Physical Foaming of Extruded Pipes Reduces Material Costs

Standards are in place to ensure that extruded plastic pipes for underground cables offer appropriate protection from environmental damage. Among other parameters, the standards specify the diameter/wall-thickness ratio of a material per running meter of pipe. To reduce cost, recyclates or inferior quality materials may be used, but the property profile and processing characteristics are highly dependent on the batch. Another way to reduce cost is to physically foam the pipes by injecting gases such as carbon dioxide or nitrogen into the plastic prior to extrusion. During the pipe extrusion process, the gases form a fine-pored foam. Less plastic is consumed through this lightweighting technique, resulting in lower material costs. In a joint project, Hans Weber Maschinenfabrik GmbH and Promix Solutions AG have evaluated the feasibility, practicality, and savings potential of physical foaming. Weber supplied a grooved barrel extruder type NE7.40 for the foamed middle layer and a grooved barrel extruder type NE5.40 for the inner and outer layers. A Weber PKM250 three-layer pipe head was used as the die. Based in Kronach, Germany, Weber is an almost 100-year-old family-run company steeped in mechanical engineering expertise. Its wide-ranging portfolio includes extrusion technology products, wood and metal grinding equipment, gantry systems, and robotics.