Blasformen

Blasformen, also known as blow molding, is a manufacturing process for forming hollow plastic parts by inflating a heated plastic tube or preform inside a closed mold. The technique is widely used to produce containers with thin walls and complex shapes from thermoplastics.

The primary methods are extrusion blow molding, injection blow molding, and stretch blow molding. In extrusion blow molding, a molten thermoplastic parison is extruded and captured in a two-part mold; compressed air inflates the parison so it contacts the mold interior. After cooling, the mold opens and the part is ejected. Injection blow molding uses an injected preform or parison that is transferred to a blow mold, where air expands it to the final shape. Stretch blow molding combines elements of injection and blow molding by preforming the blank, reheating, and then stretching it longitudinally (and sometimes radially) before blowing, producing high-strength bottles, particularly PET.

Common materials include HDPE, LDPE, PP, and PET, as well as blends and copolymers. The process is valued for producing lightweight, sturdy hollow parts with good moisture barriers at relatively low tooling costs, making it popular for beverage bottling and consumer packaging. Limitations include material thickness distribution, design constraints to maintain parison stability, and higher costs for small runs due to mold setup.

Equipment centers on a blow molding machine, with a parison extruder or injection unit, a mold, an air system, and cooling hardware. Environmental considerations include recyclability of materials and energy use.