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ROBO 3D hotend breakdown and repair (the road to dual extrusion)

Discussion in 'Mods and Upgrades' started by MakeJeff, Apr 24, 2019.

  1. MakeJeff

    MakeJeff New Member

    Sep 7, 2014
    Likes Received:
    I bought a R1 years ago and upgraded the lead screws soon after. so I have the R1+ with the R1 ramps (I.E. E1 is unused and functional, Z is slaved dual motors).

    hotend had an issue and started leaking from above. order a cheap Chinese hotend off amazon($12). along with a pair of bowden extruders($14). in the comedy of errors getting to this point, I blew my mega(pushing the bed to fast?), reset the vref on the steppers(the vref for the dual Z motors is the same as the X or Y due to the low power needed for to move it and the noise and missed steps you get if you crank it up to double! all my vrefs are about .5) , set the values for ROBO in a fresh copy of marlin 2.0. DEFAULT_AXIS_STEPS_PER_UNIT had to be recalculated for the extruders (about 88 for the direct drive with 12mm gear, from the stock 700+). and the big mess was getting the right Z_PROBE_OFFSET_FROM_EXTRUDER took many trial and errors and feeler gauges. I used a K40 laser cutter to make the wood parts to lock in the hotend section.
    looks like Frankenstein's monster but it printed a 20x20 cube and so next is a new carriage to hold it solid. I am designing a carriage with a bolt on top plate to hold the hot end. the goal is cyplops dual extrusion and I want to be able to change out the top plate for one designed for a NF TC-02($30) I ordered on a slow boat from china. I also ordered some TMC2130s to use in SPI while I was at it just to make it all more painful.
    things I don't like about the robo design. the bed rocks/deflects went probed. (remote extruders lightened up the weight on the tip and I hope that improved). the Z endstops on either end tend to rock so either one can go off with unpredictable results.(wouldn't a spring-loaded hotend be nice for a z stop!) the noise (minor) - slightly improved with vref adjustment, hoping the 2130 will do more.

    final goal is to print good detail mini figures and I think I need dual extrusion with a dissolvable filament for that... and possibly a smaller nozzle.

    hints? tips? linear bearing advice?
    thanks in advance for the input.
    #1 MakeJeff, Apr 24, 2019
    Last edited: Apr 26, 2019
    mark tomlinson likes this.
  2. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
    Staff Member

    Feb 21, 2013
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    If nose is an issue (it isn't for me) you can try the IGUS DRYLIN BUSHINGS.
    Good work :)

    Dual extrusion is not for the faint of heart.

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