What Moldflow simulation actually catches, and when to bother

Moldflow fill simulation at end of fill showing last-filled zones on the outer wall

Gating position and filling

The first and most valuable answer. Move the gate and you move the weld lines, the last-filled areas and the pressure required to fill. On a cosmetic part this is usually the whole reason to run the study.

Cycle time

Cycle is piece price on a high-volume part. The simulation shows where the part is still too hot to eject and therefore what is actually setting the cooling time, which is often one thick section rather than the part as a whole.

Venting, air traps and sinking marks

An air trap is an enclosed volume that fills last. Trapped air burns the material or leaves a short shot, and the fix is a vent in a specific place. The result view marks those positions on the model.

Clamping force and machine tonnage

Projected area times cavity pressure decides the machine. Getting it wrong means either a tool that flashes on the machine you own or a machine rate you did not budget for.

Cooling efficiency

Cooling circuits that look symmetrical on a drawing are often not symmetrical in effect. The study shows which side of the part is running hotter, which is where warpage comes from.

Deformation and distortion

The last question, and the one buyers usually ask first. Distortion is a consequence of the five answers above, which is why it is addressed by fixing them rather than by adding a straightening fixture.

The six questions, as TJ-Teck states them

To verify gating position and filling
To shorten molding cycle time
To optimize venting and avoid air traps and sinking marks
To define clamping force and IMM tonnage
To check cooling efficiency
To reduce deformation and distortion

Frequently asked questions

When is simulation not worth it?

On a simple straight-pull part with one obvious gate position, a generous wall section and no cosmetic requirement. Say what the part is and you will get an honest answer.

Does the study come with the tooling quotation?

It is offered where the part warrants it and is listed as its own line, so you can see what it costs and decide.

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