Historically, a majority of subcontractor Reginson Engineering’s turnover came from the aerospace sector, with oil and gas generating most of the remainder. So, when Covid struck in early 2020 and aerospace contracts dried up, the Nuneaton-based, AS9100 accredited, Rolls-Royce approved company was deeply affected by the contraction in business.
It was mitigated somewhat by the company joining the Ventilator Challenge UK. During April 2020, Rolls-Royce asked Reginson Engineering to manufacture 113,000 components in 10 days to support the build of 8,000 ventilators. Towards the end of that month, within 36 hours of an order being placed for a pair of Cincom A20-VIIs sliding-head CNC turning centres to enable the medical contract to be fulfilled, the machines were delivered by Citizen Machinery UK. Both have LFV (low frequency vibration) chip-breaking capability, which not only improved swarf control, raising reliability and reducing the need for operator intervention, but also enhanced the surface finish on components.
The medical work was only temporary, however, so the family-run business owned by Steve Hatch set about finding business elsewhere. What transpired altered the company’s fortunes entirely, as a contract from a jewellery manufacturer combined with strong growth in aerospace conspired to increase turnover so dramatically that by 2023 it was 447% higher than before the pandemic.
Even better is to come. The jewellery company is so pleased with the quality of the mainly titanium jewellery pieces already supplied that it has signalled its intention to increase the annual quantity of parts from 100,000 to 1 million per month over the next few years. The machine tools underpinning both the quantity and quality of the jewellery parts produced at the Nuneaton factory are yet more Citizen Cincom sliding-head lathes.
Reginson Engineering is a long-time user of these Japanese-built sliders dating back to the early 1990s. In October 2020, the lathes were joined on the shop floor by the subcontractor’s first Citizen fixed-head model, a 64 mm bar capacity Miyano ABX64-SYY twin-turret, twin-spindle turn-mill centre. The user describes the machine as being fantastic, as it has allowed cycle times to be slashed compared with using other turning plant on site. Shortly after its arrival, it more than halved the cycle time for producing a component from 4 minutes 30 seconds to 117 seconds complete.
The upturn in throughput generated by the jewellery contract required much more sliding-head capacity, so the subcontractor has bought 14 new Cincoms in the last couple of years. They are seven 20 mm bar capacity A20-VIIs and the same number of 12 mm capacity L12-VIIs. Twelve of them are devoted to jewellery component manufacture and the other two were acquired to boost production of smaller aerospace parts. The latest influx of new lathes plus the recent purchase of two new 5-axis machining centres brings the total number of CNC machines in the Nuneaton factory to nearly 100.
Machine shop manager and family member Tom Hatch said, “We chose twin-spindle sliders for the jewellery work because positioning cutters on gang toolposts for the next operation is much faster than indexing turrets in a fixed-head lathe. It means we can produce components more quickly, not only because there is less idle time, but also because there is more scope for reducing the number of second and subsequent operations.”
He added that the machines are easy to set and operate, to the extent that he and one other staff member run 12 Cincom’s located in an adjacent factory unit that has been leased recently for the new project. The finish of the turned surface achieved on the lathes is 0.2 µm, which lessens the amount of polishing that has to be done in Nuneaton or by the customer.
Similarly, the performance of the Cincoms when producing aerospace parts is excellent due to the extreme rigidity of the machines, despite having to cut materials ranging from tough nickel alloys to titanium and stainless steels. Tolerances down to ± 3 µm are often turned, saving the time and expense of grinding parts in another operation. Surface finish is also high at up to 0.8 µm when required.
Reginson Engineering additionally runs UPR, a subsidiary company in Pune, India, which it set up in 2014. The facility has more than 20 CNC machines and 60 employees, enabling the firm to offer low-cost components to customers worldwide, mainly in the aerospace, wind turbine, medical and oil and gas industries.
An increase in annual turnover from £3 million in 2016 to £8 million currently is reported by contract machining specialist Unicut Precision Engineering, Welwyn Garden City, which has spent £1.7 million in the last two years on new production and inspection equipment.
About half of the investment went on two more Cincom sliding-head lathes and two additional Miyano fixed-head lathes from Citizen Machinery UK, bringing the totals of the bar-fed lathes on site to 24 and 11 respectively. The remaining funds were used to purchase three new items of inspection equipment and to extend the automatic pallet storage and retrieval system linking three 5-axis machining centres on site.
Jason Nicholson, owner and managing director of Unicut commented, “Efficient production is not just down to automation but also depends on how well you monitor the machine tools on the shop floor and use the data to make informed decisions.
“We use PSL Datatrack to help with this and will shortly be progressing from manual extraction of production data from our machine tool controls to directly downloading it over a network for remote monitoring.”
Regarding turning, which currently accounts for 85% of Unicut’s turnover, he said that standardisation on Citizen lathes with their user-friendly, intuitive Mitsubishi controls greatly helps to mitigate the current shortage of skilled setter-operators, which he sees as a worldwide problem. Use of this CNC system throughout the factory also speeds the training of staff and allows operators to swap easily between machines.
Programs are normally prepared offline with Esprit CADCAM and also using Citizen Machinery’s own Alkart CNC Wizard programming aid. The latter guides operators through creation of part programs with the help of a built-in code library for machining processes, reducing the amount of time spent typing in G and M codes and consulting manuals or other programs.
The latest turning centre additions were two 65 mm bar capacity Miyano BNE-65MYY models, each featuring a pair of Y-axis turrets and the latest Mitsubishi 15-inch touchscreen control. They joined five smaller fixed-head lathes in the same series to form a seven-machine cell for producing hydraulic and pneumatic components in large volumes, typically from 2,000- to 10,000-off. This industry accounts for about one-fifth of Unicut’s turnover, with the aerospace, high-end automotive, oil and gas, electrical connector and paint spraying equipment sectors also regularly served.
Mr Nicholson continued, “Flexibility of production in a contract machining environment is crucial, as it is the key to profitability and to being able to compete with subcontractors in low-wage countries.
“Having two Y axes in the latest BNEs rather than one enables the preparation of programs that closely balance front and back working cycles at the main and sub spindles.
“It means that a wide range of work can be tackled efficiently and parts come off the lathes faster, as one of the spindles is not waiting around for the other one to finish off the machining.”
Each turret has 12 live stations, so an extensive variety of milling, drilling and other driven tool operations can be carried out in-cycle, almost always enabling one-hit production of parts. Sometimes prismatic machining accounts for more than 90% of a cycle, so at first glance the components look as though they have been produced on a mill.
Two-axis CNC movement of the sub spindle facilitates superimposed machining, whereby tools on both faces of the top turret can simultaneously cut front-end features on bar stock and reverse-end features on a parted-off component. With the lower turret also working at the main spindle performing pinch turning, milling or drilling, for example, or perhaps OD turning while axial drilling is in progress above, three tools can be in cut at the same time.
