Aerospace contracts account for a growing proportion of HPC Precision Engineering’s business; the remainder involves supplying the automotive, agricultural, medical, petrochemical and other high-technology industries.
Components are varied, and due to their complexity often require as many as four operations on up to six sides. Because they are frequently ordered in small quantities — or even one-offs — they are difficult to machine economically. Furthermore, HPC’s customers change their schedules often, sometimes daily, so the ability to prioritise work quickly and easily is essential.
Against this background, it was apparent back in 2005 that the versatility offered by a flexible manufacturing system (FMS) would allow the Sussex-based sub-contractor to respond faster to the needs of its customers. Consequently, HPC bought a Fastems automated storage and retrieval system for machine pallets; this was installed to serve two — now three — Makino horizontal machining centres (HMCs) of 1m-cube capacity.
Order turn-round times improved dramatically, and both machine down-time and labour costs were minimised, increasing competitiveness. Based on the success of this first installation and a steady increase in work, mainly in aerospace, HPC bought a second FMS last year that now comprises five 0.5m-cube twin-pallet four-axis Matsuura HMCs linked by another pallet store from Dartford-based Fastems Ltd (
www.fastems.com).
HPC, which is accredited to AS 9100 Rev C/BS EN 9100:2009 and ISO/TS 16949: 2009, has so far produced around 60 different jobs with this second system; four-fifths of these have been for the aerospace sector, the remainder for automotive customers. All are machined from aluminium to prevent cross-contamination of different materials.
Ferrous parts will be processed in the coming months by selecting one or two machines specifically for the purpose, but aluminium and other aerospace alloys will never be mixed with other metals in one machine tool. Material is segregated, traceable and safely locked away within the FMS, which many customers stipulate.
Impressive up-time
As with the first FMS, the dramatic increase in efficiency with which work is presented to the Matsuura spindles allows 95% utilisation of the machines, compared with typically 50-85% when producing parts on stand-alone twin-pallet HMCs (in this case, utilisation means the proportion of time fixtured components on pallets are within the working areas of the machines).
A figure as high as 95% means that unit production costs are improved, which will lead to rapid amortisation of the investment in the latest FMS.
The high level of system up-time is a result of the Fastems MMS-5 controller automatically routing work on machine pallets to the first Matsuura H.Plus-500 HMC in the system to become available. The machines have similar cutters resident in their 240-tool magazines, a 20,000rev/min high-torque spindle and 800mm travels in the linear axes. The Fanuc Series 30i control fitted to each is linked into the MMS-5 to allow the direct transfer of programs and the upload of production data, via a 1GB data server.
All machines could complete any of the jobs in the work queue, but for expediency they are not necessarily instructed to do so. If a batch of 30 parts is required, one machine will be proved out for the job, whereas a run of 100 parts might be sent to four machines. Prove-out time is minimised by off-line simulation using Vericut software.
High-density storage
Workpieces fixtured on pallets — previously set up at one of two load/unload stations at one end of the system — are held in 48 of 68 available positions on three levels of racking, resulting in high-density storage in a compact footprint.
Some of the pallets hold work-in-progress — components that have already undergone one or more operations. Raw material, which enters and leaves the system via a separate input/output station between the load stations, is stored in wooden stillages in the 20 remaining positions.
Peter Howell, business development manager at HPC, says: “We are continuing our policy of automating production as far as possible, as it greatly enhances the service we can provide. It makes us more competitive and gives us a commercial advantage over other sub-contractors, especially in key markets like aerospace, which HPC is keen to penetrate further.
"HPC’s competitiveness comes not just from efficient use of plant, but also from lean manufacturing practices. For example, two operators can easily run the five-machine FMS, whereas it would not be realistic for one operator to look after two stand-alone machines.
“There would have been no point trying to boost output and cost-effectiveness by buying a couple of extra machine tools, as they would never be productive enough unless we were machining long runs of the same part.
"If you try to achieve that level of productivity on shorter batches, you would have pallets with fixtures spread out all over the floor and be forever fork-lifting them on and off the machines. The economical use of labour is a big advantage to us when calculating our hourly rates, helping to keep costs down for customers. We are already considering a third FMS for machining automotive parts and a mixture of work for other industries.”
Chris Pellett, HPC’s sales manager, adds: “When producing small runs, we find that the output frm around three conventionally loaded horizontal machining centres can be generated by one machine within an FMS. The level of efficiency makes it economical to produce, say, 30 parts for delivery to a customer, whereas before we would make 100 to achieve a similarly competitive manufacturing cost per part — then stock the remainder on consignment, tying up money and space.
“Furthermore, Fastems systems are good at coping with sudden increases in demand. The MMS-5 controlling the new system is the latest browser-based version with touch-screen programming, enabling increased interactivity and faster communication.
It includes adaptive scheduling, which can over-ride — in real time — the optimal work list set automatically by the system’s planning software. The most urgent workpieces are therefore always dispatched to the machine tools, as order priority changes.”
System operation
Running on rails along the length of the store, the three-axis CNC stacker crane with a mast and load-handling device transfers pallets into and out of the storage positions and on and off the outer pallet position of the twin-pallet machines.
Monitoring of the crane, load/unload stations and material station is built into the kernel of Fastems’ MMS-5 software. The main window of the control displays a mimic of the entire FMS and uses colours and icons to advise the real-time status of all main elements of the system; there is also statistical reporting of performance.
In addition, HPC opted for the machine surveillance software called Fastems Fadector; this monitors production in each machine automatically via eight I/O signals over a seven-day period — or a user-specified period — eliminating errors that might be generated by manual collection of information from the shopfloor.
The data is analysed to give management a wealth of information, including machine availability, utilisation rate, mean time between failures and mean down-time.
When a pallet is sent from a load station into the system, a manufacturing route defines its flow through the FMS. A DNC interface ensures that the correct program is downloaded to the appropriate machine and is instigated when the job reaches the top of the queue and the pallet with fixtured component arrives.
Software modules for the management of tools and material — and for remote system monitoring — have also been supplied.