Author: Luke

Glenn Poleykett began his career in manufacturing in 2006 at his uncle’s firm, making components for darts on Cincom sliding-head and Miyano fixed-head mill-turn centres. They are built by Citizen in Japan and sold in Britain and Ireland through subsidiary company Citizen Machinery UK. He quickly realised that sliding-head lathes with driven tooling were capable of producing virtually any part, provided that it was from 32 mm diameter bar or smaller, whereas fixed-head models were incapable of machining shaft-type components to tight tolerances.

Twelve years on, when he decided to start his own subcontracting business, Stellar Precision Components on the Raynham Road Industrial Estate in Bishops Stortford, he remembered that lesson. He went to the same supplier to purchase two Cincoms, an L32-VIIILFV and an A20-VII. They have since been joined by a third sliding-head lathe, an L20-VIIILFV, which arrived on the shop floor in April 2020.

Mr Poleykett said, “In the intervening years I worked at a number of subcontractors on various makes of slider, but I always regarded Citizens as the best machines.

“My opinion was reinforced when a few years ago the manufacturer introduced its patented LFV (low frequency vibration) operating system software in the Mitsubishi control system.

“It is programmable via G-codes to start and stop during any program, breaking what would normally be stringy swarf into smaller chips that cannot wrap around the tool or component and damage them.”

He witnessed LFV in action at Citizen’s UK headquarters and technical centre in Bushey before he bought the first two lathes and described the functionality as “incredible”. When machining short-chipping metals such as mild steel, 303 stainless and brass, he does not employ the function as it is not needed and the extremely short periods of air cutting slightly lengthen cutting cycles.

However when turning and drilling 304 or 316 stainless, aluminium, copper and plastics, he always turns on the function for at least part of the cycle. It has the effect of greatly improving production output through not having to stop the lathe to clear swarf and by being able to leave the machine to run unattended with confidence. He would have ordered an LFV version of the A20-VII, but it had not been introduced on that model at the time, which is why the machine is devoted to producing components from free-cutting metals.

LFV oscillation of the tool by tens of microns not only breaks the 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, significantly shortening cycle times.

Swapping between the two modes of LFV is a simple matter, according to Mr Poleykett. If the second, more vigorous chip-breaking action is required, for example when cutting plastics, and the other mode has been inserted in a program by Citizen’s Alkart CNC Wizard off-line part programming software, manual insertion of a single line of code at the start and finish is all that is necessary.

It is noteworthy that, as is the case on more and more Cincoms and on some Miyano lathes, the most recent L20-VIIILFV delivered to Bishops Stortford has the chip-breaking functionality on both the main and sub spindle, whereas on earlier models it is applied to the main spindle only. The latest machine at Stellar was purchased for manufacturing ventilator parts for the NHS. Funding through Citizen UK Finance and a six-month payment holiday smoothed the acquisition process at a difficult time.

Much of the subcontractor’s throughput is destined for the aerospace, medical, electrical connector and pneumatics industries. Batch size ranges from 10 to 40,000 pieces and the factory operates 24/7, with two manned shifts per day and three hours of lights-out operation during the early hours of the morning. The security of operator attendance for a majority of the time is needed, as many of the components that the subcontractor produces are of very high accuracy, from a general tolerance of ± 0.1 mm right down to ± 5 microns.

Components up to the maximum bar size can be produced on both L-series lathes either when the guide bush is in place or in guide bush-less mode, the latter being a standard feature of the machines. The L32 was installed with an optional extension kit that allows bar up to 38 mm diameter to be accommodated, higher than the lathe’s nominal capacity of 32 mm. This additional capability is regularly used and has allowed new business to be won.

Mr Poleykett takes full advantage of non-guide bush operation when producing shorter components, as it avoids having to use expensive ground stock. Plastic rod, which is always oversize, can be accommodated as well as unground bar of harder metals on which high spots can catch in the guide bush, alarming out the machine. A further benefit is material savings due to much shorter remnants.

