Velocity/pressure switch-over options

There are a variety of options available to control the velocity/pressure switch-over point.

Automatic

Select this option if you want the flow simulation to estimate an acceptable time to switch from velocity to pressure control. The switchover will occur early enough to avoid an end-of-fill pressure spike. The transition point is selected such that if the ram stopped instantaneously, there would be enough melt decompression in the runner, gate and cavity to just fill the cavity. This can be imagined as a scenario in which the injection flow suddenly stops, but the polymer keeps flowing within the cavity, with no short shot, until pressure everywhere reaches zero.

By %volume filled

Specifies that the switch-over from filling to packing will occur when a particular percentage of the cavity volume is filled. By default, this percentage is 99%.

Note: For Injection-Compression Molding analysis only, the by %volume filled option specifies the percentage of design part weight (not cavity volume, as for other analyses). Design part weight is defined as the density at room temperature and atmospheric pressure, multiplied by the cavity volume at the design thickness. Volume is not used because the total volume (including the extra space created by the press open distance) is updated at each time interval as the compression press moves. That is, once the press moves, the total volume keeps changing and is different from the original total volume. Further, the by %volume filled option controls only the injection unit, not the compression unit.

By injection pressure

Specifies that the switch-over from filling to packing will take place when the machine reaches a specified injection pressure.

By hydraulic pressure

Specifies that the switch-over from filling to packing will take place when the machine reaches a specified hydraulic pressure.

By clamp force

Specifies that the switch-over will occur when the clamp force reaches a specified limit.

By pressure control point

Specifies that the switch-over from filling to packing will occur when a specified pressure is reached at a specified location on the mesh.

By injection time

Specifies that the switch-over from filling to packing will take place at the specified time from the beginning of the cycle.

By whichever comes first

Select this option if you want to specify one or more of the switch-over criteria listed above. In this case velocity/pressure switch-over will occur as soon as one of the set criteria is met.