Case Study: Hydraulic valve blockredesign for additive manufacturingBy VTT Technical Research Centre of Finland Ltd & Nurmi Cylinders Oy

Case Overview

Nurmi Cylinders Oy: Finland-based manufacturer ofhydraulic cylinders for heavy-duty applications inoffshore, industrial, marine and mobile environments

Design Challenge: Redesign a hydraulic valve blockto take full advantage of the benefits of additivemanufacturing

Traditional valve blockStraight and circular drillingsAuxiliary drillings that need to be plugged afterwardsInitial weight: 2.5kg

Benefits of AMImprove shape of internal channels for optimal flowEliminate need for auxiliary drillings – reduced potentialfor leaksReduce size & weightProduce small, tailor-made series to suit customer’sneeds

Initial design space provided by Nurmi Cylinders Oyhttp://www.vttresearch.com/

Initial Printability Check

Original channel design requires supportsdifficult/impossible to removeSolution: Internal channels are now straight (~45° to baseplate) with elliptical cross-section

Initial Design Space Final Design Space

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Topology Optimization

Engineering RequirementsSafety factor

Yield stress: 1,8Tensile strength: 2,7

Material should withstand marineenvironment

Corrosive resistant materialFirst iteration H13 Tool steelFinal material: still under investigation

Elongation: 11-20% acceptableLoads

Channel pressure: 300 bar(optimization), 420 bar (final test)Bolt preload: 17,9 kNSide loads: 100kg Design space

Non-design space

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Optimization & Result Interpretation

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Preliminary Design Analysis

Material: H13 tool steelMaximum acceptable stress: 640 MPa (tensile/2.7)Maximum stress: 946 MPa (*note – only a few elements have stress levelsabove 500MPa, all are in non-design space and can be modified)

Colored elements have stressesexceeding 500 MPahttp://www.vttresearch.com/

Smoothing + Final Design Analysis

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Mass after smoothing operations: 578.4 g;compared to original mass 2.5 kg 76% reduction

Reanalysis with test pressure (420 bar)Design meets defined stress requirements

Support Design and Printing

After Support Removal

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Summary

Designing specifically for AM makes it possible to take full advantage ofthe design freedom offered by this manufacturing technique

Successful printing of a part necessitates knowledge about the specificrequirements for a given AM technology, material being printed, builddirection and orientation, supporting structures and their removal, andpost-processing procedures.

VTT has experts in advanced manufacturing techniques, structural designand analysis, and material science all under one roof. Knowledge sharingwithin these areas of expertise can help ensure successful design andcreation of additive manufactured parts.

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Significant massreductionleads to lower materialcost & faster print time

Improved flowdue to smooth transitionsbetween internal channels

No need forauxiliary drillings,less chance ofleakage

The bionic design andsmall series were idealfor AM

TECHNOLOGY FOR BUSINESS

DESIGN OUTSIDE THE BOX