Building on the strengths of previous generations of Miyano fixed-head mill-turn centres, the BNA-42SY is Citizen Machinery’s latest addition to the range. The CNC lathe is the first BNA model to have a 12-station turret giving ± 35 mm of Y-axis movement, all tool positions now being live, and a new design that lends itself to easy automation.
Compared with current BNA models, machining efficiency has been upgraded by more powerful spindle motors, which are rated at 7.5/5.5 kW (15min/cont) for the 6,000 rpm main spindle and 5.5/3.7 kW for the 5,000 rpm sub spindle. Acceleration and deceleration are quicker on both spindles, improving productivity further by minimising idle times.
The machine’s rigid bed, the weight of which has been greatly increased to 1,823 kg, brings thermal control advantages and more capacity to house a larger coolant tank. The base casting has been prepared with space at the right hand side for robotic load / unload equipment. If a user intends to take advantage of automation, the machine can be supplied with a swarf conveyor that exits to the rear as an option.
The automation may be employed solely for unloading components that have been mill-turned from bar stock up to 42 mm diameter, either directly from a spindle or via a parts catcher and conveyor. Alternatively, or in addition, it may load and unload billets or near net shape workpieces like castings or forgings up to 135 mm in diameter. A workpiece stocker is positioned at the right hand side of the machine to accommodate the finished components.
Mounting points have been included to provide an option to add an overhead gantry if only chucking is to be carried out, in which case a raw material stocker can be positioned to the left of the machine in place of the bar magazine. For complete flexibility in layout, top shutter and auto door options are offered.
At 285 mm, the turret’s Z-axis travel has been increased by more than 20 percent, expanding the machining range of this compact, space-saving lathe. The turret and spindles are mounted on hand-scraped box slideways for improved rigidity and damping characteristics, leading to high metal removal rates, prolonging tool life and maintaining high accuracy.
The diameters of the X- and Z-axis ballscrews have been upsized from 25 mm to 32 mm, increasing rigidity further. Forced lubrication is provided to the ballscrews in all axes, the BNA-42SY being the second Miyano lathe to benefit from this feature.
The latest FANUC 0i-TF Plus CNC system with 10.4″ colour LCD screen controls the machine. Cutting times can be shortened by simultaneously completing complex reverse-end turning and milling at the sub spindle while front-end machining is ongoing at the main spindle, despite there being only one turret. It is achieved by superimposed machining, where the sub spindle tracks the turret and compensates for its movements while it is cutting at the main spindle, enabling a machining cycle on a parted-off component to be executed using tools mounted on the reverse face of the turret. This can be accomplished due to the ability of the sub spindle to move in the X-axis.
As with all modern lathes from Citizen Machinery, both Miyano fixed-head and Cincom sliding-head models, the BNA-42SY is an environmentally friendly machine. Use of an inverter controlled hydraulic unit results in a large reduction in power drawn. Standby power consumption is just 0.661 kW, as servomotor readiness is automatically turned off when it is not needed, for example during program editing. Overall energy consumption can be visualised via a power monitor window on the control screen.
When physics graduate Paul Cobb asked his father Reg in 1997 to help him invest in a subcontract machining business specialising in CNC sliding-head turning, Mr Cobb senior groaned; he knew it would mean a sizeable investment. At the time, both father and son were partners in the family’s subcontracting firm in Stapleford, Hemlock Engineering, which specialised in producing mainly prismatic parts and continues to do so.
However, Paul was keen to embark on a project of his own. He chose not to become a computer programmer or geological analyst but instead started HPC Services. A small factory unit was rented in nearby Ilkeston and a Japanese-built Citizen Cincom L25 sliding-head, bar-fed, turn-mill centre was installed. At the time it was the first of a new, updated design to arrive in the UK.
From that moment onwards, HPC’s approach has been to acquire the very latest, most highly productive CNC equipment available on the market, designed to slash production times, reduce costs and improve component quality. Under Paul’s influence, it has become Hemlock’s maxim as well.
