The term quality is very often used in an inflationary way and is often overused. By definition it means: A desired quality results from a controlled process if the parameters for the mean position and dispersion of the characteristic values of the process itself or its result practically do not change or change only in a known way.
This means that a certain quality is only achieved if the totality of previously defined characteristic values of a product is adhered to. A characteristic is a measurable or countable physical quantity of the product. A reduction in quality is caused by errors. The term “defect” is formulated in legal terms and occurs when the object of purchase deviates from the condition corresponding to the purchase agreement.
In our case of resistance welding, this means that features such as spot diameter, head tensile forces or surface finish are used as characteristics or criteria for quality. The classic feature is the spot or lens diameter in resistance spot welding. The welding lens diameter is specified in the DVS leaflets and in manufacturer guidelines, and shall be described in a quality agreement.
Depending on the user and definition, there are also very different requirements, so that it is also specified in a large span (the minimum diameter dL » (3 – 5) * Öt in mm).