1. Got a question or need help troubleshooting? Post to the troubleshooting forum or Search the forums!

Partially Solved Issues Related to Problematic Extruder Design

Discussion in 'Troubleshooting' started by robodobo, Apr 16, 2017.

  1. robodobo

    robodobo New Member

    Joined:
    Aug 8, 2016
    Messages:
    12
    Likes Received:
    7
    When I set up the C2, I followed the instructions in the beautifully designed Quick Start Guide. One step didn't seem right, that's when you're asked to press the filament release button (blue lever). It doesn't budge until you stand up and use your upper body to force it down. Then all six rods on top bend and the print head sinks precariously. This just doesn't feel right. There's no way to make the kind of pressure needed with one hand, the whole extruder assembly is too slippery.

    My observation is that the pressure on the filament seems excessive.

    Other than my fear of breaking something when loading the printer, there are three or four more problems that are related to this observation:
    • The clicking sound when the extruder motor skips. The filament will not be ground down because the motor does not have enough torque to so. That's good, less chance of clogging up the printer.
      But is the motor is designed to withstand prolonged abuse if something goes wrong during a long print?
    • The motor does not have sufficient torque to drive PETG through a 0.2mm nozzle even at 250C. Thus at any time in the print, extrusion stops with clicking sounds. Same problem during priming, where the temperature is not set to that of the material, but at 210C if I remember right. The motor must spend a lot of its energy just deforming the filament. There's a pic below where the bottom strand has become clouded and much flatter after a trip through the extruder gear. The strand on top is still shiny and less flattened after the same treatment but after a repair that I describe below.
    • The horizontal rods that pop out of the machine. There are 20 set screws for the horizontal rods; this is by itself problematic for a consumer friendly machines. The popping is expedited by the extreme force that must be applied to load filament.
    • The message "Main Board Not Detected" is sometimes triggered when loading filament. That's from the little PCB that sits on top on the extruder. It's protected only by the thin top cover. Everything wobbles.
    • The M3 screw that holds the roller against the gear seems entirely underdimensioned.
    [I bought the C2 to print PETG with 0.2mm nozzle, which I installed after initial repairs made it possible to print with the installed 0.4mm nozzle. The nozzle change is a scary experience at 250C, where custom made wrench and socket would make it much easier, but that's another story. Other manufacturers make nice little kits for this. Robo 3D instead made a so-far unfulfilled promise of a quick change nozzle.]

    Capture.PNG


    The repair: I used a Dremel with a grinding wheel to remove about 1 1/2 turns from the spring.

    This results in the less flattened filament (top). So I can now print PETG, no clicking sounds. Also, rods haven't popped out again. And Main Board Not Detected doesn't come on.

    My conclusion: The extruder design must be changed to allow adjustments to spring compression, involve stronger parts, and some way of one-handed operation of lever.
     
    #1 robodobo, Apr 16, 2017
    Last edited: Apr 16, 2017
    mark tomlinson likes this.
  2. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
    Staff Member

    Joined:
    Feb 21, 2013
    Messages:
    23,912
    Likes Received:
    7,338
    Not sure what filament button you are discussing. If it is the blue lever arm one on the extruder it should be tough to press down. You want to have it press the filament to the feed gear pretty strong.

    What speed are you trying to print with a 0.2 nozzle? Is it a best half of what the 0.4 speed was? You need to drop print speeds in a linear relationship to nozzle size. Otherwise you will get a lot of backpressure which on the direct style extruders is a problem that needs solving. Something like the GregsWade (a heavily geared extruder) does not have those issues. My delta uses a direct similar to the C2 and I fought with that for a good while.

    I have not tried PETG with the C2 so ... no comment there.

    The spring on mine was not what I would call overly strong.

    Also, the comments regarding the extruder and printer design are best sent to Robo3D, not the community at large since we just use the printer and Robo HQ does not spend much (really not any) time reading the forum comments. :) I know people think that this forum is a direct line to them, but ... not really the case. It is a wonderful community and lots of other users here to assist with problems that others have encountered. Your fixes listed are a nice resource for the others, but don't think that this information is getting beamed in the RoboHQ ...
     
    #2 mark tomlinson, Apr 16, 2017
    Last edited: Apr 16, 2017
  3. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
    Staff Member

    Joined:
    Feb 21, 2013
    Messages:
    23,912
    Likes Received:
    7,338
    My rods were knocked loose in shipping and they were a pain to get properly re-positioned (see my long unboxing thread for details).
    I wish those were more securely fastened.
     
  4. robodobo

    robodobo New Member

    Joined:
    Aug 8, 2016
    Messages:
    12
    Likes Received:
    7
    Thanks, Mark, I edited: the official name is "filament release button" (from guide). Yes, it should be firm.

