Oct. 18, 2003 WINWARD TECHNOLOGIES, LLC 1

Systematic Molding

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MOLDING:

Art or Science?

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Injection Molding Approaches

Traditional Molding (Art)

Decoupled Molding (Science)

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Traditional Molding

Fill & Pack on first stage

Use only enough first stage pressure to pack the mold

Subject to large shot to shot variation

Shorts, flash, warp, dimensional issues

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thick

thinvi

scos

ity

flow rateslow fast

As speed increases, the plastic gets thinner and easier to push

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thick

thinvi

scos

ity

flow rateslow fast

High sensitivity to fill speed variation

Low sensitivity to fill speed variation

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Decoupled Molding

A method of process control that minimizes variation in parts by:

separating the filling stage from pack & hold

Utilizing the machine controls to manage fill, pack & hold

 

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Decoupled Molding

Set first stage hydraulic pressure control “high”

 

Allow machine to provide whatever pressure needed to deliver constant fill speed

Set first stage velocity for constant and fast fill speed

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Decoupled Molding

Separate the filling (velocity) phase from packing phase

Transfer to pack at ~ 95% of full shot (by position)

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Benefits of Decoupled Molding

Fast fill at constant speed 

Reduce part variations due to material viscosity variations

Won’t flash 

Pack consistently 

Gives the most robust, repeatable process

Reduces cycle time, improves quality

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Philosophy of molding from the plastics point of view

Non-Newtonian

Flow rate, temperature, pressure, cooling rate

Use optimum constant flow rate

Separates fill from pack and hold

Cavity pressure controls process

Systematic Decoupled Molding

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Total Process Control

Flow Rate

Temperature

Pressure

Cooling Rate

PROCESS VARIABLES

Material Viscosity

EXTERNAL VARIATION

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Rigorous methodology to launch a new part

Arrives at the optimum process

Drives the set-up sheet

Should be done at prototype

Systematic Decoupled Molding

Process Optimization

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Total Process Control

Dimensions

Surface

Structure

Correlates: PART CHARACTERISTICS

To: PROCESS PARAMETERS