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Solved Extruder (locking arm question)

Discussion in 'Troubleshooting' started by JWW, Jan 22, 2018.

  1. JWW

    JWW Member

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    I removed and installed a new Robo extruder, which I've done once before about a year ago. I am assuming the thermistor was history but haven't been able to test it yet. I can't get the set screw out of the block. BTW, what size is the allen wrench?

    Secondly when I installed the new extruder I can't get the 'locking arm' fully closed? What could be the problem, I'm clueless. When I did it last time it wasn't necessary to loosen any screws anywhere, I simply moved the locking arm out, removed the extreder, installed a new one, then closed the locking arm. I recall it took a little force to do so. What's the trick? Could the machining tolerances be off a touch on the extruder?

    Robo hot end locking arm.jpg
     
  2. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    M3x3mm or M2.5x3mm IIRC. I don't have one handy to measure.
     
  3. JWW

    JWW Member

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    Has anyone ever experienced the extruder locking arm scenario I mentioned above? Is there a solution?

    Thanks,
    -JW:
     
  4. Geof

    Geof Volunteer Moderator
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    If it doesn't close its possible the bearing and pin are slipping out or place or its broken and needs printed :)
     
  5. JWW

    JWW Member

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    Pretty simple operation. Open the lever, push the new extruder in, close the lever. When you looked at the new extruder installed you can see it's crooked (images below). Also the new extruder top is different than the original. One image below is looking at the extruder opening from below (like you were laying on the print bed).
     

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  6. JWW

    JWW Member

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    Thanks trying to help out. I haven't a clue where the bearing is located you mentioned or where the pin might be that you are talking about. The extruder locking lever looks fine to me physically, it doesn't wobble, no slop in it up and down etc. and closes tight when no extruder is installed.
     
    #6 JWW, Jan 24, 2018
    Last edited: Jan 24, 2018
  7. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    Scrape the red gunk off. It is a dunsel. I have no clue why they stocked them that way :)
     
  8. JWW

    JWW Member

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    ... thanks but the problem isn't solved if I do.
     
  9. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    The default hotend does not use the red gunk, the replacement should not have it either.
    Your call :)

    I can't see it well enough in the pictures to judge, but I assume if you stick the original hotend back in there it will close?
    If not then something mechanical has gotten askew.
     
  10. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    I would have thought the red gunk would prevent it from mating fully up into the socket and that would then partially block the quick release plate.
     
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  11. Geof

    Geof Volunteer Moderator
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    Misunderstood the issue. Yes removing tge red gunk should sort it otgerwise tge quick release (lever) has an issue. Both screws tight when installed ?
     
  12. JWW

    JWW Member

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    E'gad(s), so hard to explain this problem but I will try again. I am NOT going to use the extruder that has the red gunk on it, so let's eliminate that from the issue. It's what my Robo R1 plus came with originally. It's pretty obvious to me that it worked because the red gunk is 'soft'. You can 'clearly' see the depression in it from the extruder bores 'top'. It simply smashed it down. Sorry I even brought it up. That topic is history please.

    Next, I'm not talking about the tension arm that has a roller bearing and two spring loaded screws which apply pressure onto the filament being feed into the top of the extruder.

    The whole brief story is ... I had a bad thermistor months ago, probably 10 months ago, can't remember. Some people told me I had to fabricate them. Robo didn't have them in stock, so I didn't use my printer for a long time and I went back to machining (Bridgeport mill, lath etc.). since I didn't want to deal with it as I had numerous other real machining projects I had to finish. Then weeks/months later I noticed Robo had complete new extruders in stock and I ordered TWO of them and a couple extra thermistors that also were in stock. So the extruders finally arrived. I installed one of the new extruders about a month ago, no problem. Opened the extruder locking arm, inserted the new extruder, then closed the extruder locking arm. Pretty simple and straight forward. Wired it back up, fired up the printer and started printing. I've been printed for about a month now on a prototype project, sweet, no issues, nice looking prints etc. Then something happened. I 'assume' the thermistor when out on the newly installed extruder and caused a clog. I couldn't replace the thermistor because the allen screw head strippped out. I have metric allen wenches etc., and thought I had the correct size, dunno, but regardless the head is rounded. I don't care about the screwed up allen set screw and don't want to discuss that either. I will machine it out someday, use an easy out, whatever, throw it away ... that's not an issue. So to save time and get back to printing my prototype pieces I installed the second spare extruder. I can't get the locking lever to close all the way, plus you can clearly see the extruder nozzle is cooked (not parallel with the bottom of the plastic housing). The extruder locking lever seems physically fine to me, it's snug when I close it with no extruder in the bore, no up and down wobble, I did notice two screws on the extruder housing but I've never messed with them. The phillips head is accessible on the bottom of the extruder housing. I assume the 'other' is a screw too but I can't see the head of it without taking the fan off. Surely this isn't necessary to simply install a new extruder? I didn't have to do this on the last new extruder I installed a month ago (that the thermistor when out). I wasn't able to nail the focus with my cell phone on the second image. That't a pic of the BOTTOM (looking up) of the extruder housing. The first is obviously of the locking arm.

    I'm simply confused as to what it could be going on and looking for help.

    Regards,
    -JW:
     

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  13. Geof

    Geof Volunteer Moderator
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    If that quick release is indeed good then your 2phillips screws are loose allowing the hotend to tilt. Yes to access the 2nd Phillips you need to remove that fan, normally not necessary but the front screw is to change the hotend or should be. If your original hotend goes in fine then it's possible the replacement hotend has an issue, grab your calipers and double check it to ensure all is well and no manufacturing issue happened.
     
