Do It Right The First Time (DRIFT) Plastic Design

More often than not we experience poor plastic designs, causing toolability and moldability issues, or the plastic parts fail structurally. These issues would not only cost unnecessary time and money, it will also ruin one’s reputation, and thus, long term customers.

Those with job functions in CAD, FEA, NPI, SQE, CQE, manufacturing, process improvement, production, marketing, program management, purchasing and contract manufacturing, problems you would have likely encountered are:

• Warpage
• Sink Marks
• Voids
• Drag Mark
• Air Trap
• Short Shots
• Flashes
• Slver Streaks
• Jetting
• Brittleness

You might experience poor work/life balance due to:

1. Repeated tool modifications due to the above problems
2. In reactive mode, fire-fighting to root cause the problems
3. A modification to one part incurs modifications to adjacent parts in the final assembly, thus wasting more time and resources
4. Plastic parts breaking on the production line; worse than that the part breaks in the customer’s site, and within the warranty period
5.  Attempts to solve that broken part are guesswork (trial and error), leading to repeated delays and unfulfilled promises to the customer

What you will learn:          

1. Design a plastic part that is highly toolable and moldable.
2. Achieve one prototype for validation of a structural part, then on to production tooling, with no modifications. Save the bother of soft-tooling. Others have achieved this.
3. Projects stay on schedule, on cost, on quality.
4. Gain insight how to design for structural applications without failure in short-term and long-term in the field.
5. Learn new methods in FEA to ensure your part will be the strongest with minimum material usage.
6. More than 90% of FEA situations are nonlinear solutions. Nonlinearity accurately predicts force-deflection performance.
7. Some designers said they performed FEA simulation on the part but the failure still occurred. Why?
8. Understand how to transpose boundary conditions and loads from actual situations to the FEA model.
9. Apply your knowledge of engineering fundamentals in the FEA solution.
10. Learn to detect erroneous FEA results in order to re-check the data input and modeling assumptions.

Day One

Morning:

1. An Introduction To Plastic materials
2. Physical Properties And Terminology
3. Mechanical Properties
4. Thermal Properties
5. Structural Analysis

Afternoon:

1. Design For Moldability
2. Design For Precision
3. Design For Appearance
4. Assembling Plastic Parts
5. Design For Manufacturability And Assembly
6. Plastic Part Rapid Prototyping

The itinerary of Day One will be interspersed with group work sessions on five case studies. The participants will be asked to list down their (CAD and FEA) considerations for a successful part.

The probable solutions to those case studies will be discussed in detail on Day Two Afternoon.

Day Two

Morning: Fundamentals of FEA and its applications to structural FEA simulation of plastic parts.

1. What is FEA? Why use FEA?
2. Major steps of an FEA simulation.
3. Non-linear behaviour of plastics requires special treatment in FEA.
4. Other non-linear FEA situations, required for accurate predictions.
5. What is the significance of Area Moment of Inertia?
6. Iterative FEA vs Dead-End FEA. FEA takes too long, or does it?
7. Analyze a single part or an assembly of parts?
8. What boundary/load conditions to use in transposing the actual usage situation to an FEA model?
9. Why some designers use FEA but get wrong results.
10. How to spot erroneous output results from an FEA simulation.

Afternoon: Case studies of actual applications whereby the plastic parts failed during testing, during production, or in the field.

1. Case study #1 – T-pipe burst under water pressure.
2. Case Study #2 – LCD bezel caused LCD to go blank.
3. Case study #3 – Plastic housing with O-ring water seal application.
4. Case study #4 – Plastic spring arm broke.
5. Case study #5 – Warpage caused dimensions out of spec.