Integrated Product Development - A249

 

Integrated Product Development
Practice article
Document Type	Article
Document Identifier	249
MSTE workflow	Development
Prerequisites	Practice

Overview

This section of the KPC will guide you through advancing your part and process configurations anywhere from a conceptual state up to the production state. The integrated product development process begins with the design process initializations steps of defining the functional requirements, before moving on to selecting shape and materials. This is followed by an iterative process where the factory cells are identified, developed and subsequently assessed for feasibility. The assessments are done for both individual cells and for the factory as a whole (considering all cells). This loop is iterated over until the factory is fully defined with all its cells and process steps at a production state and the assessment of the part and process against the functional requirements is passed.

Feasibility for Using Composites

Before starting the design process for a composite product and manufacturing facility, it is important to consider if a composite material is the best option for your application. A common misconception of composites, and carbon fiber in particular, is that it is viewed as “black metal”. The design methodology is done in the same way one would a metallic component and then simply replaced with a carbon fibre composite part. While that may work in some cases, it is rarely the best case or optimized scenario. From the composites manufacturing perspective, geometries that are common and easily produced using metallics are often difficult, expensive, or impossible to manufacture out of composites. Therefore, the misconception that a designer can simply replace a metallic component directly with composite laminates is a mistake that will yield a part without the desired results.

Below is a table comparing three different considerations and an example case where composites are well suited and one where they are a poor choice.

Geometry
Well-Suited for Composites	Complex curvature with gentle transitions and generous radii
Difficult to Accommodate into Composites	Aggressive & sharp curvature with tight features
Mechanical Performance
Well-Suited for Composites	High strength-to-weight ratio required
Difficult to Accommodate into Composites	Large concentrated point loading scenarios
Environmental Performance
Well-Suited for Composites	Corrosive environments
Difficult to Accommodate into Composites	Extreme temperatures - i.e. continuous exposure between -40°C and 180°C

Development Process

The development process for composites is inherently different due to the orthotropic properties caused by the fibers and the matrix, among other characteristics. In addition to this, the production of composites is not only about shaping the material, but also creating it during the manufacturing of a product. This means that each step in the production line has an effect on the final properties of the composite, leading to a design process where the selecting, shaping and creating of a material is part of the same system. When doing composite part development in a structured and linear manner, the process will allow for reiteration and looping back to previous steps as changes are made down the line. The integrated product development approach uses MSTE considerations in each step and will guide the user through the process.

The KPC has split the development process into two major sections: a product development stage, and a process development stage. The product development will guide through establishing functional requirements of the product before moving on to selecting material systems and shapes. Lastly the section will guide the user into selecting their process steps which best fits their product. The process development section guides the user through each key cell in the factory and gives best practice on how to develop these steps. Firstly, the factory cells are designed using a conceptual screening, preliminary selection and detailed finalization approach, allowing for a complete process to be developed for the specific product. Then the development will guide the user through qualification, commissioning and approval for the process step. Lastly, the section will provide a selection of best practice documents for how to perform and avoid common issues during the production step.

Below is a flowchart of the steps that will be taken in the integrated product development process. The flowchart illustrates the iterative nature of composite part development with many gateways to loop back in the design process and make changes as decisions and considerations are made further down the line.

Development workflow

Product Development

Using the MSTEP figure for design, one must first establish the function at the top of the pyramid. This will include all the requirements that the product and production must have, ranging from production rate to structural requirements to certifications. Once these are established, material and shape can be established with regards to the functional requirements. Using these material systems and shapes, the required processes can be selected and an outline of the factory can be made. To begin the development, see Practice for Developing a Product.

Process Step Development

With the process steps defined and grouped into factory cells, practice documents specific to each step can now be followed in order to make design decisions regarding the material and shape, as well as the tooling and equipment that are specific to that cell. By following the practice documents, you will be guided to consider all the important aspects relating to composite manufacturing system interactions. Furthermore, you will understand what is important to consider, control, measure, and evaluate in order to make good development decisions and advance towards production. Assessment of the function of the cell on its own is a consistent focus of these practice documents.

Collection of practice documents to develop process steps are available in Practice for Developing a Process Step.

Assess

After each iteration of the loop (where each cell is developed and assessed individually) it is important to assess the factory as a whole and ensure that the interfaces of all cells with each other work properly and that the sum total of all the operations performed by the cells produce a part that meets the cost, rate, and functional requirements. In order to satisfy the factory assessment, the factory must be fully defined (all factory cells and steps ready for production) and all cost, rate, and functional requirements identified at the beginning of the design process must be met.

This step is covered in P113.

Explore this area further

• Integrated Product Development - A249
  • Practice for Developing a Product - P111
    • Composite Production Part Drawing - P169
    • Selecting Functional Requirements - P152.0
    • Shape Development - P151.0
      • Sandwich Panels - A325
    • Material Selection - P153
    • Practice for Identifying Process Steps - P102
  • Practice for Developing a Process Step - P104
    • Practice for Developing a Receiving and Storage Step - P154
    • Practice for Developing a Deposition Step - P157
      • Resin degassing - P166
    • Practice for Developing a Demoulding Step - P159
    • Practice for Developing a Consolidation Step - P158
      • Debulking - P167
      • Consolidation of Thermoplastics - P170
      • Vacuum Bagging - P168
        • Vacuum Bagging for Prepregs - P172
        • Vacuum Bagging for Vacuum Infusion - P173
    • Practice for developing a thermal transformation process step - P105
      • Developing production scale tooling - P129
  • Maintaining equivalency during cure for different fibre architectures - P118
  • Ensuring tooling choice meets part quality metrics - P128
  • Ensuring quality during curing of thick parts - P125
  • Ensuring quality during production of variable thickness parts - P127

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Engineered materials (designed to have specific properties) made from two or more constituent materials with different physical or chemical properties. The constituents remain separate and distinct on a macroscopic level within the finished structure.

Carbon fibres are composed of large aromatic sheets similar to those in graphite. These graphitic layers form the basic structural units in the shape of ribbons. The structure of carbon fibre ribbon is believed to be a columnar arrangement of disoriented graphite crystallites parallel to the ribbon length. The idealized tetragonal crystallites are stacked above one another, with slight disorientation between the crystals in the direction of fibre axis, trapping sharp needle like voids, where the boundaries between the stacks represent the disordered regions.

The continuous material phase that binds the reinforcement together, maintains shape, transfers load, protects the reinforcement from environment and damage, and provides the composite support in compression.

Desirable characteristics:

• Moisture/chemical resistance
• Low density
• Processability

Any manufacturing and/or decision making activity that occurs during any stage of the development design cycle (e.g. conceptual design to production).

In the context of Knowledge in Practice, practice refers to the systematic use of science based knowledge to reduce composites manufacturing risk, cost, and development time.