When you're specifying a mold base, the first decision is almost always two-plate versus three-plate. A standard A/B plate two-plate setup handles the majority of single-face parts and keeps the runner on the parting line, which simplifies ejection. But once you need gating on the top face or multi-cavity balance with a cold runner, the three-plate floating cavity plate earns its extra height. In practice, a 3535 base with a 100 mm A-plate and 80 mm B-plate covers a lot of small-to-medium jobs, but you must check the support plate deflection under injection pressure—anything over 0.05 mm across the cavity can flash thin-wall parts. That's why we often add support pillars or step up to a 400-ton press frame even when the tonnage calculation says 250 tons is enough.

Hot runner systems change the game, but they also introduce thermal expansion headaches. A 16-drop valve-gate manifold running at 240°C will grow about 0.6 mm over a 300 mm span. If your manifold plate is bolted rigidly to the frame, something will crack—usually the nozzle tip or the gate seal. The fix is to use slotted mounting holes and pre-load the manifold with disc springs so it can float. For engineering plastics like PBT or PA66 with 30% glass fill, we also spec hardened gate inserts (HRC 52–54) because glass fibers will wash out a soft gate in under 50,000 shots. And don't forget the wire routing: a hot half with 24 zones needs a junction box that can handle 40 amps per zone without cooking the insulation.

Ejection and cooling often get less attention than they deserve. A stripper plate works better than ejector pins for thin-walled cups, but you need to guide it with at least four leader pins and keep the stripper travel within 0.1 mm of parallel. For cooling, a baffle or bubbler in a deep core can cut cycle time by 15–20% compared to straight drilling. We've seen 30% cycle reductions just by switching from a single circuit to a series of baffles in a 150 mm core. If you're sourcing mold bases or hot runner components, visiting MoldWorld (www.moldw.com) gives you a quick way to compare suppliers and standard sizes before you lock in your design.