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FIXED-HEAD TURNING UP TO 40% FASTER AND TOOL LIFE DOUBLED ON SLIDING-HEAD LATHE

In August 2020, Merseyside subcontractor Bryken took delivery of its sixth Miyano BNE-51MSY turn-mill centre, having bought its first as recently as June 2018. Operations director Phillip Taylor says that regular investment in new plant is key to thriving in a competitive global marketplace and he makes sure that no machine tool stays on the shop floor for more than 10 years. The company, which has 95 employees and a £10 million annual turnover, derives 40 percent of its business from the oil and gas industry and is also a major supplier to the high-voltage power sector, amongst others.

Citizen Machinery UK, which supplied the fixed-head Miyanos, is also the source of four Cincom CNC sliding-head lathes currently on site, which have been in use at the Prescot factory since the mid-90s. A dozen older models, which took over from six times as many cam autos, have all now been replaced. It leaves three 32 mm capacity Cincom sliders installed since 2014 and a more recent 20 mm capacity model that uses Citizen’s proprietary LFV chipbreaking technology.

Mr Taylor, son of one of the company founders, runs the subcontracting business together with his brother Stewart and sister Natalie Lund. He explained, “Ninety percent of our turnover comes from producing precision turned parts, many of which require a lot of prismatic machining as well, so choice of turn-mill centre is crucial to our success.

“We started to upgrade our fixed-head lathes by replacing them with Miyanos in 2018 in response to an upturn in demand, which gathered pace at the beginning of this year when we bought three more BNE-51MSYs in the space of two months. The 51 mm bar capacity, twin-spindle turning centre with its two 12-station live turrets, the upper one with a Y-axis, is ideal for our needs.

“It is highly efficient at balanced machining of complex routines at both spindles, so we can take chunks out of cycle times, which are between 20 and 40 percent faster than on previous lathes. It meets the increasing demand for the supply of high added value parts at competitive prices.”

He added that other makes of lathe were looked at during the plant renewal process. In comparative trials, the BNE-51MSY offered the quickest TAKT times and was also much better value for money than others he considered. The lathes were also shown to hold 20 microns total tolerance easily on machined dimensions.

One reason for the lathe’s impressive speed is Citizen’s superimposition control technology, which allows the sub spindle to track the upper turret for cutting reverse-end features while the same turret is performing front-end operations on bar at the main spindle. If the lower turret is operational at the same time, three tools are in cut simultaneously, delivering the performance of a triple-turret lathe for a significantly lower capital outlay.

Another benefit that Bryken operators appreciate is their ability with the Mitsubishi control to use the handwheel to run through an entire machining cycle to verify the program and detect any potential clashes.

Over the years, market forces have dictated a move at Bryken towards more fixed-head turning for the production of larger diameter, complex components, the simpler work having largely disappeared overseas. Nevertheless, nearly one-third of the lathes on-site are still of the sliding-head variety. The four Citizen Cincom models are the most recently installed, three M32-VIII lathes and an L20-XIILFV, the cardinal numbers representing maximum bar diameter.

The latter machine, installed in May 2018, was bought to produce sub-sea oil and gas components from tough materials such as Monel, Inconel, titanium alloy and 440C stainless steel. These metals produce stringy swarf that benefit greatly from the low frequency vibration (LFV) functionality built into the operating system of the Mitsubishi control.

Mr Taylor continued, “We saw a demonstration of LFV in Citizen’s Bushey showroom and were impressed with the way chips break up and do not clog the machine, or wrap around the component or tool. It means we can leave the machine running unattended for long periods.

“LFV can be simply switched on and off by G-code in a program. We use it for turning at the main spindle and axial drilling at the sub spindle of the L20 and switch it off to maximise metal removal rate when milling with the live tools.

“We tried making parts from these exotic materials on other sliders but the swarf was not chipping, even with high pressure coolant. Tool life was so poor it was taking away a lot of the profit. Now cutters last at least twice as long, plus there is less machine downtime and scrap is more or less eliminated.”

Low frequency vibration technology has started to be rolled out across the Miyano fixed-head lathe range with the introduction of the BNA-42GTYLFV and Mr Taylor is keeping a close eye on this development. He pointed out that subcontractors rarely know the orders that will be coming in next and which materials they will be asked to machine. As LFV is not a pecking macro that tends to prematurely wear out tools, but is integral within the control system, having this built-in chipbreaking capability is of great benefit when machining stainless steels, copper and plastics as well as the nickel and titanium alloys.

Mr Taylor concluded, “We source a lot of lathes from Citizen because they have a wide range of machines that use advanced technology. We also receive good support from them, especially the applications engineering and training they provide. They and their equipment have made a big improvement to our operational efficiency.”

LUBRICATION EQUIPMENT MANUFACTURER PRODUCES PRISMATIC AND PRESSED PARTS ON NEW LATHE

Established in 1942, Coventry-based Adams Lubetech is member of a leading European group of specialist manufacturers of single-point and centralised lubrication equipment for OEMs in the food and beverage industry, compressor and conveyor sectors, and across industry in general.

Consistently rising sales worldwide meant the company needed extra production capacity. So in early 2020 the firm purchased its first lathe from Citizen Machinery, a fixed-head Miyano BNJ-51 turn-mill centre, to machine not only rotational parts but also components that were previously produced on a manual mill or a power press.

