Precise, resilient, ready for series production: closed die forging is an integral part of modern metal processing. Particularly in sectors such as the automotive industry, aerospace and mechanical engineering, this forming process enables the production of complex, high-strength components with exact dimensional accuracy. But what exactly are the advantages of closed die forging compared to other processes – such as open-die forging?
In closed die forging, a heated workpiece is brought into the desired shape between two precisely fitting dies under high pressure. The result: forged parts with excellent grain flow, high dimensional accuracy and minimal reworking. These advantages are particularly important for safety-relevant components such as crankshafts, steering knuckles or steering levers.
In this article you will find out:
- How closed die forging works technically
- What specific advantages the process offers
- Which materials and industries prefer to use it
- And what to look out for when it comes to burrs and post-processing
How exactly does closed die forging work?
Closed die forging belongs to the group of pressure-based forming processes and enables the precise production of complex metal parts in series. The process is technically demanding – but standardized: A preheated workpiece is placed in a two-part die that contains the exact negative shape of the desired component. Forming is then forced by a hammer blow or pressing pressure.
The workpiece passes through several phases:
- Heating: The blank – usually made of steel or aluminum – is heated to up to 1,250 °C to increase its formability.
- Positioning: The hot material is placed precisely between the die halves.
- Forming: The die closes quickly and with enormous pressure – the material flows into the cavities.
- Burr formation: Excess material emerges as a so-called burr – this is removed later.
- Cooling & post-processing: The raw parts cool down in a controlled manner and are mechanically processed if necessary.
The resulting drop-forged parts are characterized by high strength, repeatable quality and excellent structural integrity. A decisive advantage: the directional grain flow is retained and ensures optimum material properties – this is particularly important for components under continuous load.
Typical features of closed die forging:
| Feature | Meaning |
| Die | Forming tool with negative mold |
| Ridge | Excess material that is cut off |
| Forming temperature | Mostly 1,100-1,250 °C |
| Materials | Steel, aluminum, titanium, brass, bronze, copper |
| Manufacturing | Automated or semi-automated |
What are the advantages of closed die forging compared to other processes?
The process has a number of technical and economic strengths that clearly stand out, especially in comparison to open-die forging or machining processes such as milling.
The most important advantages of closed die forging:
- High dimensional accuracy: The precisely shaped die tools produce components with very little dimensional deviation – ideal for series production.
- Excellent fiber flow: The workpiece material is “pressed” into the desired shape, not cut – resulting in particularly high strength.
- Repeat accuracy: Automated processes enable consistently high quality, even for large quantities.
- Less material loss: Compared to machining processes such as turning or milling, more material is retained in the end product.
- Diverse materials: Whether steel, aluminum or titanium – drop forging can be combined with numerous materials.
- Cost efficiency for series production: Despite higher tool costs, the process pays for itself very quickly from medium to large batch sizes.
An often overlooked point: the advantages of closed die forging are not only evident in production, but also in component performance in later use – e.g. under heat, pressure or bending loads. This makes drop-forged components the preferred choice in safety-critical industries.
Closed die forging: Burr – why does it occur and how is it removed?
The flash is a typical by-product of closed die forging – and a crucial point in quality control. It occurs when excess material is pushed out of the mold when the die is closed and protrudes at the edges. As annoying as this may sound at first, the flash does fulfill a technical function – and its removal is an integral part of the process.
Why does flash occur during closed die forging?
- The workpiece volume is usually slightly larger than the actual die cavity – this ensures complete mold filling.
- The ridge acts as a safety valve: it prevents cavities from being filled unevenly or air pockets from forming.
- Without targeted burr flow, uncontrolled material displacement could occur, which would impair dimensional accuracy and grain flow.
After the forming process, the burr is removed in a separate work step, usually while still hot, by punching in a forming tool.
Important: In so-called low-burr die forging, attention is already paid to reducing burr formation to a minimum in the design of the die moulds – for example through optimized material flow or more precise volume control.
Burr removal methods at a glance:
| Method | Advantages | Suitable for |
| Mechanical deburring | Precise, automatable | Series production |
| Thermal deburring | Fast, for ridges that are difficult to access | Complex geometries |
| Chemical deburring | Gentle, selective | Precision mechanics |
What are closed die forgings – and where are they used?
Closed die forged parts are metallic workpieces that have been brought into their final or near-final shape by closed die forging. This produces high-strength, dimensionally accurate components that are specially designed for applications with high mechanical loads. These parts are characterized by an ideally aligned grain flow, very good material utilization and low tolerances.
Typical properties of closed die forgings:
- Made of steel, aluminum or titanium
- High strength with comparatively low weight
- Good weldability and machinability
- Tight dimensional tolerances without complex machining
- Ready for use after minimal post-processing
closed die forged parts really come into their own where safety, fatigue strength and cost-effectiveness are required.
Closed die forgings from Bharat Forge CDP
Bharat Forge CDP manufactures components for the automotive, agricultural and railroad sectors to the highest quality standards. Typical drop forged components in the product portfolio include Lever, Steering knuckle, stub axles and Crankshafts and components for hybrid engines that are characterized by maximum strength, optimized fibre flow and high fatigue strength. Depending on customer requirements, axle components such as axle beams can be forged or produced in hybrid manufacturing processes. With precise forging technology, high material efficiency and a global manufacturing presence, Bharat Forge CDP delivers high-performance solutions for safety-critical applications.
Die forging in transition – modern technologies and precision
Closed die forging has developed significantly over the last few decades: From hand-held hammers in the Middle Ages to fully automated production lines with digital process control. Today, this technological evolution ensures greater precision, higher energy efficiency and shorter throughput times – without compromising the basic principles of forming.
Modern closed die forging hammers and presses work with precisely controlled movement profiles. Sensors monitor temperature, material flow and die filling in real time. This allows quality deviations to be minimized and repeat accuracy to be brought up to series level.
Innovations in the drop forging process:
- Simulation-based die development: CAD models and FEM simulations enable precise predictions of material behavior and burr formation.
- Tool coatings & cooling: Significantly increase the service life of the dies and reduce tool costs.
- Automated handling systems: robot arms take over the loading and unloading of workpieces – efficiently and safely.
- Data-driven monitoring: process data is stored, analyzed and used for predictive maintenance.
One example: According to the VDMA, modern closed-die forging systems achieve energy savings of up to 30% compared to older generations – while maintaining the same cycle rate and shape accuracy.
Frequently asked questions about closed die forging (FAQ)
What is closed die forging?
Closed die forging is an industrial forming process in which a heated workpiece is pressed into its final shape between two dies. It belongs to the group of pressure forming processes and enables high-strength components with precise geometry.
What are the advantages of closed die forging over other processes?
Advantages include high dimensional accuracy, excellent fiber flow, minimal reworking and repeat accuracy in series production – especially in comparison to open-die forging or machining processes.
What are typical closed die-forged parts?
Typical closed die-forged parts are steering knuckles, crankshafts, levers, gear wheels or carrier parts – wherever high loads and precise dimensional accuracy are required, e.g. in the automotive or aviation industry.
What does the term “flash” mean in closed die forging?
The flash is the excess material that emerges at the edges when the die is closed. It is removed mechanically or thermally after the forming process. Modern processes increasingly rely on flash-reduced forging.
What is meant by the term “form stretching”?
Shape stretching is a special technique within the forging process in which the material is stretched into the desired shape. It is often used in die forging for material distribution.
Which materials are suitable for closed die forging?
Suitable materials are primarily steel alloys, aluminum, titanium or high-strength non-ferrous metals. Their formability at high temperatures is important – materials are heated to over 1,000 °C for this purpose.