Author: Luke

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Nine Miyano machines have been purchased over the years and many have been replaced by newer models.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.

Continued investment

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.

Purchasing decision

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.”

In response to an upturn in business over the past few years, Merseyside subcontract machining company Wealdpark is to treble the size of its factory. The first phase of expansion, due to begin immediately, will add an extension a little larger than the 6,000 sq ft unit it presently operates in Sutton Road, St Helens. By the end of 2023, another 5,000 sq ft unit is scheduled for completion on an adjacent plot that was purchased recently.

Mainly a precision turned parts subcontractor, the family owned and run firm operates two vertical machining centres and 15 sliding-head lathes on the shop floor, alongside six Miyano fixed-head turning centres from Citizen Machinery UK.

The latest to arrive, in April 2022, was a Miyano ABX-64SYY, bringing to four the number of these 65 mm diameter bar capacity machines purchased since 2014. In use also are 51 mm and 42 mm capacity models. All have twin spindles and twin 12-station, Y-axis turrets with driven tooling for efficient, one-hit production. Despite the machines being bar fed, 40 percent of the time they are employed for turning billet in 6-inch and even 8-inch chucks, enabling the production of much larger diameter parts with an operator in attendance.

Together with father Jim and brother Steve, Phil Smith is a director and joint owner of Wealdpark. He said, “We have increased turnover by a quarter in the two years since the start of the pandemic and sales during each of the first five months of 2022 were at a record level compared with previous years.

“Production of parts for the hydraulic, pneumatic and yellow goods industries is particularly strong at the moment. We are also active in the aerospace, automotive, electrical fastener, fire-fighting, military and temperature measurement sectors.

“Manufacture of parts for ventilators has been an established part of our business for many years and it of course continued through 2020 and 2021. We have been able to turn this into a growth area by supplying similar components to Europe and North America.

“Admittedly part of the rising sales figures is down to an increase in material costs but the underlying growth is undeniable, due in part I believe to the trend towards re-shoring.

“It has given us the confidence to invest in new infrastructure and capacity to develop our business and part of that strategy will be the continuing purchase of top quality plant like Miyano lathes, which we have used since 2007.”

There are no other makes of fixed-head turning/milling centres in the factory. It is because once Wealdpark’s directors had satisfied themselves that the Japanese-built machines are of good quality and value, reliable and accurate, the acquisition of further similar lathes provides the flexibility to be able to swap tools and programs easily across the shop floor.

In fact it was other members of the British Turned Parts Manufacturers Association (BTMA) that recommended the Miyano brand in the early days when the subcontractor was transitioning from a cam auto shop with 53 machines to a fully CNC-equipped company. The process started in 2001 and was complete within a decade.

Both Phil and production manager Neil Ireland are waiting for Citizen to introduce its LFV (low frequency vibration) chipbreaking software, which is already available on a pair of 42 mm bar capacity Miyano models, to larger machines in the series. It will certainly be adopted in the St Helens factory, as it will be ideal for automatically breaking up stringy swarf into manageable chips when machining certain materials.

They include highly ductile C101 copper, much of which is turned, milled and drilled in the St Helens factory for producing electrical components, and AMS5629, a martensitic, precipitation-hardening stainless steel used widely by the aerospace industry. Both are problematic in their tendency to birds-nest when machined, as are aluminium and a number of plastics. Even EN3B mild steel, which is supposed to have good machinability, is proving difficult to turn without swarf clogging the working area, due perhaps to the current shortage of good quality material.

Another issue that occupies Neil’s thoughts is whether to continue using twin-turret fixed-head lathes or progress to triple-turret models. For example, instead of the latest ABX-64SYY 9-axis CNC lathe with upper and lower turrets, Citizen Machinery could have supplied a 12-axis Miyano ABX-64THY with a third Y-axis turret positioned above the spindle centreline. All three tool carriers can be in cut simultaneously to achieve very high levels of productivity.

