Bowden tube solution and both barrel nuts removed.

 

 

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