Both of the BNE-65MYYs have been fitted with an Iemca Maestro 80 low-vibration bar magazine that allows ergonomic loading of stock at waist level. Bar from 10 mm diameter upwards can be turned at the lathe’s maximum rotational speed without having to change over the guide channel, minimising idle time when processing a range of different material sizes.
Mr Nicholson is also a long-time user of sliding-headstock lathes from Citizen Machinery, having bought his first one in 2000. In 2018 he was an early adopter of the lathe manufacturer’s LFV (low frequency vibration) software, which was included in the operating system of the Mitsubishi control on one of two 12 mm capacity sliders bought in that year.
At the time, he said that the ability of the programmable function to break stringy swarf into shorter chips was eliminating the need to periodically stop the lathe to clear away clogged swarf, raising productivity. The LFV lathe was therefore left with confidence to run unattended, including overnight and at weekends, even when turning ductile metals and plastics, increasing throughput further. Impressed with the trouble-free performance, he bought two similar, improved versions of the lathe with LFV in 2022.
Mr Nicholson concluded, “On this type of machine, productivity is all about getting the material to chip, because otherwise you have to keep stopping the spindle to remove swarf from around the workpiece and tool.
“On a fixed-head lathe it is possible to increase the feed rate to promote chipping, but that is not possible when turning smaller diameter parts on a slider.
“With LFV programmed correctly, the swarf never fails to chip whatever the material, even when OD turning long components.
“The function is only needed for between 10% and one-third of a typical cycle, after which it is switched off by G-code to take advantage of slightly higher productivity without the air cutting caused by LFV tool oscillation.
“After five years’ experience using this technology, I would not consider buying another slider without it – and I am looking forward to its wider adoption on the Miyano fixed-head lathes as well.”
A large proportion of work going through subcontractor C&M Precision’s Maldon factory involves machining copper bar fed into CNC mill-turn lathes. Two sliding-head models out of the nine turning centres on the shop floor, all of which have been supplied by Citizen Machinery UK, have LFV (low frequency vibration) functionality in the operating system of their Mitsubishi controls. It results in much higher productivity and increased yield when converting malleable copper into high-end electronic components for OEMs in the medical, radar, satellite and broadcasting sectors.
Owner John Cable explained that for many of these jobs, a particular grade of copper known as OFHC (oxygen-free high conductivity) has to be used, which is more than 99 percent pure. One 60 mm long, tight-tolerance component previously produced from 3 mm diameter bar on an early Citizen Cincom M16 slider without LFV had to be turned in one pass through the guide bush down to 1.20 – 1.22 mm diameter along half its length. The continuous string of copper swarf frequently damaged the component and often became lodged in the counter spindle, preventing synchronous transfer after part-off and causing the machine to alarm out. Productivity was severely impacted and up to 20 percent of parts had to be scrapped.
Mr Cable enthused, “Transferring the job to a Cincom L12-VIILFV we bought in 2019 was a real winner. With the LFV function turned on, the copper chips like brass. Yield is now 100 percent, throughput is high and we can even leave the machine to run unattended.”
The other Cincom slider on site with this chip breaking functionality, a nominally 20 mm capacity L20-VIIILFV, arrived on the shop floor in 2017, making the subcontractor an early adopter of this novel technology. Supplied with a kit that allows feeding of oversize bar up to 25 mm diameter, the lathe is also proving useful for machining other materials that tend to generate stringy swarf, like nickel alloys and plastics, which are regularly turned in the Maldon facility.
C&M Precision was established in 1992 as a CNC sliding-head, twin-spindle, mill-turning shop, following research at the time indicating that four-fifths of rotational parts produced in the UK were less than 25 mm in diameter. After starting out with a different brand of slider, Mr Cable quickly changed to Cincoms, describing the transition as “a breath of fresh air”.
The first model to arrive in 2001 was a now discontinued M12, which has been sold on. The first job it tackled was the production of 120,000 brass connectors requiring the milling of 3/8-inch hex flats. Amazingly, due to the rigidity of the lathe that Mr Cable described as “rock solid”, one 6 mm diameter carbide milling cutter completed all of the flats, 720,000 of them, and still had not worn out.
The subcontractor is an enthusiastic user of Cincom M-series machines due to their inclusion of a tool turret as well as a gang tool post, allowing the production of complex components. A 16 mm diameter bar model installed in 2004 was joined three years later by a pair of 32 mm diameter bar capacity lathes. The latter, third-generation M32 lathes have since been replaced by fifth-generation models to take advantage of Y-axis motion on the turret and an overall higher specification.
2014 and 2015 saw the arrival of three more 32 mm sliders, this time in the Cincom A-series. They have only gang tool posts, so are faster when manufacturing less complicated parts. One of the lathes does not have a guide bush, as it is devoted to relatively limited runs of short components such as mining industry connectors. The other two sliders with a guide bush produce tens of thousands of parts per week, 24/5. One example is a mild steel gas meter part which the customer orders at a rate of one million per year, with the subcontractor making weekly deliveries.
C&M Precision’s latest two acquisitions are from Citizen’s Miyano range of fixed-head lathes. Installed in January and March 2022 respectively, the twin-turret BNE-65MYY models with Y-axis motion on each tool carrier replaced two ageing lathes that had one Y-axis turret apiece.
Mr Cable continued, “It made sense to go the Miyano route in view of our good experience with the Cincom lathes. People say it is not good to have all your eggs in one basket, but in Citizen’s case it is. We now have a single point of contact for applications, backup and service and the supplier is very capable and responsive to our needs.”
He added that the Miyano lathes have similar capability at both spindles and are highly productive, with advantage taken of Y-axis machining for a large proportion of the time. Simple off-centre holes are frequently drilled and bored, flats are easier to mill up to a shoulder and roll marking is often done using the Y-axes. Parts coming off the lathes are accurate due to one-hit production. It is possible to program cycles involving superimposed machining, where three tools are cutting simultaneously, although this facility has not been used so far in the Maldon factory.
Some parts could not be produced at all on driven-tool lathes without Y-axis motion on at least one turret and would have to be put onto a machining centre for a second operation. Others, such as a pair of components – one aluminium and the other brass – for a broadcasting microphone, are produced much faster on the twin Y-axis Miyanos compared with the lathes they replaced. The more complex of the two, the aluminium part, is produced in 4.5 minutes compared with 7.5 minutes previously. As batch size is 2,000-off, the saving is considerable.
As to the future, Mr Cable sees continued purchase of LFV lathes inevitable. While high pressure coolant systems break swarf adequately on his current larger lathes, as they mainly process free-cutting materials, there is one job presently produced from malleable, oversize, Swedish iron bar on the L20-VIIILFV that would profit from being put onto a 32 mm Cincom in the same series with the chip breaking technology.
Located in Chard, Somerset, subcontract machining firm Metaltech Precision has increased the number of sliding-head mill-turn centres on its shop floor from 6 to 13, of which 10 are Cincom models from Citizen Machinery UK. It follows the purchase by the company’s owner, Expromet Technologies Group, of another subcontractor nearby, NC Precision, which specialised in this area of production.
