Cycle time savings of up to 75 per cent are reported by Luton subcontractor, Melborha Engineering, following the installation of three Index ABC mill-turn centres from Geo Kingsbury Machine Tools. Their ability to produce in one set-up what was previously carried out in separate operations on two different lathes not only results in higher productivity, but also reduced work-in-progress and better component accuracy. Said David Nash, Melborha's works manager, ' Index are the Rolls-Royce of cam auto's but we needed to check that their CNC lathes would be of similar quality.
We looked at six suppliers before going the ABC route.
'We were happy with the machine build, and the mild steel test piece - an automotive pivot plug - was completed 10 per cent faster on the Index machine than on the next quickest lathe.' That component, which now takes 38 seconds to machine at both ends using the latest ABC, previously took 92 seconds to produce on two lathes in addition to the inter-machine handling time.
All the work Melborha puts through the mill-turn centres is simultaneously machined in-cycle on the reverse end after part-off using a synchro spindle in one of the stations in the top turret and endworking tools mounted above the headstock.
'We wanted a better class of machine to attract a better class of higher-added-value business,' continued Mr Nash.
'When we moved into our current premises five years ago we embarked on CNC turning with a Taiwanese slant-bed turret machine, which was right for our needs at that time and showed us that this was the way we needed to go.
We now have a total of 13 bar-fed CNC lathes.' All stations in the upper turret of the ABC lathes are live.
One position deploys the synchro spindle while Melborha employs other stations for end and slot milling in conjunction with the C-axis.
Batch sizes are from 1,000- to 50,000-off and cycle times vary from 28 to 93 seconds, the latter being for a hydraulic motor piston.
Each ABC is fitted with an Index bar magazine for feeding stock ranging from the machine's maximum capacity of 52 mm diameter down to 14 mm currently, although smaller bar could be used if required.
There is sufficient capacity to supply the machines with up to four hours of unattended work after the two 8-hour shifts each day.
Concluded, Mr Nash, 'Despite the speed with which our components are now machined, the quality and surface finish are considerably better than before.
We have no problems holding our tightest tolerance of 0.02 mm.
Moreover, the ABCs have proved to be high availability, low maintenance machines, the first of which paid for itself in two years.
Amortisation for the two latest lathes is expected to be even quicker.'