These calculations produce guide values; the final selection has to be based on the part geometry, the mold design and the data from the material manufacturer. For an assessment specific to your application, contact our technical support team.
The shot volume should stay within 20 – 80% of the swept volume of the screw. Below the lower limit the material sits in the barrel longer than it needs to and degrades thermally; above the upper limit the screw works at its limit and no cushion is left for holding pressure.
The calculation derives the shot volume from the melt density: the material in front of the screw is molten and 10 – 25% less dense than in the solid state (PP solid 0.905 becomes roughly 0.71 g/cm³ as a melt). A calculation made with the solid density shows the utilization lower than it really is and can make a unit that is working at its limit look "suitable".
The method, the formula and the limits of each tool are explained directly underneath it, and the explanation changes with the tab you select. The results are engineering guide values; for an assessment specific to your application when choosing the final machine and equipment, contact our technical team.