Small parts FMS will pay for itself in one year

Citation

(2001), "Small parts FMS will pay for itself in one year", Assembly Automation, Vol. 21 No. 3. https://doi.org/10.1108/aa.2001.03321caf.002

Small parts FMS will pay for itself in one year

Small parts FMS will pay for itself in one yearKeywords: Assembly, Flexible manufacturing systems

At the end of October 2000, the first phase of a flexible manufacturing system (FMS) became operational at the Poole factory of Westwind Air Bearings, the world's leading manufacturer of spindles for drilling printed circuit boards (PCBs) at speeds of up to 200,000rpm (see Plate 2). Phase 1 consisted of a £185,000 Fastems MLS (multi-level system) automated storage and retrieval system (ASRS) for raw material, work-in-progress and finished components, which links two new hanging-spindle, vertical turning lathes (VTLs) and two horizontal machining centres from Hitachi Seiki in a project costing a total of £600,000 including some civil engineering work.

Plate 2 A view along the Fastems automated storage and retrieval system for raw material, work-in-progress and finished components at the Poole factory of Westwind Air Bearings

Phase 2 of the project was to be completed in February 2001, by which time a £155,000 extension to the Fastems system was to link Phase 1 with production stations further down the line. These include a Studer CNC external grinder with new conveyor for automatic load/unload as well as a variety of conventionally loaded machine tools (honing, turning, surface grinding) and also manual operations. At the same time another Hitachi Seiki VTL was to be installed alongside the other two.

This is an unusual FMS in that it combines automated and manual operations, plus material warehousing – and the more so because relatively small components are involved rather than large parts as are normally found in such low volume, large variety manufacturing systems. Moreover, accuracy of machining and assembly is particularly high.

The electronics industry, especially mobile telecommunications and the development of home video phone and digital video recorder technology, is driving much of manufacturing investment these days and Westwind has been one of the winners. Growth in the production of high speed, air-bearing spindles for PCBs has been meteoric with this area of the business now accounting for a large proportion of Westwind's turnover. More than 500 complete spindles are shipped each week, a figure that is expected to rise to 600 per week in 2001.

Clearly, a manufacturing operation of this scale needs careful planning. The company had taken the decision to arrange its core product groups into divisions. Westwind's scanning division, which makes high-speed optical spindles and imaging equipment, had recently undergone a revision of its manufacturing facilities and was used as a pilot for the rest of the business. An analysis of production requirements within the PCB division gave rise to a number of recommendations, some similar to those for the scanning division, but importantly also the FMS.

First, it was decided that shafts, the inner and outer elements of the body and the collets which retain the drill bits (down to 0.007in. diameter these days) could be produced most economically in dedicated cells. They were set up by regrouping existing machines and implementing flowline production procedures.

However, the large varieties of front and rear bearings, aluminium back caps and a similar number of thrust plates plus various other constituent parts were deemed to need an FMS for economic production, as they do not follow a predetemined route through the various manufacturing steps. Previously, a considerable amount of manual transportation of these components to machines in different locations around the shop was required.

So the shaft, body and collet cells were commissioned first, following which the remaining 35 machine tools on site were loosely assembled into an area which would become the FMS. It was calculated that a surprisingly large number of extra machines would have been needed to achieve the variable but increasing level of through-put for the remainder of the components, if cellular manufacture had been adopted.

Machine utilisation becomes a major issue for Westwind when the business cycle changes. High utilisation can be maintained by having a flexible system that can cope with sub-contract work being pulled back in-house. Dedicated cells would not have been an economic consideration for such a manufacturing strategy.

Currently, Westwind operates with a material store and another store for work-in-progress and finished components, requiring considerable handling and transport to and from the machining cells. With the new manufacturing set-up, the bar stores will go in the near future, when Westwind moves over entirely to billets or bar delivered-to-line; and the main store movements will also disappear over time as the storage capacity within the FMS is expanded down the line. This is combined with some fast moving/low cost product being converted to line-stock.

When finished, the system will measure 45m long and will be serviced by the existing stacker crane, which travels at up to 3m/s and has been specially lowered to fit within the restricted headroom at the Poole factory. The existing single work-set station will also suffice, where Westwind's own platens equipped with Wixroyd "zero point" fixtures are sent into the FMS to locate on the machining centre pallets. Each loaded platen represents around one hour of machining centre time, which will mean in practice that 30 platens will be needed within the system when it is fully operational. There is a separate load/unload station, where boxes of billets enter and empties leave for return to the supplier.

