When you sit down to specify a mold base, the first decision is almost always two-plate versus three-plate versus hot runner, and that choice drives everything downstream — parting line location, runner ejection, plate stack height, and guide pillar layout. A standard two-plate A/B plate arrangement suits the majority of single-cavity and family tools where the gate can sit on the parting line. Step up to a three-plate (double parting line) frame when you need a pin-point gate at the cavity center and can accept the extra stripper plate and longer ejection stroke. Hot runner frames trade that mechanical complexity for a manifold plate and thermal controls, but you pay for it in plate thickness and wiring clearance — plan an extra 40–60 mm of stack height on a typical 4-drop manifold versus the equivalent cold runner tool.
The details that bite you later are the boring ones. Guide pillar diameter should be sized off the mold weight and projected area, not habit — a 300 × 300 mm base carrying a heavy core insert wants at least 25 mm pillars, and offset or asymmetric layouts need a second locating feature so the halves can't go together 180° out. Return pins must be long enough to clear the ejector plate before the core closes, and spring preload on the ejector system should be checked at full open, not at rest. Clamp slots and locating ring concentricity to the sprue bushing are worth verifying on the CMM before the base goes to assembly; a 0.02 mm mismatch here shows up as flash on one side of the part and short shots on the other.
None of this is exotic, but it is exactly where new tooling programs lose weeks. Build a checklist keyed to your frame type, confirm plate parallelism and pocket tolerances against the steel supplier's certs, and log the guide pillar fit class you used so the next similar job starts from data instead of memory. For mold base standards, supplier comparisons, and sourcing references across the common frame configurations, visit MoldSo at www.moldso.com.