Over the intervening 24 years, he has bought for HPC around 20 CNC sliding-head, twin-spindle lathes of nominally 12, 20 or 32 mm bar capacity, all exclusively from the same supplier. Ten Cincoms are in operation, the others having been systematically replaced with newer models. There are also seven fixed-head, twin-spindle CNC lathes on the shop floor of the current premises, where around 30 staff are employed.
When Paul launched HPC, he took with him from Hemlock one production job to get him started, a shaft for a sell-by date label printing machine. The food industry still accounts for around one-third of HPC’s turnover. The job previously involved turning the component in two operations, after which it was ground and then milled on a machining centre, all in a total time of seven minutes. On the Citizen L25, the same job was completed in one hit in a one-minute cycle. The parts are machined today on a different slider at a rate of 1,000 per month.
Due to complete machining in one set-up, the components produced by HPC were of better quality, 5 microns concentricity and 10 microns dimensional tolerance being held reliably. Moreover, the price charged to the customer has consistently fallen in real terms due to the progressively higher level of automation on the newer lathes, which allows longer periods of unattended running, 24/7.
Paul commented, “Over the years, turned parts subcontractors from around the world have quoted for this work. However, by harnessing the efficiency and accuracy of machines like the Cincom sliders we are globally competitive on price as well as quality, even for large production volumes.
“In the past that was not the case, but it is possible now with modern, ultra-high speed plant. And of course, our delivery times are much better than Far Eastern competition can offer, added to which control over projects is easier. As a result, we are seeing a strong trend towards reshoring of work.”
Today, HPC has some 5,000 different part numbers on its books. Components are produced from 38 mm diameter bar or smaller on the Cincoms. Quantities range from 100- to 40,000-off in a vast range of materials, from exotic alloys through stainless steels, brass and aluminium to plastics. The two million parts machined annually account for two-thirds of the company’s £3 million annual turnover, the remainder being fixed-head turning. 10 percent of revenue is reinvested every year in new plant and equipment, a proportion that also applies to Hemlock’s £7 million turnover.
Fifth generation Cincom M32 lathe increases productivity by typically 30 percent and quadruples tool life.
One of the latest components produced at HPC in one hit on a sliding-head lathe requires only milling, there being no turning content at all. The parts are being machined on one of a pair of recently delivered Cincom M32-VIIIs of a radically different design compared with the earlier M32s on site. The first of the new machines was delivered in November 2020 and Paul was so impressed with its performance that a second arrived a month later.
The prismatic component looks as though it has being machined from flat bar but is in fact milled from 303 stainless steel round bar, as it is difficult to source flat bar in that material in the UK. Part of a date-coding machine, it is produced in one operation in a cycle time of 4 minutes 53 seconds on the lathe, whereas it would require four operations totalling 7 minutes on a vertical machining centre.
A year or so before the arrival of the two new M32s, which have been supplied with kits to allow bar up to 38 mm diameter to be accommodated, the chief designer from Citizen’s Japanese factory visited HPC to ask Paul what he would like to see in the fifth generation of this sliding-head lathe. His response was, “more rigidity”. The Japanese manufacturer obliged, endowing the latest model with box guideways rather than linear slides, a tang instead of a worm drive on the turret and higher power motors throughout.
Paul explained, “The difference is amazing. It is possible to machine exotic alloys at double the speed compared with on a fourth generation M32 and you get four times the tool life, especially as coolant is now delivered through the tool platen as well as the turret.
“It is a massive step up in performance. A 10 mm cutter purrs into the bar, even using a mill with carbide inserts rather than a solid carbide tool, which we need to use on the earlier M32s. Any production engineer would know that the new model is a very rigid machine.”
Other aspects of the latest design that he appreciates are the increased number of driven tools and a platen tool post with a programmable B-axis. It is useful for producing angled features on components and additionally is able to carry out front working so that the turret can be freed up earlier to perform operations on the reverse end.
Cycles for many jobs are significantly quicker. For example, when producing a particular 303 stainless steel flange from 38 mm bar, it was previously necessary to wait for the turret to become available to deburr the component. At 57 seconds the cycle time is now 25 seconds quicker, representing a saving of 30 percent.