The FMS will contain 276 bin storage locations plus 71 positions on the top level for accommodating tall containers or platens, the latter having their own dedicated home positions. A novel feature of the Fastems equipment is the space-saving, high-density design, whereby the four lower bin storage levels are very close together. Access is gained by employing cantilevered racking and a pantograph arm on the crane, which offers the bin horizontally into the location.

Take, for example, the case of a bearing travelling through the system. It starts life as a leaded gun metal billet, delivered from the supplier in a bin, which enters the FMS store through its dedicated access station. The system itself drives the kanban replenishment based on receipt of manufacturing orders raised by Westwind's host computer. Currently, data are keyed in manually to the Fastems FMS controller. However, when phase 2 is ready there will be an ODBC link in place, which will also provide for uploading information back to the business computer for more effective production management control. The FMS and machine tools are linked to Westwind's main network, enabling easy transfer of data.

The Fastems controller downloads the program number to a given machine tool, which in turn utilises a macro and Seiki Systems "Flex-Link" to call down the necessary program across the Ethernet network. Tool data are held in the NC program. The Fastems control sends the crane its instructions, routeing the billet successively first to the VTLs for front and reverse end turning, including a visit to the material station to invert the components, and then to storage to await delivery to the work-set station. Here the part-finished components are loaded into the platen-mounted fixtures, which are returned to the system either for temporary storage or for first- and second-ops on the machining centres. On completion of phase 2, the bearing will continue to various other stations within the system, whereas currently it leaves the FMS to continue its cycle of additional operations.

The complete machined bearing then goes back into the internal store to await call-up with all other component parts of the spindle for which it is destined. The Fastems manufacturing management system/flexible management execute (MMS/FME) control, having checked that all components are available within the system from Westwind's host computer, picks the necessary bins and sends them to a set of work stations for kitting prior to being sent to assembly. The software responsible for this part of the operation is linked to Westwind's materials requirement planning (MRP) system using the same ODBC link that transfers the work orders.

Throughout the entire process, operators and supervisors can monitor the progress of an order on screen. Furthermore, the whole system can be viewed remotely. Using colour-coded graphics in a Windows NT environment, the status of each machine – the program it is running, the component it is machining – is visible at a glance in real time. A live view is also afforded of the status of all storage positions, which may either be empty or contain tooling, raw material, work-in-progress or finished components. The location and status of the crane and its work list are similarly known at all times.

Double-day shift working plus a skeleton night shift will soon become full 24-hour working. The system will have a diagnostic modem link, which can call a nominated number, should a problem occur during unattended operation.

It is interesting that other solutions with more limited automated handling were considered before going for a full blown FMS. Thought was given to five-axis working and special fixturing on the machining centres to minimise handling between operations. Single-hit mill-turning instead of VTL technology was less attractive, as there is a lot of drilling on various components; and in any case the hanging spindle doubles very effectively as a handling device to pick billets from bins delivered by the crane.

Benefits as a result of installing the FMS and machine tools will accrue from reduced labour costs owing to greatly enhanced efficiency of manufacturing; in-house production of previously subcontracted work, saving a further six figure sum; and a reduction in inventory plus better control over it. Then there is the redeployment of PCB division machines and labour to other Westwind business units and manufacturing cells.

Indirect savings stem from having a more unified, IT-driven system, which affords improved management control over the manufacturing operation, in particular the ability to take a real-time snapshot of production at any given moment; and to have ordering, MRP and manufacture digitally integrated. A rationalisation of product design and some inventive tooling have helped to reduce change-over time between batches and have contributed to shorter cycle times. Lead-time reduction will result in shorter delivery times and enhanced customer loyalty. Lastly, space will be saved by doing away with two stores areas, creating valuable production area for no extra cost.

As a postscript, Robert Humphreys, head of Fastems' UK operation, who was closely involved with the project, commented: "In this application we supplied our ASRS and FMS software as a package directly to the end user, whereas usually we are involved indirectly with new systems through machine tool vendors. As with all our FMS, it can be reconfigured inexpensively as production requirements change by, for example, adding extra storage positions or another work-set station.

"Fastems' FMS solutions are open systems, capable of linking any type, make and number of machine tools with other production operations. Westwind's is an excellent practical example of this. Furthermore its skilful execution by the staff at Poole, who were 100 per cent committed to its success, makes this one of the best installations of its type in Europe and a good candidate for a manufacturing award in 2001."

Contact: Robert Humphreys, Sales Manager (UK), Fastems Division, Helvar Limited, Hawley Mill, Hawley Road, Dartford, Kent DA2 7SY. Tel: +44 (0)1322 282276; Fax: +44 (0)1322 282250; E-mail: robert.humphreys@fastems.com