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ramps 1.6+ issue

Discussion in 'Mods and Upgrades' started by John Pearsley, Jul 26, 2020.

  1. John Pearsley

    John Pearsley Member

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    I'm upgrading an R2 with a Ramps 1.6+/mega2560 set at 24v. The Z axis A4988 board burned out but not the others. I had tweeked the steps_per_axis with no effect. I tried several different version of the firmware but they all left the Z axis a4988 too hot. Any ideas about why only the z axis a4988 board would be too hot. is it likely something with the ramps 1.6+board on 24 v or in the firmware.
    Thanks for your help.
     
    #1 John Pearsley, Jul 26, 2020
  2. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    I can't speak for the Chinese modified RAMPS design (RepRap never released a design officially after 1.4 although 1.5 was a WIP).
    You can try bringing down the current for the Z axis since it really doesn't need full current from the A4988 to run the Z. I assume you do have the heatsinks on the stepper driver boards? (the a4988s)

    When it comes to 24v boards I haven't tried Arduino Mega/RAMPS, I used alternatives (like Rambo or Smoothie).
     
    #2 mark tomlinson, Jul 27, 2020
  3. John Pearsley

    John Pearsley Member

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    thank you. I do have the heat sinks on the a4988 boards. I found instructions to solder the reset/sleep pins together which I did. Since then I find that the pins are already joined on the 1.6+ board I have. probably not needed. maybe I burned something. I'll look at the other boards
     
    #3 John Pearsley, Jul 27, 2020
  4. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    @Lance Weston has a thread on a conversion he did to use an Arduino/RAMPS board in the R2. He actually has a lot of good information on it and there is a kit from PartsBuilt.com that should be available soon (if it is not already).
     
    #4 mark tomlinson, Jul 27, 2020
  5. Lance Weston

    Lance Weston Active Member

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    What steppers are you using. If it ends in 02 then set the reference voltage ( center of the pot to GND ) to 0.9v, if the stepper part number ends in 01 the set the reference voltage to 1.20v. The heatsink is poorly designed and can short out parts below. I take mica TO220 insulator washers and glue them to the bottom of the heatsink with heat sink paste (available on eBay). After the paste has dried I trim the washers with cutters leaving 1/32" all around. I then use heatsink paste and glue the assembly to the stepper board chip. This avoids shorting anything. The steppers and driver chips get the hottest when the stepper is on and not moving. At that point the driver and stepper are sitting at max current. Make sure the stepper is off when not stepping. If off you can move the print head.
     
    #5 Lance Weston, Aug 1, 2020

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