Grooved barrel single screw extruders (SSE’s) are the first choice for high molecular weight polyolefin applications such as the extrusion of blown film, pipe and blow molded article. Nowadays grooved barrel SSE’s are also used for a lot of special polymers. The grooves are classically designed with a tapered profile with a length of three to five times the screw diameter. The HELIBAR® system developed by Grünschloß has extended grooves with a more gentle tapered profile, which are also present in the plastication zone and enables reduced pressure, frictional forces and torque respectively high output at lower melt temperatures, good process stability, reduced wear and reduced energy consumption. The present work is related to a new grooved barrel SSE-design with extended grooves in the feeding and plastication zone without any tapered profile. That is without any compression and with extended diameter after the grooves in order to reduce pressure drop for metering and mixing zone. This new grooved barrel SSE-design is named SPLINE extruder emblematic following the designation of splined coupling in mechanical engineering. Results Due to the splines the mass throughput fraction of the grooves as well as the total mass throughput can be increased. The overall pressure profile could be decreased due to the larger volume at the end of the splines which is a result of this construction causing also more melt pumping capacity for metering zone and less pressure drop for mixing elements. Furthermore, the axial pressure profile is more balanced and levelled. High mass throughputs can be achieved at low melt temperatures, preferably with barrier screw concepts, as a consequence of dispersed melting effects causing specific cooling of the melt channel in barrier screws by means of individual solid particles. In summary the SPLINE polymer extruder concept offers significant benefits not only compared to smoothed barrel SSE’s, but also towards classical grooved SSE’s.