Aerospace component manufacturer reinvents itself during the pandemic

Rugby-based subcontractor Technoset, with 70% of turnover in the aerospace sector, was not a good situation last March (2020) when COVID-19 grounded most aircraft and orders plummeted seven-fold. Towards the end of 2021, the company’s production of aircraft parts is still below one-quarter of previous volumes.

With the business facing an existential crisis, managing director Kevan Kane and the firm’s owners set about restructuring the operation, positioning Technoset as a solutions provider rather than a supplier of components. It also started targeting challenging contracts for the supply of tight-tolerance components to more industries, notably lasers, fibre optics and telecoms.

The success of these policies has seen the number of components going through the shop floor for the first time for both existing and new customers more than treble from 10 to 33%. A large proportion have benefited from design-for-manufacture expertise from Technoset engineers to reduce piece part costs for customers.

The first new machine tool the company has bought since the onset of the pandemic was a highly specified, twin-spindle Cincom M32-VIIILFV bar-fed, sliding-head mill-turn centre, which was delivered by Citizen Machinery UK in spring this year (2021). Replacing two smaller M12 and M16 Cincoms that were about 20 years old, it joined a previous-generation M32-VIII bought in 2017, all numbers representing maximum bar capacity. There are also eight twin-spindle, fixed-head Miyano bar-fed lathes on-site from the same supplier for turning and milling components from stock up to 64 mm in diameter.

A primary reason for acquiring the latest M32 was a need to machine complex telecoms components, in particular a family of 12 mainly aluminium connector parts for use in the defence industry. Many of them are complex, with a lot of milled detail, and drawing tolerances are below 10 microns.

That level of accuracy is achieved reliably, even when running lights-out, partly because the lathe incorporates Citizen’s LFV (low frequency vibration) software in the Mitsubishi control’s operating system. Variants of the LFV function can be called up automatically in any part program to break what would normally be stringy swarf into manageable chips. It is no longer necessary to stop the lathe to untangle and clear potentially harmful swarf from the tool and/or component.

Productivity is therefore maximised, the operator is freed to carry out other tasks on the shop floor and the machine can be left with confidence to run unattended. The programmable chip-breaking software is not only beneficial when machining the aluminium connector parts but will also prove invaluable when Technoset restarts producing aircraft components in significant volumes from Inconel, titanium, Waspaloy, Nimonic and other superalloys, all of which tend to birds-nest when turned and drilled.

In anticipation of acceleration in the return of aerospace work, the subcontractor introduced a second shift in early September 2021. It is to ensure that contracts for aircraft components, which typically involve batch runs of 1,000 to 2,000-off, do not dominate the shop floor and dilute the production of new work that has been taken on in other industries. Consequently, aerospace work at the AS9100-accredited contract machinists is unlikely to exceed 50% of throughput in the future.

Rapid development of turning machine technology

Mr Kane commented “Citizen Machinery’s M32 sliding-head lathe, the manufacturer’s flagship model, has been the most important contributor to Technoset’s business since we bought the first one in 2000.

“Something that has surprised me is the speed with which the machine technology has advanced. Our latest M32 is of the fifth generation, which has been beefed up and completely redesigned since we installed the last, fourth generation model in 2017.

“The result has been a step change in performance. I regard the machine as the epitome of sliding head-technology in terms of productivity, flexibility and speed. It is ideal for mill-turning high value piece parts.”

Improvements to the turning centre include 1.5 times faster live tools powered by a 2.2 kW motor and a programmable, 9,000 rpm B-axis to enable simultaneous machining in five CNC axes rather than four. Combined with the back tool post whose Y-axis now has adjustable-angle tooling, it enables faster production of more complex parts. Superimposed machining allows three tools to be in cut at the same time, further shortening cycle times and raising productivity.

The 10-station turret incorporates a new tooling system employing a single, heavier duty drive, also rated at 2.2 kW, to an increased number of live cutters. Only the selected tool rotates, suppressing heat generation and vibration to enhance machining accuracy and surface finish. As nearly every part that is turned in the Rugby factory also requires prismatic operations such as milling and drilling to achieve one-hit manufacture, the improvements to the driven tool stations are of considerable benefit.