Neil’s view for the time being is that the extra time required for setting such a lathe and then programming it to incorporate the movements of a third turret cannot be justified for Wealdpark’s relatively small batch sizes of typically between 1,000- and 3,000-off. Additionally, the upper turret of the Miyanos on the shop floor often holds a U-Drill of large diameter for reverse-end axial machining and a third turret would restrict its movement. Nevertheless, the potential offered by a three-turret solution is constantly under review.

Notable also regarding the fixed-head lathes is their speed of production, despite their large size. Occasionally, when the sliding-head lathes are particularly busy, a production run is transferred to a fixed-head lathe with very little increase in cycle time. One component machined from 20 mm hexagonal bar, for example, takes 28 seconds to produce on a sliding-head lathe with gang tooling and only 32 seconds using a 65 mm capacity Miyano with turret tooling.

Generally, Wealdpark operates a 37-hour week and sets up all lathes at the end of the day for a considerable amount of unattended machining of free-cutting materials overnight and into the weekend. However, the recent increase in workload has necessitated occasional three-shift attendance and 24/7 operation.

Reliable autonomous operation of the Miyanos is ensured by comprehensive load monitoring of both spindles and of the three linear axes of both turrets, as well as of the live rotary tools. The parameters of each channel can be set separately according to the job to ensure safe operation combined with minimal disruption to production.

Programming is carried out mainly at the Fanuc Series 30i-B control on the shop floor, although offline-created content is sometimes added including engraving and deburring routines generated using the Alkart Wizard programming software provided by Citizen Machinery.

In preparation for the impending expansion, at the start of 2022 Wealdpark took on three extra staff, an experienced setter-operator and two apprentices who in September this year will start a four-year NVQ level 2 diploma course on day release to St Helens College. Further new appointments will follow to increase the company’s headcount over the next couple of years.

An electrical maintenance engineer by trade and with a solid grounding in mechanical engineering, Tom Pearce started his career as a prototype machine builder in the rubber industry. He subsequently worked for 11 years in his father’s company commissioning production machinery. In 2016 he started his own business, CIRC Manufacturing in Westbury, Wiltshire and after initially concentrating on welding, a skill that has been retained, he decided to branch out into subcontract machining.

His current CNC capacity includes a vertical machining centre and two fixed-head lathes, all pre-owned, and three Citizen Cincom sliding-head lathes also purchased second-hand due to financial constraints during the start-up phase. His stated aim is to gravitate towards using more of the latter machines to produce complex, small to medium diameter, high added value components, as this is where he sees a profitable future.

The first CNC lathes on the shop floor were the two fixed-head models with live tooling, which have no bar feeder but are able to accept a one-metre length of bar up to 65 mm diameter through the spindle. Mr Pearce took advantage of this by employing a bar puller in the turret and including a macro in his programs to advance the bar automatically after each component is parted off. It allows up to five hours’ unattended running, depending on the size and complexity of the parts being produced, and brought home to the entrepreneur the benefits of automation.

CIRC was receiving more and more enquiries for machining components of much smaller diameter, however, including from his existing customer base. To keep them happy the company was having to subcontract out this work, as it was not economical to use the relatively large lathes on the shop floor. New plant was needed and a sliding-head turning centre was the preferred option, as it is capable of producing long, slender parts as well as those of larger aspect ratio. An internet search strongly indicated that a Citizen would be the best make to buy.

So in 2019 Mr Pearce bought a 1995-built Cincom L20-VII slider with a 3-metre bar magazine sight-unseen for £4,000 from a website and used his engineering skills to refurbish it himself. He did not feel sufficiently confident to commission it so asked Citizen Machinery UK to align the bar feeder, bolt down the machine and check the axis movements. The company was very receptive to doing so and promptly sent in an engineer to complete the work.

The lathe proved to be easy to operate by simply reading the manual. Word soon spread throughout Wiltshire and further afield that the capacity was available and CIRC started receiving more enquiries for complex turned parts. Most were fulfilled, although some had to be turned down as the machine does not have a full C-axis on the main and sub spindles, only 15-degree indexing.