Just as important for reducing production costs is the ability to swap the machine over in half an hour to guide bush-less mode to save remnant wastage when producing relatively short components like the flanges. In this case, 262 parts can be produced from a 3-metre bar compared with 225 if the guide bush is in place, delivering 37 extra parts, an increase of 16.4 percent. With 5,000 of the flanges produced annually, the saving is significant.
Programmable chip breaking software is ideal for turning plastic
Citizen’s advanced technology came to the rescue a few years earlier, when HPC received a contract to produce plastic internal components for a manufacturer of high quality taps. Moulding these top-end parts is not feasible, as flash on the sealing surfaces could cause leakage and removing it would be too time-consuming. Turn-milling the components from acetyl bar was the preferred method of manufacture, but plastics are notoriously difficult to machine, as copious quantities of long, stringy swarf is produced, especially when grooving.
Citizen had recently invented its patented, low frequency vibration (LFV) software that breaks such swarf into short, manageable lengths. Running in the Cincom’s Mitsubishi control, where it is integrated into the operating system rather than being a macro, the facility can be switched in and out of a programmed cycle by G-code command.
Paul concluded, “LFV on the Cincom L20 we bought in 2017 is absolutely brilliant for turning plastic. Normally on a lathe we regularly have to remove swarf by hand that has tangled around the component and tooling, which takes ages and risks damaging the part, but that is eliminated by the software.
“It not only saves a lot of production time but also allows us to run the lathe unattended for long periods, which normally would be impossible when machining this type of material. The software will also be a big advantage if we receive contracts for producing components from ductile, long-chipping metals such as copper.”
Citizen Machinery UK, which supplies Cincom sliding-head and Miyano fixed-head turn-mill centres into the British and Irish markets, has been providing manufacturing solutions to OEMs and subcontractors in their supply chains for virtually the entire time the company has been in business. However, the degree of customisation that it is being asked to engineer into the equipment it supplies has now reached such a high level that it has decided to centralise this side of the business by setting up a dedicated centre, CMSolutions, at its Bushey headquarters.
Managing Director Edward James said, “As the largest supplier of bar fed lathes into the markets we serve and being a specialist exclusively in turn-milling, we felt it was fitting for us to raise the bar in terms of the level of support customers can expect.
“In our industry it is no longer enough to deliver a so-called turnkey package, which is subject to a lot of interpretation and often misunderstood. It can mean simply the supply of a machine, a few cutters and a couple of programs.
“Customers demand more than that these days. They want a fully worked out, end-to-end solution that has been proven off-site before delivery, complete with attachments, peripherals, in-house-written software and perhaps additional robotic functions such as cleaning and packaging. Projects are often demanding in terms of their scope, level of innovation, the process capability to be achieved and return on investment required.”
CMSolutions operates from the Bushey premises independently from the applications department there to project-manage such complex, high-level installations, from initial consultation through design, configuration, assembly and prove-out to delivery, acceptance and training.
The solution could be stand-alone or integrated into a larger manufacturing plant; and it may be a pre-existing package or designed specifically at either the customer’s request or at the instigation of Citizen. In all cases there will be a sound business case for what is delivered. It will be pragmatic, process-optimised and cost-effective, not necessarily the top solution possible, which may be overly expensive and take too long to amortise.
The Bushey venue will also house a permanent exhibition of turn-mill solutions and software, which will often involve automation such as robotic or gantry loading of billets, forgings, and near net shape parts and unloading of components. Additionally, it will show technology that is less frequently encountered, such as in-cycle laser cutting of apertures in the thin wall of a stainless steel stent.
Other specific solution examples to be presented will include the mounting of a digital microscope and a 21-inch screen to assist setting of micro tooling on a 12 mm capacity sliding-head lathe used for watch component manufacture; and the provision on a 32mm capacity sliding-head lathe of a pair of high frequency, 60,000 rpm spindles in the gang toolpost, together with mounting adapters, pneumatic and electrical supplies, custom software and displays for spindle speed feedback.
Mr James added, “We could see the direction of travel towards the need for a greater degree of machine adaptation to meet customers’ production requirements, so we have had this development in mind for several years. It was part of the justification for establishing our Turning Centre of Excellence in Brierley Hill last year.
