Residence Time in the Barrel

Machine Selection

Process

Auxiliaries & Cost

Material

Additive / filler

Shot weightgAll cavities plus the runnerCycle timesScrew diametermmScrew L/D ratioDGiven in the machine catalog; use 20 if unknown

Estimated screw channel volume372 cm³

Shots held in the barrel2.6 shots

Estimated residence time1.1 min

Zones for PP2–10.5 min recommended · 10.5–12 borderline · >12 problem

Residence time is below the recommended lower limit (2 min) for PP — the granules may not melt and homogenize fully along the screw, which risks unmelted particles and streaky color. The shot may be large for this barrel — check the utilization on the Screw Capacity tab as well.

Because the screw geometry is unknown, the channel volume is estimated from the barrel volume (29 – 37% depending on the diameter); the real figure can differ by plus/minus 15% with the screw design. The result is the average residence time — material stays longer at the screw root and in dead zones.

These calculations produce guide values; the final selection has to be based on the part geometry, the mold design and the data from the material manufacturer. For an assessment specific to your application, contact our technical support team.

How is this calculated?

A granule waits in the barrel from the moment it enters the hopper until it leaves through the runner; the longer it stays, the more the polymer chain is damaged by heat, and if it is too short the granule cannot melt and homogenize fully. The time is derived from how many shots the material in the barrel corresponds to:

Number of shots = Channel volume x Fill factor x Melt density / Shot weight

Residence time = Number of shots x Cycle time

The result is given together with three material-specific zones: the recommended band, the borderline zone where the safety margin runs out, and the problem zone where degradation is expected. The larger the machine, the larger the barrel volume — the same part that runs without trouble on a small machine can start showing burn marks and black specks on a large one. Because catalogs do not state the channel volume, it is estimated from the diameter and the L/D ratio (plus/minus 15%).

The method, the formula and the limits of each tool are explained directly underneath it, and the explanation changes with the tab you select. The results are engineering guide values; for an assessment specific to your application when choosing the final machine and equipment, contact our technical team.