When you are laying out a mold base, the first decision is almost always the same: two-plate or three-plate? A standard two-plate A/B plate setup handles the majority of single-face parts and keeps the runner system simple, but the moment you need pin-point gating away from the part edge, a three-plate floating cavity plate earns its extra stack height. In our shop, the rule of thumb is that anything under a 400-ton press with a single cavity and a side gate stays two-plate; multi-cavity tools with center gating usually go three-plate because the runner stripping plate pays for itself in reduced cycle time and cleaner degating.
The 24 typical configurations in common use break down along a few axes: plate count, runner type (cold, insulated, or hot), and ejection method. Hot runner manifolds add roughly 15–25% to mold base cost but eliminate runner scrap and cut pressure drop, which matters on thin-wall parts where you are already pushing 80–100 MPa cavity pressure. Insulated runners sit in the middle — cheaper than full hot runner, but you need to watch the cycle break or the melt freezes off. On the ejection side, standard ejector pin plates work fine up to about 60–70% of the projected area; beyond that, a stripper plate or air poppet is the safer call. Don't forget guide pillar diameter sizing: for a 500 mm wide base, 32 mm pillars with 40 mm bushings are a common starting point, and we always run at least two shouldered pillars for alignment repeatability.
What separates a good mold base from a headache is the details you spec before steel is cut: leader pin clearance, return spring preload, support pillar spacing under the core insert, and whether the clamp slots match the press platen T-slots you actually have. Get those right and the tool runs for a million shots. Get them wrong and you are shimming plates at 2 a.m. For more mold sourcing and structure reference info, visit MoldSo at www.moldso.com.