Mr Kane added, “The upgraded specification of the M32, which includes an 8,000 rpm main spindle uprated to 5.5 / 7.5 kW and an identical counter spindle, much more powerful than before, means that the machine is able to match the speed of the M12 and M16 that it replaces.

“Normally, to achieve cost-effective levels of productivity when mill-turning components from smaller diameter bar, you would not put that work on a lathe with double the bar capacity or more, as you would expect it to be slower.

“That is not the case with the fifth generation M32, which means we can consolidate jobs onto one platform. The reduced mix of machines on the shop floor promotes knowledge transfer and helps to mitigate manufacturing’s industry-wide skills shortage problem.”

He singled out Citizen Machinery UK’s engineering backup as worthy of special mention; it is applicable not only to Technoset but also to group member Technoturn, St Leonards, where a similar number of Cincom and Miyano lathes are in operation. Responsive service is appreciated, but especially beneficial is the application support.

Recently, Technoset found itself pitching for work and were stuck on a cycle time of 90 seconds, which was too long to achieve the target price. Mr Kane contacted the supplier’s Bushey headquarters by email and an engineer came back within 24 hours with an application-optimised cycle time of 60 seconds. The one-third decrease resulted in the subcontractor winning the new business.

Looking to the future

Focusing on digitalisation and automation, Technoset’s plans are wide-ranging. The turning side of the business, which currently accounts for around two-thirds of turnover, is already automated through the use of bar magazines. The milling side will take a significant step forward in spring 2022 with the installation of a 5-axis machining centre with built-in robotic component load/unload and on-board part probing. It will be the first automated prismatic component manufacturing cell on-site.

Helping to fund the purchase is a £100,000 Aerospace Unlocking Potential (Aerospace UP) grant recently awarded to Technoset. Delivered through the University of Nottingham and the Midlands Aerospace Alliance, the initiative aims to support the aerospace supply chain in the Midlands.

Part of the money will also be spent on acquiring a CADCAM suite for off-line programming, a function that is currently performed mainly by manual data input at the machines. Consideration will also be given to investment in laser cutting, part marking, a painting facility and special deburring equipment to achieve the high standards demanded by the aerospace and laser industries.

As any manufacturer knows, use of the best machine tools comes to nothing without skilled people to run them. Mr Kane ensures that highly trained setter-operators are always coming through the system by continually taking on apprentices. Thre are progressing through a four-year program with Midland Group Training Services and two are aligned with the programme delivered by the Manufacturing Technology Centre.

“We believe that investment in the very latest technology is the key to quality, reliability and competitiveness,” said Dave Zollo, joint owner of contract machinists IML (UK). He and Jerry Way started the business in 1995 and moved into the current, 14,000 sq ft premises in Weymouth in 2011. One year later the first sliding-head lathe arrived, a Citizen Cincom A32-VII with 32 mm bar capacity, followed in 2013 by a 16 mm bar model, a Cincom C16-VI.

The early investments were triggered by an increase in contracts from the medical industry and a desire to be able to manufacture components in one hit, such as endoscope cleaning equipment parts. To cope with an ever increasing level of work, including for the high-end automotive sector which has grown over the past couple of years to become more than 50% of turnover, there are now four different models of sliding-head lathe on site from the same supplier.

The latest two, designated L20-XLFV and L32-XLFV, were installed in 2018 and 2020. Unlike the first two Cincoms, they offer the flexibility to allow removal of the guide bush, as well as having the notable benefit of low frequency vibration (LFV) software built into the operating system of the control. Mr Zollo noted that the more modern machines are also more user-friendly, allow better access and are quicker and easier to set.

He explained, “These advanced, twin-spindle, sliding-head lathes are helping to keep us competitive on the world stage, as is automation throughout the factory.

“All of our lathes including four fixed-head models are bar-fed and work 24/7, with the sliders able to accommodate a wide range of batch sizes from typically 50- to 30,000-off. Dimensional tolerances of less than ± 10 microns may be easily held.

“Even smaller quantities are economical to produce, partly because we have adopted a policy of standardising on one size of stock on each of the Cincoms, so we do not have to waste time changing over bar sets.

