E-TECHNOLOGY USED TO OPTIMISE PRODUCT DESIGN AND REDUCE INVENTORY LEVELS
20 May 2006 - Castings Technology International

Since these products are supplied globally, component designs can vary to comply with local market or legislative requirements. It is these design variations, particularly with respect to the sight glass position, that have led to different body castings being used to meet different territory requirements. The concept of using a single universal body casting to replace two casting designs, the associated financial benefits this would have, and the constant drive to improve product performance, provided an engineering challenge to Emco Wheaton and their supplying foundry Walter Frank & Sons Ltd. Cti provided e-manufacturing support to the project under the ICT Carrier Programme.

The component selected for the investigation was an API adaptor valve used for loading and unloading tank compartments. It was an LM25TF aluminium gravity die casting. The gravity die process involves thermal cycling of metal dies and is exacting in terms of tooling life as the die surface is subjected to high liquid aluminium temperatures for extended periods. Due to earlier problems, new valve tooling was required.

Before the start of the E-Valve project, Walter Frank and Sons did not have 3D modelling capability. Therefore, it was necessary for them to purchase a system compatible with the ones used by Emco Wheaton and the die maker. Cti provided the CAD/CAM interface between the valve designer and the toolmaker. In addition, to ensure that the design was optimal, Cti used solidification simulation to aid the design process. The internal profile was modified to increase the feed paths to isolated heavy sections.

Key project objectives
• Develop a universal API Adaptor Valve design to accommodate 'local variants'
• Minimise the manufacturing time for new tooling
• Maximise the life of the tooling
• Enhance the accuracy of castings
• Sustainable quality, with a target rejection rate of below 0.5
• Minimise the unit cost of castings
• Produce a 3D solid model of the casting
• Use solidification simulation to optimise tooling and casting design
• Introduce 3D modelling to Walter Frank & Sons Ltd
• Achieve unambiguous data transfer of solid and surface geometries

Industrial impact
• The new universal version of the API body has been designed with a finished weight virtually identical to that of the current designs. This replaces two versions of the same valve with only minor differences required by different local markets.
• Tooling was delivered 16 weeks from start of manufacture
• an alternative die material has had a positive effect upon die life, aided by the repositioning of the ingate
• initial batches of the prototype castings have been accepted
• casting yields have been improved and gross casting weights reduced
• data transfer from the 3D modelling package improved with later versions
• solidification simulation identified casting issues and provided options for their resolution
• Walter Frank and Sons has introduced a 3D modelling package based on Cti's recommendations

Lessons learned and future research
A number of issues arose during the project that need to be addressed in the future. These were:
• greater consultation is required at the model construction stage
• selection of the right modelling package for the job is critical. The modelling package used for the initial valve design had some limitations, although later versions of the software have been enhanced
• the method of construction of the model itself is critical, particularly if modifications to the original specification are required later
• greater consideration of casting tolerances is required at the modelling stage
• increased process control over metal temperature and pouring speed is required
• repeated solidification simulations can prove expensive
• training in the correct use of the actual 3D modelling software used is essential
• data transfer of model files using .iges and alternative file types proved to be problematic throughout the design, die production and manufacturing supply chain, and was the source of significant time delays and much frustration.

Process parameter monitoring results
• the die shows no sign of cracking after production of 500 castings
• in spite of an increased number of bosses, the finished casting weight is equivalent to the old design as a result of the CNC machining of the die and resin shell core box
• casting yields have been improved by 4 due to the redesigned runner and feeding system
• solidification and total cycle times have been reduced
• die filling is now controlled by the gating system rather than the machine operator
• fill times were found to vary, dependent on the application of die spray overall, the new API body design is poured quicker than the current design
• the operating temperature of the die is lower on all surfaces, by as much as 40°C in some areas
• casting finishing has been improved due to the repositioning of ingates.

This article was adapted from the E-Valve Case Study number 3, one of eight Case Studies that present the work carried out in the E-Valve project, part of the ICT Carrier programme, managed by Optimat and funded by the DTI. Contact Colin Blackburn at Cti for more information (c.blackburn@castingstechnology.com, 0114 2728647), or visit the E-Valve website: www.evalve.org.uk

http://www.castingstechnology.com

More News:
  • For May 2006
  • From Castings Technology International
  • For Castings