lehtmetallist toodete vormimismeetodite üldnimetus, mille korral surve toorikule tekitatakse hüdraulilise vedeliku poolt elastsest materjalist (kummi, polüuretaan) diafragma kaudu (vrd kummlehtvormimine), a family of processes in which a rubber bladder backed up by fluid pressure, or pockets of pressurized liquid, replaces either the solid punch or female die of the traditional tool set (compare: rubber-pad forming)