Eric Chambers, Factory Manager at Adams Lubetech explained, “With these parts in mind, we wanted a powerful, rigid turning centre that was equally capable of milling. We selected the Miyano bar automatic primarily due to its competitive price.

“The first purely prismatic component we produced on it was an anchor block for our sister company in Belgium. We were milling and drilling the steel blocks manually in several operations, which was time-consuming, so we decided to use the Miyano as a chucker to produce them automatically.

“The support provided by Citizen’s applications engineers was brilliant. They helped us enormously by developing the process, writing the program, and setting up the machine including replacing the chucks and jaws to fixture the part. They even came on site for three days to oversee production of the first-off components.”

The lathe effectively doubles as a CNC machining centre in this application. Each part, which has large threaded holes and smaller diameter holes machined into multiple faces, comes off the machine complete in a cycle time of 139 seconds.

The Miyano is also taking work from a power press in the Coventry factory, resulting in even greater advantages. A deep-drawn part previously required seven sequential operations, removal for skimming on a capstan lathe and return to the press to be slotted. Lead-time was more than one month to produce a typical batch of 8,000 and there was a lot of manual intervention for inter-machine handling. The same part is now produced in one hit from bar on the twin-spindle Miyano in 2.5 minutes, so the entire batch can be finished and shipped in a fortnight if the job is left to run 24/7.

Mr Chambers concluded, “We operate in a global marketplace and need to reduce costs internally to compete. Production equipment like the Miyano, which has reduced cycle times on average by 20 per cent and has expanded the variety of parts that can be machined, is helping us to keep manufacturing costs down.”

USED SLIDING-HEAD LATHE RECEIVES FULL SUPPORT FROM THE MANUFACTURER

Despite starting out more than 25 years ago, Dudley-based TWP Manufacturing opened its CNC machine shop as recently as the beginning of 2019 to produce in-house most of the components needed for its proprietary products. They include photographic darkroom and studio equipment, gardening products including wheelbarrows, and security anchors. The firm also provides subcontract pressworking and injection moulding services to a wide range of industries, particularly the automotive sector.

Vertical machining centres and a single-spindle, fixed-head bar auto are to be found on the shop floor, but in May 2020 the company bought its first sliding-head twin-spindle lathe, a 20-year-old Citizen Cincom M32 equipped with an Iemca Boss 432r barfeed. It was originally sold in 2000 by the Japanese manufacturer’s agent for the British and Irish markets, NC Engineering, which in 2008 became a wholly-owned subsidiary, Citizen Machinery UK.

Phil Stanley, a director of TWP Manufacturing said, “We were previously outsourcing the production of a lot of our turned parts, including to subcontractors in the Far East.

“However it became apparent that, the way we were expanding, it would be necessary to bring component manufacturing in-house to cope with the higher volumes as well as to have more control over production.”

To fulfil the predicted quantities, the company recognised that it needed a turning centre with more speed and capability than its fixed-head lathe without driven tools, as when using this machine there was frequently a requirement for additional operations.

Sometimes a component needed to be parted off and inverted in the chuck if it required machining on the reverse end. If milling and drilling were involved, they had to be accomplished by setting up the job on a machining centre. Furthermore, many components formerly required manual depipping, adding a lot of labour cost content to their production.

None of this is necessary on the Cincom. It is able to synchronously and automatically transfer a component from the main spindle to the counter spindle for back-end machining while front-end operations are carried out simultaneously on a new length of bar. Prismatic features are added in the same cycle using live cutters and the tool carrier’s Y-axis. Components come off the lathe pip-free after parting off due to close control over the machine’s spindle speeds and feed rates. Production times have drastically reduced from, for example, 3.5 minutes down to a single one-minute cycle without any manual intervention, allowing parts to go straight to plating.

Director Phil Stanley added, “The speed and surface finish we are achieving are just incredible and the fact that there is no operator intervention means that we are able to implement lights-out production, which we are looking to do later this year.”

In the first few of months of operation, the Cincom M32 was devoted to large volume production of one particular component but another four part numbers have now been added. All are machined from 1 inch hexagonal steel bar and annual production will exceed 200,000-off.

Pre-sales time studies and cutting trials carried out by Citizen Machinery UK showed that all five components could be produced within tolerance at the required speed. The calculations were carried out following a visit by managing director Edward James and regional sales engineer Warren Garratt to the Dudley factory, during which the company was advised on how best to proceed with its in-house turned parts production strategy.

Mr Stanley concluded, “Even though the machine was 20 years old and we bought it independently on the second-hand market, from the outset Citizen have been behind us.

“First they demonstrated the same type of machine in their showroom, which I would say was a light-bulb moment for us, following which they wrote the first program and carried out a cycle time calculation, repeating the same procedure for four further components.

“They supported us through machine installation and commissioning, helped with tooling, setting-up and maintenance, and trained us to operate the lathe and their Alkart CNC Wizard programming system.

“If their assistance had not been forthcoming, without a shadow of a doubt we would not have been able to progress, especially as some of our operators have never used a machine like the Cincom before.

