Forging is a heavy engineering manufacturing process that shapes metal using compressive forces, typically delivered by hammers or presses – exemplified by typical blacksmithing. This process refines the metal’s internal structure and grain-flow, often greatly improving its strength, toughness, and durability. The process is widely used to manufacture high-quality, high-strength components for automotive, aerospace, heavy equipment and defense. Forging works with solid metal blanks that are pre-formed, often by casting, to an oversize approximation of the finished part. The process can be differentiated into hot forging, where metal is heated to a plastic state, and cold forging, performed at or near room temperature.
Overall, forging is key to producing parts that meet extreme requirements and withstand demanding conditions. It is increasingly performed on exotic material components for the most difficult applications.
Advantages of forging in manufacture
Forging offers several significant advantages in manufacturing, making it a preferred method for producing high-quality metal components. Here are the key benefits:
- Improved material properties: The process aligns the metal’s grain flow with the shape of the part, enhancing its mechanical properties such as fatigue resistance and impact toughness, in comparison to cast or machined components.
- Uniformity and consistency: Forged parts exhibit consistent mechanical properties throughout the component, reducing the incidence of weak spots and failures.
- Reduced material waste: Forging generally uses less material compared to machining, as it starts with a solid piece of metal and shapes it into a finished net-shape, with minimal waste or finishing required.
- Cost efficiency for high-volume production: While the initial tooling and establishment costs can be high, forging becomes cost-effective for large production runs due to its operational efficiency and low per-unit cost.
- High precision and tolerance: Forging can achieve close tolerances and complex shapes with minimal need for additional machining, improving the overall precision of the parts.
- Superior reliability: Forged components are often more reliable and durable in demanding applications, making them ideal for critical and high-stress environments.
- Versatility: The forging process can be adapted to produce a wide range of sizes, shapes, and materials, including complex geometries and high-performance alloys.
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DFM principles
Design for Manufacturing (DFM) principles for forging metal parts are critical for ensuring that the forged components are cost-effective, high-quality, and manufacturable. Here are key DFM principles specific to forging metal parts:
Material choice
Select a material that is suitable for forging and meets the mechanical and physical requirements of the end-use application.
Ensure the material has good forging characteristics such as ductility, workability, and resistance to thermal degradation.
Design for uniformity
Ensure that the design features allow for even material flow during the forging process. Avoid sharp corners and abrupt changes in section thickness.
Design parts with simple, symmetrical shapes that are easier to forge and require less machining.
Aim for designs that require minimal finishing and machining, reducing the need for excess material.
Optimize design for process and outcome
Calculate the optimal size and shape of the initial blank (pre-form) to minimize material waste and reduce costs.
Include allowances for the tolerances inherent in the forging process. Forging typically results in parts that are close to net shape but may still require some finishing.
Define clear and achievable tolerances in the design to avoid excessive machining or adjustments post-forging.
Design for heat treatment
If heat treatment is required, design parts that allow for even heating and cooling to avoid warping or cracking.
Clearly define any heat treatment processes in the design documentation, so the entire supply chain is aware of the needs.
Simplify and optimize tooling
Design parts with features that reduce complexity in tooling and die design. Simpler tooling can reduce costs and increase the lifespan of dies.
Design parts to minimize excessive wear on the dies, which can lead to higher maintenance costs and reduced die life.
Ensure the design promotes efficient material flow into all areas of the die. Avoid designs that create pockets or areas where material may become trapped.
Design with production volume in mind, ensuring the extrusion process is scalable for high-volume production if needed. It is common to prototype with lighter tooling and re-tool for volume once the production issues in the design have been refined. Multiple tools can allow quick ramping of productivity, where scaling is a challenge.
Part design and processing optimization
If post-forging machining is required, ensure that the design allows for easy access and is oriented to facilitate machining operations.
Provide adequate material allowances for machining in the finished forging, especially in critical areas that require tight tolerances.
Ensure that forged parts are designed with features that make them easier to handle and transport during and after the forging process.
If parts will be assembled with other components, design them to fit easily and consistently with other parts in the assembly process
Design reviews including the supplier
Conduct thorough reviews of the design with input from forging experts and manufacturing engineers to identify potential issues before production.
If feasible, produce prototypes or conduct trials to validate the design and refine it based on feedback and test results.
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Mechanical Engineer
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Conclusion
Applying Design for Manufacturing (DFM) principles in the design and manufacturing of forged parts yields substantial benefits. The enhanced efficiency, cost savings, and improved product quality are significant. By focusing on materials optimization, design simplicity, and process compatibility, DFM serves to streamline the forging process.
DFM encourages the development of designs that are manufacture-adapted and cost-effective to execute, both in tooling and processing, ensuring that forged parts are closer to net shape. The consideration of material flow, tooling, and heat treatment requirements leads to better control over the final part’s dimensions and properties.
The approach also facilitates easier handling, assembly, and integration of forged parts into final products. By proactively addressing potential manufacturing challenges and incorporating feedback from engineering and production teams early in the design phase, DFM reduces the risk of iteration delays.