“We have also invested in automation on the milling side of our business, which accounts for more than half of turnover. Our four vertical machining centres are equipped with robotic loading and remote monitoring, while two horizontal machining centres on the shop floor have a twin automatic pallet changer to minimise idle times.

“It all helps to keep costs down and allows us to quote our customers prices that are very similar to those we were charging two decades ago.”

Aluminium bar, which accounts for a significant proportion of throughput of turn-milled parts, is the villain of the piece as regards sliding-head turning in the Weymouth factory. The material is often of variable quality in terms of straightness and diameter variation, so can jam in the guide bush of sliders and requires frequent supervision by the operator to adjust the collet.

The ability to remove the guide bush on the L20 and L32 in less than half an hour allows the subcontractor to turn aluminium bar into shorter components in fixed-head mode without problems. It also has the advantage of reducing the remnant length from typically 275 mm to 100 mm. Completion of one recent IML (UK) contract consumed 300 bars, so it is clear that a lot of material and money can be saved.

When turning difficult to chip materials, Citizen’s LFV software, which is part of the control’s operating system, breaks swarf into manageable chip sizes, whereas normally it would be stringy and entangle itself around the tool and component. This capability to manage the size of swarf is in addition to any chip breaking features that may be ground into an indexable insert. Mr Zollo singles out aluminium as well as stainless steel bar to be particularly problematic in terms of bird’s nesting.

To alleviate it, the LFV function can be switched on and off via G-codes in the part program, enabling optimal use of the feature during different parts of a cycle. It is, however, not a pecking macro in the CNC program itself. As one operator looks after the four sliding-head lathes, LFV is helpful in minimising periodic attendance at the machines to disentangle clogged swarf. It is notable that the 8-axis L32 has LFV on both the main and counter spindles, allowing the oscillations that produce the chip breaking action to assist in the production of both front- and reverse-end turned, milled and drilled features.

LFV oscillation lifts the tool tip clear of the component surface by tens of microns for ultra-brief periods to allow coolant to penetrate the cut more efficiently. It reduces heat and prolongs cutter life, while at the same time enabling depth of cut to be increased, even when processing tough materials. It often eliminates the need for a roughing pass and significantly shortens cycle times. Mr Zollo advised that it is of major benefit during attended day and night shifts and especially so during the weekend when staff are not present.

He concluded, “Swarf build-up is really the only thing that stops modern bar-fed CNC lathes, which are inherently very reliable. LFV on the Citizen sliders virtually eliminates the hassle of clearing away swarf and consequent loss of production, especially during minimally attended operation.

“Even when we are running them unattended at the weekend, it is unusual for them to stop before the bar runs out. Should there be a problem, however, the on-board cameras allow us to monitor production and come into the factory if necessary to take remedial action.”

Father and son team Andy and Owen Phillips, both of whom are pilots and aviation engineering enthusiasts, started a subcontract machining business in Havant in 1994. After four years, they applied their extensive knowledge acquired over many years of building and flying aircraft to transition their firm, Andair, into a manufacturer of fuel system components for light aircraft in the sport, amateur-build and commercial aviation sectors.

The business, which is certified by QAS International and to ISO 9001:2008, is now a leading global producer of such equipment, with 90 percent of its fuel selectors, filters, check valves, gascolators and fuel pumps going to export markets. Regular customers include Cessna, Cirrus, Czech Sport Aircraft, Diamond, Grob, Grumman-Northrop, Rotax/Bombardier, Scaled Composites, Technam and Vans.

Miyano fixed-head, twin-spindle CNC lathes from Citizen Machinery UK have underpinned production of Andair’s turned and milled parts since January 2005, when the first turning centre with sub spindle was delivered to the Havant factory, a 5-axis BND-42S. It proved so efficient that a second, identical model was ordered six weeks later. Fast-forward 16 years and the company has bought a total of seven Miyanos, the latest being the first 80 mm bar capacity ABX lathe to be installed in the UK. It arrived on the shop floor in June 2020 equipped with an Iemca KID 80 short bar magazine.

