Short answer: Tablet pressing has its own vocabulary, and most of it describes either a physical part of the machine (punch, die, turret) or a stage in the compression cycle (fill, dwell, ejection). This glossary covers the terms you'll run into most as a beginner, grouped by what they describe rather than alphabetically, so related terms sit next to each other.
If a term below sends you looking for more depth, what is a tablet press covers the full compression cycle and core parts from scratch.
The Physical Parts
Die — A hardened steel disc with a precisely-machined cavity through the center that defines a tablet's diameter and shape. Powder fills the cavity; the finished tablet takes its shape.
Punch — A hardened steel rod that enters the die cavity from above (upper punch) or below (lower punch) to compress the powder. The punch face shape — flat, domed, or engraved — becomes the tablet's face shape.
Tooling — The general term for a matched punch-and-die set. "Tooling standard" refers to whether a given set of tooling physically fits a given press.
Turret — On a rotary press, the rotating plate that holds many die stations arranged in a circle, so each one cycles through fill-compress-eject as the turret spins.
Hopper — The container that holds bulk powder above the press and feeds it down to the die cavity by gravity or mechanical force.
Feeder / feed frame — The mechanism that meters powder from the hopper into the die cavity in a controlled, repeatable amount on every cycle.
Take-off blade — A fixed blade near the die table that sweeps a finished tablet off to the side once it's been ejected, clearing the die for the next cycle.
The Compression Cycle
Fill — The stage where the lower punch drops to a set depth inside the die and powder fills the resulting cavity. This is where tablet weight is determined.
Fill depth — The distance the lower punch drops before filling, which sets how much powder volume — and therefore weight — ends up in each tablet. See how to calculate tablet weight for how this connects to your target dose.
Compression — The stage where the upper and lower punches close together on the filled die cavity, applying force to fuse the powder into a solid tablet.
Compression force — How much force the punches apply, usually measured in kilonewtons (kN). Higher force generally means a harder tablet, up to the point where too much force causes capping or lamination.
Dwell time — The brief pause at peak compression force, before the punches release, that lets the compressed powder relax evenly instead of springing back unevenly the instant pressure drops.
Pre-compression — An extra, lighter compression step used on some rotary presses before the main compression, mainly to remove trapped air from the powder before full force is applied — reduces capping risk on fast-running formulas.
Ejection — The final stage, where the lower punch rises back to the top of the die, pushing the finished tablet flush with the die table so it can be swept away by the take-off blade.
Formulation Terms
Excipient — Any tablet ingredient that isn't the active ingredient — fillers, binders, disintegrants, lubricants, and glidants. See tableting excipients explained for the full breakdown.
Direct compression — Formulating by blending dry excipients directly with the active ingredient and compressing, without a separate granulation step.
Granulation — A process that binds powder particles into larger granules before compression, typically used when a powder blend doesn't flow or compress well enough on its own for direct compression.
Friability — How resistant a tablet is to chipping or crumbling under light abrasion, measured with a friability tester that tumbles a sample and checks weight loss.
Hardness — How much force a tablet can withstand before breaking, usually measured in kiloponds (kp) or Newtons with a hardness tester. Hardness and disintegration time move in opposite directions as compression force changes.
Failure Modes
Capping — The top (or bottom) of a tablet separating from the body, usually right after ejection, most often caused by trapped air or insufficient dwell time.
Lamination — Similar to capping, but the tablet splits into more than two horizontal layers rather than a single cap separating.
Sticking — Powder building up on a punch face over repeated cycles instead of releasing cleanly, usually a lubrication or moisture issue.
Picking — Small fragments of a tablet's surface pulling away and sticking to the punch face, closely related to sticking.
Weight variation — Inconsistent tablet weight across a batch, most commonly caused by inconsistent powder flow into the die rather than a press setting.
Equipment Categories
Single-punch press — A press with one die station, producing one tablet per cycle. Covers R&D through moderate production volume.
Rotary press — A press with many die stations arranged around a turret, producing many tablets per rotation instead of one.
Manual press — A single-punch press operated by hand lever rather than a motor.
Motorized press — A single-punch or rotary press driven by an electric motor rather than hand power.