“The support we have received all the way through these processes has been brilliant and has enabled us to take a massive step up the ladder in respect of in-house production of turn-milled components.”

PLASTICS MACHINING SPECIALISTS INVEST IN SLIDING-HEAD LATHE WITH NOVEL CHIPBREAKING SOFTWARE

Gloucester subcontractor Stratos Precision Engineering, a majority of whose business comes from machining plastics, has strengthened and diversified its turning department with the addition of its first sliding-headstock lathe, a Citizen Cincom L32-VIIILFV. Installed in September 2019, the twin-spindle, 35mm capacity, bar-fed turn-milling centre joined an already impressive plant list of five fixed-head, single-spindle chucking lathes for turning parts up to 650mm in diameter.

Purchase of the 7-axis CNC Swiss-type lathe was part of an investment of more than £1 million since the fourth quarter of 2018, which has also seen the arrival in Gloucester of a new big bore lathe and a 3m x 2m automatic tool change CNC router as well as refurbishment of the 8,000 sq ft premises. During the same period, the number of staff has doubled to 16 and in the last financial year, turnover increased by nearly 50 per cent over the previous 12 months.

Stratos’ managing director Jonathan Caple said, “For some years we had been looking at buying a bar-fed lathe to increase our competitiveness, win new business and enter new industries by machining larger quantities of parts with tighter tolerances. We favoured the sliding-head type over fixed-head lathes, as the short axis movements lead to higher productivity.

“The twin-spindle configuration and extensive driven tooling on the machine means one-hit production often supersedes two or three operations on different machines.

“However, to reap the full benefits of the investment, we need to be able to leave the machine to run 24/7 either unattended or with reduced labour overnight to maximise production output.

“That was previously impossible for us due to the stringy swarf that is produced when machining plastic, which regularly needs to be manually cleared by an operator.”

The situation continued until 2016, when Citizen invented and patented its LFV (low frequency vibration) software. Part of the operating system in the Mitsubishi control of Cincom machines, and switchable on and off if required during the program, it vibrates the servo axis in the cutting direction so that the tool tip leaves the surface of the material being machined for regular, ultra-brief periods.

The effect is to break the long strands of swarf normally generated when turning plastics into short lengths of just a few millimetres, preventing it from birds-nesting in the machining area and melting back onto the workpiece, which normally means scrapping the part.

A recent trend in the subcontractor’s business has been a shift to machining more metals, notably aluminium for a large packaging machinery contract but also ferrous metals including stainless steel. This material also results in stringy swarf forming around the tool and workpiece and therefore benefits greatly from using Citizen’s chipbreaking software.

Mr Caple and Stratos’ co-owner, operations director Mark Vine, recognised how beneficial LFV technology would be for the business when turning plastics. Unlike metals, whose finish can be adjusted by fettling after machining, this is not practical with plastic as it needs to come off any machine tool in a finished condition.

The importance of improving turn-milling efficiency to increase competitiveness was reinforced when Stratos was required to produce 2,000 parts over a short period and the existing machinery would only achieve 400 per day. However with the new sliding-head machine and LFV technology, Stratos is now able to produce the 2,000 parts in 48 hours.

With a new sense of urgency, the directors’ research took them to MACH 2018 and to online testimonials from other users. A series of demonstrations at Citizen’s technical centre and showroom in Brierley Hill decided the directors in favour of LFV over other chipbreaking methodologies that involve macros in the program. Additionally, as Mr Caple pointed out, Cincom machines are built from the ground up to withstand the high-frequency, low-amplitude vibration caused by the intermittent, chip-generating cutting action.

The transition on the shop floor at Stratos to the new turning technology, as well as to the first Mitsubishi control on site, has been seamless. One of the sliding-head lathe operators, who normally runs five machining centres at the Gloucester facility, quickly picked up programming of the L32 using Citizen’s Alkart Wizard off-line software. He and others received two days’ instruction at Brierley Hill, followed by a week of on-site operator training. In the period from machine installation to the end of January 2020, more than 30 jobs had been produced on the new lathe, which included some around-the-clock running.

A major benefit of a twin-spindle lathe is the ability to produce components machined at both ends in a single cycle that would otherwise require two separate operations. This is assisted by the availability of a multitude of tools including driven cutters that enable the inclusion of extra operations such as deburring, eliminating further subsequent processes.

Speed of production is consequently much higher on the bar-fed Citizen compared with the fixed-head chuckers. For example, a 400-off contract that used to take a full day is now finished in a couple of hours on the slider. It also means that Stratos often manufactures in bulk, as the bar does not need to be changed as frequently as for multiple jobs. Stratos can now run, say, 1000-off, deliver 400 to the customer and stock the remainder on consignment. The customer benefits through more flexible supply and the certainty of prompt deliveries, while Stratos gains through more economical cost-per-part manufacture, which is passed on to the customer through improved rates and prices.

Another recent example of accelerated production was the machining of 5,000-off steel pins for a chain conveyor, which was completed in five days working a single shift. The job would previously have needed two operations on a pair of chuckers requiring two operators. Either the contract would not have been economical or the margin would have been unacceptably small.

Mr Vine concluded, “The accuracy and surface finish we are achieving on the slider are fantastic.

