After finally solving most calibration issues, simply cannot extrude. :(

Discussion in 'OpenBeam Kossel Reprap and OpenBeam Kossel Pro' started by ChopOMatic, Jul 26, 2015.

  1. ChopOMatic

    ChopOMatic Active Member

    I received my printer on 6/24 and went to work on it a couple days later. Thus far I've printed exactly one successful part. Missing parts. Bad hotend had to be replaced. Flaky firmware. After finding a good firmware build and working with it on and off for a couple days, I've solved most of my calibration issues. That is to say I can click PRINT and after a normal pre-print procedure, the nozzle goes to where it should be and by all appearances behaves as it should when it gets there. Unfortunately, the nozzle is dry.

    No matter what I try, I can't get the printer to successfully extrude, at least not more than a few minutes at a time. The filament constantly got stuck in the Bowden tube. When OB replaced my hotend, they sent a new PTFE tube. Same thing. The filament constantly stuck in the tube. This is good Hatchbox filament that printed perfectly in my old printer. I bought 3mm ID / 4mm OD PTFE tubing to ease the binding. It solved the binding problem but hasn't mattered one bit in the big scheme.

    Now, no matter what I do, the Bowden tube pushes out of the fitting where it connects to the filament drive. I've even gone as far as mounting a vertical piece of perforated metal strip shortly to the right of the filament drive, and affixing the Bowden tube to the metal strip via a cable clamp. The cable clamp doesn't hold.

    The only thing I know to try now is to try to construct a metal Bowden tube from the filament drive and minimize the travel necessary through a plastic Bowden tube. Does anyone know the size and threads of the output fitting on the filament drive?

    I'm frustrated to the point of madness. $1300 and literally a month of wasting an inordinate amount of time, and still can't print. This is absolutely one of the worst buys I've ever made.
  2. bytecounter

    bytecounter Member

    Hey again Chop. Sorry to hear that you're still having issues. Hopefully the rest of us on the forum can help get you up and running proper.

    Some things to check:

    * The hot ends that come with the OBKP tend to print on the hotter side of temperatures (not so much now with the K-Head, but still on the hot side somewhat). Be sure to play with it to get in the sweet spot for your filament so nothing backs up. I can run my hot end on the low side of temperatures for the start of a print OK, but it'll eventually start clicking and grinding filament down (pre-cursor to the cold end bowden tube being pushed out).

    * For the bowden tube coming off (I presume we're talking about the SeeMeCNC part), try printing and installing Chris' clip here:
  3. David Boyd

    David Boyd Active Member

    Couple of questions to see if something triggers a suggestion:
    1. With the hotend in home position and heated can you extrude into the air?
    2. If yes, can you mark 110mm from the entrance to the easystruder then tell it to extrude 100mm - what is the resulting measure.
    3. If no, with the bowden tube removed from the effector and the hot end hot can you push filament straight into the hot end by hand and have it exit?

    The goal is to isolate where you are getting mechanical binding.
    Are you running the all metal k-head or the original modified j-head you may have mentioned in the past but I don't remember?
  4. How does he print an accessory without a working printer?
    Last edited: Jul 26, 2015
    ChopOMatic likes this.
  5. bytecounter

    bytecounter Member

    In this case? With the other printer @ChopOMatic has on hand. I am assuming it works. If not, apply creativity and ingenuity. But the bowden tube popping out is likely the symptom of another problem that when solved, should not make the clip a critical part.
  6. Terence Tam

    Terence Tam Mr. OpenBeam Staff Member Vendor

    Couple of things.

    1) On the K-Head side, make sure that the tube is pushed in as far down into the heat sink as possible. This was likely the root cause of all the jams you *were* having, before we replaced the K-Head. See this new video I shot: Bowden Tube Installation/7

    2) On the EZStruder side, your new 3mm ID tubing is likely the culprit. We have not switched to PTFE tubing supplier for our kits, but we are currently evaluating this:

    We were also told that your PTFE tubing was *missing*, not that you were hoping for a new rev PTFE tubing (which we would have told you: We don't have any).
    Virtually everyone here is using 2mm ID tubing on their machines substituting PTFE for MFA, your substitution of a tubing with a 0.5mm thick wall instead of a 1mm thick wall tube is likely the cause of the issue of the push fit not holding.

    3) Using a key chain lanyard to hold the bowden feed tube up also seems to have helped some people in some instances with their printer. See this:

    Edited to add:

    See discussion here also about PTFE tubing:

    -=- Terence
    Last edited: Jul 27, 2015
  7. ChopOMatic

    ChopOMatic Active Member

    Thanks to all you guys for taking time to offer suggestions. Much appreciated.

