Transcript Document

What Lies Below the Surface of Your Molded Parts?
Plastics Manufacturers Strength:
Revenue / ft2
• Throughput Efficiency
• Focus has been on Lean Manufacturing Principals
• New Work Cells
• Improving Plant Layouts
• Streamlining the Process from Molded Part to Loading the Truck
2008
Present
Plastics Manufacturers Weakness:
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Development and Commissioning New Projects
Grass Roots Approach
hurry up, make mistakes, try something else
just find away to get this part to meet specification
we’ll figure out how to make money at it on the backside
Concept
Product
Design
Mold
Design
Part & Mold
Commissioning
Launch
Production
CIP
So you followed all of the design guidelines and scientific
molding procedures and you still ended up with part variations.
What could possibly be going wrong?
Identical runner lengths
Identical channel radius
Identical gate geometry
Identical cavity sizes
I. Mold Steel Variations (l, r)
II. Rheological Variations (η )
Why is New Mold Commissioning Such a Challenge?
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Plastic Rheology is Not Well Understood
Shear-induced imbalances
Shrink & Warp characteristics
Cooling and thermodynamics
Regional pressure variations
Amorphous and Semi-crystalline materials
The Science Behind Non-Uniform Rheology
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Plastic is a Non-Newtonian Material
– Viscosity is affected by Shear Rate and Temperature
– As shear rate increases, viscosity decreases
– As temperature increases, viscosity decreases
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Highest Shear Rate is just
inside the frozen layer
– Shear-thinning and Shear-heating
reduce viscosity in these laminates
Influence on melt front advancement profile
Single Cavity Disk
Mold:
• Rivering flow front
• Gas trap created
1
Melt Property Distribution
3 4
1
2
1
2
3 4
2
3
2
4
4
3
More than just a “filling imbalance”...
Temperature differences
result in shrink variations
* Forces process technician to increase
cooling time and use mold as a cooling
fixture to minimize difference between
part
Result = Increase Cycle Time
Conventional Runner
Volumetric: Mold Design (Cooling)
100° F
Linear Shrinkage:
180° F
At ejection:
L  L(T )
Effect of Regional Pressure Differences
55 Mpa
ΔP at End of Fill
40 Mpa
ΔP Thick Part
55 mPa
40 mPa
x
ΔP Thin Part
70 mPa
25 mPa
Center packs under higher pressure = possible dome warp
Can this be processed out?
Packing profile can be ramped
Must also consider processing effects
Orientation-Induced Shrink: Flow Types
• Linear
– Polymers oriented in direction of flow
• Extensional
– Expanding flow front (center-gated disk)
– Dependent on part thickness and processing
• Polymers oriented in the extensional or radial direction
• Transient
– Flow direction changes during mold filling
Different filling pattern change
orientation and shrinkage
Warp in Cavities 1 & 4
Cav. 1
= o.k.
Cav. 2
= not o.
4-ca
LID
Hot run
Cold ru
tunnel
Warp in Cavities 2 & 3
Cav. 3
= not
o.k.
Cav. 4
= o.k.
Intersection Options
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Be careful of putting too much faith in simulation output. Put it
through a reality check with your understanding of plastic flow.
Solution: Patented In-Mold Rheological Control Systems
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Continually manage the melt properties within the runner system
through strategic repositioning of the high sheared laminates
– Two Rotation Types:
• Single-Axis Symmetry
• Multi-Axis Symmetry
Single-Axis
Multi-Axis
Solution: Patented In-Mold Rheological Control Systems
Naturally “Imbalanced”
+ Intra-Cavity Control
Melt Rotation: Intra-Cavity Control, Concentricity
Mold Layout
Effective Melt Temperature
Concentricity
Conventional
Conventional
Melt Rotation
Avg. ∆T = 39.3°F
Avg. ∆T = 4.8°F
Melt Rotation
Engineering for Success
Systems of the mold:
1.
2.
3.
4.
5.
Structural / Kinematic
Melt Delivery
Air Evacuation (Venting)
Cooling
Ejection
Cooling Strategies
Cooling System:
Is
there
How
conductive
What
is the
Will
the
turbulent
flow?
is thecapacity
mold
heat
thermal
improvements
of
steel?
the
material?
diffusivity?
be measurable?
The Challenge:
• Learn what is needed to Engineer for Success
• We can be good program managers, exceptional engineers, and
good stewards of our companies
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Identify areas for improvement
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Seek out the appropriate training courses that will help everyone in the
organization Engineer for Success
“Teaching you to Think From the Plastic’s Perspective...
From Design through Production”
Course 1:
“Mold Start-up, Debug & Qualification”
Course 2:
Course 3:
“Hot & Cold Runner Systems”
“Injection Molding & Root Cause
Analysis for QC/QA”
Course 4:
Course 5:
“Mold Design for Project Engineers”
Course 7:
“Understanding & Applying Flow
Simulation”
“Understanding Shrink & Warp”
Course 6:
“Plastic Flow & Design Essentials
for Mold Makers/Designers”
Benefits:
• Improve Competitiveness on the Global Stage
• Improve Customer Satisfaction
• Reduce Mold Commissioning Time and Costs
• Produce Higher Quality Parts at a Lower Cost
Next Steps:
• Sharpen the Saw
• Identify areas for improvements within your
organization
• Seek out appropriate training courses that will
improve your ability to Engineer for success
• Apply what is learned
• Measure Results
• Repeat
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