Determining Shut off Land Relief and Contact Stress in Multi Cavity Tooling
Balancing shut-off land relief area against clamp force prevents steel hobbing while holding plastic melt seal across multi-cavity injection tooling.
Prussian Blueing
Meaning
Tool steel assembly requires precise surface contact to prevent polymer flash during high-pressure injection molding. Applying prussian blueing to the mold insert surfaces allows the identification of high spots and uneven contact areas. This technique is used during the final benching and fitting of the mold halves.
Surface Contact
Mold plates must seal perfectly along the parting line under clamp tonnage to contain the molten polymer. During the execution of prussian blueing, the transfer of pigment from one plate to another reveals the contact pattern. This visual inspection guide shows where manual stoning of the steel is necessary.
Defect Prevention
Mold deflection during the filling phase causes dimensional variation in molded parts. Analyzing the contact pattern using prussian blueing ensures that the support pillars provide uniform backing across the mold base. This step avoids mold flexing under injection pressure.
Tooling Adjustment
High-precision lenses and optical parts require sub-micron alignment of the mold inserts. Executing prussian blueing before the final trial runs helps verify that the insert sits squarely in the pocket. It ensures that the parting line is secure, which prevents costly rework of the mold after it has been hardened.
This testing method improves the first-out yield of the molded parts.