“We recently ran the machine unattended around-the-clock with LFV, with coolant running to keep the temperature stable, and produced 3,000 Ultem® Polyetherimide thermoplastic parts for a customer in the flow control sector.

“All of them were within the required -0 / +0.05 mm tolerance band, which is impressive and can be difficult to achieve in this material, without having to make any adjustments whatsoever to the machine.

“Overall, our new machinery has enabled us to be a more competitive subcontractor for plastic and metal machining and is contributing towards the impressive growth of our business.”

PUMP MANUFACTURER INSTALLS FIRST SLIDING-HEAD LATHE

Two-year payback expected by bringing subcontracted work in-house

One of the UK’s largest pump manufacturers shipping more than 200,000 units per year, Charles Austen Pumps (www.charlesausten.com), has invested in its first sliding-headstock bar auto, a Cincom L20-X from Citizen Machinery UK (www.citizenmachinery.co.uk). It was installed in the OEM’s Byfleet factory in June 2019 and has taken over the turn-milling of parts up to 25 mm diameter, the vast majority of which are brass. A few aluminium, stainless steel and plastic components are also produced.

Established nearly 75 years ago by Charles Austen, the company is credited with inventing the diaphragm pump, which in the 1950s helped John Enders develop the polio vaccine. The firm’s products later assisted the development of Concorde and the Apollo 15 mission to put a rover on the moon. A wide range of pump types is now manufactured and the firm has been so successful that growth over the last six years has been an amazing 30 per cent per annum, driven by strong home sales and a buoyant export market.

Naturally that has put a strain on all areas of the operation, not least the machine shop. While prismatic metalcutting including the milling and drilling of parts for pumps, as well as injection mould manufacture, is largely carried out in-house, the two fixed-head, 57 mm bar capacity CNC lathes on site struggled to cope with the production volumes of rotational parts. The result was that lately as much as two-thirds of the turning requirement was subcontracted out at a cost of more than £100,000 per year.

Machine shop manager at the Byfleet facility Matt Wright commented, “More than 80 per cent of our turned components are between 16 and 19 mm in diameter, so we needed a lathe of relatively small bar capacity to start bringing work back to our factory. Our bigger lathes are not so efficient when machining these smaller workpieces due to their longer tool movements and slower axis travels.

“We considered fixed-head as well as sliding-head technology, as our parts are generally short compared with their diameter. We concluded that sliding-head turn-milling would be more productive because the tools are mounted on gang posts rather than turrets, so are quicker into the cuts as they have less distance to move. Also, as we do not need to use the guide bush the bar remnants are shorter, saving money on material.

“Should we ever need it, we also have the flexibility of quickly installing the guide bush for true Swiss-type turning of shaft-type workpieces over 2.5D.”

He advised that they initially reviewed most of the sliding-head lathe providers and said that their choice of Citizen was primarily down its reputation for quality machines and for providing good applications support, training and after-sales service, which since the L20-X was installed he describes as “brilliant”.

A selection of turn-milled components for the OEM’s pumps was taken to the machine supplier’s Bushey technical centre, where their engineers recommended the best machine for producing the parts. This was deemed to be the twin spindle L20-X turning centre in optional, oversize configuration capable of machining bar up to 25 mm in diameter. An Iemca barfeed for three-metre stock was also supplied as well as a workpiece conveyor.

Standard features of the machine include up to 44 cutters including rotary stations on the gang, opposing and back tool posts, with Y-axis movement of the first two tool carriers. The LFV version of the machine with its patented, 2-axis CNC chipbreaking software in the control’s operating system was not needed, as free-cutting brass is mainly machined at Byfleet.

Batch sizes produced on the Cincom vary greatly from ones and twos for the R&D department up to 10,000-off. The first job on the machine was a brass cam that ran continuously for 96 hours, from Monday morning to Thursday evening. Machined in one 105-second cycle to tolerances down to + 10 / -5 microns, including in-cycle engraving for traceability, the part previously needed two operations taking three times longer, plus additional handling for manual chamfering and stamping. Matt advised that machine attendance was minimal during the day and non-existent overnight. When he arrived at the factory the next morning and measured the parts, all were not only within the 15 microns tolerance band but right in the middle of it.

Another brass component, this time a 19 mm diameter disc-type part just 0.6 mm thick, saw its two operations in 2.5 minutes reduced to one 50-second cycle – another three-fold saving – plus elimination of handling. A third example, a double eccentric with an offset hole and an offset spigot with a 5-micron limit, is now produced in under three minutes instead of five, including engraving which previously had to be done manually. Surface finish on all parts coming off the L20-X is noticeably better, according to Matt.

An element of the service provided by Citizen Machinery prior to delivery of the lathe was the provision of programs for machining two components. Since then, the Cincom machine operators including Matt’s son Ryan have been using the supplier’s Alkart CNC Wizard programming software. It is easy to learn and a simple process to cut, modify and paste elements from the original programs and add new blocks for other features using the wizard’s G-code and M-code library built into the software.

Matt concluded, “We are already bringing turned parts manufacture back in-house and that will accelerate in the coming months. We have hundreds of component variations lined up to put on the L20-X. By Easter 2020, we should be turn-milling them all in our factory.

