Now I really need advice

New Home Forum Mostly Printed CNC – MPCNC Advice – MPCNC Now I really need advice

This topic contains 16 replies, has 3 voices, and was last updated by Profile photo of Jeffeb3 Jeffeb3 1 week, 4 days ago.

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  • #38008
    Profile photo of buurin
    buurin
    Participant

    I have installed the Z drag chain and have all three axes wired up for testing.

    First, I need to know what do I do with the tail end of the drag chain.

    IMG_20170711_160610

    This is how the Z axis currently looks. Instructions say this area is off-limits for any attachments. What can I do to fix this end of the drag chain to the Z motor?

    If there’s no way around affixing the drag chain here, can Ryan or someone tell me the design distance between the center of the middle Y rail and the Z stepper as assembled in the picture? I’ll need this distance to design a clip for the drag chain.

    Today’s testing shows a top speed of 2500mm/min X and Y. Higher and I start hearing grinding.

    For Z, I know I have 160mm travel from previous tests. when I’m testing with 500mm/min (absolute max 8.5mm/s is 510) and I give G1 Z160 F500 via RepetierHost manual control it would only go up to about 59mm (as measured as the gap between top XYZ and lower Z motor mount) and while the board thinks it has gone the whole length. I turned the allthread in the middle and it doesn’t seem to be loose. Sounds like I’m losing steps, but am I really?

    #38011
    Profile photo of Ryan
    Ryan
    Keymaster

    Sounds like you are using the wrong firmware or the wrong drivers.

    The questions in the sticky post would make this a much quicker process. You didn’t buy any of it from here so I have no clue as to what you have. I can’t see the leadscrew or all thread either.

    #38013
    Profile photo of buurin
    buurin
    Participant

    Did more testing in the meantime. Starting from Z0…
    G1 Z160 F490 does move the Z up the full 160mm.
    G1 Z160 F500 only moves up to 59mm and then it gets totally confused. G1 Z0 F500 then fails to return it to the bottom.

    The firmware I used is MPCNC511_GLCD_EB downloaded from here. No change done. It is a 5/16 allthread, hidden in the picture though.

    The motor is 42SHD0217-24B with Geeetech engraved on it. Yes, they did use this motor on their Prusa i3 clones. 1.5A. This is the closest specs I can find. ebay is down atm so I can’t show you the actual listing I bought from.

    And of other items in the checklist…
    There is no endstops.
    A Thinkpad running Fedora 25, so yeah, a PC…

    #38015
    Profile photo of Ryan
    Ryan
    Keymaster

    What drivers on what board, and what do you have them set at?

    #38016
    Profile photo of Ryan
    Ryan
    Keymaster

    Wired in series or parallel?

    #38017
    Profile photo of Ryan
    Ryan
    Keymaster

    What size are your pulleys?

    #38018
    Profile photo of buurin
    buurin
    Participant

    All drivers are DRV8825, set to about 1.05A, with heatsinks installed and all jumpers installed underneath. X and Y are wired in series. Motors are rated for 1.5A. All pulleys are 16T.

    #38022
    Profile photo of Ryan
    Ryan
    Keymaster

    1.05A or 1.05V? 1.05V is hard to maintain without some serious cooling on the drivers. try setting them to 0.7V when the steppers are energized but not moving.

    #38027
    Profile photo of buurin
    buurin
    Participant

    0.525V is my target when I set them up initially before all is assembled.

    #38028
    Profile photo of Ryan
    Ryan
    Keymaster

    Maybe you should try running my drawing test code. I don’t trust the gcode commands straight from the command line, sometimes you need to precede them with g91. There have been a bunch of issues lately that are gcode related, odd setting in slicers and things.

    Try my code and see it if works. https://www.vicious1.com/wp-content/uploads/2015/09/Test-Crown-12mms.gcode

    From this page, https://www.vicious1.com/estlcam-basics/

    #38037
    Profile photo of buurin
    buurin
    Participant

    Time to install a base board and print a pen mount…

    I also caught the board doing seppuku over a “heating failure” from the log. Would I have to reflash your non-EB firmware before actually doing this test?

    #38040
    Profile photo of Ryan
    Ryan
    Keymaster

    You don;t have to actually draw it, but see if it moves correctly.

    This is checking for a software issue vs a hardware issue.

    #38042
    Profile photo of Jeffeb3
    Jeffeb3
    Participant
    Did more testing in the meantime. Starting from Z0…
    G1 Z160 F490 does move the Z up the full 160mm.
    G1 Z160 F500 only moves up to 59mm and then it gets totally confused. G1 Z0 F500 then fails to return it to the bottom.

    It’s not a steps/mm issue if the F490 works. I thought 8mm/s (F480) was pretty close to some theoretical maximum for Z.

    You’re probably either skipping steps because something is tight, or you’re skipping steps because the software can’t count that fast.

    #38150
    Profile photo of buurin
    buurin
    Participant
    You don;t have to actually draw it, but see if it moves correctly.

    This is checking for a software issue vs a hardware issue.

    I ran the test. It acts like it’s drawing the crown just fine, except it still committing suicide over a non-existent heater. Let me try flashing the no-extruder version.

    Reflashed with no-extruder version. I had to change the baudrate to 115200 for my laptop to be able to talk to the stack at all. Haven’t seen the heating error so far.

    #38160
    Profile photo of Ryan
    Ryan
    Keymaster

    Nice

    #38246
    Profile photo of buurin
    buurin
    Participant

    What about the drag chain then? And one firmware that can handle with or without extruder?

    #38248
    Profile photo of Jeffeb3
    Jeffeb3
    Participant

    Wrt the drag chain. Ryan suggests attaching nothing to the z axis. Ryan also doesn’t use drag chains, but that’s probably less of a vendetta and more of efficiency.

    I printed a bracket to attach the drag chain to the z axis conduit. Any force from the drag chain is going to try to move the bit, and it will have a very strong lever arm to do so. It needs to be very smooth. You could also let 12″ or so of the cables out of the drag chain and find a way to attach it to the center. That wouldn’t affect your z axis.

    W.r.t. firmware, I think the trouble is that the extruder has a temp gauge, and the firmware that prints needs to see that temp gauge. If you don’t change the firmware, you can either leave the hot end’s thermistor attached, or install a resister to fake out the firmware. Either way, you’ll flash the _E0 version

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