Clamp Open

The clamp (clamping unit) is the half of an injection molding machine imm that closes, locks and opens the mold and holds it shut against injection pressure — the counterpart to the injection unit that melts and injects the plastic. ## Main components - Platens: the fixed and moving plates the mold halves bolt to. - Tie bars: the four (sometimes two) columns the moving platen slides on; they carry the clamp load. - Clamp mechanism: toggle (mechanical link), direct-hydraulic, or two-platen designs that generate and hold the tonnage. - Ejector: drives the mold's ejector system for part ejection. ## What it does in the cycle 1. clamp close: the moving platen advances and locks the mold. 2. Hold: it keeps the mold shut with enough clamp force tonnage so the melt cannot blow the parting line open. 3. Open & eject: after cooling, it opens and triggers ejection; then the molding cycle repeats. ## Why it matters The clamp's rated tonnage sets the largest part the machine can run without flash. Too little tonnage flashes the part; an oversized clamp wastes energy and floor space. Tie-bar wear, platen parallelism and toggle lubrication all affect part quality and mold life. ## Related terms - See also: injection molding machine imm, clamp force tonnage, injection unit, clamp close, part ejection ## What is the clamp in injection molding? It is the clamping unit — platens, tie bars and a toggle or hydraulic mechanism — that closes the mold and holds it shut against injection pressure. ## What are the types of clamping units? Toggle (mechanical), direct-hydraulic, and two-platen clamps, chosen by tonnage, speed, precision and footprint. ## What is the difference between the clamp and the injection unit? The clamp closes and holds the mold; the injection unit melts and injects the plastic. They are the two halves of the machine.

Clamp close is the stage of the molding cycle where the clamp advances the moving platen to bring the mold halves together and lock them up before injection. It is the first motion of every cycle. ## The three speed phases 1. Fast approach: the platen moves quickly across most of the stroke to save cycle time. 2. Slow / mold protection: near touch it slows to a low-pressure creep so the controller can detect an obstruction — a stuck part or misplaced insert — before metal hits metal. This is "mold protect". 3. High-pressure lock-up: the toggle or ram builds full tonnage, applying the clamp force tonnage that holds the mold shut against injection pressure. ## Why it matters - Mold protection prevents expensive damage: if a part did not eject, the low-pressure phase senses the resistance and stops instead of crushing the tool. - The speed profile trades cycle time against safety — too aggressive a close risks the mold, too slow wastes time. - Only after lock-up do the injection stages begin. ## Related terms - See also: clamp, clamp force tonnage, molding cycle, injection stages, part ejection ## What is clamp close in injection molding? It is the cycle stage that closes and locks the mold before injection, in three phases — fast approach, slow mold-protection, and high-pressure lock-up to full tonnage. ## What is mold protection during clamp close? A low-pressure, slow phase just before the mold touches, so the machine can sense an obstruction (an unejected part or insert) and stop before damaging the tool. ## What happens after clamp close? Once full clamp tonnage is reached, the injection stages begin — first-stage fill, then pack and hold.

Part ejection is the final stage of the molding cycle, where the cooled molded part is pushed out of the open mold so the next shot can run. It happens after the clamp opens and the part has solidified enough to hold its shape. ## How parts are ejected The ejector system pushes the part off the cores: - Ejector pins: the most common — round pins behind the part. - Ejector sleeves / blades: for bosses and ribs. - Stripper plate / ring: pushes on a large rim to avoid pin marks on cosmetic parts. - Air ejection: a puff of air breaks the vacuum on thin, deep parts. ## How the part leaves the cell - Free-fall: the part drops onto a conveyor or bin — typical in an automatic cycle. - Robot / eoat end of arm tool: picks and places the part for handling, gating or inspection. - Manual: an operator removes it (semi-automatic). ## Why it matters Eject too early (before enough cooling time) and the warm part distorts, sticks or shows ejector-pin push marks; too late and you waste cycle time. Proper draft, polish and ejector layout let parts release cleanly without drag marks, white stress or warpage. ## Related terms - See also: molding cycle, molded part, cooling time, eoat end of arm tool, automatic cycle ## What is part ejection in injection molding? It is the final cycle stage where the cooled part is pushed out of the open mold by ejector pins, sleeves, a stripper plate or air, then removed by free-fall, robot or by hand. ## What causes ejector pin marks? Ejecting before the part is cool enough, too few or too small ejector pins, or insufficient draft — the pins push into a still-soft surface and leave witness marks. ## How is part ejection automated? Either by free-fall onto a conveyor in a fully automatic cycle, or by a robot with end-of-arm tooling that picks the part for downstream handling.