Andair had been waiting eagerly for the launch of the 80 mm version of this twin-spindle machine with two Y-axis turrets, having since 2015 been producing 3 inch and 2.75 inch diameter components from billet held in a Hainbuch chuck in the main spindle of a smaller ABX-64SYY, of which there are two in the Havant factory. The high requirement for components of this size meant that the lathes were being used for chuck work 60 percent of the time.

Owen said, “Production efficiency of our larger components used to be lower because we could only manufacture a limited number of components from a billet, say five or perhaps seven. In the case of the aluminium body for an oil-air separator we are currently machining, we could only produce one per billet.

“Now all these parts can be machined from bar using the 80 mm capacity lathe, saving a lot of time. It runs continuously throughout the day and although we are not set up for 24/7 operation at present, with this machine and our other Miyano bar autos is it is feasible in the future.”

The other lathes in the factory all have twin turrets and Owen had ordered a similar specification for the 80 mm model. Due to the cancellation of the MACH 2020 machine tool exhibition, however, which should have been held in Birmingham last April, Citizen Machinery had in stock a triple-turret ABX-64THY (80 max dia) 12-axis model with a Fanuc control system that it had intended to launch at the show. Owen was initially hesitant when offered the machine, having never used a lathe of that configuration before, but decided to buy it anyway as it was available immediately. It turned out to be a revelation.

He enthused, “I would not buy another twin-turret machine in future, because having three turrets is so much more productive. I would like a four-turret version if Miyano made one.

“It is no problem to transfer work to the more complex lathe, as a new program can be checked easily using the manual retrace function in the control, avoiding any possibility of interference between tool and workpiece.”

He explained that the two turrets positioned above the spindle centreline, each with 12 live stations, are dedicated to working at the main and counter spindles respectively. The third turret is located below and has unrestricted travel to operate at either spindle to provide flexibility for balancing front and reverse end machining. Three tools can be in cut simultaneously to achieve very high levels of machining efficiency.

About 60 different parts have so far been produced on the new lathe, all from 3 inch diameter bar. In fact, in one instance where a customer required a large valve machined from a 4.5 inch diameter billet, Owen turned the end of it down to 80 mm so that it could be machined in the collet.

In the case of the oil-air separator body, it is now possible to machine five from bar in 30 minutes whereas before, with an operator loading billets manually into the chuck of an ABX-64SYY, it took at least 45 minutes to achieve the same output. In other words, productivity has been boosted by more than 50 percent. A further benefit to Andair is that the two 64 mm bar lathes can now be devoted to the collet work for which they were originally intended.

Another example of where the 80 mm bar machine has introduced benefits is when machining one of the few Andair components the pilot actually sees, a fuel selector fascia plate that requires a very high surface finish, which is achieved on the aluminium part using a diamond tipped tool. The plate is also engraved to indicate which tank has been selected. Previously, after turning it from a billet, a second operation was required on a machining centre to mill material from the reverse and to drill four holes.

The method of manufacture has now been altered, whereby milling and drilling as well as turning are carried out from bar on the Miyano, leaving only a small operation to clean the bore on a separate machine. Cycle time has been reduced by at least two minutes and an operation has been eliminated.

In the case of another component, in fact the first part that was made on the ABX-64THY (80 max dia), all three turrets had almost an identical amount of work to perform. Cycle time is 2 minutes 15 seconds including parting-off and the component comes off finished, whereas previously the cycle was 4 minutes, plus there was a need for a second operation, requiring extra time for both metalcutting and inter-machine handling.

Aluminium accounts for three quarters of throughput at the Havant factory, with a wide range of other materials also machined including brass, bronze, plastics, tool steel and other steels including stainless. Batch sizes are relatively low, normally between 100- and 500-off, so there is a lot of machine preparation.

The Miyanos are quick to set up however, as they have built-in tool setters and programs are prepared off-line using an Esprit CAM system. Typical tolerance that needs to be held is ± 0.02 mm and Owen declared that if it is exceeded on any occasion, it is always the tool that is at fault, as the machines do not move.

He concluded, “I am a big fan of Miyanos. They are very productive, accurate machines and have beautiful spindles that produce excellent surface quality. I wouldn’t look at another make of lathe.

“Support from Citizen has been fantastic, from sales to delivery, installation and commissioning – they are absolutely incredible.”

