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Metal Stamping | OEM Engineering | Design for Manufacturability
A precision stamped metal component may look simple when viewed as a finished product. However, its manufacturability depends on much more than the final shape.
Consider a compact stamped metal bracket featuring an elongated mounting slot, multiple bends and several formed tabs.
The component is designed to meet assembly requirements while maintaining a compact structure and sufficient mechanical strength.
From a product design perspective, these features make sense. The elongated slot provides positioning flexibility, the folded sections create the required three-dimensional geometry, and the formed tabs support the intended assembly function.
But what happens when these design requirements interact during stamping production?
Three reasonable design decisions can introduce challenges in punching, bending, material forming and tooling development.
This is where Design for Manufacturability (DFM) becomes essential.
A stamped bracket with an elongated slot and multiple formed features involves several manufacturing operations.
Depending on the actual component design, these may include:
Blanking and piercing.
Slot punching.
Bending and forming.
Tab forming.
Final part separation and dimensional inspection.
Each operation affects the next.
The position of a slot can influence the material available around a bend. The material grade can affect forming loads and springback. The arrangement of multiple forming features can influence the progressive die layout and production sequence.
Therefore, the component should be evaluated as a complete stamped structure rather than a collection of independent features.
An elongated mounting slot is commonly used when a component needs positional adjustment or flexible assembly alignment.
Its length and width are determined by functional requirements, but both dimensions should be considered during tooling design.
The narrow width of an elongated slot is particularly important because it determines the effective punch width.
If the slot is too narrow relative to material thickness, the punch may become vulnerable to excessive loading, wear or breakage.
Other potential concerns include:
Punch strength and durability.
Burr formation along the slot edges.
Slug control and removal.
Slot width and dimensional consistency.
Clearance between the slot and nearby material features.
Unlike a conventional circular hole, an elongated slot also has two different geometric dimensions that need to be evaluated independently.
DFM considerations:
Review slot width in relation to material thickness and strength.
Check the radius at both ends of the slot.
Evaluate punch geometry and die clearance.
Maintain sufficient material around the slot.
Specify acceptable burr height and dimensional tolerances.
The objective is to achieve the required assembly function without creating unnecessary punching difficulties.
The second design decision is to maintain a compact component layout while incorporating several bends and formed tabs.
This is often necessary in electrical equipment where internal assembly space is limited.
However, reducing the distance between an elongated slot and nearby bend lines may create additional manufacturing constraints.
During bending, the material experiences tensile deformation on the outer surface and compressive deformation on the inner surface.
If a slot is positioned too close to a bending region, the surrounding material may deform and affect the final slot geometry.
Potential consequences include:
Slot distortion or dimensional variation.
Localized deformation near the bend.
Reduced material strength in narrow sections.
Difficulty maintaining assembly tolerances.
Multiple bends also introduce another consideration: the order in which forming operations are performed.
An unsuitable forming sequence may cause interference between the workpiece and tooling, or make it difficult to maintain consistent part positioning.
DFM considerations:
Review the distance between the slot and bend lines.
Check the minimum inside bend radius.
Evaluate the material available between adjacent formed features.
Consider forming sequence and tool accessibility.
Verify critical dimensions after all bending operations.
A compact component is not necessarily a more manufacturable component. The available forming space and operation sequence must also be considered.
Figure 1. Illustration of slot-to-bend distance considerations and potential slot deformation during bending.
The third design decision concerns material selection.
A stamped bracket must satisfy its structural and assembly requirements. However, choosing a material based only on strength may introduce forming challenges.
Material strength, elongation, hardness and anisotropy all influence stamping performance.
For example, higher-strength steel may require greater forming loads and exhibit more pronounced springback. If its local formability is insufficient for the selected bend geometry, cracking may occur.
Material selection also influences punching performance, particularly when narrow slots and small forming features are involved.
DFM considerations:
Confirm material grade and thickness.
Review yield strength and tensile strength.
Evaluate elongation and bendability.
Consider rolling direction for critical bends.
Validate material performance through forming trials where necessary.
The most suitable material is not necessarily the strongest one. It is the material that meets the component's functional requirements while remaining compatible with the intended manufacturing process.
The relationship between material properties, punched edges and forming performance has been investigated in published engineering research.
A 2017 SAE technical paper, Practical Evaluation and Prediction of Edge Cracking in Forming Advanced High Strength Steels (AHSS), studied DP980 and TRIP780 advanced high-strength steels.
The researchers compared different hole-expansion testing methods and investigated the influence of hole-edge preparation on formability.