That prompted Mr Pearce in 2020 to approach Citizen Machinery UK directly for a machine with C-axis spindles and he also wanted higher speed driven tooling. The supplier offered a K16E-VII built in 2011, a 16 mm capacity slider that ticked the right boxes and is one of the fastest lathes that Citizen has ever manufactured. The supplier duly delivered the machine and in Mr Pearce’s words “nailed the installation and commissioning in one day, then provided a full day’s training the next”, so the lathe was quickly into production.

A copper contact pin, a development part that was being produced on the L20-VII, required holding a ± 5 µm tolerance on diameter, which was difficult to achieve. Additionally, cycle times were unduly long. The work was immediately transferred to the K16E-VII and at the same time, as luck would have it, the batch size increased dramatically to 20,000-off. The accuracy needed was easy to attain and the cycle time fell threefold from one minute to 20 seconds, which translated into much more economical production. The contract has since expanded and the subcontractor is now producing a family of pins in long runs for a customer in the electrical industry.

Mr Pearce added, “If we don’t run the K16E-VII overnight, it needs to be warmed up in the morning to achieve the tight tolerance on the connector pins. After 40 minutes the lathe, with its 45-degree tool platen driven by two ballscrews to achieve high resolution movement, is able to hold ± 5 µm all day.

“We currently use three digital micrometres and a toolmaker’s microscope for quality control of these parts, but intend to invest in an optical, non-contact shaft measurement machine to take over this metrology task.”

Having seen the benefits of more modern sliding-head turning technology, he was keen to harness it for the production of components larger than 16 mm diameter. Accordingly in January 2022 he bought a two-year-old Citizen Cincom L20-VIIILFV, again on the open market, and achieved another step change in productivity.

Although nominally a 20 mm capacity sliding-head lathe, the guide bush is removable (as an option) to allow stock up to 25.4 mm (1 inch) to be turn-milled in fixed-head mode. The first job put on the machine was the production of 20,000 stainless steel gland nuts of 22.22 mm (7/8 inch) diameter for an electrical equipment manufacturer.

When interviewed towards the end of April 2022, Mr Pearce had produced numerous different components on the machine but the guide bush had still not been used. He says the advantage is that the roundness and straightness of the bar is not so critical when the lathe is used in this mode, added to which the remnant lengths are much shorter, both of which saves cost and results in more economical production. He estimates that the guide bush will only be used for about one-quarter of the jobs produced on the machine, underlining the flexibility of modern sliders.

The L20-VIIILFV has even faster and more powerful spindles and live tooling than the previous two Cincoms installed in the Westbury factory. It also has integral driven tools for reverse end working and an uncluttered working area to provide more space to facilitate cutter exchange at up to 37 tool positions. After installation, the machine immediately started taking sub-20 mm diameter workload off the fixed-head lathes, freeing them to produce larger parts. Across a wide spread of components from 1 mm to 1 inch diameter, the L20-VIIILFV is executing some extremely fine work involving, for example, a 0.3 mm slitting saw and profile boring of a pre-drilled, 1.5 mm diameter hole.

There are generally two impediments to lights-out production, according to Mr Pearce, namely component dimensions drifting out of tolerance and swarf build-up in the machining area requiring operator attendance to remove it. The latest lathe avoids both problems and therefore frequently runs unmanned overnight. The first issue is addressed by the presence of thermal compensation sensors around the machine and the second by Citizen’s LFV (low frequency vibration) technology running in the operating system of the Mitsubishi control.

Mr Pearce explained, “Sliding-head lathes when used with the guide bush in place have an inherent drawback. It is not really feasible to rough and then finish turn a part, as the smaller diameter of the roughed section when drawn back into the guide bush would cause vibration and impair the finishing pass.

“It is therefore necessary to turn to size in one operation, but that tends to produce long, stringy swarf when machining certain malleable materials. The LFV software prevents this from happening by lifting the tool tip away from the surface of the material periodically for a few microseconds.

