Hey, attached is an example of a pipe heat exchanger which is one of the key units in energy and process engeering. For the modulation mainly solids were used, to cut the bunch of pipes from the main frame. Check also the feature definitions, to see how to write objects in lists and create one solid from the every single object in that list. If you have many solids like in this example and you want to do boolean actions, it is important seperate the different solids to avoid errors. Check therefore the small groups of solids. regards Carsten heatexchanger_04.fdb