“The showroom and technical centre there is now the main location for machine arrivals, configuration and despatch, leaving Bushey free to concentrate on technology advancements and their permanent display and demonstration.
“Customers are looking for stable running of their lathes over long periods. We already have our LFV non-macro chipbreaking software to assist in that goal, which is programmable and especially beneficial when cutting materials that tend to produce stringy swarf. It is another example of the importance and focus Citizen places on technological progress.”
As a postscript, he mentioned that Citizen as a group reinvests one-quarter of its annual profit into research and development and is continually launching new machines and technology, such as LFV, which has been extended recently from the main spindle to the sub spindle on many Cincom lathes and is increasingly available on the Miyano range of fixed head lathes also. Another recent innovation is an automatic tool changer on the L20 Cincom sliding-head model.
There will be a significant and ground-breaking new launch in the first half of 2021 of a lathe designed by Citizen Machinery UK that the Japanese parent company has agreed to manufacture. All of this activity dovetails neatly with the formation of CMSolutions, which Mr James predicts will gain in importance as manufacturing industry moves forward after the pandemic and looks for ever more efficient methods of production and return on investment.
He also thinks that opportunities will be enhanced by increased reshoring of manufacturing from China and elsewhere, coupled with the emergence of electromobility, which will be beneficial for Citizen and other lathe suppliers in particular, as plug-in hybrid electric cars contain a higher proportion of rotational parts than conventional vehicles.
Components are becoming more and more complex and drawing tolerances ever tighter. The ability of live turret tooling in a CNC mill-turn centre to move in the Y axis as well as in X and Z has therefore become increasingly important to facilitate high accuracy, one-hit machining. If travel in only the latter two axes is provided, milling of flats, deburring, and the possibility of machining pockets and off-centre features in-cycle are either difficult or impossible.
The latest Miyano fixed-head lathe from Citizen Machinery UK to be equipped with a Y axis turret, in this case with all 12 tool stations driven, is the new BND-64SY for turning parts from bar up to 64 mm diameter. Joining a similar model that accepts bar up to 51 mm diameter through the main spindle, the 4.75-tonne machine is a mid-range, multi-purpose, twin-spindle turning centre. A ribbed, monobloc bed slanted at 30 degrees carrying precision-scraped, square guideways provides high rigidity, optimal thermal and mechanical stability and excellent vibration damping.
These characteristics result in high accuracy of mill-turned components and longer service life of the tools, which may be mounted flexibly in the turret using multi-tool holders at any turret position. The robustness of machine construction allows turning as well as milling of tough alloys and metals in their hardened condition, even when taking intermittent cuts. Polygon turning and thread milling are both options in the FANUC 0i-TD control, which is capable of simultaneous 4-axis interpolation.
The specification of the Japanese-built machine includes turret travels in X / Y / Z of 175 / 75 / 435 mm, 530 mm sub spindle axis travel, up to 20 m/min rapid feed rate, 2.2 kW / 20 Nm / 6,000 rpm driven tools, a 15/11 kW main spindle and a sub spindle rated at 5.5/3.7 kW, both offering rotational speeds up to 5,000 rpm. A parts catcher and conveyor are supplied as standard, while the chip conveyor is optional.
Japanese CNC mill-turn centre manufacturer, Citizen Machinery, has announced improvements to three of its Cincom sliding-head models, all designed to shorten cycle times and raise productivity when producing components from 32 mm diameter bar and larger. The machines are available in the UK and Ireland through subsidiary company Citizen Machinery UK.
LFV added to the M32
The company’s flagship M32 model, which can produce parts from bar up to 38 mm in diameter with cutters in a gang toolpost with B-axis, a 10-station turret and a back tool post with Y-axis, has gained the manufacturer’s low frequency vibration (LFV) chipbreaking capability on the main spindle.
It makes the machine ideal for efficient turning, threadcutting and drilling of malleable materials, as the normally stringy swarf is broken automatically into shorter chips that do not wrap around the tool or workpiece, without any need for high pressure coolant. Productivity is maximised by avoiding having to stop the machine repeatedly to remove clogged swarf, facilitating minimally attended operation and enabling lights-out running.
