The tip wire is weakened where it is bent and has higher resistance/length unit
in that area, plus thermal runaway due to the positive temperature coefficient
of copper and other alloys used for this. A special purpose tip made of
stainless steel works even better (stainless has very low termal conductivity
compared to other metals). All this is well known in industry and is actually a
bit of a problem when the electrode is not supposed to heat up too much
(example: spot welding electrodes).

Peter

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