FMS installed as machining operation moves

The entire machine shop operation of Westinghouse Brakes (UK), Chippenham, has been transferred to Precimax in nearby Corsham, and the company has purchased a Heller flexible manufacturing system too

The entire machine shop operation of Westinghouse Brakes (UK), Chippenham, has been transferred to its principal subcontractor, Precimax in nearby Corsham, which has worked for the rail braking system manufacturer for 15 years.

The unusual deal has seen half of the 140 machine tools relocated from the Westinghouse shop floor, virtually all the remainder auctioned, and 35 staff transferred to Precimax.

The move into a new unit adjacent to the subcontractor's existing premises was completed in just one week in June 2003 to minimise disruption to production.

By October the company had made a key additional purchase - a flexible manufacturing system (FMS) from Heller comprising two of its MC16 horizontal machining centres integrated into a Finnish-built Fastems system for automated storage and retrieval of 48 machine pallets.

It brought the total investment in the project to UKP2 million.

A similar FMS will be exhibited on the Heller stand number 4628 in hall 4 at MACH 2004,19 - 23 April, NEC, Birmingham.

Operating round-the-clock, seven days a week, as does the rest of the Precimax operation, the FMS was essential for three reasons.

First, the four 10-pallet stand-alone cells that it replaced would have taken up twice as much floor space, which Precimax wanted to save for other production equipment.

Secondly, out of 1,300 different Westinghouse components, the subcontractor wanted to reduce the unit manufacturing time, in particular of 250 so-called 'OEM runners' - parts that are produced regularly in relatively small batches of between one- and 50-off to meet production demands.

Thirdly, the pallet-pool machines were in any case over 12 years old and coming to the end of their useful life.

Said Alan Matthews, Operations Director at Precimax, "Even though the number of spindles and the space occupied have halved, production output from the FMS is equal to, or even better than, that of the four pallet pool machines.

"This is partly due to always having work fixtured on a pallet waiting to be sent to one of the Heller machining centres, so it arrives within 10 to 15 seconds of pressing the button.

Spindle up-time is therefore very high.

"The other important factor is the speed of the Heller machines once the cutting cycle starts.

Idle times are minimised by 60 m/min rapid traverse in all axes, 1g acc/dec and 2.8 seconds chip-to-chip time, while in-cut performance is also high due to the 16,000 rpm/30 kW spindle and 60 m/min maximum cutting feed rate." He went on to point out that also having tools and programs ready for immediate use is crucial to capitalising on the production potential of the FMS, otherwise the pallet will wait around unnecessarily before the cycle can start.

The Heller MC16s each have a 160-tool magazine, which is sufficient to machine almost all of the OEM runners without having to change a tool, unless it wears out.

This degree of rationalisation is made somewhat easier by the majority of parts being made from aluminium.

The Fastems controller schedules work through the system and orchestrates the entire FMS.

Programs are held within the Heller machine controls and the relevant fixtured pallet is sent to the MC16 that has been allocated to produce the next part(s).

Simple checks such as program readiness and tool availability are carried out before the machining cycle starts.

Re-engineering of the original programs has been continuing apace since the FMS was installed, despite Precimax having to continue producing the OEM runners on the existing pallet pool machines, which have been retained temporarily in the Westinghouse machine shop in Chippenham.

Transfer of jobs to the FMS has been facilitated by the experience of Westinghouse production staff, and by having a Heller applications engineer on site for 10 weeks to oversee the re-engineering of 15 parts and programming of 13 new ones.

By June (2004), 30 per cent of the 250 parts will be running on the FMS and the exercise is expected to be complete before the end of the year.

New carbide tooling has been specified to extract maximum productivity from the faster Heller machines, and cutters have been selected so as to be suitable across as many jobs as possible to economise on magazine space.

Programs have been revised to take account of the increased feeds and speeds.

The 630 mm3 working envelope of the Heller MC16s is slightly larger than that of the pallet pool machines, so it has been possible to use existing fixtures without fear of collision when the pallet rotates.

Re-engineering, including proving out, can therefore be as quick as one day and takes a maximum of five days for the most complex parts.

Continued Mr Matthews, "When we were looking to invest, there was never any question in our minds that we would go down a pallet system route.

It can take up to four hours to set up a pallet for a new job, but there is in effect no set time at all now with the Fastems system, as the pallets are already in the cell, waiting to be machined.

"Another difference with set-up is that only two load/unload stations are required to serve the FMS, rather than four, as fixturing of multiple parts means that the resulting pallet cycle times of between 30 minutes and four hours are long enough to ensure that pallets are always in the store, ready to be sent to the machines.

"We have 40 pallets across the four old machines at Chippenham and just eight more in the new FMS.

The big difference is that any job can be directed to either of the Heller MC16s, whereas jobs set up on the pallet pool machines can only go to one spindle, which complicates production planning especially with regard to tooling.

"Moreover, provision has been made in the Fastems FM multi-level pallet storage and handling system to accept a third MC16, which will be installed next year provided that the workload increases as fast as we anticipate, so production flexibility will be even greater." The Fastems system was chosen for this application due to the simplicity of interfacing with the Heller machines, the speed of the rail-guided stacker crane which travels at up to 2 m/sec loaded, and the economical price.

Each 400 mm x 500 mm machine pallet has been supplied by Heller mounted on a 500 mm2 sub plate so that it may be picked up by the crane forks without the need for a mechanism first to raise the pallet clear of its location on the machining centre table.

By the time all the Westinghouse OEM runners have been re-engineered and are being produced on the FMS, it will have 30 per cent spare capacity.

Other Precimax customers have already expressed interest in having their work included in the system to take advantage of more cost-effective and timely production, particularly of smaller quantities.

It is this enthusiasm from other manufacturers that leads Mr Matthews to expect that the third machining centre will be needed sooner rather than later.

In parallel with bringing the FMS on stream, Precimax has been revising its other production disciplines to take full advantage of the ability of the Fastems software to schedule work through the system.

Mr Matthews is moving to what he describes as a bin-and-kit system, which by June will have replaced the current Westinghouse purchase order system for OEM runners.

The bins will be replenished on a kanban schedule by raw material suppliers and the resulting machined parts needed to make up Westinghouse braking system products, which can contain as many as 30 different items, will be supplied to Chippenham as a kit rather than as individual components.

The Fastems software provides integrated control over all functions.

Within the scope of the base MMS-1000 module, in addition to controlling movement of the hardware elements of the FMS, are advanced diagnostics and stacker crane utilisation data supported by on-screen graphics showing in real time the position and status of pallets, load stations and crane.

Sitting above MMS-1000 are numerous additional software modules controlling pallet management and delivery, work list generation, and capacity simulation for production planning and scheduling.

The system can be upgraded at a later date so that all 160 tools in each Heller magazine are mirrored in the controller and continuously monitored as to their position and remaining life as well as the location of any sister tools.

At the front of each part program is a tool list with cutting times, which allows the controller to carry out tool magazine planning.

By the end of the year, the system at Precimax will have developed to the point where Westinghouse could download weekly lists directly to the Precimax host computer, from where it will be transferred to the FMS controller for completion of the production schedule with minimum human intervention.

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