Match Before You Mount: Spotting and Fitting Mold Plates
What spotting verifies
Spotting presses mating surfaces together with a marking compound — the classic 'blue check' — to reveal contact points. Plates, inserts and shut-off surfaces are adjusted until contact is even, so the mold closes with the intended kissing contact on the parting line.
High or low spots invisible to the eye show up as colour transfer, and are corrected by hand stoning or localised machining.
Why the base quality matters here
Fitting work assumes square, flat, parallel plates. A base with flatness or squareness errors forces the fitter to compensate by hand, consuming hours and embedding stress into the assembly. That is why plate accuracy in the base is not a paper spec — it is fitting hours saved.
Documented fitting also sets the maintenance baseline: when a mold comes back for service, technicians restore to the fitted condition rather than re-inventing it.
FAQ
What is blue checking for?
It shows real contact between mating surfaces. Even transfer means even parting line contact; bare spots show where material removal is needed.
Can plates be fitted if the base is not accurate?
Only by compensating by hand, which costs fitting time and may not hold. Accurate base plates are the cheaper path to a good parting line.
Is fitting a one-time job?
Fitting happens at build and is repeated after major service. Records of the fitted state make refurbishment predictable instead of exploratory.
All figures above refer to standard product data sheets; final confirmation is subject to written quotation.