In rapid prototyping field ,Usually PP parts are made as a single one ,no gluing .That would lost the features and performance of material if PP part split during manufacturing process .No matter big or small part .For simple part ,it’s easy ,but for complex part, that would be high demanding to manufacturer ,from CNC programmer to the operator .It demands high handling ability , especially for a big PP part with complex structure and external shape .more information please visit https://www.prototype-rapid.com/how-do-we-make-big-polypropylene-plastic-prototype-by-cnc-machining/