Tool Steel Recutting Strategies versus Process Window Optimization Dynamics
Recutting tool steel establishes a stable process window that lowers long-term scrap costs and cycle times compared to forced parameter tuning.
Metal-Safe Recutting
Meaning
Machining strategies for injection moulds prioritize the removal of steel over the addition of material to ensure dimensional accuracy. Designing a tool for metal-safe recutting means making the initial steel dimensions slightly smaller than the target for a hole or larger for a boss. Exacting offsets are applied to critical dimensions during the initial tool build to allow for fine tuning.
This approach allows the toolmaker to adjust the fit by milling or grinding away more metal after the first samples are measured.
Steel Allowance
Standard offsets range from a few microns to several tenths of a millimetre depending on the resin shrinkage. Because metal-safe recutting avoids the need for expensive welding or plating, it is the preferred practice for tight-tolerance engineering parts.
Tolerance Control
Fine adjustments to the fit of mating parts become possible once the actual shrinkage of the resin is known. If a hole is slightly too small in the plastic sample, metal-safe recutting of the core pin will increase the hole size. Precision components rely on this iterative process to reach their final specifications.
Modification Risk
Adding metal back to a cavity through welding can change the hardness of the steel and lead to visible witness lines on the plastic. By sticking to metal-safe recutting, the structural integrity and surface finish of the original tool steel remain intact.