“With the amount we have been spending lately on subcontracting services, I calculate that the Citizen Cincom slider will pay for itself in a little less than two years.”

Chance purchase of a second-hand lathe triggers transformation of subcontractor’s machine shop

When a customer of subcontractor Apsley Precision Engineering suddenly stopped manufacturing components in-house, one of the redundant machine tools, a Miyano fixed-head, twin-spindle, single-turret lathe, was purchased by the contract machinist’s managing director, Peter Aymes.

Its arrival in 2012 on the shop floor at the company’s 12,000 sq ft facility in High Post, near Salisbury, heralded the start of a big improvement in CNC turning capability. Following the purchase of two more second-hand Miyanos, August this year (2019) saw the arrival from Citizen Machinery UK of the first new model, a BNJ-51SY twin-spindle, twin-turret lathe with a Y-axis.

Mr Aymes said, “We were aware of this make of bar auto and knew they rarely come onto the second-hand market, so we were lucky to be able to buy the first machine, a BND-51S twin-spindle lathe with live tooling in the turret.

“Compared with our single-spindle, bar-fed lathes without driven tools, it approximately halved cycle times for machining parts up to 51 mm diameter. Generally we were able to start producing components in one hit rather than two or three operations, reducing handling and work-in-progress.

“That in turn improved accuracy and allowed us to manufacture more cost-effectively, so we became more profitable. It is difficult to overstate the improvement the machine made.”

Another notable benefit was that an operator could set the Miyano and walk away for long periods to carry out other tasks, as it is unusual to have to change offsets owing to the consistency of machining. That is not the case with the subcontractor’s other bar autos, which tend to occupy an experienced setter for much of the time, raising the labour cost content of manufacture.

Based on all these advantages, a second Miyano BND arrived one year later. Purchased at auction, it turn-mills parts from bar up to 42 mm in diameter but is otherwise similarly specified to the first machine. Despite being 12 years old at the time, it was and still is capable of holding tolerances down to ± 5 microns, which Mr Aymes describes as “amazing”.

He continued, “By that time it was abundantly clear just how good these machines are. They are heavy, compact and very robust, which leads to high accuracy, repeatability and reliability. They need very little money spent on them for repair, so cost of ownership is low.

“It is rare to operate a machine that is almost completely trouble-free. With the Miyanos, that applies to the electronics and electrics as well as the mechanics.”

The third Miyano to be installed at the High Post factory, in 2015, was a second 42 mm machine of similar age acquired from another subcontractor, this time a BNJ model with two turrets. It was bought to cope with the increasing amount of work these machines were generating and to exploit the higher productivity possible due to the presence of a second turret to serve the sub-spindle while the other turret operates at the main spindle. It resulted in higher production output, better prices for customers and shorter delivery lead-times.

With a view to increasing production output still further, as well as to access the latest technology and provide back-up for the 51 mm capacity lathe, the subcontractor’s first new Miyano, a BNJ-51SY, was delivered in July 2019 by Citizen Machinery UK. As its designation implies, the machine has additional Y-axis movement on the main turret that is proving invaluable for machining off-centreline and providing flexibility and accuracy of milled features.

Mr Aymes cited one component that is produced much more efficiently with this feature. It is a tubular, thin-wall aerospace part machined from solid 304 stainless steel bar of 38 mm diameter. It requires a blind, longitudinal hole to be drilled and bored and the outside diameter (OD) to be turned to leave two lugs. Not only does the Y-axis allow the lugs to be drilled in-cycle, instead of the component having to visit a machining centre for completion, but by being able to program both Y-and C-axis movements into the OD turning, cutter deflection is minimised and accuracy is improved. As the component is required in batch sizes ranging from 200 to 800, the benefit is considerable.

Even more advantageous with the new machine, however, is the ability to take advantage of ghost-shift running, which is theoretically possible with the other Miyanos but practically not feasible due to the absence of load monitoring to detect worn or broken tools and automatically stop the machine.

The latest lathe, with its fail-safe features and reliability, is regularly left to operate unattended overnight. So also is a multi-pallet, 5-axis machining centre added to Apsley’s prismatic machining department in April 2018. Mr Aymes predicts that these two machines will pay for themselves faster than all the others on the shop floor. He asserts that if a production centre is capable of running lights-out and is of the right quality, rapid amortisation renders the initial purchase price much less important.

When Citizen installed the latest lathe, it also supplied the subcontractor with the latest version of its Alkart CNC Wizard programming software. It assists and simplifies the creation of even complex cycles using a built-in G-code and M-code library plus reference material and diagrams. Inexperienced users in particular benefit, such as Apsley’s Jay Pritchard, who is halfway through a four-year mechanical engineering apprenticeship. He said he finds the wizard useful when operating the new Miyano if his mentor is not available and the relevant manuals are not to hand. It also helps with understanding how to use the machine.

Founded in 1984 by Peter Aymes’ father Graham, the subcontract engineering firm has always split its machining approximately half and half between turning and milling. Key sectors supplied with high tolerance, complex parts and assemblies are aerospace, defence, medical and pharmaceutical. Non-kanban batch size is typically in the range 20 to the low hundreds and the company also operates a toolroom facility for smaller batch runs, prototype production and the manufacture of tooling and fixtures.