“The frequency of the oscillation can be adjusted in the part program to control the size of the much shorter chips, added to which the LFV function can be turned off by G-code when it is more expedient, i.e. slightly quicker, to cut without it.

“Overall, productivity is increased by enabling reliable unattended operation, eliminating the need to include axis shuffles in programs to shake swarf off components, especially from grooves, and avoiding the need to stop the machine to clear swarf.”

The job on the lathe when it was photographed, a tubular Duplex stainless steel weld collar for the oil and gas industry, is a good example of how the benefits of LFV can be utilised. The high strength material has a tendency to work harden as it is being machined, the impact of which can be reduced by taking deep cuts to remove the work-hardened layer from the previous pass.

The problem is that taking deep cuts in such tough, ductile materials inhibits chip breaking and normally results in a bird’s nest of swarf wrapping itself around the component and tool, to the detriment of both and perhaps even rendering them useless. LFV prevents this from happening, so every part produced is perfect and tools last longer. In the case of the weld collar, LFV is switched on for facing the bar and turning a chamfer, then to maintain a high production rate it is switched off for simultaneously boring and turning the OD.

Mr Pearce is enthused that the chip breaking software also reduces problems and raises productivity when machining other materials such as pure copper, exotic alloys, other stainless steels and most plastics, especially nylons.

Combined with the availability of high-pressure coolant on the L20-VIIILFV, the chipping function will also prove useful in the production in one hit of CIRC’s single proprietary product, a ballpoint pen housing and cap turned from Nitronic 60 stainless steel alloy. The use of carbide tooling and neat cutting oil in its production gives each individually-numbered writing instrument a beautiful micro-planished surface.

Mr Pearce concluded, “The three Cincoms are the bedrock of our subcontract machining service. All feature main and sub spindles, full length bar feeds and a multitude of tools for driven cross working, end face milling and off-centre drilling.

“They enable us to offer economical done-in-one manufacture, without the need for secondary operations. This in turn allows us to run our machines unmanned, so we can offer competitive prices and hence fantastic value to our clients.

“The only thing holding us back at the moment is difficulty in finding skilled machinists to employ.”

Good quality machine tools operate reliably and hold tolerance for two decades or more. The problem is that technology moves ahead so fast over such an extended period that the productivity of older machines cannot match that of their newer counterparts.

This was the situation Redruth subcontractor DP Engineering found itself in until it purchased three new Cincom lathes from Citizen Machinery UK. They are an L20-XLFV installed three years ago, an identical machine that arrived in autumn 2021 and an M32-VIIILFV bought at the end of last year. The latter two machines were direct replacements for equivalent 20 mm and 32 mm capacity sliders of similar type and make bought around the turn of the millennium, several machine generations ago.

Philip Anthony, DP Engineering’s Sales and Marketing Director commented, “The faster rapid traverses and higher power and speed of the main and sub spindles as well as of the driven tools on the new lathes have increased our capacity considerably. One stainless steel aerospace part we previously turn-milled in one hit on an L20 that is 20-plus years old now takes half that time to produce on its modern replacement.

“It is a similar story on the 32 mm machine, which is more user-friendly than the former generation lathe and has better access and visibility into the machining area. Moreover, the addition of a rotary B-axis on the gang tool post enables us to machine more complex parts than was previously possible on our sliders.”

LFV programmable tool oscillation for automatic chip breaking

A notable technological advance from Citizen since DP Engineering purchased the earlier Cincoms was the introduction five years ago of its proprietary LFV (low frequency vibration) chip breaking software running in the Mitsubishi control. It has resulted in a significant increase in productivity when machining malleable materials such as titanium and stainless steel.

It is particularly beneficial for the subcontractor, as one-third of its turnover is derived from the aerospace sector in which the use of such materials is commonplace, as it is in the medical industry, which has also generated more work since the start of the pandemic. Normally during machining, stringy swarf often entangles itself around the tool and component, risking damage to both and necessitating lathe stoppage to clear it from the machining area.