The strategic acquisition in May 2022 underlines the intention of the UK casting and machining group to strengthen its Swiss-type mill-turning capability. Nevertheless, Metaltech is also strong in fixed-head turning as well as prismatic metalcutting on numerous machining centres, there now being a total of 58 CNC machine tools in operation, providing an extensive suite of machining capabilities to meet customer needs.
The latest sliding-head lathe was installed in September 2022, having originally been ordered by NC Precision. It is a Cincom L32XIILFV capable of mill-turning parts from bar up to 35 mm diameter. Notably, the machine has LFV (low frequency vibration) functionality. It can be switched on by G-code during sections of a machining cycle that would normally result in stringy swarf being generated. Instead, it is broken automatically into chips of manageable size that fall away from the machining area for easy extraction.
Steven Ward, operations manager at Metaltech said, “We were already familiar with and impressed by LFV, having installed a smaller Cincom L20XIILFV four years ago to simplify the production of a particularly difficult component.
“The ongoing job involves machining a tough, malleable iron that has a high tendency to cause bird’s-nesting when turned, but LFV completely solves the problem by allowing the chipping to be controlled.
“It means that we are able to leave the lathe running unattended for long periods, whereas before an operator needed to be in attendance virtually all the time to constantly clear away the swarf.
“This labour cost element, which has now been removed, was contrary to the whole concept of bar turning, yet was necessary to maintain consistency of production and minimise scrap.”
During the acquisition process of the L32XIILFV, the order was placed by NC Precision and honoured by Expromet. It is a clear sign of the group’s ongoing commitment to development and continual investment in up-to-date plant, allowing Metaltech to remain at the forefront of technological advances and providing extended capabilities along with capacity.
The purchase of the second LFV lathe last autumn, with its chipbreaking function, facilitates more options for fulfilling contracts that may come along involving titanium, nickel alloys or other metals that tend to result in stringy swarf. Until now its full potential has not been utilised, except to assist the smaller LFV lathe in producing more of the malleable iron components to cope with rising production volumes.
Another area where the L32XIILFV has benefited Metaltech is in taking the load off a higher specification M-type 32 mm capacity Cincom on site that incorporates cutters in a turret. The gang tool-only L-type machine with its more nimble axis motions is quicker at producing relatively simple parts, leaving the M32 free to concentrate on more complex work.
One example was the transfer of production from the M32 to the L32 of a brass component on which only about 10% of the cycle involves turning operations, the remainder being milling and drilling. Although the spindle drives and driven cutter stations in the gang tool carrier lathe are a little less powerful than in the turret-type machine, it was nevertheless possible on the L-type lathe to produce the part from free-cutting brass in four minutes and four seconds, 20 seconds faster than on the M32.
Mr Ward explained, “Although this represents a reduction of only 7 to 8%, the batch size was 6,000-off, so a significant saving was made. Measures like this help us to maintain our reputation as a rapid response, short lead-time service provider with excellent on-time delivery results.
“It also helps us to control costs, even on parts like this that are predominantly prismatically machined on a driven-tool lathe yet require 20 µm positional tolerance to be held in certain areas, ensuring we provide best value and quality to our customers.”
Metaltech has been using sliding-head lathes from Citizen since 2008, when it installed its third machine, a Cincom A20. Purchase of another two and acquisition of seven more from NC Precision has brought not only increased capacity, but knowledge from the latter company as to how to lower production costs on the more recently installed sliders on which it is possible to swap the guide bush in and out in about half an hour.
Historically, the technique had not been available to the subcontractor owing to the age of the first two Cincoms and the dedication of the third to a single, awkward job. However, the newer lathes from NC Precision do incorporate a swappable guide bush.
When removed, it allows less expensive bar to be turned and results in much shorter rest lengths when the material has been used up, leading to significantly more economical production of shorter components up to typically 2.5 times their diameter. For the right type of work, Metaltech will harness this benefit in the future.
It is often said that a subcontractor does not know what type of work will be coming through the door the next day, so needs versatile machine tools to be able to produce a wide variety of components. The diversity of work is particularly large in the case of contract machinists Repro Engineering, 80 percent of whose turnover derives from turn-milling, components being mainly in the diameter range 19 to 51 mm. Throughput in a variety of different plastics typically accounts for one-third of the total, but at times is as much as 50 percent, the remainder being mainly mild and stainless steels.
The mainstay for production of a large proportion of the turned parts are CNC turning centres from Citizen Machinery, both Miyano fixed-head lathes and Cincom sliding-head models. The first Miyano to be installed was a BND42S twin-spindle lathe with live tooling. It arrived in 1997 and departed just three years ago after 23 years of service, having produced more than 2 million components, most in one hit and a large proportion in lights-out operation. The second Miyano, a BND51S, was bought in 1998 and sold in mid-2022 after an even longer period on the shop floor.
Repro Engineering’s owner and managing director Richard Palmer said, “We have a policy of regularly reviewing our capacity and keeping plant up to date. In the case of the Miyanos, however, earlier exchange simply wasn’t necessary, as the machines continued to hold tolerance. Not having to spend money on replacing them earlier helps to keep costs down for our customers and makes us more competitive.”
The replacement for the BND51S was a more capable BNJ-51SY, which arrived in May 2022. Featuring two turrets and Y-axis movement of the main turret, the lathe allows complex machining operations to be carried out at the main and sub spindles simultaneously. The turning centre also sports many more tool positions than the older model, so fewer tool changes are needed. It is normally possible to put the next part up without any cutter exchange at all.
Nine Miyano machines have been purchased over the years and many have been replaced by newer models. The subcontractor’s current tally of bar-fed lathes of this make is five, accounting for nearly half of its fixed-head lathes. Three of the Miyanos have a Y-axis function and all are fitted with short bar magazines for feeding one-metre stock up to 51 mm diameter. Additionally, the subcontractor operates a Miyano LZ-01R chucker for billet work, especially components that need hard turning.
Regarding Repro Engineering’s sliding-head capacity, the subcontractor operates three Cincom lathes capable of machining parts from up to 32 mm diameter bar. There are also five smaller capacity sliders of a different make on site. Impressed with the quality and longevity of the Miyano machines, Mr Palmer decided to approach Citizen for larger Swiss-type lathes capable of producing bigger diameter, often shaft-type components. He purchased a Cincom A32-VII in 2009, followed by a more highly specified M32-VIII with a B-axis in 2013, and another A32-VII two years later.
All were bought before the Japanese lathe manufacturer had introduced its novel LFV (low frequency vibration) chip breaking software, otherwise Mr Palmer would definitely have specified it. The programmable function, which breaks stringy swarf into short chips, is ideal for turning plastics and stainless steel efficiently. Instead, Mr Palmer relies conventionally on high-pressure oil to promote chip breaking and prevent bird’s nesting.