However, one-third of the company’s business derives from supply of components and assemblies just-in-time, providing price stability through the ability of the subcontractor to produce much larger quantities for consignment stock, with customer call-off typically at a rate of 1,000 pieces per week.

TWIN-SPINDLE TWIN-TURRET LATHES ARE IDEAL FOR HYDRAULIC COMPONENT PRODUCTION

A second pair of Miyano BNE-51MSY turn-mill centres from Citizen Machinery UK has been installed at contract machinists Unicut Precision, Welwyn Garden City. Joining two identical twin-spindle, twin-turret lathes with live tooling and a Y-axis on the upper turret supplied at the end of 2017, they form the mainstay of highly efficient production of complex components for the hydraulics industry, which accounts for a large proportion of Unicut’s business.

Established in 1990 by 24-year-old Jason Nicholson and a partner, who has since left the company, in a double garage in East Barnet with £5,000 to spend on second-hand manual and cam-controlled machines, Unicut has been a turned parts subcontractor for most of its existence, progressing to CNC turning in 1993. However, in 2017 the company diversified into prismatic machining with the purchase of a multi-pallet machining cell, followed quickly by a second. A third cell is now on order for delivery later in 2019, which will be a record year for capital investment at £2.3 million.

Over the years, Mr Nicholson has bought 104 CNC lathes, 93 of which were either Citizen Cincom sliding-head models or fixed-head lathes from Miyano, which merged with Citizen in 2011. Today, Unicut operates 22 Cincom lathes with up to 13 CNC axes, 80 cutting tools and 2,000 psi coolant pressure, as well as eight Miyano machines deploying up to 72 cutters. The machines are usually replaced every five to seven years to take advantage of the high residual value of the lathes at that age.

While turning machines have been sourced mainly from this supplier, each purchase is rigorously analysed by Mr Nicholson with respect to machine cost and achievable cycle times to ensure lowest cost per part produced and the most rapid return on investment. Ease of machine integration and use and the desired quality of component are also paramount considerations. Additionally, prompt provision of service is an important deciding factor.

1999 saw the first Cincom sliding-head lathe delivered to Unicut, a 12 mm bar auto, and within a year three more were installed followed three months later by a 32 mm model. The first Miyano appeared on the shop floor in 2002. The CNC lathes replaced cam-controlled turning machines, which had all gone by 2003. CNC equipment was by then achieving similar cycle times to cam-type lathes, with the added advantages of higher quality and unattended running including overnight, leading to much higher profitability.

To distinguish Unicut from other subcontractors, Mr Nicholson decided early on to adopt a different business model by approaching OEMs, analysing their main cost drivers, investigating the possibility of re-engineering components for more efficient production, establishing desired cycle times, identifying machine tools needed to machine components within those times and then proposing to make the required capital investments, subject to the manufacturer’s commitment to a fixed-term contract. Strategic supplier status is what Unicut seeks in its business relationships with customers and 80 per cent of throughput at the Welwyn Garden City factory is produced on this basis.

For machining larger diameter parts, a 51 mm capacity Miyano costs about the same as a top-end 32 mm Cincom slider. Unless a high component length-to-diameter ratio dictates otherwise, Mr Nicholson prefers the fixed-head option based on a number of factors including rigidity, thermal stability, value for money and speed. Bar capacity is greater, offering more flexibility; spindle power is higher, leading to increased productivity; cycle times are comparable; access is easy for setting up, despite the compact machining area; and the Mitsubishi control supports superimposed machining whereby three tools can be in cut at the same time, a facility regularly used at the Welwyn Garden City facility for elevated levels of productivity.

Once a BNE-51MSY is set, Mr Nicolson said that it will produce a run of say 1,000 components to very high accuracy without having to touch the machine by the simple expedient of including macros in the program to offset tools automatically after a predetermined number of parts have been produced. Tolerances down to ± 2 microns can be held and surface finish is described as impeccable. He favours the Mitsubishi CNC system fitted to Miyano and Cincom lathes due to its flexibility and ease of operation using the drop-down menus and comprehensive graphical support. Citizen’s off-line Alkart Wizard software helps to ensure jobs are quickly into production. However, for larger production runs, time can generally be cut from a cycle by tweaking the program at the control.

Citizen’s operating system in the CNC system fitted to one of Unicut’s Cincom sliders features patented LFV (low frequency vibration) software that operates in two CNC axes simultaneously, allowing stringy swarf to be broken into shorter chips of a length to suit the material being cut and the swarf conveyor. The feature is popular with operators, as it enables uninterrupted production without having to stop the lathe due to birds nests clogging the workpiece and tools.

Citing a 320 stainless steel part that was previously impossible to run unattended even during the day, yet is now routinely left to run lights-out with LFV, Mr Nicholson said, “The feature is easy to use and does not require any special skill set. The software can be switched on and off, either manually or within a program, and parameters can be adjusted. It is especially good for processing plastics unattended as well as other difficult-to-machine metals such as Duplex and titanium. It just works.”

In conclusion, he shared his thoughts on the current buoyancy of the subcontract machining sector due to the weakness of the pound against overseas currencies. It has cut 20 per cent off the price of components that Unicut exports and has boosted turnover, despite raw material and indeed the equipment on which to machine it being more expensive to buy. The firm’s first order from China was delivered in August this year and exports overall currently account for 40 per cent of turnover, up from 10 to 30 per cent in previous years.

