poor print quality with direct drive

Discussion in 'BigBox General Chat' started by smifff75, Sep 1, 2016.

  1. smifff75

    smifff75 Member

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    hi there,

    been printing with a new BB hybrid dual (double titan), ive noticed that while printing with the direct drive nozzle the titan extruder moves while retracting and re-engaging. this doesnt obviously happen with the bowdened extruder.

    the corner of the part that mounts on top of the carriage also lifts up in the corner. ive checked that the nozzle isnt blocked, ive also checked that the temperature settings are correct. the only reason i can fathom is that the force of inserting the filament into the nozzle is bending the carriage plastic.

    This bending is causing flow rate issues on all prints, have no idea how to fix this issue.
     
  2. Spoon Unit

    Spoon Unit Well-Known Member

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    Sounds like something has come loose there. Are the extruder parts self printed or delivered? Can you create a video of what you're observing so we can see clearly? If you look closely, can you see a break in any of the mount pieces?
     
  3. Dr Jeep

    Dr Jeep Well-Known Member

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    Duals have O ring mounted hotends right, so you can balance the height ? What I am thinking is that if the screws aren't tight enough that the o-ring is adequately compressed then it will squash during retraction.
     
  4. smifff75

    smifff75 Member

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    i shall create a video when i get an opportunity.

    spoon: there doesnt appear to be any creaks, delaminations, stress marks on any parts.

    Dr Jeep: i suspected the O-rings but discounted as the actual nozzle does not move but i believe i have got my terminology incorrect, by extruder i mean the titan drive system. the system actually feeding in the plastic. the actual drive system moves up and down by approx 0.5-1mm.

    the parts where delivered as the kit was brought complete.
     
  5. Dr Jeep

    Dr Jeep Well-Known Member

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    Hmm interesting, the forces can be quite significant. I managed to actually break a printed hotend mount on my old k8200 due to having a problem with aggressive retraction settings and undercooling of the heatbreak.
     
  6. smifff75

    smifff75 Member

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    I believe i may have found the solution to the issue but literally voicing the issue on here. checking the retraction settings on S3D, it was set at 70 mm/s (stock settings), on every printer i have ever used (UM1,UM2,UM2+,M90,Prusa i3's, deltas etc.....ive been working with printers for a long time), the retraction was always <40mm/s.

    while i can tell the titan is capable (the bowdened titan handles perfectly), the mount for the duals is only is 2 places in the opposing corners. The high force during the retractions was deforming the plastic parts. i might consider redesigning the carriage of the dual to include increased rigidity, maybe by shifting the screw holes of the block that attaches to the carriage. Alternatively just shift to a completely bowdened design.
     
  7. Spoon Unit

    Spoon Unit Well-Known Member

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    My retraction is set at 4500 mm/min. No trouble with any parts I've printed using this. Also, with the ram purging, I think this was even pushed higher and that never caused issues.
     
    mike01hu likes this.
  8. Montague Flange

    Montague Flange Active Member

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    I've noticed my hot end system moved a bit up and down in the titan. Pain when levelling it. I'm going to try and make a shim to lock it tight.
     

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