Aerospace contracts account for a growing proportion of HPC Precision Engineering's business, while the remainder involves supplying the automotive, agricultural, medical, petro-chemical and other high technology industries. Components are varied and due to their complexity often require two, three or even four operations on up to six sides. As they are frequently ordered in small quantities or even one-offs, they are difficult to machine economically. Customers change 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 Burgess Hill subcontractor to respond faster to the needs of its customers. Consequently, HPC invested in a Fastems automated storage and retrieval system for machine pallets, which was installed to serve two (now three) Makino horizontal machining centres (HMCs) of one-metre-cube capacity.
Order turnaround times improved dramatically and in addition, machine downtime and labour costs were minimised, raising competitiveness.
Based on the success of this first installation and a steady increase in work, mainly in aerospace, in 2013 HPC invested in a second FMS, now comprising five half-metre-cube, twin-pallet, 4-axis Matsuura HMCs linked by another pallet store from Fastems.
HPC, accredited to AS 9100 Rev C / BS EN 9100:2009 and ISO/TS 16949: 2009, has produced around 60 jobs in this second system so far, four-fifths of which have been for the aerospace sector, with the remainder of parts delivered to 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 or in any case find reassuring.
As with the first FMS, the dramatic increase in efficiency with which work is presented to the Matsuura spindles allows 95 per cent utilisation of the machines, compared with typically 50 to 85 per cent when producing parts
on stand-alone, twin-pallet HMCs. For clarity, utilisation means the proportion of time fixtured components on pallets are within the working areas of the machines. A figure as high as 95 per cent means that unit production costs are improved, which will lead to rapid amortisation of the investment in the latest FMS.
The impressive 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 20,000 rpm high-torque spindle and 800 mm travels in the linear axes. A Fanuc Series 30i control fitted to each is linked into the MMS-5 to allow direct transfer of programs and upload of production data, via a 1GB data server.
All machines could complete any of the jobs in the work queue, but for expediency are not necessarily instructed to do so. If, say, a batch of 30-off is required, one machine is proved out for the job, whereas a run of 100-off might be sent to four machines. Prove-out is speeded by off-line simulation in Vericut software. The length of the cycle times, which can be up to an hour, also has a bearing on machine allocation.
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, ie components that have already undergone one or more operations. Raw material, mostly solid aluminium billet, which enters and leaves the system via a separate input / output station between the load stations, is stored in wooden stillages in twenty of the remaining positions.
Peter Howell, Business Development Manager at HPC, commented, 'We are continuing our policy of automating production as far as possible, as it greatly enhances the service we are able to provide. It makes us more competitive and gives us a commercial advantage over other subcontractors, 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.
'So there would have been no point trying to boost output and cost-effectiveness by spending the capital investment budget on a couple of extra machine tools, as they would never be productive enough unless you are 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 forklifting them on and off the machines.
'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, added, 'When producing small runs, we find that the output from 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-off for delivery to a customer, whereas before we would make 100-off to achieve a similarly competitive manufacturing cost per part and stock the remainder on consignment, tying up money and space.
'Furthermore, Fastems systems are good at coping with sudden increases in demand from a customer. For example, 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, in real time, can override 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.'
Running on rails along the length of the store, a 3-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 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, with statistical reporting of performance.
In addition, HPC has opted for machine surveillance software called Fastems Fadector. The data collection system monitors production in each machine automatically via eight I/O signals over a 24-hour, 7-day or user-specified period. In this way, errors that might be generated by manual collection of information from the shop floor are eliminated. The data is analysed to provide management with a wealth of detailed information including machine availability, utilisation rate, mean time between failures and mean downtime.
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 fixture component arrives. Software modules for management of tools and material, and for remote system monitoring, have also been supplied.