DFM : Design For Manufacturing

Introduction

Design for Manufacturing (DFM) is a vital component of the broader Design For Excellence (DFX) methodology, which encompasses various principles to improve product quality and reliability, reduce costs, and enhance overall manufacturability.

DFM specifically focuses on designing products that simplify the manufacturing process, ensuring that products can be produced cost-effectively and with high quality.

Elon Musk uses Design for Manufacturing as part of his 5-step design method. I recommend reading the article: Five-step design method by Elon Musk.

Main Goals of DFM

The primary goals of DFM are:

• Cost Reduction: The DFM methodology helps companies significantly reduce production costs. This includes minimizing the number of parts, using standard components, and designing for efficient material use. Cost reduction achieved by the DFM method fully aligns with the concept of Design for Cost (DFC).
• Improved Quality: DFM helps reduce defects and variability in the manufacturing process, leading to higher-quality products.
• Shorter Time to Market: Simplifying the manufacturing process can lead to faster production times, enabling quicker product delivery to the market.
• Enhanced Efficiency: DFM aims to streamline the manufacturing process, making it more efficient and less prone to errors.

Main Aspects of DFM

The following are the example elements of DFM, focusing on aspects associated with component manufacturability.

Select adequate material

Select material based on availability, cost, manufacturability, and suitability for the intended application. The goal is to use materials that are easy to process and meet the product's performance requirements.

Eliminate a process step

The best way to optimize a process is to eliminate it and still get results. Use a detailed process flow chart to understand all the steps required to manufacture a part. Then, consider product design changes that would allow the process steps to be eliminated. For example:

• Eliminate the need for a silkscreen on the PCB's bottom side or, if possible, both sides. It will eliminate the silkscreen process.

Reduce tools required

For some products, reducing the required tools to manufacture a part may be feasible. For example:

• Consider standardizing THT hole diameters in the PCB layout. Could 1.1mm and 1.0 mm holes be replaced with 1.1 mm only? This would require fewer drill variants.

Optimize dimensions and tolerances

Understanding the manufacturer's capabilities and process limitations is very important. The designers shall define product characteristics with adequate dimensions and achievable tolerances. Examples:

• PCB: Use wider tracks than the manufacturer's minimum achievable width. This will simplify the etching process and reduce the risk of open connections (over-etched tracks).
• Plastic enclosure: To enhance manufacturability, add a 1-3 degree draft angle to all vertical walls. This adjustment facilitates easier mold release, reducing the risk of parts sticking and minimizing surface defects. It also reduces wear and tear on the mold, extending its lifespan and improving the overall surface finish of the part.
• Metal castings: Incorporating appropriate radii can significantly improve manufacturability. Instead of using sharp corners, design the part with a minimum 3-5 mm radius at all internal and external corners. This modification enhances the flow of molten metal into the mold, reducing turbulence and the risk of stress concentrations. By smoothing out these transitions, the likelihood of defects such as cracks and voids is minimized, resulting in a higher-quality cast part and reducing the need for extensive post-casting machining and finishing.
• CNC: Specifying wider tolerances for non-critical dimensions can improve manufacturability by reducing the precision required during production. This speeds up the machining process and lowers costs while still maintaining acceptable part quality.

Regarding assembly-related topics (joining various parts together), read the Design For Assembly (DFA) article.

Standards and Guidelines

I recommend familiarizing yourself with industry design standards. In electronics manufacturing, such guidelines can be found in documents created by the IPC organization. For example:

• IPC-2220 (a series of documents related to PCB design)
• IPC-7351 Generic Requirements for Surface Mount Design and Land Pattern Standard
• IPC-7352 Generic Guideline for Land Pattern Design
• IPC-7093 Design and Assembly Process Implementation for Bottom Termination Components (BTCs)
• IPC-7095 Design and Assembly Process Implementation for Ball Grid Arrays (BGAs)

Pros and Cons of DFM

Pros of DFM

• Cost savings: By optimizing designs for manufacturability, companies can reduce production costs significantly.
• Improved quality: Products designed with DFM principles tend to have fewer defects and higher overall quality.
• Reduced time to market: Simplified manufacturing processes can lead to faster production times, enabling quicker delivery to the market.
• Greater efficiency: DFM helps streamline manufacturing processes, decreases cost, and improves overall efficiency.

Cons of DFM

• Initial investment: Implementing DFM principles can require an initial investment in training, tools, and redesign efforts.
• Design constraints: Focusing on manufacturability might limit design creativity and innovation in some cases.
• Complexity in implementation: Integrating DFM principles into existing design processes can be complex and time-consuming.

Summary

Design for Manufacturing (DFM) is a crucial methodology within the broader DFX framework that focuses on designing products to simplify and optimize the manufacturing process. DFM helps companies produce high-quality products at lower costs and faster speeds by prioritizing cost reduction, quality improvement, and efficiency.

Designers should understand the manufacturing process of the products they create, including various manufacturing methods, their limitations, and common quality issues. Direct contact with the production team is highly beneficial. Ideally, designers should spend time working on the process to learn about manufacturing techniques, challenges of rework or repair, and costs associated with poorly designed products. This hands-on experience helps in creating better, more cost-effective designs.