Headline Filters in Aylesford (Kent), has taken a big step towards streamlining the manufacture of its components by adopting twin-spindle turning and five-axis machining to reduce the number of set-ups required — and take advantage of ‘lights out’ machining.
New process routes for about half of the factory’s production of bonded microfibre filter housings involve four new CNC machines installed between September 2018 and July this year.
They are three turning centres (each with a with Y axis) from the Italian manufacturer Biglia, plus a German-built Spinner five-axis machining centre with trunnion-mounted rotary table.
All were supplied by the Kenilworth-based UK agent Whitehouse Machine Tools Ltd (www.wmtcnc.com
A backlog in multi-operation turning and milling of a particular filter part — a complex stainless-steel head designated ‘112’ — prompted Headline Filters to look for a more productive solution.
The obvious choice was a lathe with powerful driven tooling and twin opposed spindles to enable the in-cycle machining of the reverse end of the component.
With space limited on the shopfloor in Aylesford, and the machine that was initially considered being too large to be conveniently installed, Whitehouse demonstrated how the more-compact Biglia B565-YS lathe (which was half the price) could do the job — provided it was fitted with double, triple and quad tool-holders in its 12-station turret, so that the required number of tools could be deployed.
Programs were written and time studies carried out on the component (as well as two others) at Whitehouse’s technical centre.
This confirmed the feasibility of all suggested processes, and the first Biglia B565-YS was installed in Aylesford in September last year; it ran for several months to clear the ‘112’ component production backlog.
Headline Filters director Rob Hibberd said: “As soon as we saw the lathe in action on our shopfloor, producing the stainless-steel components in one hit, we knew it was the way forward and quickly ordered a second identical lathe, which arrived at the end of last year.
“The previous production method involved turning on two separate single-spindle lathes and three set-ups on a three-axis vertical machining centre, so five ops in all.
“The total cycle time was 17min — including 3min for repositioning the part on the VMC.
“The new cycle time of 16min on the Biglia is not much different, as its driven tooling cannot compete with the milling power of a machining centre.
“However, the big advantage now is that there is no inter-machine handling or work-in-progress; and because production is minimally attended, the operator can look after several machines.
“Even more important is the fact that we can take advantage of unmanned ‘ghost’ shifts for extra production output.
“We gain up to 8hr overnight when machining aluminium and brass parts, and a couple of hours when running stainless steel — before the tips become blunt and the lathes shut down automatically.”
Mr Hibberd said a further advantage of single-hit production is that it is easier to hold tolerance, as no cumulative errors are introduced by repeated re-clamping — adding that run-out is better and a tolerance of ±0.05mm is easily held on O-ring seal faces.
“Surface finish is also improved, due to the stability of the Biglia lathes and the ability to run modern tooling at the recommended feeds and speeds, so less subsequent polishing is needed.
“It is also notable that tool life is greater, such is the rigidity of these lathes.”
Another before-and-after example is an aluminium ‘360’ filter head that was previously needed turning on a lathe and prismatic metal cutting on a machining centre; this took 12min, including handling between the two machines.
The part is now produced in one hit in an 11min cycle on a B656-YS bar auto.
Again, the main benefits are a reduction in work-in-progress, better accuracy and the ability to automate production.
Whitehouse facilitated unattended running by fitting each lathe with a Hydrafeed MSV80 bar magazine (for feeding 1m-long stock through the spindle) and a Rota-Rack rotary parts accumulator to collect finished parts (delivered via a parts catcher and component conveyor).
Furthermore, the B565-YS lathes were supplied with a larger spindle bore than usual — 75mm rather than 65mm, to enable production of Headline Filters’ larger parts needed in high volumes.
Batch sizes are smaller above this diameter, but the manufacturer’s US distributor recently started to request bigger products in higher quantities, which put pressure on Headline’s single large-capacity turning machine.
Positive experience with the first two Biglias steered Mr Hibberd towards Whitehouse, which in April 2019 supplied a twin-spindle Biglia 750-YS 8in chucker with a Y axis and C axis — the largest-capacity version of this machine range.
This machine can turn components up to 552mm in diameter x 765mm long, although this is far larger than needed.
Furthermore, it is possible to use a bar puller in the turret — or the counter spindle — to feed stock up to 100mm in diameter through the bore of the main spindle and into the working area, thereby simulating the advantages of having a bar feeder.
A 38kW main motor and 17.5kW driven tools (capable of speeds up to 10,000rev/min) in the 16-station turret — plus the availability of high-pressure coolant — promote high-productivity machining.
An early example of time advantage offered by this machine involved the production of a ‘380’ aluminium filter head in one operation in a cycle time of 15min 50sec.
Previously, using the other large lathe (which is of single-spindle design and without driven tools), the part had to undergo two operations and then be transferred to a machining centre for milling and drilling.
The three operations took 21min 15sec — plus handling between machines.
Because 15,000 of these parts are needed annually, the production cost saving is considerable.
Moreover, work-in-progress is eliminated, avoiding having batches of (typically) 400 part-finished components in storage; and as Mr Hibberd points out, each part can be assembled into a filter for delivery and invoicing straight away, not days or weeks later after all machining operations have been completed.
A difficulty in the factory had been that six lathes with limited or no live tooling were feeding components to two overloaded entry-level VMCs (with 7,000rev/min spindles) for milling and drilling.
This difficulty was alleviated by the arrival of the three Biglia lathes with their powerful driven cutters, enabling the machining centres to cope; but with an eye on the future, Headline Filters decided to invest in its first five-axis machining centre to boost prismatic metal-cutting capability.
Supplied by Whitehouse in July this year, the Spinner U5-630 five-axis VMC has a 12,000rev/min BT40 spindle and provides more-productive machining, as higher rotational speeds increase metal removal rates and also allow the use of more-capable tooling.
A magazine for 32 tools, high-pressure coolant and Blum probing for setting tools and workpiece datums also form part of the production package.
The extra power and rigidity offered by the Spinner will help when producing filter parts from tough materials; these comprise not only stainless steels but also nickel and titanium alloys.
Jason Rose, engineering and workshop manager at the Aylesford factory, said: “We use the Spinner mainly in 3+2-axis mode for automatic workpiece positioning to reduce the number of manual set-ups.
“Nevertheless, we have a certain amount of contour milling to do, and when I design new products in future, I will have greater flexibility to incorporate features that would be uneconomic or impossible to complete on a three-axis or even a four-axis VMC.”
He also says the U5-630 is significantly faster at cutting metal than the other machining centres on site.
In one example, a 12min cycle was reduced to 7min; in another example, a 45min cycle was reduced to 20min.
There is potential to improve on these times further, as Headline Filters’ operators become more familiar with the new cutters they can now use.
In conclusion, Mr Hibberd referred to the high standard of operator training provided by Whitehouse, at both Kenilworth and Aylesford, saying that it was not only exemplary but also without limit or additional charge.
“Telephone support is similarly comprehensive, and if a service engineer is called out, they are on-site the next day at the latest.
“This back-up has been invaluable, as our staff had no previous experience of either Fanuc or Siemens controls, or of twin-spindle turning — or five-axis machining.”