CITIZEN’S NEW 32 mm SLIDING-HEAD LATHES HAVE LOW FREQUENCY VIBRATION SOFTWARE

Two new sliding-headstock, twin-spindle, turn-milling centres of 32 mm bar capacity have been added to Citizen Machinery’s Cincom programme. Designated L32-X LFV and L32-XII LFV, both feature the firm’s patented, low frequency vibration software in the control’s operating system that acts in two axes to convert what would normally be long, stringy swarf into short, more manageable chips. It is particularly helpful when machining stainless steels, plastics and copper and can be applied not only to turning but also to grooving, thread cutting and drilling.

Unlike the two other L32 bar autos in the range, the 8-axis L32-X adds a Y2 axis to the Z2 axis on the back tool post. So also does the 9-axis L32-XII, which additionally has +90 / -45 degree B-axis swivel on the front gang tool post, whose rotary tools can work at either spindle to produce angled holes. Both machines are available in 35 mm and 38 mm bar diameter versions and all may be used with or without the guide bush to suit the application.

The new L32 design is modular, enabling a user to optimise their manufacturing costs by selecting functions that achieve the ideal machine configuration for their needs, while retaining the option of being able to add extra functionality later. A workpiece conveyor is standard equipment. Control is by the Industry 4.0-ready Mitsubishi 800 CNC system, which allows up to three tools to be in cut at the same time.

Up to 44 tools for front, back and cross machining are available in the -X model, while the B-axis -XII version accepts four fewer. Speed range of the 3.7 / 7.5 kW main spindle and 2.2 / 3.7 kW counter spindle is up to 8,000 rpm. Both have a C-axis for use in conjunction with driven tool stations in the three tool carriers. Fast acceleration of tool rotation up to 6,000 rpm minimises cycle times. Rapid traverse in the linear axes is 32 m/min except in Y2, which moves at 24 m/min.

VERSATILE BAR AUTO IS HIGHLY PRODUCTIVE

A new, twin-spindle, 10-axis CNC turn-mill centre, the Miyano BNA-42GTY LFV, has been introduced by Citizen for manufacturing complex components in one hit from bar stock up to 42 mm diameter. The hybrid machine is of fixed-headstock design, but the head is also able to move in and out of the working area for extra versatility, similar to that offered by a sliding-head machine operated in non-guide bush mode.

The 8-station, 3-axis turret including Y-axis movement has a half-indexing mechanism that allows tools to be mounted at up to 16 positions, while multiple toolholders can further expand the number of cutters deployed. There is also Y-axis travel on a gang toolpost, giving extra flexibility when machining at either spindle, especially as the counter spindle moves in the X-axis as well as the Z-axis.

In total, up to 45 tools can be resident in the working area. A superimposition function within the Mitsubishi M730VS control provides the possibility for shortening cycle times even more by enabling up to three tools to be in cut simultaneously at both spindles.

The 3.74-tonne BNA-42GTY enjoys the same rigid, high precision build and thermo-symmetrical design as other lathes in the Miyano range, leading to high accuracy machining. Slideways are hand scraped in all axes and have exceptional damping characteristics, enabling heavy metal removal and helping to prolong tool life. Machine specification includes a 6000 rpm / 11 kW main spindle with 0.001° C-axis, a 5000 rpm / 5.5 kW C-axis counter spindle and feed rates up to 30 m/min.

Numerous options are available to add to the flexibility of the turning centre, including high-pressure coolant, spindle air blow, chip conveyor, parts catcher, parts conveyor and drill breakage detection. Likewise, the capable control can be augmented with the addition of helical interpolation, corner radiusing, synchronous tapping and multiple canned cycles.

The BNA-42GTY is the first Miyano machine to gain the benefit of Citizen’s LFV chipbreaking software, until now exclusively provided on the manufacturer’s Cincom Swiss-type lathes. The patented, two-axis chipbreaking functionality is part of the control’s operating system and involves the axis servo drives and spindle drives.

The position of the tool tip is oscillated by 20 microns, just sufficient to break the swarf. The number of oscillations per revolution (mode 1) or the number of revolutions per oscillation (mode 2) determines the length of the swarf removed from any type of material. The user can define the exact chip length in the program, giving the ability to choose the optimum size for the swarf conveyor to handle efficiently.

The more exotic and difficult to chip the material, the more effective LFV is. It means that high pressure coolant is not needed to assist in breaking long stringy swarf, such as that generated when machining such materials as stainless steel, copper and plastic. So it is no longer necessary to stop the cycle to remove accumulated swarf that is hampering the machining process. Shorter chips also take up less room in the swarf bin, so it needs emptying less frequently.

In some applications, particularly when processing exotic materials, productivity can be increased fivefold due to not having to stop the machine repeatedly to clear swarf that has entangled itself around the tool or workpiece, or both.

With LFV there is an element of air cutting, which allows more coolant to access the point of contact between the tool and the material. Enhanced coolant penetration lowers the operating temperature of the tip, so it can last five or even 10 times longer. This is especially the case if, as frequently occurs on other makes of CNC lathe, a chipbreaking macro has been written into the program. These are notorious for causing rubbing of the tool, built-up edge, machining inaccuracy and premature failure of the tip.