Extensive use is made of Citizen’s Alkart Wizard CNC programming software to prepare programs for both the Miyano and Cincom lathes. It guides operators through the creation of part programs, calling on a built-in code library and reference diagrams to optimise machining of different materials. It cuts down the amount of time spent typing in G and M codes, or consulting manuals, and validates the program before it is run.
Repro Engineering also operates four machining centres, which generate the other 20 percent of turnover. One machine is part of an automated cell with robot loading and some are equipped with a fourth CNC axis, but for indexing, not turning. It means that all components produced that require both turning and milling go onto the lathes.
Mr Palmer points out that, in this respect, a twin-spindle bar-fed turning centre is the ideal platform for unattended production in one hit of complex components, even prismatic parts requiring all six sides to be accessed. Cycle times tend to be longer on mill-turn centres, which in any case normally require an operator to be present. He does not hesitate to put onto his lathes parts that require no turning operations at all except parting-off.
Mr Palmer concluded, “All Citizen lathes are real workhorses. They are robust, compact and some have hand-scraped guideways, which leads to excellent machining quality.
“The Miyanos in particular are so heavily built, they are almost over-engineered. They just keep going and going, maintaining their accuracy and repeatability for decades. Consequently for machining parts up to 51 mm, they are our preferred lathes.
“Likewise, for turning and milling in sliding-head mode, we have standardised on Cincom when machining parts from larger diameter bars up to 32 mm.”
Founded by Mr Palmer’s father Davin in 1967 and now operating 24/7 from a 12,000 sq ft premises in Waterlooville, Hampshire, Repro Engineering produces batch sizes typically in the range 1,000 to 50,000, although prototype batches down to 100 are not infrequent. Some parts are machined to very tight tolerances down to 10 microns total.
Customers are mainly in the motorsport, defence, sports and leisure, electronics, medical and fluid power sectors and many take advantage of the subcontractor’s consignment stocking service. The company is accredited to ISO9001:2015 and AS9100 Rev D, ensuring high quality standards. In addition, it is registered on the International Aerospace Quality Group’s OASIS (Online Aerospace Supplier Information System) database.
Prismatic machining on BT30 and BT40 machining centres accounts for a majority of throughput at the Mildenhall factory of subcontractor CTPE, which produces complex, high precision components for the medical, marine, scientific, defence and electronics sectors. However, productivity on the turning side of the business received a significant boost in mid-2022, when an ageing, 2-axis, fixed-head bar auto was replaced by a Miyano twin-spindle turning centre with twin Y-axis turrets and live tooling, fed by an LNS Alpha SL65 S short bar magazine.
Supplied by Citizen Machinery UK, the 10-axis ANX-42SYY lathe is fitted with the latest Fanuc 31i 15-inch touch-screen control incorporating a new HMI. It also features the company’s superimposed machining, whereby three tools can be in cut at the same time thanks to X-axis movement of the sub spindle. Three-axis simultaneous interpolation and double Y-axis cutting are also enabled.
The sub spindle offset has the additional advantage of allowing reverse end machining of long parts with extended tools, while simultaneous machining of the front end of the next component is in progress at the main spindle. Otherwise that would have to wait due to interference caused by back end operations, lowering production output.
Chipbreaking software is a big benefit
Advantage is regularly taken of the machine’s other stand-out feature, LFV (low frequency vibration) chipbreaking software in the control’s operating system. The function is independent of the programmed cutting cycle, apart from it being switched on by G-code when expedient to break up stringy swarf, which is particularly problematic when taking finishing cuts. LFV may similarly be switched off when it is not needed, avoiding a slight reduction in metal removal rate due to high-frequency oscillation of the tool tip away from the component surface. In practice, at Mildenhall LFV is on for 10 to 15 percent of a typical cycle.
CTPE’s operations director Alex Taylor said, “We saw LFV demonstrated on the Citizen stand at MACH 2022. The function is extremely useful when machining aluminium, which constitutes most of our work, and is even more effective on plastics, which accounts for about 25 percent of our throughput.
“We struggle with bird’s nesting when internally boring both materials, as the swarf tends to leave marks that affect the bore diameter and in the case of plastic can cause burning. LFV avoids these problems, so machine stoppage for swarf clearance is no longer needed, increasing productivity and enabling reliable unattended operation overnight.
“Program preparation is simple using Citizen’s Alkart Wizard software, which offers suggestions for optimal LFV parameters, and activation only requires one extra line of code. We know we have this functionality in reserve if we have to machine exotic alloys or stainless steels, especially 304 which strings readily, although we have not used it yet on those materials.”
One example of the chipbreaking software’s effectiveness involves a defence electronics part regularly produced from aluminium bar. After experimenting with dwells and pecking macros to improve chipbreaking, which require time to insert patches manually into programs, Mr Taylor was only able to run off 50 components before having to stop the machine to clear away the swarf. That was therefore the maximum number that could be produced lights-out. The situation was acceptable when the customer was ordering batches of 250, but as volumes grew steadily to 2,000 per order, it was denting the profitability of the contract.
The problem has been resolved by having the chipbreaking software switching in and out on the Miyano during difficult parts of the cycle, so the machine can confidently be left to run throughout the night. Moreover the cycle time has fallen from three minutes on a twin-spindle, single-turret, fixed-head lathe, or two minutes when the work was put onto a sliding-head bar auto, to just one minute and 40 seconds on the Miyano. So around 400 finished parts are waiting for staff when they return in the morning.
More tools needed
Before he bought the Miyano, Mr Taylor had already moved along the path of fixed-head, twin-spindle mill-turning, having in 2020 purchased the above-mentioned lathe with a single, 15-station Y-axis turret. However, it meant that retooling was often needed when changing over to a new job, as there were insufficient cutters in the working area to cope with a high mix of work, which is characteristic of a subcontractor’s business.
What he really wanted was an increased number of tools so there would be more likelihood of the next job starting as soon as a new program was loaded. The 12 live tool stations in each of the two Miyano turrets provide him with that flexibility. He is able to leave more pre-set tools in the machine, speeding up changeover and maximising spindle uptime.
Most accurate machine ever
The 6.2-tonne machine occupies only 2,650 mm x 1,630 mm of space on the shop floor. Both main and sub spindle have a bar capacity of 42 mm diameter and are powered by 11 kW / 6,000 rpm built-in motors, while the live tools are rated at 6,000 rpm / 2.2 kW. Rapid traverse rates are fast at up to 30 m/min, which has been achieved by adopting linear guideways.
Mr Taylor concluded, “The Miyano is the most solidly built, accurate machine we have ever bought. Lathes tend to suffer more than machining centres from thermal movement when they are switched on in the morning. They are typically 30 microns out for about 15 minutes while they warm up, but not the ANX.
“After we power it up, it immediately starts producing a part we were machining the previous afternoon to exactly the same single-figure-micron accuracy, without any offsets being entered. Some tolerances we hold are down to ± 5 microns, which we have no trouble achieving.”