Two findings are particularly relevant to stamped components with slots and punched openings:
Finding 1: Test methods can reveal different material behavior.
The study reported differences in hole-expansion ratio (HER) of up to 11% between DP980 and TRIP780 using a 75 mm hole test method, while the standard 10 mm hole test showed less than 1% difference.
Finding 2: Hole-edge preparation affects formability.
Waterjet-cut samples demonstrated approximately twice the hole-expansion ratio of punched samples for both tested steel grades.
These findings highlight the importance of punched-edge condition when evaluating components that undergo further forming.
Although the research investigated specific advanced high-strength steels rather than this particular bracket, its findings provide useful engineering insight into the interaction between material properties, edge quality and forming performance.
For an elongated slot, the same principle is relevant: the condition of the punched edge should be considered when evaluating subsequent deformation.
Figure 2. Schematic illustration of punched-edge characteristics and the influence of edge preparation on hole expansion performance.
The three design decisions should not be reviewed independently.
A more effective approach is to evaluate their combined influence on the manufacturing process.
Design feature | Engineering review | Potential manufacturing impact |
|---|---|---|
Elongated slot | Slot width, end radius and punch clearance | Punch wear, burrs and dimensional variation |
Slot near bend | Slot-to-bend distance and local material deformation | Slot distortion and cracking risk |
Multiple formed tabs | Bend radius and forming sequence | Tool interference and dimensional variation |
Material selection | Strength, elongation and thickness | Forming load and springback |
Combined geometry | Progressive die layout and carrier design | Tooling complexity and production stability |
This integrated review helps identify problems before they require changes to completed tooling.
For components with elongated slots and multiple forming features, progressive die planning should consider the complete manufacturing sequence.
Figure 3. Conceptual progressive die sequence for a stamped component with slots, formed tabs and multiple bends.
A typical engineering review may include the following:
1. Flat Pattern Evaluation
Check the slot position, material margins, feature spacing and blank geometry.
2. Punching Operation Planning
Evaluate punch dimensions, die clearance, punch strength and slug removal.
3. Forming Sequence Development
Determine the appropriate order for bending and forming operations while considering tool access and potential interference.
4. Carrier and Strip Layout Design
Ensure that the strip provides sufficient support and stability throughout the progressive stamping process.
5. Tooling and Production Validation
Verify critical dimensions, burr conditions, bend angles and part consistency during tooling trials.
The actual sequence depends on the component geometry and production requirements. Not every stamped component requires the same number of stations or the same tooling configuration.
The objective is to develop a practical manufacturing process that supports repeatable production.
At HAIPART, precision metal stamping is part of our broader focus on functional components for electrical equipment and circuit protection applications.
Components with elongated slots, multiple bends and formed tabs demonstrate why stamping design requires coordination between product geometry, material selection and tooling development.
A manufacturing-oriented approach should consider:
Geometric Requirements: Slot dimensions, feature spacing, bend positions and formed structures.
Material Characteristics: Thickness, strength, ductility and forming behavior.
Tooling Considerations: Punch design, die clearance, forming sequence and progressive die layout.
Production Requirements: Dimensional accuracy, burr control and batch consistency.
Considering these factors together helps identify potential manufacturing challenges before mass production.
Good stamping design starts before tooling development.
Are you developing a precision stamped metal component for an electrical application?
Contact HAIPART to discuss your component drawings, material specifications and manufacturing requirements.
The slot width, length, end radius, material thickness, punch strength and die clearance should all be evaluated. The narrow dimension is particularly important when checking punch durability.
It depends on the material, slot dimensions, bend radius and forming sequence. Insufficient spacing may cause slot distortion or localized deformation during bending.
Material properties affect punching loads, bendability, springback and cracking risk. Material strength should be considered together with elongation and forming requirements.
The order of forming operations affects tool access, workpiece positioning and potential interference. An appropriate sequence helps maintain dimensional consistency and production stability.
DFM should ideally begin during the component design stage, before progressive die development. This allows geometry, material and tooling requirements to be reviewed together.
Kim, H., Shang, J., Dykeman, J., Samant, A., and Hoschouer, C. (2017). Practical Evaluation and Prediction of Edge Cracking in Forming Advanced High Strength Steels (AHSS). SAE Technical Paper 2017-01-0308. DOI: 10.4271/2017-01-0308.
Dayton Lamina. Birth of a Hole – Perforating Basics.
ASM International. ASM Handbook, Volume 14B: Metalworking: Sheet Forming.