Embedded in the operating system of the Mitsubishi M800-series control, LFV synchronises the motion of the axis servo drive with the speed of rotation of the main spindle. The function is highly controllable, as it can be programmed using G-codes to switch on and off during a cycle and either increase or decrease the size of the resulting chips. It is distinct from traditional pecking macros in a CNC program which tend to cause built-up edge, compromising machining accuracy and shortening tool life.
Other notable features of the lathe are simultaneous 5-axis machining, up to three tools in cut simultaneously and the possibility to change over in half an hour to use the machine in guide bush-less mode to reduce remnant length when turning shorter components.
Cincom L32 with LFV on both spindles
In line with Citizen Machinery’s systematic rollout of LFV on all its Cincom sliding-head turn-mill centres as well as currently on one fixed-head Miyano lathe, the 32 mm bar capacity L32 slider has also benefitted from the chipbreaking technology. It already had LFV on the 3.7 / 7.5 kW main spindle but now it boasts the same capability on the 2.2 / 3.7 kW sub spindle.
LFV oscillation of the tool by tens of microns not only breaks swarf but also allows coolant to penetrate the cut more efficiently for the brief periods when the tip lifts clear of the component surface, reducing heat and prolonging tool life. Depth of cut may be increased substantially even when processing tough materials, often eliminating the need for a roughing pass and significantly shortening cycle times.
In addition to the 7-axis L32-VIII, there are two other L32 models 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 a +90 / -45 degrees B-axis on the front gang tool post, whose rotary tools can work at either spindle to produce angled features. All machines are available in 35 mm and 38 mm bar diameter versions and may be used with or without the guide bush to suit the application.
D25-VIII expandable to accept 32 mm bar
Turn-milling of components up to 32 mm diameter bar with the extra productivity benefits of LFV is now also possible on the nominally 25 mm capacity Cincom D25-VIII, as an expansion kit is being offered to enable the lathe to machine the larger size of bar in both guide bush and non-guide bush modes.
Manufacturers of larger components may therefore take advantage of the lathe’s Industry 4.0-ready Mitsubishi 800 CNC system with touch screen and QWERTY keyboard. It provides the ability to have up to three tools in cut simultaneously for increased productivity and enables simultaneous 5-axis machining to maintain precise cutter orientation with respect to the surface of a complex workpiece.
The machine is equipped with twelve CNC axes including independent Z2-axis movement in addition to X2 and Y2 on the rear gang toolpost. Twin platens enable balanced turning, threading, milling or drilling, or simultaneous rough and finish turning. A 135-degree swivelling B1-axis has been added to the X1 and Y1 motions of the front tool post, which carries up to four driven tools on either side to service the main and counter spindles, a configuration Citizen Machinery believes is a world first.
A manually-set angular spindle can be mounted on the rear gang carrier and the back toolpost. In addition to the major advantage of programmable control of chip size, LFV has the ability to help eliminate deflection when turning small, precise diameters. An optional, two-axis, opposed tool carrier next to the counter spindle provides a facility for deep hole drilling at the main spindle.
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.”
Complex components up to 65 mm in diameter may be turned and milled from bar on a new Miyano fixed-head lathe launched by Citizen Machinery UK. The 8-tonne BNE65-MYY is equipped with two turrets having Y-axis travel in addition to X- and Z-axis movements. One turret is positioned above and the other below the centreline of the twin-opposed spindles and both tool carriers have 12 live stations. A C-axis on each spindle and movement of the sub spindle in X and Z bring the bar auto’s CNC axis tally to 10.
The 2-axis movement of the sub spindle facilitates superimposed machining, whereby tooling on both faces of the top turret can simultaneously cut front-end features on the bar stock and reverse-end features on a parted-off component. With the lower turret also working at the main spindle performing pinch turning, milling or drilling, for example, or perhaps OD turning while axial drilling is in progress above, three tools are in cut at the same time.