He added that this was the first machine tool they have purchased from Citizen Machinery and that the supplier has performed well in terms of service and back-up, especially applications training, which is important for a relatively small subcontracting firm. CTPE joined the BTMA in September 2022 and in 2021 was accredited to ISO 9001:2015.
Corby firm maximises productivity while minimising waste
Fastener manufacturer and turned parts subcontractor Technifast has transformed its business over the past three years, doubling the turnover generated by production of parts at its Corby factory to £120,000 per month. That is despite the company employing two fewer people, now three including managing director Louis Speed, rather than five. Much of the increased business on the subcontract side, which accounts for half of turnover, comes from existing customers impressed at the high quality components produced on nine Citizen Cincom sliding-head turning centres.
Not only is turnover up but profitability has also increased. It is largely down to lights-out running made possible by the latest, modern, 32 mm bar capacity Cincom lathes, two (soon to be three) of which are equipped with swarf conveyors and LFV (low frequency vibration) software. The latter allows reliable, uninterrupted, unattended running, as it is not necessary to stop the machines to clear away stringy swarf that can damage components and shorten tool life.
More efficient turning is only part of the story, however. Many other production aids have been introduced under Mr Speed’s ongoing initiative ‘to make one improvement to the operation every day’. The last three years has seen investment not only in six new Cincoms, the final one due to arrive in March 2023, but a host of other equipment as well.
It includes Keyence non-contact measurement for first-off inspection, a burnishing machine from Cogsdill, three extra Escomatic coil-fed lathes to bring the number on site to seven (mainly used for turning simple, tight-tolerance stainless steel pins), a Sharmic vibratory bowl finishing machine filled with maize for polishing components, and a workstation positioned by every Cincom on the shop floor. They keep in one place everything required to set the sliding-head lathes and inspect the parts coming off them.
Three decades of progression
The period from 2019 to the present has accelerated Technifast’s progression from purely a fastener manufacturing company, which was started by Mr Speed’s father John in 1990. Business prospered and Mr Speed senior started responding to an increasing number of requests for precision-turned components. A succession of second-hand Cincom lathes was purchased to fulfil the work. They were mainly of 20 mm capacity, plus a couple of 16 mm bar machines. Their continued arrival prompted a move in 2005 to much larger premises on the Oakley Hay Industrial Estate in Corby.
The first CNC lathe purchase, in 1992, was a Cincom L16. At the time, it was virtually impossible for Technifast not to buy this twin-spindle machine or a similar production lathe, as the company had just received an order for an unusually large quantity of 100,000 bespoke fasteners and the Emi-Mec Sprint plugboard lathes on the shop floor were unsuitable for the work.
They only accepted a single bar, enough stock for about 100 parts, before a fresh bar had to be placed manually into position. So extended periods of unattended running were not feasible, yet were essential in order to compete with manufacturers in low-wage countries. Moreover if one of these single-spindle machines had been used, the fasteners would have needed deburring by hand, an unacceptably tedious, time-consuming and expensive task.
Technifast continued to receive orders for parts in quantities from a few hundred up to 200,000, so over the ensuing 16 years, 15 further Cincoms were purchased, some of which are recent models that have replaced older versions. End users of the components produced in Corby are mainly in the classic motorbike, motorsport, horticulture and marine sectors.
Chipbreaking software enables unattended running
The first lathe to be purchased from new was a Cincom L20-VIIILFV with a Mitsubishi control that allowed low frequency vibration operation. It arrived in 2018, after a 10-year gap in investment by Technifast, and was an eye-opener for Louis Speed in three respects.
The first surprise was the big improvement in dimensional accuracy, surface quality and repeatability that can be attained compared with using second-hand machines. Notable also was the speed of changeover, as new machines are much faster to set, increasing spindle up-time and productivity. The third and most important aspect of the new lathe was the programmable, low frequency vibration functionality.
Mr Speed said, “LFV is able to fragment long strands of swarf into shorter chips, avoiding entanglement in the cutting zone and preventing clogging of the working area. It is especially effective when turning, grooving, parting and drilling certain materials like stainless steel and plastics, which tend to generate stringy swarf.
“Even mild steel previously caused problems. For example, drilling spacers could not be left to run overnight due to difficulty with swarf accumulation. Now we have no problems with lights-out running. When producing parts requiring a short cycle time, the bar magazine has run out by the time we arrive the next morning.”
He added that when turning some simpler parts, such as dowel pins, LFV is not needed and is omitted from the program. It avoids the small reduction in productivity resulting from the short periods of air cutting when the tool oscillates away from the bar surface to break the chips. For the same reason, the function is turned off by G-code within a program if it is not needed for any particular operations.
Two further 20 mm capacity Cincoms, A20-VIIs, were installed in 2020. They were purchased for the production of price-sensitive components, the advantage being that the machines cost less than L20-series sliders as they have a lower specification, and LFV is not included.
The first was already on the shop floor when the initial Covid-19 lockdown was imposed, which was fortuitous as Technifast immediately received a large order for hand sanitiser components. The machine started running 24/7 to produce the components, half-paying for itself before the contract ended. Subsequently, towards the end of 2021, a third A20-VII was installed with a newly available Fanuc control capable of running LFV programs.
In 2007, the Corby firm started investing in 32 mm sliding-head capacity in order not to have to turn down contracts for parts over 20 mm diameter. As is frequently the case, once word got around that the company had new capacity, work built up in this size range.
After LFV technology had been launched in 2017, and Mr Speed had subsequently gained an insight into the far-reaching benefits of the chipbreaking software through the use the following year of the L20-VIIILFV, he took the decision in mid-2021 to invest in an L32-VIIILFV to upgrade his 32 mm capacity. It was followed by a second in August 2020 and a third is on order, which is the machine mentioned earlier that is due for installation in March next year.
Guide bush-less (GBL) operation for economical production of shorter parts
The first thing Mr Speed noticed about the new generation of L32s is, as with the 20 mm lathes, how much quicker they are to set than the model he bought second-hand in 2007, which was built in 1999. A further advantage is that the Iemca Boss bar magazine feeding the latest lathes can comfortably handle stock down to 6 mm diameter with the requisite guide channel, whereas with the earlier L32 it was not feasible to process bar of even double that diameter.
The second aspect of the new design that he exploited straight away was the ability to remove the guide bush for more economical production of parts with short length-to-diameter ratios up to approximately 2.5 to 1. In fact, after the first new L32-VIIILFV arrived, he swapped the guide bush in and out a couple of times in the first six months, then took it out permanently. One benefit is that the quality and dimension of the bar are not so important, as it is gripped in a collet while the headstock moves in and out of the machining area, rather than the bar sliding through the guide bush insert.