    I was able to successfully print another small part tonight, amid perhaps 5-6 failed attempts. Raising the extruder temp to 235 instead of 225 seemed to help, but it still hasn't really solved the issue. I'm attaching a pic of the last failed attempt. As noted in the annotations on the pic, while the printer was laying down the big solid area up top, I was manually holding the Bowden tube in the motor fitting and the pressure was so strong that it was tough to hold it there. As you can see, there's some weirdness going on with the extrusion. The instant the effector moved to the bottom part, the backpressure on the tube disappeared and I was able to let go of it.


    Byte: Yes, I have another printer. Unfortunately, it was in the middle of an upgrade to E3D v6 hotends when I bought the KP. One of my very first print projects on the KP was gonna be to print the parts I need to finish the upgrade of the other printer, a FlashForge Creator Dual.

    David: I'm running the all-metal K-Head. On whether I can extrude into mid-air, usually not. After a lot of hits and misses, however, I did get it to do so and I marked off 100mm on the filament and then did a 100mm extrusion. I was doing this measurement with a ruler so it wasn't terribly precise, but it was very close to 100mm. As to manually feeding filament directly into the hotend, I removed the Bowden tube from the effector, then inserted a short piece (10" or so) of PTFE into the hotend for the test. (I didn't want to feed filament "nakedly" into the hotend.) I was able to push it in and it extruded out the bottom without undue force from me. It definitely felt like the hotend was pretty free.

    Terence: Yes, I've been very careful to be sure the Bowden tube is seated into the top of the heatbreak. I like the retractable lanyard mod; I have several of those around here and will definitely implement that. Not sure what you're talking about with regard to my saying my PTFE tubing was missing. The only thing I've said to you guys on this topic was this, which was in a PM to Mike: "And if you haven't shipped it yet, you might include a new Bowden tube, as well. In addition to the jamming hotend, the filament seems to actually stick in the Bowden tube quite a bit, between the filament drive and the hotend."

    I've ordered some 2mm ID 4mm OD PTFE from Amazon, along with what look to be higher-quality SMC push-connect fittings. We'll see how that goes. As I've mentioned a couple times, with both the original Bowden tube in the kit and the replacement that Mike sent, I've had the filament stick in the tube on multiple occasions. It's Hatchbox ABS filament, and I've pulled off a good amount from the spool and measured it in about a dozen different places along the length. The range is 1.71 to 1.82, and most of the measurements were 1.77. By "most," I mean seven or eight of the dozen measurements were 1.77. In fact, both of those tubes have filament in them right now that I've been unable to pull out, despite serious efforts to do so.

    Again, big thanks for the dialog, guys.
  8. Terence Tam

    Terence Tam Mr. OpenBeam Staff Member Vendor

    FWIW, that is the exact push fit connector that we're shipping with our kit. I've had it fail a few times, although recently with a printed clip it's been failing way less. And it's only a 5 minute print or so, so I'd suggest printing that when you have a moment.

    With regards to the back pressure - it can be a sign of non-flat auto levelling (which we are trying to address with the FSR modification). It should go away on the second or third layer, can you confirm that?

    -=- Terence
  9. ChopOMatic

    ChopOMatic Active Member

    Hmmm, you're right; sure is the same connector, Terence.

    I've only tried manually holding the tube in place one time, and that's during the print that resulted in the pic I posted last night. Not sure how many layers it laid down, but the backpressure definitely didn't go away. Or at least it didn't go away when it was on that area of the print.

    Are you saying the replacement tubing Mike sent with the new hotend was not PTFE? I just assumed that it was; it looked distinctly different from the tube that came in my kit. If it wasn't, tomorrow will be my first attempt with 2mm/4mm PTFE. Maybe it'll be the fix.

    What's the status of the FSR mod?
  10. ChopOMatic

    ChopOMatic Active Member

    @bytecounter @David Boyd @yay_another_forum_account @Terence Tam

    After trying everything I could think of and everything you guys could think of and everything I could find out there on the big old Internet to stop jamming and start extruding, as a last gasp I tried something different. I switched to a cheap, Chinese heatbreak that I'd bought a few of on AliExpress. They cost a buck each. I printed without a hitch the first time with it, and every time since. Not a single jam with it thus far.

    One-dollar heatbreak on AliExpress
    Terence Tam likes this.
  11. Terence Tam

    Terence Tam Mr. OpenBeam Staff Member Vendor

    Awesome. So the issues are resolved and you're printing?

