investment casting Case Study: Re-engineering a Crane Braking Component

Case Study: Re-engineering a Crane Braking Component investment casting

By Mr.Sun

Table of Contents

Background

In 2022, an Italian Original Equipment Manufacturer (OEM) specialising in crane systems was in the R&D phase for a new crane model. A key part of this development was the design and sourcing of a braking component. The initial design concept proposed by the OEM was a sheet metal welded structure.

The Initial Inquiry and Design Rationale

The OEM contacted Dawang Metals. The client’s preference for a sheet metal welded structure for the braking component was based on several common assumptions in the early design stages:

Cost Efficiency: Sheet metal fabrication is often considered a lower cost entry point for components, especially when initial tooling investment for other processes is a concern.
Assumed Production Simplicity: The client thought the manufacturing process would be relatively straightforward, cutting, bending and welding standard sheet metal.
Rapid Prototyping & Production: Welded structures can sometimes offer quicker turnaround times for initial batches if complex tooling is avoided.

The initial discussions, via video conference between the OEM’s design team and Dawang Metals’ technical specialists, focused on understanding the functional requirements, load conditions and aesthetic expectations for this externally mounted braking unit.

Technical Review of the Welded Design

While we understood the client’s reasoning, Dawang Metals’ engineering team reviewed the proposed welded design against the application’s demands. Several potential limitations and challenges were identified:

Aesthetic and Perceived Quality Concerns: As an externally visible component on a new, high-end crane, the inherent appearance of a welded structure, often with visible weld beads and potential distortion, could compromise the overall premium aesthetic and quality perception the OEM was looking for.
Mechanical Performance Limitations:

Stress Concentrations: Welded joints, by their nature, can introduce stress concentrations, potentially becoming fatigue points under cyclic loading typical in braking systems.
Material Differences: The properties of a welded assembly are not uniform throughout, with Heat-Affected Zones (HAZ) potentially having different mechanical properties than the parent metal.
Load Capacity: For a component subjected to high intermittent stress, impact loads and sustained operational forces, the inherent strength and fatigue resistance of a fabricated sheet metal structure may not be sufficient for long term reliability and safety margins.

3. Manufacturing Complexity and Consistency Issues:

Complex Welding Operations: The specific geometry of the braking component, if produced as a weldment, would require multiple complex welding sequences. This complexity increases the likelihood of human error, dimensional inaccuracies and weld defects (e.g. porosity, incomplete fusion).
Instability and Rework: Each welding step introduces thermal stresses and potential distortion, requiring rigorous quality control and potentially high rates of rework, thus impacting consistent output and lead times.

The Engineering Pivot: Proposing a Sand Casting Solution

Driven by a deeper understanding of the client’s unspoken needs for long term reliability, safety and product integrity, Dawang Metals’ engineering team spent two weeks in technical analysis and internal design workshops to develop a solution that met the functional requirements and offered better value.

The conclusion was a fundamental change in manufacturing methodology: switch the component from a sheet metal welded structure to a sand cast design.

Hengke Metals presented a comprehensive proposal which included:

Holistic Structural Redesign:The component was re-designed as a single unit. This eliminated the multiple joints inherent in a welded fabrication which are often the weakest points. The optimized geometry aimed to distribute stresses more evenly.
Material Selection Optimization:The proposal specified low-alloy steel as the material of choice. This was based on its excellent balance of strength, toughness and castability, making it suitable for high stress, durable components. The final cast part was designed to weigh 30kg.
Enhanced Mechanical Properties:The monolithic nature of a casting, combined with the properties of low-alloy steel, would provide better tensile strength, fatigue resistance and impact toughness than the proposed welded structure.

Addressing Client Concerns: Cost vs. Lifecycle Value

The OEM’s engineering team understood the technical merits and rationality of the cast design. However, a big concern was the higher per-unit cost of a casting compared to their initial estimate for a welded part.Dawang Metals addressed this by presenting a detailed breakdown of Total Cost of Ownership (TCO) and lifecycle value:

Welded Component Lifecycle

Lower initial unit price.
Lower load-bearing capacity and higher fatigue risk.
Shorter service life, more replacement cycles.
Higher in-field failure rate, more warranty claims and reputation damage.

Cast Component Lifecycle

Slightly higher initial unit price (due to pattern-making and foundry processes).
Much better mechanical performance and load-bearing capacity.
3-4 year longer service life than the welded alternative.
Lower risk of premature failure, higher product reliability.

Additional benefits of the cast design contributing to overall cost savings

Simplified Assembly:A single cast part reduces assembly time and complexity compared to fitting and joining multiple fabricated parts.
Streamlined Post-Processing:While castings require finishing, the complexity could be less than correcting distortions or preparing multiple surfaces in a complex weldment.
Improved Batch Consistency:The casting process, once patterns and processes are established, offers higher dimensional repeatability and consistency in mass production.
Better Overall Production Economics:When you factor in reduced rework, longer component life and simplified assembly, the slightly higher initial cost of the casting was offset by long term savings and value.

Conclusion and Technical Implications

After evaluating Dawang Metals’ technical proposal and value analysis, the Italian OEM approved the switch to the sand cast design. This resulted in:

Better Component Reliability:The new braking component had better structural integrity and resistance to operational loads, directly impacting the safety and reliability of the crane.
Longer Product Life:The longer life of the cast part meant less maintenance and replacement costs for the end-users.
Improved OEM Manufacturing Efficiency:Simplified assembly and higher consistency benefited the OEM’s own production process.

A Case for Design Optimization through Manufacturing Expertise

This is a great example of an engineering win where material science, manufacturing processes and application requirements came together to deliver a better product. Going from a seemingly simpler welded fabrication to a more robust sand cast part, initially raised a cost question, but ultimately delivered a part with better mechanical performance, longer life and more lifecycle value. It shows the importance of early supplier collaboration and the technical expertise required to identify and implement the right manufacturing strategy for critical components. This is a great example of how to re-engineer components from welded to cast when application requires it.