tined wires in screw terminals... bad idea?

Discussion in 'Calibration, Help, and Troubleshooting' started by Stefan, Mar 4, 2016.

  1. Stefan

    Stefan Well-Known Member

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    Just a question, I'm connecting the Rumba to the PSU... here in good old Germany we have law or something that you are not allowed to have tinned wires in screw terminals (in cars), because of vibrations can cause the wire to break.
    And in the printer there are a lot of vibrations I guess.

    On the other side it makes sense since the contact surface of the raw copper is much bigger than the tinned wire which leads to bigger currents that can flow.

    Or do am I mistaken? .... I'll most likely cut the wire to remove the tin.

    What do you guys think?

    bye
     
  2. PsyVision

    PsyVision Moderator
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    I think tinning is okay, or ferrules are better. i wouldnt worry too much with what you do though! personal preference
     
  3. Stefan

    Stefan Well-Known Member

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    I would agree that ferrules are better but only if the screw terminals are the once without the metal fin thingy.
     
  4. elmoret

    elmoret Administrator

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    Actually tinning wires in screw terminals is not a good idea. Over time, thermal cycling can cause solder creep.

    In terms of industry standard, bare stranded wire is fine for connections that are not disconnected/reconnected frequently. For frequently changed connections, bootlace ferrules are ideal to prevent breakage of individual wire strands. This is from what I've observed personally, and conversations with others in industry. It is also confirmed and explained more in depth here:

    http://reprap.org/wiki/Wire_termination_for_screw_terminals
     
  5. Mike Kelly

    Mike Kelly Volunteer

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    That's interesting. I've assumed that tinning allows more compressibility between the terminal and the wire meaning that you have less chance of shearing copper strands, though after reading into it a bit more it seems as though that's only true when you're screwing directly onto it, like on a terminal block, but the tab method it makes more sense to not, since you're not twisting the wires and instead pressing down, so you're less likely to shear it.

    Learn something every day.
     
  6. mike01hu

    mike01hu Well-Known Member

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    We stopped tinning stranded conductors back in the 1960's, the reasons being that solder is a very soft material and will extrude from between the strands over time and make the connection loose. Copper naturally hardens due to working e.g. such as being compressed by a screw terminal, and the connection should remain firm; solder works agaist this and the copper may not reach peak hardness due to the cushioning effect of the solder and this further creates the chance of connections becoming loose. The electrical and electronics industry does not recommend tinning multistrand conductors when used in a screw terminal but tinning is fine to contain the strands if the joint is to be soldered.

    Mike
     
  7. Henry feldman

    Henry feldman Well-Known Member

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    On my X-carve I ferruled every connection. Seems like anything other than a very solid connection is likely to fail given the insane level of vibrations on that device. The manual strongly recommends ferrules, and against tinning. Inventables has a very nice kit. Note if you are going to use ferrules you really need a ferrule crimper to produce the proper square crimp.
     
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  8. Stefan

    Stefan Well-Known Member

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    I think I will go with blank wire because of the terminals have wire guards.
    But I in general do not like small screw terminals... it always feels like I will break them of the PCB when tighten the screw.
    Maybe its because of my "Wurst Finger" or the I'm a "Grobmotoriker" some times :D
     

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