Use of thermoplastic molding compositions comprising, as essential components, A) from 29 to 99.8% by weight of a polyester, B) from 0.2 to 2.0% by weight of alkali metal salts of aliphatic carboxylic acids or a mixture of these, based on 100% by weight of A) and B), and also moreover C) from 0 to 70% by weight of further additives, where the total of the % by weight values for A) to C) is 100%,
for producing laser-transparent moldings of any type.

A method for producing a resin part includes: preparing an intermediate body comprising a first member and a second member, the first member containing a resin; and welding the first member with the second member by performing scanning of the intermediate body with a first laser beam and a second laser beam. In the welding of the first member with the second member, the scanning with the first laser beam and the second laser beam is performed in a state in which a center of a second spot is located on a rear side in a direction of the scanning with the first laser beam and the second laser beam as compared to a center of a first spot while at least a part of the first spot and at least a part of the second spot overlap with each other.