Residence Time - Fake News

RESIDENCE TIME is not a definitive data point.

It’s a reference only.

A reference that makes the Tooling Engineer say . .

" Hmmmm, that could be an issue;

Worth checking out a bit more. "

You are probably thinking - I thought Residence Time was a clear go - no-go?

Why is Residence Time just s reference?

Seems different to what I have been taught. Help me understand this better.

A five minute vs seven minute residence time should be a clear decider.

It's science . . . RIGHT?

Well

Kinda

Yes and No

This needs several extra blogs to explore.

How can a seven minute residence time be ok for one part,

and . . . a killer for another?

Answer

Because each part and tool comes with a truck load of variables.

  • Part size

  • Wall section

  • Flow length

  • Tool size

  • Cavitation

  • Feed system

  • Molding process

  • Different machines

  • Different flow patterns

  • Material preparation

  • Complicated geometry

Every part is unique.

Every part has a different combination of the above elements.

Every part has a different hierarchy listing for the above factors.

Now you have a more nuanced understanding of Residence Time as a single data point.

A data point in a cloud of inter-acting variables.

Residence Time is a single variable.

It’s the blade of grass the golfer throws in the air

to judge wind speed and direction.

Here’s an exaggeration to help you capture the concept

Part A

Ten minute residence time.

MFI and mechanical performance are good.

Part B

Six minute residence time.

MFI is high. Mechanical performance is poor.

Residence Time is not the Full Picture

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