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What Lies Below the Surface of Your Molded Parts?.

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Presentation on theme: "What Lies Below the Surface of Your Molded Parts?."— Presentation transcript:

1 What Lies Below the Surface of Your Molded Parts?

2 Plastics Manufacturers Strength: 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 Revenue / ft 2 2008 Present

3 Plastics Manufacturers Weakness: 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 Mold Design Part & Mold Commissioning Product Design Launch Production CIP

4 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 II. Rheological Variations ( η ) I. Mold Steel Variations ( l, r)

5 Why is New Mold Commissioning Such a Challenge? Plastic Rheology is Not Well Understood Shear-induced imbalances Shrink & Warp characteristics Cooling and thermodynamics Regional pressure variations Amorphous and Semi-crystalline materials

6 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 The Science Behind Non-Uniform Rheology Highest Shear Rate is just inside the frozen layer –Shear-thinning and Shear-heating reduce viscosity in these laminates

7 Single Cavity Disk Mold: Rivering flow front Gas trap created Influence on melt front advancement profile

8 Melt Property Distribution 1 1 3 4 3 4 3 4 1 2 2 3 4 2 1 2 2 1 2

9 Conventional Runner 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

10 180° F 100° F Volumetric: Mold Design (Cooling) At ejection: Linear Shrinkage:

11 Effect of Regional Pressure Differences Center packs under higher pressure = possible dome warp ΔP at End of Fill ΔP Thick Part 55 mPa 40 mPa ΔP Thin Part 70 mPa 25 mPa 55 Mpa 40 Mpa x Must also consider processing effects Can this be processed out? Packing profile can be ramped

12 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

13 Warp in Cavities 2 & 3 Warp in Cavities 1 & 4 Different filling pattern change orientation and shrinkage

14 Be careful of putting too much faith in simulation output. Put it through a reality check with your understanding of plastic flow. Intersection Options

15 Solution: Patented In-Mold Rheological Control Systems –Two Rotation Types: Single-Axis Symmetry Multi-Axis Symmetry Continually manage the melt properties within the runner system through strategic repositioning of the high sheared laminates Single-Axis Multi-Axis

16 Naturally “Imbalanced” + Intra-Cavity Control Solution: Patented In-Mold Rheological Control Systems

17 Melt Rotation: Intra-Cavity Control, Concentricity Mold Layout Effective Melt TemperatureConcentricity Conventional Melt Rotation ConventionalMelt Rotation Avg. ∆T = 39.3°F Avg. ∆T = 4.8°F

18 1.Structural / Kinematic 2.Melt Delivery 3.Air Evacuation (Venting) 4.Cooling 5.Ejection Engineering for Success Systems of the mold:

19 Cooling Strategies

20 What is the heat capacity of the material? What is the thermal diffusivity? How conductive is the mold steel? Is there turbulent flow? Cooling System: Will the improvements be measurable?

21 The Challenge: Learn what is needed to Engineer for Success We can be good program managers, exceptional engineers, and good stewards of our companies Identify areas for improvement Seek out the appropriate training courses that will help everyone in the organization Engineer for Success

22 Course 1 : “Mold Start-up, Debug & Qualification” Course 3 : “Injection Molding & Root Cause Analysis for QC/QA” Course 5 : “Mold Design for Project Engineers” Course 7 : “Understanding & Applying Flow Simulation” “Teaching you to Think From the Plastic’s Perspective... From Design through Production” Course 2 : “Hot & Cold Runner Systems” Course 4 : “Understanding Shrink & Warp” Course 6: “Plastic Flow & Design Essentials for Mold Makers/Designers”

23 Benefits: Improve Competitiveness on the Global Stage Improve Customer Satisfaction Reduce Mold Commissioning Time and Costs Produce Higher Quality Parts at a Lower Cost

24 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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