It means that the expense of buying various bush inserts to accommodate different stock diameters is avoided, and less expensive bar can be purchased. The cost of having a standard insert sparked out if a bar delivery is oversize is also saved, which Mr Speed says typically costs an extra £150 for a 20 mm capacity slider and £250 for a 32 mm machine. A further financial gain is that the remnant length when GBL turning is three to four times shorter than when sliding-head turning, so less bar is wasted.
As this L32-VIIILFV had become a permanent GBL lathe, the second model installed adjacent to it has its guide bush kept in place all the time for sliding-head turning of shaft-type components. The first machine was supplied with an expansion kit to enable the nominal 32 mm bar size to be increased to 38 mm in fixed-head mode, providing greater versatility. It was unnecessary to order the second lathe with the bar conversion option, since it cannot be used for sliding-head turning.
Recycling for increased profit
Mr Speed concluded by offering a piece of advice: “One thing I would like to impress on all sliding-head turned parts machinists, almost all of whom use neat oil as a coolant and lubricant, is that they should spin their swarf to reclaim the residual oil it contains.
“We recycle and reuse 100 percent of the oil in the swarf from our nine Citizen lathes, so we only need to buy one or two 205-litre barrels of oil per year to top up the levels in our machines.
“If we did not spin our swarf, we would need to buy dozens of barrels every year at a cost of around £750 each, so the monetary saving is huge. In addition, we get a better price from recycling swarf that is dry – and we are also helping the environment.”
These days when turning and milling components less than 38 mm in diameter, it is difficult to justify using a fixed-headstock CNC lathe, such is the high level of capability, productivity and flexibility of modern sliding-head turning centres (sliders). This is the view of Martin Lock, owner of 55-years-established subcontract machining firm PES Engineering, Burnham-on-Crouch, who took delivery of a Cincom L32-XLFV slider from Citizen Machinery UK in April 2022.
He said, “We held off investing in this technology before, as up to about five years ago sliding-head lathes were not as flexible as their fixed-head counterparts in terms of their power or the number of tools in the working area. Consequently they could not produce such a wide variety of components, but that is no longer the case.
“Modern sliding-head lathes are able to produce anything a fixed-head equivalent can, and on average completes the same cycles in two-thirds of the time. It is down to the speed of movement of the gang tooling and the wealth of static and live cutters that can be deployed.”
Chipbreaking software is a game-changer
PES Engineering has over the years developed a reputation for supplying components in small to medium size batches, typically 3,000- to 5,000-off. Larger quantities are often produced and stocked at Burnham-on-Crouch for Kanban call-off by customers. Materials range from stainless steels, which account for half of throughput, to plastics, which make up another 20 percent. Both tend to generate stringy swarf when machined on the subcontractor’s fixed-head lathes.
Swarf invariably wraps around the tool and the component being machined, risking damage and prematurely wearing the cutting edge of the carbide inserts. Feed rates have to be reduced to mitigate abrasion, lowering production output. Furthermore it is generally necessary to stop a lathe regularly to remove the swarf, making light-outs running virtually impossible unless a free-cutting material like brass is being processed. All of this negatively impacts productivity and profitability.
Such problems are not encountered on the Cincom slider, as it is equipped with Citizen’s programmable low frequency vibration (LFV) software in the operating system of the Mitsubishi control that breaks the swarf into smaller chips. Launched five years ago, the three modes of LFV developed to improve turning, grooving, drilling, boring, threading and parting-off not only avoid bird’s-nesting, but also reduce or eliminate the need to use expensive and energy-hungry high pressure coolant equipment.
Mr Lock continued, “LFV has removed much of the aggravation of turning stainless steels, which gives us a much easier life. We can machine efficiently everything from 304, which is billed as free-cutting but really is not, through to highly alloyed marine grades.
“With LFV, oscillation of the spindle relative to the axis feed motion momentarily and repeatedly lifts the tool clear of the component surface. It has the effect of breaking the swarf before it has a chance to form a string and also lowers the temperature at the point of cutting, reducing work hardening of the metal and preventing built-up edge on the insert.
“We have LFV switched on permanently when machining plastics and it works perfectly, even on nylon. When processing stainless steel, for nine out of 10 components we produce it is engaged for typically half of the cycle and always for parting-off. Programming the function to stop when it is not needed limits the milliseconds of slightly decreased metal removal rate when the tool is air cutting.”
Strategies that Mr Lock previously used to control swarf length included introducing peck feeding and dwells, which extended cycle times and accelerated tool wear, and experimenting with different chipbreaker designs on the insert. None of this is needed any more, as he says most materials chip like brass simply by selecting cutting parameters out of Citizen’s LFV manual.
At the end of last year, two 40 mm capacity fixed-head lathes producing 304 stainless steel medical parts broke down on the same afternoon, prompting Mr Lock to look for a replacement. As sliding-head technology had advanced sufficiently to consider it, he decided to go down this route. He was in regular contact with another subcontractor with which he occasionally shares work, and that company operates 10 Citizen lathes including LFV Cincoms that have proved to be reliable and accurate over the years. Once a machine is warmed up and set, tolerances do not move and machining to within microns is routine.
It therefore made sense for PES Engineering to opt for the Citizen brand. An L32-XLFV was duly ordered with a conversion kit that allows stock up to 38 mm in diameter to be fed from an Iemca three-metre bar magazine. Immediately apparent was the sheer speed of the machine, with many parts coming off more than twice as quickly compared with the output from one of the ageing fixed-head lathes. In one extreme case when turning a plastic part unattended, 400-off were produced in two hours instead of over a full manned shift.
Two tools can be in cut simultaneously on the slider for high levels of productivity. Moreover the latest-generation L32-XLFV has a Y2 axis on the sub spindle, allowing cutting operations to be shared more evenly between it and the main spindle, minimising cycle times.
In the first three months of operation, the slider produced 20,000 parts of around three dozen varieties, all but one of which were in length less than 2.5 times the diameter. The majority were therefore not classical sliding-head work, so Mr Lock plans to take advantage of the ability on most Cincoms, including the L32, to remove the guide bush. The main advantages are the ability to use less expensive bar, as straightness and dimensional variation are not so much an issue, and a four-fold reduction in remnant length at the end of each bar, leading to significant material savings.
The Cincom is not only the first slider that Mr Lock has bought, but it also represents the first time he has dealt with Citizen Machinery UK. He has been impressed with the supplier’s service, which he describes as “refreshing”.
He added, “We have had fantastic human interaction and service from everybody in the company, from the sales team through ordering, machine installation and commissioning to service back-up.
“If we email or phone Citizen’s service department, we receive a call back in half an hour – sometimes within a couple of minutes – something other suppliers never seem to do in our experience.
“With the Cincom being our first slider, we were reliant on prompt and comprehensive telephone advice at the outset and still are to some extent. It has proved invaluable.”
About PES Engineering
Established in 1967 by Mr Lock’s father Clifford and a partner who subsequently left, PES Engineering derives its turnover from milling and turning in approximately equal measure. Industries served are mainly aerospace, automotive, medical, hydraulic, rail and electronic connectors, and customers are to be found throughout the UK as well as in the US and Germany.
