AbstractTwo twin‐screw extruders of different size and centerline distance CL were compared. To understand better the performance of the extruders, the operation points were optimized for an HDPE (high‐density polyethylene) film product, and the performance of screw configuration was qualitatively analyzed with some numerical methods at the operation points. The machinery with narrower CL was found to have lower average shear rate, higher conveying capacity, and more channeling in the conveying flow. That means also a need for severe processing in the kneading zone. The extruder with narrow CL had a narrow operation window, and that made it more difficult to combine homogenization and degradation of the product.