    (At least with this K-Head design, you guys can't yell at me for being "proprietary". We designed it to be able to use as many E3D parts as possible. :p)
  12. ChopOMatic

    ChopOMatic Active Member

    Well, I was. :(

    Printed several ABS parts without a hitch. Switched to some Colorfabb PLA and nothing but trouble since. Radically under-extruding, and that's after I jacked the temp up to 250. At PLA-appropriate temps it wasn't putting out anything. And even at this temp, it's putting out something that looks about like a spiderweb. I expect small since I'm trying a .30 nozzle, but that same nozzle was doing fine with ABS. Now this is what I'm getting with the PLA. Sadly, I think it's time for me to give it up and return this printer.

    2015-07-31 19.33.11.png
  13. David Boyd

    David Boyd Active Member

    @ChopOMatic - So ABS did Ok but PLA immediately choked. I am almost wondering if it is a cooling problem. If the PLA gets too
    hot as you know it will soften which can keep it from extruding.
    Have you verified your cooling fan is running and in the correct direction?
    When this is happening do you feel the filament skipping?
    What happens if you go back to the standard 0.4 nozzle - the smaller nozzle will create more back pressure and
    that could cause PLA softened by heat to not extrude?
    How chewed up is the PLA when you remove it after this?
    Can you go back to ABS and print?

    This one is a stumper and has me intrigued. I am in the process of installing my k-head now and looking at the heat sink I
    worry about temp with PLA given the low surface area and small fan cooling it.
  14. chadman

    chadman Member

    Out of curiosity, how fast are you printing?
  15. ChopOMatic

    ChopOMatic Active Member

    2015-08-01 17.10.48.png
    @chadman I think the print pictured was at 30mm/sec for outer and inner perimeters and 40mm for infill.

    @David Boyd, you're probably right on target. When I removed the Bowden tube, the PLA at the end (the area that was inside the heatbreak) was swollen and clogging the tube. And though I feel like an idiot for not having checked the fans before now, now that I have, it explains a lot: Not one of the three fans ever comes on at any phase.

    Issuing M106 S255 turns on the right fan. (See pic for orientation.) Anyone know the codes for turning on the other fans?

    Perhaps I'm running the wrong firmware?

    2015-08-01 17.10.48.png
    Last edited: Aug 1, 2015
  16. ChopOMatic

    ChopOMatic Active Member

    UPDATE: The pic in my post immediately above this one shows an attempted ABS print during which I confirmed that no fans were running. I tried a few things after that:

    1. I inserted manual starting Gcode of M106 S255. The extruder would never get above 180ish.

    2. I inserted manual starting Gcode of M106 S128. The extruder never got above 200ish.

    3. I inserted manual starting Ccode of M106 S80. The video is what's in action right now.
    Last edited: Aug 2, 2015
  17. AndyG

    AndyG Member

    First off you need to locate the always on fan. It is hardwired directly to 12V? so as soon as your turn on the printer it turns on and it's designed to never be off (IE there are no commands in software to disable it). This is the cooling fan for the heatsink and it is opposite the big hole where you can see the heatsink on the end effector. On my printer I would consider it to be on the "front" side of the printer. The fan in the attached picture is the always on fan.

    My printer is printing so I can't get a picture of the base but if your LEDs are working your wiring harness is probably OK and you'll need to look at which posts the fan is connected to. Do you have a multimeter?

    Attached Files:

  18. ChopOMatic

    ChopOMatic Active Member

    Thx, @AndyG. Yes, I have a multimeter. I'm running a G30 auto-calibration at the moment but as soon as that finishes I'll check that fan's terminals for power.
  19. ChopOMatic

    ChopOMatic Active Member

    @AndyG, found and fixed a lead from the always-on fan that had come loose from its wee mooring.

    You know, there are a lot of things about the design of this printer that I like, and I said so often during my criticism of the terrible instructions. When I got to the effector assembly, however, I was completely baffled (and still am) as to this part of the design, requiring the connection of tiny-gauge wiring to screw terminals, as opposed to having something like...oh, I don't know...plug-in connectors. SIGH.

    Big thx to you and others for reminding me to check the obvious: fans.
  20. Terence Tam

    Terence Tam Mr. OpenBeam Staff Member Vendor

    Ironically, this was the one part of the printer that was most heavily influenced by "Design by committee". The overall goal was to try to design it to be as compact as possible.

    It is also very high on the list of things that I am re-engineering for future release / upgrades. Let's just say we've learned some very expensive and tough lessons. We got lucky that we could make the K-Head work for all the existing units out there, but we'll be fixing it properly in the next revision.

    -=- Terence

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