The engineering question
A cold runner adds solidified material to each shot and to the material-accounting record. A hot runner can reduce cold-runner scrap but does not remove the need to document shot, cushion, residence behavior, and temperature control.
What to document
Runner geometry affects material use, pressure drop, thermal history, and balance; it is not merely a cost input.
Practical workflow
Use Runner Volume, Sprue Volume, and Material Cost as separate accounting steps.
Validation boundary
Use manufacturer documentation, grade-specific supplier data, controlled process records, and trials for any equipment, quality, material, or commercial commitment. A static calculator is a transparent starting point, not a simulation or approval.