Best Principles to Efficiently Convert a Concept Design into Design for Manufacturing (DFM)

This informal CPD article, ‘Best Principles to Efficiently Convert a Concept Design into Design for Manufacturing (DFM)’, was provided by Saghar Ali Rabbani at Mechesol Co., who deliver high-quality innovative product development solutions for domestic and industrial clients.

In the world of product development, transitioning from a concept design to a design for manufacturing (DFM) is a crucial step. A concept design, often referred to as a draft, serves as a visualization or blueprint to give stakeholders an idea of the project. It outlines the product's aesthetics, functionality, and overall vision. In contrast, DFM is the refined version of this design, meticulously tailored for production. This transformation ensures the design is practical, cost-effective, and ready for fabrication. Here, we will discuss the principles required to convert a concept design into a DFM, focusing on various materials and manufacturing methods.

The Difference: Concept design vs. DFM

Concept Design


•    Purpose: Visualization and conceptualization.
•    Focus: Surface, Aesthetics, basic functionality, and overall product vision.
•    Outcome: Provides a preliminary look at what the product will be.


Design for Manufacturing (DFM)

  • Purpose: Ready for production.
  • Focus: Practicality, manufacturability, cost-effectiveness, and compatibility with manufacturing processes.
  • Outcome: Detailed design files that manufacturers use to fabricate the product.

Material and Production Method Selection:

The first step in designing for manufacturing is selecting the right material for the product. Industrial goods are primarily made from either plastic or sheet metal. Let’s take a closer look at these two categories.

Prototyping Methods:

FDM (Fused Deposition Modeling):

  • Overhanging Angles: Avoid overhangs greater than 45 degrees. If unavoidable, consider splitting the model into parts that can be assembled post-printing.
  • Wall Thickness: Ensure consistent wall thickness to maintain structural integrity, typically around 0.8-1.2 mm for small parts, but it all depends on the nozzle diameter of printer.
  • Tolerances: Design with a tolerance of ±0.3 mm.
  • Supports: Utilize automatic supports in slicing software, but manual supports can offer more control in complex areas.

SLA (Stereolithography):

  • Structural Enhancements: Add ribs, cutouts, or textures to large flat areas to reduce warping.
  • Hollow Parts: Design with internal lattice structures and drainage holes to balance strength and reduce material usage.
  • Clearances: Maintain clearances of 0.1-0.2 mm between fitting parts for assembly ease.
  • Overhangs: Minimize overhangs or design them to avoid excessive support requirements.
  • Wall Thickness: Ensure a minimum wall thickness of 1-1.5 mm to maintain structural integrity.

Mass Production Methods

The most used bulk production method for plastics is “injection molding”

Injection Molding:

  • Draft Angles: Include draft angles of at least 1-2 degrees; increase to 3-5 degrees for textured surfaces.
  • Wall Thickness: Maintain a wall thickness between 1.5 mm and 4 mm, typically around 3 mm.
  • Rib Design: Ribs should be 40-60% of the wall thickness, with fillets at the base.
  • Boss Design: Ensure bosses have a height-to-diameter ratio of around 2:1 to 3:1 and are supported by ribs.
  • Eliminate Undercuts: Design to omit undercuts or use side actions to simplify the geometry.
  • Corner Fillets: Add fillets with a radius of at least 0.5 times the wall thickness for internal corners and round external edges.
injection-molding-mass-production-cpd
Injection molding machinery for plastics production

Sheet Metal Fabrication:

For sheet metal designs, specific adjustments are necessary to ensure manufacturability and structural integrity.

  • Material Thickness: Choose the appropriate thickness based on strength and application requirements, typically between 0.4 mm and 6 mm.
  • Bend Radius: Use a minimum bend radius equal to the material thickness to avoid cracking.
  • Minimize bends: Use simple uniform bends with generous radii to reduce stress and improve manufacturability.
  • Wall Thickness: Ensure walls meet the minimum thickness requirements.
  • Avoid Sharp Corners: Use rounded corners to reduce stress concentrations.
  • Tabs and Slots: Incorporate these features for easy assembly and alignment.
  • Minimize Warping and Distortion: Use symmetrical designs and add ribs or flanges to strengthen large flat areas.
  • Allow for bend relief: Incorporate bend reliefs to prevent material tearing or distortion during bending.
  • Ensure easy access: Design for ease of access to all areas of the part for inspection, welding, or assembly.
  • Use minimal fasteners: Where possible, use snap fits, tabs, or other fastening methods to reduce assembly time.
  • Tolerances and Fits: Define clear tolerances, typically ±0.1 mm to ±0.5 mm, to ensure proper assembly.

Enhancing Design for Manufacturability

General Principles

  • Simplify Geometry: Reduce complexity to lower manufacturing costs and improve reliability, the extent of design complexities will directly influence the cost and manufacturing intricacies.
  • Standard Components: Use standard sizes and parts where possible to streamline production and reduce costs.
  • Optimize Part Orientation: Consider the manufacturing process's specifics to determine the best part orientation for production.

Industrially Proven Techniques

  • DFM Analysis: Use DFM analysis software to simulate the manufacturing process and identify potential issues.
  • Collaboration with Manufacturers: Engage with manufacturers early in the design process to get feedback on feasibility and cost implications.
  • Iterative Prototyping: Create multiple prototypes and refine the design based on testing and feedback to ensure it meets all manufacturing and performance requirements.

Conclusion

Converting a concept design into a DFM is a detailed process that requires a deep understanding of the intended manufacturing methods and materials. By focusing on the specific requirements of each production technique, from FDM and SLA prototyping to injection molding and sheet metal fabrication, designers can ensure their products are ready for efficient, cost-effective manufacturing. By employing these Principles, you can confidently move from concept design to a fully realized product, ready for the market.

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