The first sliding-head turn-milling centre to be installed at the Ferndown, Dorset factory of Air Bearings Ltd (ABL) is a Citizen Cincom L20-VIII LFV. Delivered in June 2019, it has brought in-house the production of nearly all shaft-type components, saving around £8,000 per month previously spent on subcontract Swiss-type turning. As a consequence, the machine paid for itself within 18 months.

Speeds up to 350,000 rpm are attained by ABL’s air bearings, which are used globally in machinery for semiconductor wafer slicing, printed circuit board drilling, and micro-machining applications as diverse as polymer lens manufacture for cataract operations, edge grinding of toughened glass for mobile phone screens, watch component manufacture and milling of coining dies. The high rotational speeds demand that sub-micron tolerances be held on some turned bores and other features of component parts of the air bearing.

This in turn means that operations prior to diamond turning and grinding of the bore and outside diameter must also be very accurate to meet pre-finishing requirements. In this department, ABL operates two vertical machining centres, seven 2-axis chuckers, two multi-axis, bar-fed, fixed-head lathes and now the Citizen L20 slider.

Only top-end machine tools are purchased by ABL to meet the levels of precision required to ensure rotational motion of the air bearing spindle to within a couple of microns. The shaft assembly with its six key parts is especially critical.

ABL’s senior production controller Dave Stacey advised, “Take the collet, for example, produced from 13 mm diameter tool steel bar. The concentricity of the front bore to the taper is tied up to 30 microns TIR (total indicator reading).

“Dimensional tolerances on diameter and length need to be within 50 microns or sometimes 25 microns to allow post machining to sub-micron accuracy, while there is a 6-micron limit in the bore.

“Originally, before our decision to use subcontract services, these collets were machined in-house in two operations – turning and boring on a fixed-head lathe and then drilling of eight radial holes on a machining centre.

“The time-consuming process led to our pre-finishing department only producing the quantity that was needed, which could be as low as 15-off, yet external heat treatment and stress relieving before final finishing still cost £250 a time, irrespective of component quantity.

“Now, with single-hit turn-milling of the collets on the Cincom L20, we run off typically 500, representing three months’ supply, at a fraction of the cost of subcontracting them out, added to which we can take full advantage of the fixed-cost heat treatment service.”

It is a similar story with the other rotational components in the shaft assembly of an air bearing spindle, such as the EN57 stainless steel collet studs and guide pistons, of which there are six variants. All are produced more economically on the slider, as they involve classical Swiss-type turning from bar less than 13 mm in diameter.

The largest part produced on the Cincom L20 is a 250 mm long push rod turned from 16 mm silver steel bar down to 7 mm diameter in one pass. It would not be feasible to turn the component in several passes, as it is longer than the guide bush; while recourse to turning between centres using the sub-spindle would unduly extend the cycle time and leave a witness mark.

Taking a 9 mm depth of cut in this high carbon steel over much of the component’s length is an ideal time to activate Citizen’s patented LFV (low frequency vibration) chipbreaking software in the Mitsubishi control. It allows what would normally be long, stringy swarf to be broken into shorter lengths, the size of which is determined within the program, to avoid birds-nesting around the component and tool and the need to remove the swarf repeatedly from the machining area by hand. Economy of production is greatly increased, as there are no stoppages for swarf clearance, and the lathe can be left to run unattended. Additionally, absence of chatter improves the surface finish on machined components.

Notably, LFV may be switched on and off during a cycle by G-code command, but is not a chipbreaking macro within the program itself. Instead, and distinct from other systems, it is part of the CNC operating system and as such does not compromise tool life.

Mr Stacey concluded, “The Cincom lathe is so fast at producing rotational parts from bar for our air bearings, even with the larger batches we are running, that the machine is often waiting for work during the day.

“We are therefore looking at putting classical fixed-head work onto the machine, parts that are shorter compared with their diameter, which will provide an opportunity to bring further subcontracted turning in-house.

“For this purpose, the ability to run the Cincom L20 in guide bush-less mode to save material by shortening the minimum bar remnant will provide an additional saving.”