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  14. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    This. Sadly the Hexagon is not as high a quality as other all-metal hotends that size. While I don't think it is common, it is certainly something check. After all you have eliminated everything except the hotend :)

    If the old hotned fits and the new one does not, there is clearly a problem with the new one.
     
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  15. JWW

    JWW Member

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    Still haven't solved the problem. I have talked with tech support so now I'm back here. Here's what I think. Hopefully I can describe the problem clearly, if not, let me know. I think the Heatblock is screwed on to far on the Heatbreak, which in turn narrows the gap between the top of the Heatbock and bottom of the Heatsink. When the Hotend assembly is inserted into the bore the top of the heatblock (see A below) actually touches the bottom of the bore housing BUT the Heatsink itself isn't in the bore enough so the locking arm can't grab the machined ring properly. The Heatblock is preventing the clamp from pulling the assembly UP any further. I could be wrong but I'm pretty sure I'm right.

    I've never had one of these apart so I'm not sure of the procedure OR assembly protocol? There are 'flats' on the Heatbreak but I don't have a wrench that fits. What's the procedure in loosing the Heatblock? Just guessing it probably only needs to be unscrewed about 1/2 turn, maybe a full turn. Doing so will allow the entire assembly to insert MORE into the bore so the latch will catch. My old Hexhead assembly is broken (second pic below) and I can't screw the heatblock on more (which it needs), it just spins but it fits and locks in place. Why, because there is a larger gap between the top of the Heatblock and bottom of the Heatsink. If I pull on the 'old one' it just comes apart like the last picture below depicts).

    Question, how do I go about loosing the Heatblock to lower it. If so, does it screw anything up. If I put a pair of needle nose pliers on the Heatbreak flats and if it holds, do I simply back off the Heatblock? I don't want to break this one considering how long it took me to get it.
     

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  16. Geof

    Geof Volunteer Moderator
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    I'm not sure I follow what the heatblock is hitting? The fan shroud? but regardless to remove the heatblock the hotend needs to be heated. You use a wrench to hold the block and a wrench to break loose the nozzle. When the nozzle is loose you'll leave it "unscrewed" 1/4 turn from the heatblock and thread the heatbreak (threaded pieces that goes from the hex fins on the cold end to the heater block) until it touches the nozzle on the inside of the heatblock (that makes your seal). Then you'll heat up again and snug down the nozzle to finish making the seal.
     
  17. JWW

    JWW Member

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    What a PITA. It shouldn't be this way. Something is assembled incorrectly. The pic below explains it the best I can. It's pretty simple to understand. If the Heatblock is screwed on to far it doesn't allow the entire assembly to go into the bore enough. The TOP of the Heatblock acts as a STOP (no go). It determines or gages how far the whole assembly inserts into the bore (the opening). If exaggerated and the Heatblock is screwed on as far as possible, the assembly won't insert in the bore as far and then the latch won't come close to going into the machined groove once closed. On the other hand, if the Heatblock was screwed nearly OFF the entire assembly would go all the way into the bore very easily but there would be a huge gap between the top of the Heatblock and the bottom of the bore housing. It's my opinion that once upon a time Robo designed the Hexhead assembly to be a touch flexible so that the DISTANCE from the TOP of the Heatblock to the machined groove wasn't super critical and the rubber gunk on top was compressible so the assembly could be pulled up in place (a touch) once the arm was closed.

    The two new assemblies I have distances from the top of the Heatblock to the bottom of the groove are off slightly. When I try to close the locking arm the assembly isn't in the bore far enough and the locking arm is pushing the TOP of the assembly over and cocking the entire thing and also won't close because of that. I haven't been able to make the tech support guy understand the concept and now trying here and looking for a solution.
     

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    #17 JWW, Jan 31, 2018
    Last edited: Jan 31, 2018
  18. Geof

    Geof Volunteer Moderator
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    will you measure the cut away from the old to the new one? Something looks funny there. I'm guessing at this because without putting hands on it myself it still makes no sense but what I'm guessing is your cold end fan "mount" is not allowing the wires to clear the fan which is whats pushing it over. take out the thermistor and heatercore and see if it fits. Your original hotend is not assembled correctly.
     
  19. Geof

    Geof Volunteer Moderator
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    worse comes to worse I'm prettty sure I have a hexagon without a thermistor and heater I can drop in the mail if you feel like paying postage and you can install that one.

    (FYI- Robo did not design the hexagon, its just a hexagon hotend :D)
     
  20. JWW

    JWW Member

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    Thanks for the offer, it is appreciated but that's not the problem.

    The old finned hexagon and the new finned hexagon are the same, measurement wise. The 'problem' (and I'm positive) is nothing more than how far the Heatblock screws on. I tried to illustrate that in my last posting. If the Heatblock screws on to far the "Hotend assembly" won't insert into the bore far enough, then the latch won't close in the machined groove because the groove is to LOW. I am positive that is the problem.

    Since I am positive that is the problem (like without a doubt) I didn't want to break the new Hotends by un-screwing the Heatblock a little. The last time I had a clog I took it apart I broke it. It just spins, plus I can pull the whole tube and everything out. I posted a pick of that a while back, holding it in my hand (like 5 postings above). I didn't want to go through that again and waste the other two new ones I have.

    I also didn't know if backing off the Heatblock messes anything up internally, or generates a cold spot inside that will create mo jambs in the future.

    -JW:
     

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