A particular specialism is design for manufacture, i.e. redesigning components to simplify their manufacture and reduce the cost of production, while maintaining the part’s full functionality in service. In one recent case, an injection moulded plastic component that was proving difficult for a US customer to assemble with other parts was re-engineered so that it could be turned from plastic bar at an acceptable price. The result was highly satisfactory and the contract is ongoing.
In conclusion, Mr Lock observed, “Automating the turning side of our business using a bar feeder is much easier, cheaper and less space consuming than retrofitting one of our machining centres with robotic machine tending.
“So I decided that investment in autonomous turning and milling of components in one hit was the way forward and it is proving to be the right choice.
“We will now progress to turning on the L32 without the guide bush for all but the longest shaft-type components, which are rare orders for us at the moment as we are not known as a sliding-head shop, but of course we are now in a position to fulfil that work.
“The expectation is that we will also use the Cincom for machining purely prismatic parts with no turning at all apart from parting-off, which will go some way to automating production of some of our milled parts as well.”
In 2006, entrepreneur David Swaffield started his own contract machining firm, DWS Engineering, in Crewkerne after gaining a mechanical engineering apprenticeship at a nearby packaging machinery manufacturer. He started out using manual machine tools, progressing to CNC prismatic machining in 2009 and fixed-head CNC turning the year after.
Frustrated at not being able to find pre-war British Standard Whitworth threaded nuts, bolts and other components for the family-owned 1923 Aveling and Porter eight-tonne steam roller he was refurbishing, he decided to make them himself, leading to the inauguration in 2017 of another company, Historic Threads. It was then that Mr Swaffield discovered the capabilities and production potential of CNC sliding-head lathes from Citizen Machinery.
During the Second World War, the diameters of Whitworth threads were reduced to save metal. It is easy to obtain the later sizes, but the original larger varieties used to be scarce and difficult to source. That was until Mr Swaffield identified a business opportunity through his subcontracting activities and via Facebook groups run by steam-driven vehicle enthusiasts.
Now a vast range of legacy threaded components, from the biggest Whitworth to the smallest BA (British Association) size and everything in between, is manufactured by Historic Threads and sold on its website www.historicthreads.co.uk. This business now accounts for 60 percent of Mr Swaffield’s turnover. Despite its recent inception, the company is probably the largest stockist and supplier of pre-WWII threaded components in the world.
Although nuts, bolts, studs and pillars tend to have a small length-to-diameter ratio and can be satisfactorily produced on fixed-head lathes, Mr Swaffield learnt early on in his career of the benefits of sliding-head turning, namely that the gang tooling allows short parts to be produced faster and the lathes are additionally capable of turning shaft-type parts if required. His father-in-law owned a subcontracting company half an hour’s drive away on the south coast of England and he was a prolific user of Citizen Cincom sliding-head capacity.
In 2017, the first Cincom L32 purchased second-hand from Citizen Machinery was delivered to Crewkerne. The 2001 machine was installed, levelled and aligned the next day by a Citizen engineer and is still producing thousands of nut and bolts every week, albeit of low complexity due to the machine’s lack of driven tooling. It was recognised that in-cycle milling and other prismatic operations would be useful for machining more complicated components in one hit, so a second-hand Cincom M32 of a similar age with live tools arrived in March 2021.
As with most sliding-head lathes, the Cincoms are capable of producing components from bar up to 32 mm diameter, so a fixed-head bar-fed lathe of 65 mm capacity was purchased from another source for manufacturing the larger sizes of historic nuts and bolts.
Then in March this year (2022), due to the steep rise in demand worldwide for the legacy threaded components, a third sliding-head lathe was installed, this time a new Cincom L32-VIIILFV. The modern machine design has advantages in that it has been supplied with an expansion kit to enable the nominal 32 mm bar size to be increased to 38 mm, allowing for instance a 3/4-inch nut to be turned from round bar.
An additional advantage is that the guide bush assembly can be removed in an hour to produce in fixed-head mode relatively short components that do not require sliding-head turning. Remnant lengths are substantially shorter, reducing material wastage and costs.
Shortly after the machine was delivered, Mr Swaffield received DWS Engineering’s biggest ever single order for the supply of brass, aluminium and stainless steel parts from 10 to 20 mm in diameter for use in the assembly of make-up brushes and pencils.
The latest Cincom is ideal for fulfilling this contract. For example, the low frequency vibration (LFV) chipbreaking software built in to the control is able to avoid stringy swarf when drilling a 100 mm long, 8.5 mm diameter hole down the centre of a 10 mm diameter stainless steel pencil, even though the machine is not fitted with optional high pressure coolant.
LFV is also proving useful in avoiding birds-nesting when producing plastic components, such as a batch of 2,000-off, 20 mm diameter black Delrin spacers that went through the shop recently.
The chipbreaking function is programmable, so it can be switched on and off by G-code in the cutting cycle. It may therefore be stopped during parts of the cycle where it is not needed, avoiding the slight material removal rate penalty due to the short periods of air cutting when the tool tip oscillates away from the component surface to break the swarf into short chips. Users tend to employ LFV differently to suit their requirements; Mr Swaffield always makes sure it is switched on during parting-off, for example, as it results in a big increase in the life of the indexable inserts.
The chipbreaking function on the latest Cincom is also proving useful for producing in one hit in a four-minute cycle various EN16 stems for six sizes of patent-pending staple driver Mr Swaffield invented while he was bored during the 2020 lockdown.
LFV provides more latitude when selecting feeds and speeds, as even EN16 can generate stringy swarf unless parameters are set exactly. This new side to the business – www.stapledriver.co.uk – looks set to generate further significant sales revenue. In addition to being sold online, Mole Valley Farmers is stocking the product on a trial basis in 10 of its 55 stores around the country.
The decision by sliding-head lathe builders to introduce the ability to remove the guide bush heralded a natural successor to the single-spindle cam auto
Top quality brass lampholder manufacturer S Lilley & Son Ltd, now in its sixth generation of family ownership, has nearly finished phasing out the 20 or so cam-type, single-spindle bar autos it has used in its Birmingham factory since the 1950s. In their place are to be found 11 modern CNC, twin-spindle, bar-fed lathes up to 65 mm capacity with driven tooling, six of them supplied by Citizen Machinery UK.
Two are Miyano BNA42-MSY fixed-head turning centres of 42 mm capacity installed in 2017 and 2021, while the other four are Cincom sliding-head models (sliders), two for turning, milling and drilling 32 mm bar and two for processing 20 mm stock. Interestingly, to achieve the high speed of production for which outdated cam technology is renowned and couple it with the inherent advantages of CNC technology, namely unattended running and rapid changeover for smaller economical batch sizes, the company operates the sliding-head machines almost exclusively without the guide bush in place.