    Oh, I think it much worse than linear, resistance to flow grows by x 16 when halving the nozzle diameter! Anyways, it's necessary to go slow, extremely slow, about 10 mm/s for sufficient detail quality --- I don't limit speed per se usually, I limit acceleration to about 10-15 mm/s^2 and my objects are small.

    Also, your comments about other extruders are well-taken.

    Well, that would be a concrete question to the Robo engineers: how many newtons to release? In my case, the spring is way too stiff. I think it it exerted many times the amount of pressure needed. Thus the poor little motor is exhausting itself just flattening the filament.

    My opinion is that if they don't bother to read the Troubleshooting forum that the users of the their shiny new generation printer turn to, then there's no hope. Anyways, a couple of the issues that I encountered have been discussed before, so they're offered as a possible solutions in some situations.

    Also, I should say that the C2 now prints better than the R1, this is probably because the fans are much more effective on small objects. The extruder, now that I've gotten it to work, may also offer better control of pressure but I'm just guessing.
     
  5. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
    Staff Member

    Joined:
    Feb 21, 2013
    Messages:
    23,912
    Likes Received:
    7,338
    Perhaps, but in reality a linear reduction in speed has worked for me as long as I have used FDM printers (so going on 5 years now).
    If I drop the nozzle from 0.4 to 0.2 and cut my print speed in half life will go on as normal.

    This is not a direct line to Robo :)
    It is entirely a community of Robo users.

    Do they ever come over here? Not often.
    @Harry is the official admin and comes by to make sure we have not started a civil war or anything every so often, but the main players? Very seldom. If you want Robo to see that information you collected I would suggest using their "contact us" links :)
     
    Geof likes this.
  6. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
    Staff Member

    Joined:
    Feb 21, 2013
    Messages:
    23,912
    Likes Received:
    7,338
    As for the tension on the gear/filament... our delta uses an EZRStruder and it mashes the heck out of the filament to the drive gear. The spring it uses is double the size and strength of the Robo one.

    I am not a real fan of the direct extruders regardless of brand, I am more of a fan of geared ones. We even (at one point) converted our delta to use a geared extruder (printed a GregsWade for it) but eventually got the direct extruder working good enough by swapping hotends to lower the backpressure.

    When we did the dual-extruder conversion thread for the C2 we also used a direct extruder, but a different style. Details are in the thread for that project.
     
  7. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
    Staff Member

    Joined:
    Feb 21, 2013
    Messages:
    23,912
    Likes Received:
    7,338
    Overall you are at least providing good information to those willing to dig in and hack their own (like our dual-extruder thread). Just don't expect that the main players at Robo3D are seeing this information. That I would not assume and I want to set your expectations (don't be surprised at the "sound of silence")
     
  8. daniel871

    daniel871 Well-Known Member

    Joined:
    Apr 18, 2015
    Messages:
    1,322
    Likes Received:
    510
    Also don't be surprised when people like me post about how low an opinion of Robo printers they have.

    I'm surprised PETG prints at all on the C2 with anything like reliable adhesion on the build plate. Did you add a heater to the bed?
     
  9. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
    Staff Member

    Joined:
    Feb 21, 2013
    Messages:
    23,912
    Likes Received:
    7,338
    The surface you print on is not plastic, but rather something similar to PEI. My experiments show darn near everything will stick. Some exotics though really want a heated bed (even if not at high temperatures) so I wouldn't (for example) suggest trying full-on nylon. Clearly ABS is a no-no as well.
     
  10. robodobo

    robodobo New Member

    Joined:
    Aug 8, 2016
    Messages:
    12
    Likes Received:
    7
    No surprise! I was about to look for my voodoo dolls. But with the capital infusion, grown-ups may help steer the company and get over this hump. And I got my printer work...
    No, I'm pleased so far with the performance of the raw build plate for PETG -- no stickers. I do use rafting + a very thin coat of unscented All Weather Aqua Net, the hairspray. Rafting is mandatory in most of my applications anyways. With the C2, there's lots of headroom for a quick dusting that avoids the mechanical parts.
     
    mark tomlinson likes this.
  11. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
    Staff Member

    Joined:
    Feb 21, 2013
    Messages:
    23,912
    Likes Received:
    7,338
    When you start expanding your inventory you learn to dislike a number of others in that same price range even more...
     
    Geof likes this.
  12. daniel871

    daniel871 Well-Known Member

    Joined:
    Apr 18, 2015
    Messages:
    1,322
    Likes Received:
    510
    Yeah. I still get flashes of irritation whenever I print something on my Monoprice V2.1 knockoff of a knockoff of a knockoff and remember that particular object never printed properly on the R1.
     

Share This Page