Old printer needs some love...

Discussion in 'Calibration, Help, and Troubleshooting' started by Max Pinkney, Jun 28, 2018.

  1. Max Pinkney

    Max Pinkney Member

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    So i've had my bigbox for coming up 2 years now. It was a home build back at the time, which up until about the last 8 months I have had running some what smoothly (excluding the occasional resolved fault here or there). Recently though it has been failing to print consistently and now the last few attempts have produced nothing and I spend hours looking at adjusting material settings to no avail. My conclusion is that it has to be a hardware fault somewhere.

    Usually the failure is through the PLA getting dragged off the glass by the nozzle. But I'm also experiencing the filament getting jammed in the nozzle A LOT, which is causing jamming halfway though a print - very annoying. But now it's at the point where I won't even attempt a long print for fear it will fail.

    With a printer this old, undoubtably there's some TLC that needs to happen to tune it back up, so i'd like to know what's the first port of call to look at testing/replacing.

    Thanks for the help!
     
  2. jfb

    jfb Well-Known Member

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    I assume from what you've said that you've redone/rechecked the calibration, nozzle height etc...

    I also don't claim to be any kind of expert, so I can only suggest where I'd start :)

    Sounds like you may have 2 problems:
    1) Jamming
    2) possibly inaccurate z height - maybe skipped steps?

    Basically, you're probably looking for worn parts or electrical issues. If you tend to get the issues only after some time through a print, then I think that's likely to be electrical - either a component failing maybe due to heat, or possibly stress fractures in the wiring.

    It's a case of go though each part looking for issues - sometimes the exact way a failure happens can give clues - for example it it always in the same place in the same print - that might be electronics suffering from heat issues perhaps.

    Mechanically, I'd probably start by looking at the extruder/hotend components. Wear in either can cause a lot of issues, and as with all mechanical parts, wear is a fact of life. I'd also check for any looseness/slop in the bearings on the x & y carriages. I've replaced all bearings in my bigbox once so far, and on my cheap i3 clone at least twice. Sooner or later the rods will wear too, but bearing are likely to go first.

    Other things to look for might be motors and cables - motors are probably fine unless getting overly hot and I'm unsure how to test them anyway (swap them round and see if the problem moves?) - maybe someone can suggest a way?, but I've had issues (not on the bigbox) where motor cables started to fail at flex points - you can measure that with a multimeter while moving the cables around. Motor drivers can fail too or get cranky if too hot - maybe swap some around and see if the problem moves. The extruder driver gets a lot of work, and if it's playing up then that could cause you problems with extrusion - check how hot it's getting. That's also true with the z motors and drivers if they're constantly moving to compensate for bed alignment.

    Check that the hotend is clean and has no blockages, and if you can, check for wear or scratches internally. Personally I'd probably replace the nozzle anyway if you haven't already. If you have the tools handy, check that the nozzle temperature seems to match more or less what you think it should be, and check the resistance of your heater and pt100 - I doubt that's the issue, but it's an easy check and therefore easy to eliminate. The expected resistances are somewhere on the forum - sorry you'll have to search as I can't remember them offhand.

    Next I'd do a few tests on how repeatable and consistent your z sensor is - if that's not reliable it could cause you issues. I can see some accumulation of some kind on my IR sensor - presumably from filament fumes over time. That's not caused me an issue (yet), but I'd not be surprised if it does sooner or later. If you can do any prints at all, I'd be tempted to see how accurate your z movements are - print a few small calibration towers and measure the height - worn z screws or some such could be an issue, as could skipped steps, and it doesn't take a lot. If you can't or don't want to print some towers, then you might try this
    - move the bed to zero and check the nozzle distance (feeler gauges are great for that ig you have some) - if not, use paper.
    - move the bed, say 100mm
    - move it back 100mm
    - repeat a few times
    - Check the gap from nozzle to bed again - if it's the same as step one, then that would seem to say that's fine.
    A similar test using many shorter moves might allow you to find if you're missing steps after a while (eg after the motors have gotten hot) - I'd probably create a gcode file for that.

    I think it's really going to be a process of elimination - start at the hotend, then on to the extruder, then moving out from there to bearings, motors, wiring etc.

    I realise that's not very well structured - I wrote it mainly as thoughts occurred to me, and I'm too tired to go back and clean it up - but I hope it helps until someone with more ideas comes along
     
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  3. jfb

    jfb Well-Known Member

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    I've probably over complicated it above :)

    Check the hotend is clean and has no blockages - then start looking for worn components and faulty/tired electronics - moving out from the hotend. Bearings, wires and high-stress components are all good places to check, and redo the configuration and commissioning bits.
     
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  4. MyMakibox

    MyMakibox Well-Known Member

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    Several of us have experienced problems like you're experiencing caused by the PT100 having a loose connection. The loose connection causes the firmware to detect a temperature spike, so it cuts power and lowers the actual hot-end temperature, thus causing a jam. It's an intermittent fault that may only show up after an hour of printing.

    Replace your PT100 with this:
    https://www.aliexpress.com/item/Tri...for-E3D-V6-HOTEND-2017-PT100/32828593452.html
     
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  5. Old_Tafr

    Old_Tafr Well-Known Member

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    I would look for things simply coming loose (as well as all above on worn bearings, things in general wearing and moving even if not actually loose)

    I found that the two horizontal smooth rods that support the X-Carriage came loose at both ends where they are clamped. These rods are in effect the only support for the front of the frame. As the frame is open at the front this is the one weak point in the mechanical design and the X-Carriage rods therefore become the point where any stress is applied.

    I have as well as checking the tightness of the clamps holding the rods also used a piece of threaded rod as a support across the front of the frame. This rod just fits through the third hole up in the front line of square holes. The rod just fits below the pulley holding the Y direction belts and goes just above the camera, so no stress on the two X-Carriage rods now. I fitted nuts on the inside as well as the outside, and nylock is preferable to just tightening them.

    A general check of the tightness of the whole frame etc. is not a bad idea.

    Did you repeat the whole commissioning process to ensure that everything is adjusted properly?
     
  6. Spoon Unit

    Spoon Unit Well-Known Member

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    How about a nice shiny new nozzle? If you have a blockage in the nozzle of some sort, maybe a cold pull will clear it, or heat it high and push through some filament to try to clear it. I've had a couple of nozzles develop this issue and a new nozzle solved it each time. It's completely unrelated, but if you've had the machine running a long time, do a visual check of the motion system. The suggestion to repeat the commissioning process is good. Check the belt tensions (mine went loose after some time), and also the gear wheel on the motors can come loose and create motion problems if they ride to somewhere they shouldn't be.
     

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