An LFV oscillation results in a turned face that is no longer flat by an amount measured in microns. The machine control knows where the oscillation took place and on the second revolution the high spot on the face is turned away. If required, on the third revolution the tool will finish that process to eliminate the waviness completely at that location.

As an element of air cutting – albeit miniscule – is introduced by LFV, productivity can be slightly reduced when the function is switched on. However, it can be turned off at the control, allowing the possibility of maximum output during attended day shifts when an operator is present to clear swarf. It may be, however, that these machine stoppages lower production output by more than LFV.

Switching the function on at night allows a ghost shift to be instigated without fear of swarf build-up automatically halting production during unattended running. So a manufacturer is virtually guaranteed a full shift’s worth of good components on arrival the next morning.

LATHE WILL PAY FOR ITSELF IN 18 MONTHS

Installation by Citizen Machinery of a fixed-head Miyano BNE-51MSY twin-spindle, twin-turret turning centre at electrical wiring conduit manufacturer ABB Cable Management Product, Coleshill, heralds a fundamental change in the way the company turn-mills its cable end fittings.

Cycle time savings of up to 70 per cent with more to come, reductions in manufacturing cost, scrap and returns, and elimination of the need to outsource 10 per cent of production to subcontractors will combine to amortise the cost of the Miyano well within 18 months of its installation at the beginning of January 2019. Manufacturing unit manager Andrew Fellows describes this payback time on a major item of capital expenditure as “brilliant”.

Every week, 100,000 metres of flexible metal conduit and 65,000 metres of nylon conduit find their way predominantly into the automotive, rail and mining industries across Europe, the Middle East, China and as far afield as Australia, while some are destined for installation in the parent group’s robot systems. From these numbers it is clear there is a high demand for the mainly brass fittings, plus some stainless steel, aluminium and plastic varieties, that are needed at both ends of every length of conduit.

Fittings needed in large volumes are produced in-house on six cam-type multi-spindle autos, while the shorter runs are completed on four single-spindle, single-turret CNC lathes and now the Miyano twin-spindle, twin-turret turning centre, which replaced a similarly specified, ageing model on which one of the turrets was defective.

Comparing the performance of the latter two lathes, Mr Fellows advised, “In the first two weeks of the Miyano arriving, we transferred onto the new machine the manufacture of four fast-moving products, all of which benefitted from drilling on both end faces simultaneously at the main and counter spindles.

“Average cycle time saving was 59 per cent. The largest reduction was 70 per cent in the case of a fitting that previously required 133 seconds to produce. The turn-mill cycle now takes 40 seconds to complete on the Miyano.”

Senior operator Dan Gardner added, “We have only taken advantage so far of cutting with two tools at a time, but the superimposition function in the Mitsubishi M730VS control, coupled with Y-axis movement of the upper turret and X-axis travel of the counter spindle, allows three tools to be in cut at the same time.

“After five days’ training from Citizen, both on- and off-site, we carried out a time study on a complex fitting that will see an 80 per cent reduction in cycle time from 230 to 46 seconds.”

He went on to describe a further benefit that comes from the ability to have 6,000 rpm live tools with 20 Nm of torque at all stations in both turrets, a total of 24 positions. Whereas 85 per cent of production on the single-spindle lathes is currently from hexagonal bar, the plan is to reduce this to zero in favour of round bar over the coming years as the machines are upgraded and powerful driven cutters are able to mill the flats economically. This process is starting with the Miyano.

The main advantage will be longer service life of the lathes and of the bar magazines feeding them due to the absence of interrupted cutting of hexagonal stock and hence lower vibration levels. In the case of the Miyano, it will also allow round bar at the full 51 mm diameter capacity to be rotated in both spindles at the maximum speed of 5,000 rpm, whereas it would need to be backed off by 75 per cent to run the largest possible size of hexagonal stock. For this reason, such material currently machined on the BNE-51MSY at Coleshill is restricted to 38 mm, which can be rotated at full speed.

Mr Gardner advised that despite utilising mainly hexagonal stock at present, the rigidity provided by the Miyano machine’s bed, hand-scraped box slideways, spindles and turrets is nevertheless sufficient to allow total tolerances down to 30 microns to be held on fittings, a level of accuracy needed for explosion-proof and watertight conduits.

Data collection and display on dashboards of overall equipment effectiveness has been instigated by Mr Fellows since his arrival at the factory in July 2018. Optimisation of every aspect of around-the-clock production has resulted in 24 per cent more output in five days than was achieved before in seven days, lowering manufacturing cost by 17 per cent and raising competitiveness.

Installation of the Miyano, with its elevated level of productivity, will improve these figures further. So also will the imminent arrival of a presetter for off-line tool setting, which will cut two-thirds to three-quarters off the present 60-minute changeover time for the next batch run, which can be as low as 50-off.

According to Mr Fellows, selection of the Citizen Miyano BNE-51MSY was down to the capital cost being 30 to 40 per cent less than two alternatives considered by ABB Cable Management Product, in line with company policy. Lead-time from order to delivery was also the shortest at just 12 weeks.

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