The reason S Lilley & Son Ltd is able to do this is that most components for the light fittings it makes are shorter than 3.5 times their diameter (3.5D). Normally a ratio of 2.5D is approximately the limit when stock is not supported in a bushing (or by another means such as a tailstock or sub spindle), otherwise the protruding length of bar deflects under pressure from the tool, causing inaccuracy during machining. However, the relatively open tolerances of the lampholder parts produced in Birmingham allows the company to push the limit higher, lowering the cost of manufacturing parts up to 40 percent longer by taking advantage of higher speed production without the guide bush.
Advantages of guide bush-less operation
The rationale for investing in sliding-head lathes and choosing to operate them without the guide bush for most of the time, rather than buying a fixed-head lathe, is due to the sheer speed of production that is possible using the in-line ganged cutters typically found in a sliding-head machine. It allows the linear cross slide to effect very fast tool changes between cuts. Cycles times are considerably shorter and sometimes even halved compared with using a fixed-head turning centre, in which the tool carrier is generally a revolving turret that takes longer to index the next cutter into position.
Due to the bar being clamped by a collet closer to the spindle nose on a slider when it is used without the guide bush, Z-axis stroke is restricted to around one quarter of what is possible when stock slides through a bushing. It is because the whole spindle head rather than just the bar moves in and out of the working area to present the part to platen-mounted tools that can only move in X and Y. However, the shorter Z-axis travel is unimportant in the Birmingham factory, as most components are less than 3.5D.
As the collet grips the bar much nearer the work than in classical sliding-head turning, the more rigid clamping allows deeper cuts to be taken without chatter, resulting in further efficiency gains as well as better surface finishes, even when machining demanding materials.
Guide bush-less operation on a slider brings with it numerous other advantages in addition to all the productivity benefits. Bar of lower dimensional quality and price can be tolerated, as there is no bush for it to seize in. The remnant after the last part has been machined from a bar is around one-third the length left after true sliding-head turning, so there is less material wastage. It can equate to a considerable monetary saving, especially when prices are as high as they are presently, the more so when expensive alloys are being processed. Notable also is that bar of cross section other than round, such as hexagonal or extruded, may be machined if the guide bush is not present.
Indeed, if support is not necessary for the stability of a part during machining, it is better to remove the guide bush as it can actually compromise accuracy. Holding roundness then becomes easier on short components, as the ability to achieve tolerance is dictated by the high quality spindle rather than the bushing. Furthermore it is possible to run at higher rotational speeds to achieve better production rates and surface finishes.
An extra benefit of turning outside diameters in this mode is that multiple passes are feasible, so shallow roughing cuts may be taken to alleviate the chip breaking problems of turning to size in one pass, plus there is potential to prolong tool life. It is not possible to retract components of reduced diameter back into a guide bush if they are longer than the land area of the bush, as the component would not be supported and vibration would occur.
Transition from cams to CNC
S Lilley & Son Ltd’s transition from cam-type to CNC lathes started in 2008, somewhat later than in many manufacturing companies for three reasons. First, as tolerances on its electrical products are not particularly tight, their production is relatively unaffected by the age of a machine tool; second, the fittings are frequently needed in large volumes commensurate with single-spindle cam auto operation; and third, the company was fortunate to employ a highly skilled cam auto setter-operator who retired as recently as 2019. That was when the penultimate cam-controlled machine was sold, the single remaining auto being devoted to a particular long-running job.
The employee’s departure was the trigger for the Lilley family to accelerate the purchase of Cincom sliders. A pair of 20 mm capacity A20-VII models was installed, one in 2019 and another in 2020, as direct, more productive replacements for the former single-spindle cam autos. The A20s also have the advantage of a compact footprint on the shop floor, the area of which is limited in the Birmingham factory.
The new sliders joined an L32 Cincom model installed in 2012 for producing parts up to 32 mm diameter. The machine was swapped in 2017 for a more modern L32-XII. Likewise, this slider is only occasionally used with the guide bush fitted for producing some longer components from bar or tube.
Director Simon Lilley is of the opinion that, even though cam-type lathes can produce more components per hour than their CNC counterparts, the ability to set the latter machines so much more quickly and run them unattended through the night during the week and into a ghost shift on Saturday mornings means that in terms of production output, one Cincom is able to do the work of three of the older single-spindle cam autos.
He described as “a massive advantage” the ability to produce long runs of components on the CNC machines without an operator in attendance, for example 100,000 Lilley hexagonal lock nuts. During the daytime the sliders are ideal for producing smaller quantities of say 500-off, whereas cam-type lathes would need to be set to run a minimum of 10,000-off to be economical and in any case most of this type of work has long since disappeared overseas. Being able to reduce economical batch size so substantially, down to about 100-off, has resulted in substantial savings in inventory and space and the cost of holding large stocks.
Moreover, CNC turning centres seamlessly include what would traditionally be separate second operations. The need for these previously made certain jobs uneconomical on lathes with cam-actuated slideways if a suitable and often expensive attachment could not be sourced.
Chip breaking software raises efficiency
In January 2022 a fourth Cincom arrived, an L32-XIILFV with Citizen’s latest low frequency vibration (LFV) chip breaking technology in the Mitsubishi control. The three existing sliders plus the Miyanos and other fixed-head lathes were approaching full capacity, so the new machine provided flexibility to swap work around on the shop floor and it is also back-up for the remaining, ageing single-spindle cam auto.
Additionally it is the mainstay for manufacturing increasing quantities of a particular type of screw lampholder known as the Edison E14, a heavy brass product available in a range of decorative finishes that is proving extraordinarily popular on world markets.
As with the other sliders on site, the machine is rarely used with the guide bush fitted. So resolute is S Lilley & Son Ltd’s policy in this regard that longer parts up to 5D, which could be regarded as being best produced by sliding-head turning, are instead machined half way in the main spindle and transferred to the sub spindle for the remainder of the turning and milling to be completed. It saves half an hour’s work installing the guide bush and another half an hour removing it, maximising productivity.
More than 95 percent of the Birmingham firm’s turned parts are made from free-machining brass bar, but lately there has been an increase in demand from its customer base for aluminium parts up to 32 mm diameter and for plastic components such as acrylic LED lenses and acetal grommets. About a quarter of the company’s throughput is contract machining of such special components for luminaire manufacturers already buying Lilley brass lampholders and lighting accessories.
Craig Lilley, another director and family member concluded, “Anodising quality 2011 T3 aluminium is not as free-machining as it is made out to be and the 6026 T9 grade we turn is even worse in terms of its tendency to generate stringy swarf. Most plastics are similarly problematic when machined.
“LFV repeatedly oscillates the tool clear of the bar surface for a fraction of a second, fragmenting the swarf into manageable chip sizes. There is no longer a need to stop the machine to clear swarf tangled around the tool and component, so production output is maintained.
“By the simple insertion of G-codes, the function can be programmed to cut in and out during a cycle. It is turned off automatically when it is not needed for chip breaking, so the slight reduction in material removal rate during LFV machining is minimised. It really could not be more flexible.”