Mold closing has three stages: fast travel, deceleration, and in the last few millimetres, the "mold protection zone". In this zone the platen must move slowly with the lowest possible pressure, and clamp pressure should build only after the two mold halves are in full contact.
Setting the safe distance: the protection zone must start before the first point where anything could be trapped between the halves, meaning the longest core, slide or guide pin, plus a part that may not have dropped, plus a little room for the platen to brake. Too short, and the platen hits the obstacle at speed; needlessly long, and you just waste cycle time.
The ideal: in the danger zone, pressure is close to zero, only enough to overcome the platen's friction and inertia. If there is an obstacle, motion simply stops and nothing is crushed. Alongside it, set the monitoring time to the actual time needed to pass the zone plus a small margin, so any delay raises an alarm and opens the mold. On all-electric machines the same logic is applied through a motor torque limit.
Test the setting: place a soft plastic part or thick cardboard on the parting line and close the mold; the machine must stop without damage.
An important reminder: mold protection protects the mold and the machine, not people. Operator safety relies on the safety gate and its electrical, hydraulic and mechanical interlocks, and no setting replaces them.
This article is general guidance. The figures depend on each plant's conditions; for decisions, measurements on your own line are what count.