The Ram speed, recommended result defines an injection profile that keeps the flow front velocity constant.
The warpage of a part is often related to variations of the flow front velocity during the filling stage of the analysis. The higher the velocity in the fountain (flow front) region, the higher the surface stress and the degree of molecular orientation.
The Ram speed, recommended result, displayed as an XY plot, is used to maintain a constant flow front velocity throughout filling. The ram speed is pro-rated by the flow front area calculated at every instant: the larger the flow front area, the higher the ram speed needed to maintain a constant flow front velocity.
Stress is related to the pressure drop. For a given cross-sectional area, a higher flow rate corresponds to a higher pressure drop, and therefore, a higher stress. To minimize stress, it is desirable to have a slower flow rate through smaller cross-sections, while it is possible to have a faster flow rate through larger cross-sections. Maintaining a constant flow front velocity by changing the ram speed of a closed-loop process controller helps to minimize variations in surface stress during the process, and thus decreases the tendency of the part to warp.