Initial setup: z axis, thermistor and coupler issues

Discussion in 'Tool heads & ToolChanger' started by sph711, Aug 8, 2022.

  1. sph711

    sph711 Member

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    Hi everybody,

    My toolchanger with 4 Hemera direct extruders just came alive and I am very excited to use it for my research.

    I have some issues with the initial setup though, maybe you can help me solve them: (I am operating with the Duet 2 Wifi running RRF 3.2.2. This is my first experience with the RepRap firmware, so please excuse potentially dumb questions).

    Issue 1: The z axis moves roughly double the supposed distance. (x and y are fine, as far as I can tell). The steps are set in the "config.g" file as 1600 with the command "M92 X100Y100Z1600 C91.022 E834:834:834:834" as per default. I read somewhere that this issue can be caused by a broken motor cable, so I checked the individual wires of the z axis motor cable with a multimeter and they all read about 1 Ohm, so I guess the cable is fine?

    Issue 2: The thermistors for Tools 2 and 3 read about 10° while the thermistors for the bed and Tools 0,1 report 26° which corresponds well to my room temperature. The thermistors for tool 2 and 3 are both connected to the duex 5, while the others are connected to the duet 2. When I change the thermistor cables from the Duex to the Duet 2, it reads the correct value, so the thermistors themselfes are fine (I also checked the resitance of the individual thermistors and consistently get around 93kOhm). Is this a firmware issue or a hardware failure on the Duex board? The configuration in "config.g" is the same for all four thermistors as per default.

    Issue 3: Homing of the coupler mechanism. When homing the coupler, it does not return to a fully horizontal position. It is a few degrees of. Same when executing the macros for locking and unlocking, the coupler position is not fully vertical or horizontal. Did I maybe build it wrong, or can this too be fixed with firmware settings?

    I appreciate every input I can get.

    Thank you very much.

    Cheers, sph711
     
  2. sph711

    sph711 Member

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    Okay, I think I have found the solution to issues 1 and 3. Maybe someone can confirm my line of thinking here.

    ISSUE 1:
    I noticed this line of text on the toolchanger frontpage (https://e3d-online.com/products/toolchanger-motion-system-bundle)
    This increased pitch would explain the additional distance moved on the z-axis, and bring down the motor-steps per mm to 800.

    So I checked the pitch on my z leadscrew, and it was 2mm :/
    However, I noticed that the leadscrew has two starts and according to this source, its not actually the pitch of the leadscrew that determines the distance a nut will advance on the screw for one turn, but the lead. Which is the number of starts times the pitch.
    I therefore conclude, that the text on the toolchanger frontpage should actually be "The lead screw has been updated to feature a 4mm lead" and most calculators for calculating the steps per mm on a lead screw are mising an important input quantitiy, the number of starts on the lead screw.

    ISSUE 3:
    That one was easy, just tuned down the number of steps for the coupling axis to about 87 instead of the 91.022 in the default "config.g" code.



    The thermistor issue is still open. Does anybody have an idea how to solve this?

    Cheers,
    sph711
     
  3. dc42

    dc42 Well-Known Member

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    @sph711 I have replied to the thermistor question you posted on the Duet3D forum.
     
    sph711 likes this.
  4. sph711

    sph711 Member

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    thank you for your reply.

    yes this solved the issue. As explained by dc42 here, the v0.11 duex 5 board has different internal resistors (2.2k instead of the 4.7k) for the thermistor ports. This issue is dealt with automatically with RR3.4, but for older firmware versions you can update the internal resistor value for the tools 2 and 3 with "M308 S# R2200".

    Cheers,
    sph711
     
  5. red0eye

    red0eye New Member

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    Hey here is my first post had the same issue resolved it in the middle of the night :)
    E834:834:834:834 is also false E3D says you should start with 397...

    I had the best bug/feature because both z and extruders where double the steps per mm so it came out good but double in height! (see picture)

    best regards
    Simon
     

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