Mr Anthony explained, “The first L20 we bought in 2019 has LFV. We knew about the technology and sent a team of engineers to Citizen Machinery’s Brierley Hill centre to see demonstrations of the chip breaking function in action.

“For certain parts of cycles, it is very effective at ensuring that what usually becomes a bird’s nest of swarf is broken up into shorter chips, avoiding having to stop the machine to remove it and the consequent loss of production.

“The best part is that LFV can be programmed to stop during a cycle when it is not needed by inserting a G-code, minimising the slight reduction in metal removal rate during the periods when the tool oscillates away from the component’s surface to break the chips.

“On some jobs, even when cutting stainless steel, we don’t have to use LFV at all. It depends on the component design, the tolerances that have to be held and the tooling used. However, it is fantastic to have it there for when we need it.”

He added that, in practice, LFV is particularly effective at controlling swarf on the L20s during turning and drilling operations, while on the M32 it speeds roughing and also plays a role when thread cutting. Overall, having complete control over swarf generation ensures that processes are more reliable and repeatable, added to which tool life is noticeably increased.

Guide bush-less operation saves costs

Another attribute of the latest three Cincom lathes that increases their versatility, apart from the extended periods of spindle uptime and unmanned running made possible by the LFV chip breaking software, is the ability to turn-mill shorter components in fixed-head mode without the guide bush, which can be removed and replaced within half an hour.

This allows lower quality, unground bar to be used, increases by several millimetres the maximum diameter of stock that can be accepted and also reduces bar wastage due to much shorter remnant lengths. Consequently this mode of operation is frequent in the Redruth factory, especially for the significant amount of kanban production fulfilled by DP Engineering for its customers.

Mr Anthony remarked that overall, taking into account the higher speed of machining, the LFV chip breaking function and the option of guide bush-less operation, the latest three lathes give DP Engineering not only considerably higher productivity but also a lot more flexibility when allocating jobs to the 18 turning machines around the factory, including the current tally of five Cincoms.

A couple of dozen jobs have already been transferred from multi-turret fixed-head lathes to the new sliding-head models for one-hit machining, freeing up the former for other production duties. Such versatility is ideal for a subcontracting environment, leading to faster deliveries to customers, enhanced reputation and more orders.

Mr Anthony also pointed out that as space on the shop floor in Redruth is fairly limited, replacing machines with models that are much more productive is an ideal way to grow the business without the expense and disruption of having to move to larger premises. This is especially important in respect of his turned parts production, which accounts for three-quarters of throughput.

About DP Engineering

DP Engineering is a cog in the wheel of Cornwall’s £732 million manufacturing industry. It was the brainchild of a keen motorcycle rider, the late David Paull, who was frustrated at not being able to obtain engine parts for his bike and decided to machine his own. In 1952 he started a motor reconditioning business, David Paull Motor Cycles, which led him into subcontract machining and was the forerunner of the current firm.

In 2008, DP Engineering gained AS9100 accreditation in addition to ISO 9001: 2000 and established itself as a supplier to the aerospace industry. Due to business expansion, in 2014 the company purchased a purpose-built, 17,000 sq ft premises in Redruth, where the subcontractor operates today under the watchful eye of CEO Martin Legg.

Major sectors served include aerospace, defence, oil and gas, marine and renewables. The company is known for being a low-to-medium volume shop, producing parts typically from 10- to 50,000-off. Lean manufacturing principles allow cost effective production, from prototypes through to batch work, and over 500 kanban items can be produced for next day delivery.

Other capital investments made by the subcontractor within the past 12 months, apart from the two Cincom lathes, include a Matsuura 5-axis, 10-pallet cell for automated machining of prismatic components, an Aberlink coordinate measuring machine to inspect them, and a ViciVision optical, non-contact measuring machine for quality control of rotational parts.