Engineering tools

Residence time in injection moulding — estimator and pigment test

Residence time is how long melted polymer sits inside the heated barrel before it reaches the cavity — the product of how many shots the barrel holds and how long each cycle takes. Too long, and heat-sensitive materials (PVC, POM, flame-retardant grades, many nylons) degrade before they are ever moulded: brown streaks, brittleness, odour. It is the hidden reason a small part should not run on a big machine, however attractive the machine availability looks.

The pigment test — the accurate method

Estimates assume; the barrel knows. Drop a few granules of a contrasting masterbatch into the throat, and count the shots until the deepest colour appears in mouldings: residence time = that shot count × cycle time. Ten minutes of production time gives you the true figure for that machine, that screw, that shot — worth doing whenever a heat-sensitive material moves to a new machine.

Residence and shot utilisation are the same decision

A shot at 15% of a machine's capacity almost guarantees long residence; that is the real engineering behind the utilisation window in our shot-size calculator. Check both before locking a part to a machine — or ask us to.