Hybrid Manufacturing Solutions: Combining Additive and Subtractive Processes for Complex Hydraulic Manifolds

 

Content Menu

● Introduction

● Design Considerations for Hybrid Manufacturing of Hydraulic Manifolds

● Hybrid Manufacturing Process Workflow for Hydraulic Manifolds

● Real-World Examples

● Cost Considerations

● Practical Tips for Implementing Hybrid Manufacturing

● Conclusion

● Q&A

● References

 

Introduction

The manufacturing landscape is rapidly evolving with the integration of advanced technologies that enable the production of complex, high-performance components. Among these innovations, hybrid manufacturing-combining additive manufacturing (AM) and subtractive manufacturing (SM)-has emerged as a powerful approach to address the challenges of fabricating intricate hydraulic manifolds. Hydraulic manifolds are critical components in fluid power systems used across aerospace actuators, automotive fluid systems, and industrial pumps. Their complexity, precision requirements, and functional demands make them ideal candidates for hybrid manufacturing solutions.

Traditional manufacturing methods for hydraulic manifolds, such as machining from solid billets, impose geometric constraints and often result in heavy parts with suboptimal flow paths. Additive manufacturing, particularly metal AM techniques like laser powder bed fusion (LPBF) and directed energy deposition (DED), offer unprecedented design freedom to create internal channels and optimize fluid flow. However, AM parts frequently require post-processing to achieve dimensional accuracy and surface finish, which is where subtractive manufacturing complements the process.

This article explores the synergy of additive and subtractive processes in hybrid manufacturing for hydraulic manifolds. It discusses design strategies, process steps, cost considerations, and practical tips, illustrated with real-world examples from aerospace, automotive, and industrial applications. The goal is to provide manufacturing engineers with a comprehensive understanding of how hybrid solutions can enhance manifold performance, reduce weight, and optimize production efficiency.

Design Considerations for Hybrid Manufacturing of Hydraulic Manifolds

Embracing Design Freedom with Additive Manufacturing

Additive manufacturing enables the creation of complex internal geometries that are impossible or prohibitively expensive with traditional machining. For hydraulic manifolds, this means:

• Optimized flow paths: Smooth, curved channels reduce pressure losses and turbulence, improving system efficiency.

• Part consolidation: Multiple components can be integrated into a single manifold block, reducing assembly complexity and potential leak points.

• Weight reduction: Lightweight lattice structures and optimized wall thicknesses minimize mass without compromising strength.

For instance, Renishaw’s redesign of a hydraulic block manifold achieved a mass reduction of up to 79% while improving flow efficiency by 60% through AM-enabled internal channel optimization. This redesign replaced the traditional drilled passages with smooth, continuous flow paths that minimized abrupt junctions causing flow separation and stagnation, common in conventionally machined manifolds.

Addressing Limitations with Subtractive Manufacturing

Despite AM’s advantages, parts often require precision finishing to meet tight tolerances and surface quality demands. Subtractive manufacturing processes such as CNC milling and grinding are used to:

• Refine critical surfaces: Machining sealing faces and connection ports to ensure leak-tight interfaces.

• Achieve dimensional accuracy: Correcting deviations from nominal geometry caused by AM process variability.

• Remove support structures: Cleaning up areas where AM supports were necessary during build.

Hybrid manufacturing systems integrate these processes, allowing additive building and subtractive finishing in a single machine or closely coordinated workflow, reducing handling and lead times.

Hybrid Manufacturing Process Workflow for Hydraulic Manifolds

1. Conceptual Design and CAD Modeling

   The design begins with CAD modeling, incorporating design for additive manufacturing (DfAM) principles to exploit AM’s geometric freedom. Designers focus on:

   • Internal channel layout for optimized fluid flow.

   • Wall thickness balancing strength and weight.

   • Integration of locating features for subsequent machining.

2. Simulation and Optimization

   Computational fluid dynamics (CFD) simulations validate flow efficiency improvements. Topology optimization tools help reduce material where unnecessary, enhancing weight savings.

3. Additive Manufacturing Build

   The manifold is fabricated using metal AM processes such as LPBF or DED. LPBF offers fine resolution suitable for intricate channels, while DED provides faster deposition for larger parts but with lower resolution.

4. In-Process and Post-Build Inspection

   Non-destructive testing methods like CT scanning verify internal geometries and detect defects. Dimensional inspection identifies areas needing machining.

5. Subtractive Finishing

   The part is mounted in a CNC machine for milling critical surfaces, drilling ports, and removing residual supports. Hybrid machines enable this step without transferring the part between different equipment.

6. Final Testing and Assembly

   Pressure testing and flow validation ensure functional performance. The manifold is then integrated into the hydraulic system.

Real-World Examples

Aerospace Actuators

Aerospace hydraulic actuators demand lightweight, compact manifolds to reduce aircraft weight and improve fuel efficiency. A case study from Diegel et al. demonstrated redesigning a hydraulic manifold for additive manufacturing, achieving significant weight reduction while maintaining structural integrity. The hybrid approach allowed precise machining of sealing surfaces after AM build, ensuring aerospace-grade tolerances and reliability.

Automotive Fluid Systems

In automotive applications, hydraulic manifolds control fluid flow in braking and transmission systems. The ability to integrate multiple flow paths into a single block reduces assembly complexity and potential leak points. A project redesigning an industrial hydraulic manifold using 3D printing (AM) with aluminum alloy and stainless steel showed improved flow performance and reduced pressure loss, lowering production costs and weight.

