Modular design saves time

Advanced CAD is crucial to remaining competitive when making high reliability components. Tom Shelley reports.

Complex electro mechanical components for critical applications can now be designed in a few weeks, thanks to re-use of modular CAD data which is now being linked to up to date cost data. This ensures speedy and reliable designs – because of the applications, customers are increasingly demanding that they be 20 years maintenance free – which are also cost competitive.

Moog Components Group in Reading, formerly IDM Electronics, produces slip rings. Most of the products were saw being made there are for the military: ships, tanks and helicopters, but the company also designs slip rings for wind turbines. These carry power into and take monitoring and position data out of the hubs, in order to be able to control the pitch of the blades and de-ice them in cold climates.

The company designs with one of the major CAD packages – we cannot say which one since they decline to endorse any of their supplied products. Senior design engineer Nik Corbas told us that using it, "Has changed my life". We won't say what he was using before either, and while he admits that what he is using at Moog is, "tricky to get started", he insisted that, "Once you get into it, is pretty intuitive and certainly helps with the workflow." Data for manufacturing is exported to suppliers as STEP and IGES files, and a PLM package from the same vendor as the CAD system provides a user interface to the database.

Formerly CAD files were stored in folders but having made the change, Corbas said, "Finding parts is now really easy." Formerly, he said designers had to remember part numbers in order to be able to locate them. "The hard bit is transferring the data into it", he admitted, but even though he has only been using the facility for a month, he finds it, "Most helpful."

Cost information, crucial to getting competitive but profitable quotations out, and doing designs in the most economical manner is presently held in Excel spreadsheets, but the company's software VAR also supplied the company's ERP system and there is a program under development to pull real time cost information out of this.

The need to produce products that are truly reliable is even more crucial with regard to wind turbines than it is for military customers, since wind turbine nacelles are often 150m above ground, and in the case of offshore installations, require use of a crane barge. Corbas told us that each design of slip ring is different. Largest currents that have to be transferred are currently 200A per ring, but as turbines become larger, the company is already receiving enquiries about 350A.

There can in addition be hundreds of rings to transfer data which can be in a multitude of different protocols. Electrical contact is through silver alloy fibre brushes rubbing silver alloy tracks. In order to save both design and production costs, the products have become increasingly modular. Corbas says: "Very few components are now bespoke", which means that most have been designed before, and can be extracted from the database, and used again.

Assembly is assisted by drawings, although shop floor staff can interrogate aspects of designs as eDrawings, should the paper drawings not always be clear. Once a set of drawings has been produced, there is, we were told, a discussion with the production engineers so they can develop and issue a set of assembly instructions. The wind turbine slip rings are mostly assembled in China. Finite element analysis, when required, is referred to company FEA experts in Canada, so electronic transfer of data is now a crucial aspect of the business.

Design Pointers
• Designs are modular, allowing re-use of data
• Model exports to manufacturers are as STEP and IGES files but shop floor staff are able to interrogate designs as eDrawings
• Cost information is currently held on Excel spreadsheets but the move is to extract it from a the company ERP system

Tom Shelley

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