Twist by mandrel: every plastic mandrel has a “natural bending” from production, when we bend new mandrel after extrusion line on drum – mandrel inside warm and when cool down, mandrel has bending – this bending can cause twist at every steps production, when hose bending with mandrel is against natural bending
2. When connect after extracting mandrels together again, and the bending direction of both ends is not same – twist
3. Braiding – if the tension of all carries in clockwise and opposite clockwise direction is in summary not same, we get torque