Industrial Pumps

Additive manufacturing has been applied to hydraulic pump components to reduce pressure drops by 45-85% and weight by approximately 35%. The hybrid manufacturing approach enabled the creation of hollow piston blocks with internal channels, impossible to machine conventionally. Subtractive finishing ensured tight dimensional control of moving parts, critical for pump efficiency.

Cost Considerations

Hybrid manufacturing involves balancing the higher material and machine costs of AM with savings from part consolidation, weight reduction, and reduced assembly. Key cost factors include:

• Material costs: Metal powders for AM are more expensive than raw billets but enable design efficiencies.

• Machine time: AM build times can be lengthy; however, hybrid machines reduce total production time by integrating finishing steps.

• Post-processing: Subtractive finishing adds cost but is essential for functional surfaces.

• Tooling and fixtures: Hybrid systems reduce the need for specialized tooling by using digital fixturing and sacrificial features designed into the part.

Economic studies suggest that with optimized design and process planning, hybrid manufacturing can achieve comparable or better cost-effectiveness than traditional methods, especially for low to medium production volumes and highly complex parts.

Practical Tips for Implementing Hybrid Manufacturing

• Design for hybrid process: Include locating features and datums in the CAD model to facilitate machining setup.

• Use simulation early: CFD and topology optimization guide design decisions to maximize performance and manufacturability.

• Select appropriate materials: Aluminum alloys offer lightweight and machinability; stainless steels provide wear resistance but increase weight.

• Plan inspection steps: Incorporate in-process and post-build inspections to ensure quality and reduce rework.

• Leverage hybrid machines: If possible, use integrated additive-subtractive systems to minimize handling and improve accuracy.

• Train design and manufacturing teams: Understanding both AM and SM capabilities is crucial for successful hybrid manufacturing.

Conclusion

Hybrid manufacturing, combining additive and subtractive processes, represents a transformative approach for producing complex hydraulic manifolds with enhanced performance, reduced weight, and improved cost efficiency. By leveraging the design freedom of additive manufacturing and the precision of subtractive finishing, engineers can overcome the limitations of traditional manufacturing methods.

Real-world applications in aerospace actuators, automotive fluid systems, and industrial pumps demonstrate the tangible benefits of hybrid solutions, including significant mass reductions, improved flow efficiency, and part consolidation. While costs and process complexity remain considerations, advances in hybrid manufacturing systems and design methodologies continue to lower barriers to adoption.

For manufacturing engineers, embracing hybrid manufacturing requires a holistic understanding of both additive and subtractive technologies, integrated design strategies, and careful process planning. The result is a new paradigm in hydraulic manifold production that meets the demanding requirements of modern fluid power systems.

Q&A

Q1: What are the main advantages of hybrid manufacturing for hydraulic manifolds?
A1: Hybrid manufacturing enables complex internal geometries, reduces weight through part consolidation, improves flow efficiency, and achieves precise surface finishes by combining additive building with subtractive machining.

Q2: How does additive manufacturing improve hydraulic manifold design?
A2: AM allows the creation of optimized internal channels with smooth flow paths, reduces the number of components by integrating parts, and enables lightweight structures not possible with traditional machining.

Q3: Why is subtractive manufacturing still necessary in hybrid processes?
A3: Subtractive machining is essential for achieving tight dimensional tolerances, refining sealing surfaces, and removing support structures, ensuring the part meets functional and assembly requirements.

Q4: What materials are commonly used in hybrid manufacturing of hydraulic manifolds?
A4: Aluminum alloys (e.g., AL 6061-T6) are favored for their light weight and machinability, while stainless steels (e.g., SS 316L) are chosen for higher wear resistance despite higher weight and machining costs.

Q5: What are practical tips for engineers adopting hybrid manufacturing?
A5: Incorporate design features for machining setup, use CFD and topology optimization early, select suitable materials, plan inspection steps, utilize integrated hybrid machines if possible, and train teams on both AM and SM processes.

References

Design for additive manufacturing process for a lightweight hydraulic manifold
Olaf Diegel, Juan Schutte, Arno Ferreira, Yuk Lun Chan
Industrial and Manufacturing Engineering, December 2020
Key Findings: Demonstrated redesign of hydraulic manifolds using AM for weight reduction and improved flow; reviewed design methods and constraints.
Methodology: CAD redesign, simulation, AM fabrication, and testing.
Citation: Diegel et al., 2020, pp. 1375–1394
Link

Hydraulic block manifold redesign for additive manufacturing
Renishaw Collaboration, April 2025
Key Findings: Achieved up to 79% volume reduction and 60% flow efficiency improvement through AM redesign; hybrid manufacturing enabled stainless steel use with weight savings.
Methodology: CAD redesign, AM build, subtractive finishing, iterative testing.
Citation: Renishaw, 2025, pp. 1–12
Link

Additive manufacturing in fluid power with novel application to hydraulic pump design
Anton Wiberg, Liselott Ericson, Johan A. Persson, Johan Ölvander
International Design Conference, 2024
Key Findings: Demonstrated 45-85% pressure drop reduction and 35% weight reduction in hydraulic pump components using AM; highlighted potential for part count reduction.
Methodology: Literature review, pump redesign, simulation, comparative analysis.
Citation: Wiberg et al., 2024, pp. 1889–1905
Link

Additive Manufacturing

Subtractive Manufacturing