what are the main spot welding defects?

-- hiddo hiddo (hiddo18@hotmail.com), April 13, 2002

Answers

Nice name Hiddo. Anyway, the main defect I can think of are:

* Not a strong enough weld (The weld should be stronger than the metal around it. If you pull appart the metal that was just welded, it should rip the welded nugget out and leave it behind).

* Not a pretty enough weld -- from splatter, scaring, pitting, etc.

More?

-- Sam Snow (2snows@mailandnews.com), April 13, 2002.

I find the main defect is expulsion. This weakens the assembly, because of the metal lost at the point of attachment (weld spot). In my corner of the world, automotive, expulsion is not considered harmful, because the material has much more strength that it needs to do the job. The successful automotive crash tests prove this. My objection is the increased maintenance due to part sensors and locating pins geting plated with expulsion. Expulsion also removes part of the welding tip, reducing tip life. Another thing that is often overlooked, it drives the modern current regulation feature to overcorrect, as there is no current in the rest of the half cycle following expulsion, so the regulator turns the heat up! Recovered single cycle weld data clearly shows this, but not all weld controllers make this easily available.

-- David Bacon (dbacon@updatetechnology.com), April 18, 2002.