Together with the double Y-axis movements, the configuration provides great flexibility to balance front and back working cycles with considerable precision, maximising production output by not having one spindle waiting around for the other to finish.
Contributing further to high productivity are fast rapid traverses up to 20 m/min, plus main and sub spindles with generous power ratings of 18.5/15 kW (30min/cont) and 11/7.5 kW (15min/cont) respectively. As both spindles rotate at up to 5,000 rpm, productive turning is maintained even when machining smaller diameter sections of a workpiece. Rotary tool specification is also impressive at 4 kW / 6,000 rpm.
The slant-bed design encourages efficient chip flow so that production can continue uninterrupted. Lapped slideways have been adopted for all but the cross motion of the sub spindle to ensure a high level of rigidity as well as effective vibration damping for delivering maximum cutting performance and precision together with long tool life.
Control is by the Mitsubishi M830W, which has a new HMI with a 15-inch touch-screen control for convenient operation, including on-screen selection of the turret tooling. Intelligence built into the control simplifies programming, especially of superimposed cycles by automatically synchronising those sections of the program. A new colour scheme has been adopted that is said to convey information more efficiently to the operator.
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.”
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.”
When turning long-chipping malleable materials, Citizen’s low frequency vibration (LFV) software fragments swarf into manageable chip sizes, whereas normally it would become a stringy bird’s nest entangled around the tool and component. The latest sliding-head bar auto on which the technology has been made available is the new Cincom A20-VIILFV, while it can also be found on one of the company’s Miyano fixed-head models.
All machines have been fundamentally redesigned with uprated ballscrews, lubrication system, guarding and other elements to provide additional strength for withstanding the oscillation caused by very short periods of intermittent air cutting that produce the chipbreaking action. Productivity is maximised by avoiding having to stop the machine repeatedly to remove clogged swarf, facilitating minimally attended operation and enabling lights-out running.
A further advantage is the avoidance of the need to fit a high pressure coolant system to encourage swarf breakage, which involves high capital investment and increased running costs.
Embedded in the operating system of the control system, the chipbreaking software synchronises axis servo drive motion with the spindle speed. The software version on the A20 is suitable for longitudinal and face turning as well as drilling and involves multiple oscillations per revolution of the main spindle. The function is highly controllable and can be programmed using G-codes to switch on and off during a cycle, as required.
This is distinct from the functionality being part of the program itself, as is the case with alternative CNC pecking macros, which have the disadvantage of rubbing the tool. It raises the temperature, causing workpiece distortion as well as built-up edge on the tool, shortening its life.
In contrast, LFV oscillation of the tool by tens of microns allows coolant to penetrate the cut more efficiently for the brief periods when the tip lifts clear of the component surface, reducing heat and actually prolonging cutter life, in some instances by as much as five-fold. For the same reason, depth of cut may be increased substantially even when processing tough materials, often eliminating the need for a roughing pass and significantly shortening cycle times.
The Cincom A20-VIILFV can be used with a guide bush as a conventional Swiss-type automatic for machining shaft-type workpieces, or without a guide bush for producing shorter parts from less expensive stock with minimal bar remnant wastage. The guide bush can quickly and simply be mounted and removed. In sliding-head mode, machining length per chucking is a generous 200 mm to reduce cycle times when producing long, slender components.
The 7-axis A20 machine platform, which is capable of 2-axis simultaneous cutting, offers a high performance-to-price ratio for the production of parts from 20 mm diameter bar, optionally extendable to 25 mm (1 inch). The main spindle is rated at 3.7 kW / 10,000 rpm for optimal machining of smaller diameter stock and has an opposed 1.5 kW / 8,000 rpm sub-spindle with an X2-axis enabling simultaneous machining on the front and reverse ends of components. Both spindles have one-degree indexing and a 0.001-degree C axis.
Tool capacity is 21, with four driven stations for cross machining having a maximum speed of 6,000 rpm. The four back tool post stations may optionally be live. Positioning speed is fast at 32 m/min for short non-cutting times. Idle times can be reduced further using the pre-processing function in the Fanuc-based Cincom control dedicated to this machine model. It analyses the machining program before it is run to minimise processing and calculation times.