Today's KNOWLEDGE Share : Why injection speed profiles matter more than a single “fast” setting.

Today's KNOWLEDGE Share

Why injection speed profiles matter more than a single “fast” setting.

Most people set one injection speed and call it done. But a single speed rarely works well across an entire cavity fill. The material doesn’t flow uniformly, the geometry changes, and the gate sees different pressures at different stages.

That’s why speed profiles matter. Early in the fill, you might want a slower speed to prevent jetting or trapped air. Once the flow front stabilizes, you can speed up to fill the bulk of the cavity efficiently. Near the end, slowing down again reduces shear and helps avoid flash or overpacking thin areas.

A good profile does a few things:

1. Reduces cosmetic issues like flow lines, splay, and gate blush.

2. Controls how the air vents out of the cavity, preventing burns.

3. Balances pressure across multiple cavities, especially family molds.

4. Lowers clamp load by avoiding a sudden spike in pressure.

When you run one constant speed, you’re forcing the same pressure and shear across every section of the cavity. It’s simple, but it often creates more variation than you realize.

So here’s a question: how often do you review your fill profile? Are you running the same “fast fill” setting because it works, or because it’s the only thing that’s been tried?

Speed profiles aren’t about overcomplication. They’re about controlling how the part fills so you’re not chasing defects later.

source : Roman Malisek

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