At the subcontract machining facility of Witon Engineering, Barnstaple, turn-milling of relatively complex components from 16 mm diameter bar used to be carried out on 32 mm capacity sliding-head lathes, rather than smaller capacity models, to take advantage of the extra CNC axes and tools available on the larger machines. This type of work has now been transferred to a more nimble, 25 mm bar capacity Citizen Cincom D25-VIIILFV sliding-head turning centre, installed in January 2021. The first two jobs have shown significant cycle time reductions of 20 percent or more.

Since the mid-90s, the contract machinist has bought 17 bar-fed lathes from this supplier, of which one was a 42 mm bar capacity Miyano fixed-head machine, the others being various Cincom sliding-head models for turning up to 32 mm stock. There are currently 11 Citizen machines on the shop floor, earlier models having been exchanged over the years. Lathes from this supplier therefore account for approaching half of the 25 of bar autos in the factory, comprising 13 sliding-head models, eight single-spindle fixed-head turning centres and four CNC multi-spindle automatics.

The first component to be transferred to the D25 was an EN1A steel shaft for a lawnmower. The part was formerly produced on an L32-VII, of which there are three on site. As 180,000 have to be produced to fulfil the current contract, the 20 percent cycle time reduction leads to a significant production cost saving.

The second component benefiting from being machined on the D25 is a 304 stainless steel fuel inlet fitting for an automotive customer. It used to be turn-milled on one of a pair of Cincom M32s in a cycle time of 72 seconds. This has been cut to 53 seconds, representing a 26 percent saving. With 55,000-off needed, the economy gained is significant.

Ian Clapp, workshop manager at the Barnstaple factory explained, “We operate a couple of 20 mm capacity, dual-platen sliders of another make and knew this configuration offered quick cycle times.

“However, we saw what our longstanding sliding-head lathe supplier Citizen was offering in the D25, a machine with larger bar capacity plus the ability to carry out work up to 32 mm diameter without the guide bush for more economical material usage when producing shorter components.

“The model also has the benefit of a programmable B-axis, so we decided to go for this option.”

The gang tool platens are in front of and behind the spindle centreline, with Z-axis motion provided on the rear carrier to allow balanced turning, milling or drilling, or simultaneous rough and finish turning. The B-axis on the front post, carrying up to four driven tools on either side to service either the main or counter spindle, swivels by up to 135 degrees. A further feature of the lathe is that three axis groups can be controlled simultaneously by the Mitsubishi 800 CNC system, so three tools can be in cut at the same time.

Another potential benefit of this 12-axis CNC turn-mill centre is that it incorporates Citizen’s programmable LFV (low frequency vibration) chipbreaking technology in the control. It automatically breaks into smaller pieces the long, stringy swarf produced when machining materials such as copper, plastics and high alloy steels. Birds-nesting around the tool and component and the consequent damage that may be caused is therefore avoided. Although LFV cycles have not been included in programs run so far on the D25 at Barnstaple, it is nevertheless there to use when appropriate jobs come along.

Witon Engineering underwent a change of management at the end of 2016 when second-generation owner and managing director Ian Sheldon retired. The firm is now run by Ian’s son-in-law Tom Courtney, who is the general manager and Ian’s daughters, directors Hayley Neate and Gemma Courtney. Operations still predominantly centre on precision turned parts production on CNC lathes, the cam multi-spindle auto shop having closed in 2018. Two 3-axis, vertical-spindle machining centres are also in use.

Large batch runs are the norm: one electrical connector part is produced at a rate of 100,000 per month and even one of the machining centres is currently completing a contract for 500,000-off prismatic components.

Mrs Neate commented, “We are keeping Witon Engineering basically on the same trajectory, with the accent on turning and long periods of unattended running of our bar autos during the day and to the end of a twilight shift finishing at 12.30 am every weekday.

“The onset of the pandemic reduced business early on, especially as work for the automotive sector, traditionally a large proportion of our business, was badly affected. However, we have gained extra contracts in other sectors to compensate, such as parts for lubrication systems and household goods.

“When the automotive work returns, our production throughput will be at a record high and we will carry on investing in top quality plant like Citizen lathes to meet the demand.”