In single-screw extrusion, the demand for extruders with high throughput rates, compact sizes and an optimum melt quality has increased continuously. The invention of a grooved plasticizing zone in combination with a barrier screw has met these requirements successfully. With this extruder system, high specific throughput rates can be achieved while at the same time melt temperatures are kept low, wear is reduced and energy efficiency increased. Homogenization of the melt takes place in the last part of the screw, the mixing zone, by means of helical shearing and mixing parts. A wave screw in combination with a grooved plasticizing zone promises a fragmentation of the solid bed already in the melting zone. The two flights and the periodical variation of channel height allow for the molten material to flow back and forth, which leads to early mixing. In contrast to a barrier screw, which has the purpose to separate molten and solid material, this early mixing should result in an improved material and thermal homogeneity at the same high specific throughput rate. For the first time, the investigation of a wave screw is carried out in an extrusion barrel with a grooved plasticizing zone. The wave screw is compared with a conventional barrier screw under identical conditions. The relevant investigated parameters include melt homogeneity, pressure and temperature profile, energy consumption and throughput rate. For this purpose, a wide screw speed range is used with a 35 mm extruder for the processing of different polyolefines. The grooves in the barrel are of helical shape and extend from the feed zone to the mixing zone. After an evaluation of the experimental results, improvements in the design of the wave screw are deduced.