When you're specifying a mold base, the first decision is almost always two-plate versus three-plate. The two-plate (A/B plate) design remains the workhorse for direct-gated parts: simple ejection, shorter cycle, lower tooling cost. But the moment you need multi-point gating or a center gate offset from the sprue, the three-plate (A/B/C plate) layout earns its keep, even though it adds a stripper plate cycle and roughly 15–20% more open stroke. In practice, I keep a three-plate base on the shelf for family tools where gate location flexibility matters more than a few seconds of cycle time.

Hot runner systems change the game entirely. A properly manifolded hot runner base eliminates sprue and runner scrap, but it also introduces thermal expansion calculations you can't ignore—manifold plates typically grow 0.3–0.5 mm per 100 mm at 250°C, so dowel and pocket clearances must account for that. Insulator pads, thermocouple placement, and gate seal-off are the details that separate a stable hot runner from a drooling nightmare. For commodity parts, a standard 2-plate cold runner with a balanced layout still wins on cost per shot. For engineering resins and high-cavitation tools, the hot runner base pays back in material savings and cycle consistency.

Other structures worth knowing: stripper plate bases for thin-wall cups, stack molds for high-volume thin parts (two or four faces, double the output from one press), and unscrewing bases for threaded closures. Each adds complexity to the ejector system and plate alignment—don't underestimate guide pillar spacing or return pin preload. If you're sourcing mold bases or comparing standard vs. custom configurations, visiting MoldWorld (www.moldw.com) gives you a solid starting point for supplier specs and real-world pricing.