A method for bonding tubes into an article, each of which is formed from a thermoplastic polymer, especially an aliphatic polyamide. The article has a plurality of channels into which tubes are placed in sliding engagement. The article is moved towards a heating block having pins, such that a pin is inserted into each tube. The article and heating block are brought into a juxtaposed position such that the polymer of the tubes melts and forms a coating on said article. The method is particularly useful in the formation of tubed heat exchangers, for example with 100-300 or more tubes, in one cycle.