Home JGAurora A5 & A3S Getting Started & Troubleshooting

Warning: Heated Bed Power Clamps

AETEKAETEK Posts: 106🌟 Super Member 🌟
Hello,
After the work I wanted to test the function of the A5. For this I printed a small object (shopping cart coin dummy) and tried on this occasion also new start GCODE. This time I did not print the object as usual in the middle of the print bed, but in front of the edge.
After the Nozzle Priming Line, the nozzle touched the front left metal retaining clip.
At that moment, I could see a clearly perceptible spark. This has nothing to do with stray voltage. I have installed my isolators and the A5 has printed from the SD card, no USB connected. Fortunately, nothing bad has happened yet.
Now I wanted to know how something like that can be. During printing, I measured at the cold end and the bed's retaining clips. I noticed an applied voltage of more than 16 Volts. The strong spark, which was previously created, indicates that a strong current must have flowed. After the end of printing, I repeated the measurement and in fact the voltage of 16.56 volts is still applied to 3 of 4 retaining clips.

I recently checked the wiring of the Hotend Thermistor and the Hotend Heater Cartridge when it received the printer. There was no reason to complain. According to my current knowledge, the problem is the retaining clips, which are very tight.

The underside of the heated bed contains the PCB tracks supplied with 24 volts. Due to the flow of current, the heated bed gets warm. These tracks are insulated by a protective paint.
It will probably be the case that the paint was scraped off by the clamp when attaching the retaining clips. Then the retaining clip is connected to the circuit of the heating bed!
This is a time bomb for the electronics of the printer. The only remedy is to remove the clips or to insulate them proper.

But then this must be a stable and heat-resistant insulation. Maybe Capton tape? I do not have that here. Normal plastic insulating tape can melt in the heat :( 

I want to say this warning first, before others are less fortunate and then the electronics are broken.
With this "improvement" JGAURORA has installed another source of error.
Too bad that I have to make such warnings.

Greetings from Germany
AETEK










Post edited by AETEK on

Comments

  • seafianseafian Posts: 20🌟 Super Member 🌟
    Hi Aetek,
    that might be the reason for the blue tape glued onto the heatbed (below the clips) when the A5 was shipped. I removed the blue tape, as I considered it as being some transport protection.

    Will verify if I have that issue as well and insulate the bottom side with either Kapton tape or maybe insulation pads like for mounting TO-220 cases

    Regards
    Andreas
    Thanked by 1Samuel Pinches
  • AETEKAETEK Posts: 106🌟 Super Member 🌟
    Hello,
    I have found remnants of 0.5mm printed circuit board copper coated.
    Then I etched the copper away and mounted the PCB material down between the clamp and the heated bed. This is glass fiber reinforced plastic, which withstands temperatures of over 200 ° C during soldering and is also very robust mechanically. After the installation, I measured again with the multimeter and now everything is ok. I also adjusted my start G code so that the nozzle no longer hits the clamp.
    At delivery I had no blue tape at the bottom of the clamps.
    That could actually be considered a transport protection.

    cheers
    Andreas, too

    Thanked by 1Samuel Pinches
  • Samuel PinchesSamuel Pinches Posts: 2,985Administrator
    This is not acceptable JGAurora :disappointed:
  • AETEKAETEK Posts: 106🌟 Super Member 🌟
    Hello,
    Today I exchanged the original heated bed springs.
    At Ebay you can buy a cheap bag 10 pieces extra strong extruder springs. These springs fit my A5 and have no mechanical contact with the heated bed PCB. I've heard that even the springs seem to damage the heated bed paint when they come into mechanical contact with the PCB. Then you have a permanent short circuit with far-reaching consequences.



  • lsh60lsh60 Posts: 38🌟 Super Member 🌟
    :*:* Hola a todos.
    Voy a tener en cuenta vuestras experiencias en mi A5
    Gracias por vuestras soluciones.
    Luis
  • compman2compman2 Posts: 19Member
    I to have had the spark issue.  When I was leveling the bed with a metal feeler gauge.  On one corner if the feeler gauge was in contact with the nozzle and would touch the clip there was a spark.  I will try a thin shim of insulating material.
  • maki2003maki2003 Posts: 2Member
    Has JGAurora already improved the insulation of the clamps?

    Today my JGAurora A5 arrived and when checking the clamps I noticed that the heating bed is apparently isolated at the clamps. There is therefore no danger of a short circuit.
    Or is this deceiving me and I still have to isolate the clamps?

    Greetings from Lower Bavaria
    Martin


  • Samuel PinchesSamuel Pinches Posts: 2,985Administrator
    edited September 2018
    Thanks for sending the photo. That looks better - but I still don't think that is sufficient though to completely avoid any risk as the coating is thin, and not scratch resistant. I would still recommend adding some electrical tape or other tape just as a safeguard.

    Hello from Melbourne! :smile:  - welcome @maki2003 !

    Post edited by Samuel Pinches on
  • maki2003maki2003 Posts: 2Member
    I had already thought of something like this and also believe that this " isolation " will not hold in the long run and/or possibly rubs through. In any case I will stick Kapton tape under it.

    Greetings from Lower Bavaria
    Martin
  • AlexAlex Posts: 4Member
    I have got the same issue. Burned out one of my USB port at the PC recently. And I also had to replace 22R resistor from the USB to COM convertor on the  MK board. Don't want to use this poorly designed HB anymore. 
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