Citizen Machinery UK has supplied six of the sliding-head CNC lathes most recently installed at the Wishaw, near Glasgow, factory of turned parts subcontractor Swissmatic. Ian Corbally, son of the company’s founder Jim, says it is principally because the Japanese-built, bar-fed, turn-milling centres have many outstanding attributes, in particular their reliable productivity even when left to run unattended and their low power consumption.
Trouble-free lights-out machining is largely down to Citizen Machinery’s low frequency vibration (LFV) chip-breaking functionality, which is especially effective when machining malleable materials. Built into the Mitsubishi control’s operating system, LFV breaks what would otherwise be stringy swarf into short, manageable chips, without lengthening run times by inserting macros into cutting cycles. It prevents damage to the workpiece and/or tooling and avoids the need for an operator to be in attendance to clear accumulated swarf periodically from the working area. It is a decade since LFV was rolled out globally and the sliding-head turning community is now well versed in its merits.
Less familiar are Citizen Machinery’s environmentally-friendly technologies, Eco II and EcoBalance (see descriptions below). In a similar time period since the mid-2010s, one of the most significant changes in manufacturing has been the inexorable move towards reducing the power consumption of machine tools. The issue is now viewed just as seriously as a machine’s productivity, since geopolitical tensions and shifting energy markets have caused the price of electricity to skyrocket, especially in the UK. Due to the negative impact this has on profit margins, what used to be a minor afterthought has morphed into a major consideration.
Mr Corbally is adamant that energy efficiency is “100 percent” at the forefront of Swissmatic’s purchasing decisions and has been for many years. It is factored into the total cost of owning each item of capital plant and heavily influences purchasing decisions. It is noteworthy in this connection that in October 2023 the subcontractor installed 319 solar panels on the factory roof, which have reduced by about a quarter the power drawn from the grid, averaged over a 12-month period.
The latest Citizen Cincom sliding-head lathe to arrive on the shop floor in Wishaw was a Series 2 L32-XII B5 LFV with a B-axis swivelling tool carrier, the first of its type to be installed in the UK and one of only a few that currently sport the newly-upgraded 4-axis LFV capability. Operating in X and Z at both spindles simultaneously, it removes the need to compromise by switching the function in and out by G-code at one spindle only.
Replacing a less advanced, 32 mm diameter bar capacity sliding-head lathe, the 9-axis CNC machine features +90 / -45 degree B-axis rotation of a driven tool post positioned at the far end of the front gang tooling, enabling full 5-axis simultaneous machining. For maximum versatility, the rotary tools can work at either C-axis spindle to produce angled features. The lathe is also capable of superimposed machining, which uses a master-slave relationship between linear feeds of the sub spindle and the tool carriers to lower cycle times through the ability to have more than one tool in cut at the same time.
Before this machine was installed, the previous two Cincoms purchased by Swissmatic were M-series lathes having gang tool posts and a rotary turret with 10 driven tool positions. The latter is not a feature of any other make of sliding-head lathe in the Wishaw factory, which means that Citizen is the preferred supplier of such machines for more complex production applications. An M32-VIII LFV was delivered in mid-2022 and a smaller M16-VIII LFV arrived at the end of 2023.
Two years prior, a pair of 12 mm bar capacity Cincom L12-VII LFVs was acquired to fulfil a contract for the production of medical components from plastic bar, a material that accounts for about a quarter of Swissmatic’s annual throughput. The lathes were the first on-site with LFV and proved highly effective for producing parts 24/7 unattended, without the formation of birds-nests of plastic swarf risking having to stop production. Among the other materials processed in the Wishaw factory that routinely benefit from LFV chip-breaking are 304 stainless steel, aluminium and a small amount of copper.
Summing up the benefits of using Cincom lathes, Mr Corbally commented, “We have been using Citizen’s sliding-head turning machines since 1981, one year after my father started the business. They began replacing cam-type lathes and rotary transfer machines, which were finally phased out here 17 years ago.
“Jim had used this brand of lathe in a previous job and we have installed 22 of them over the years, although with our policy of continuous plant renewal, there are currently six on the shop floor, all but one with LFV.
“We manufacture components ranging from one-off prototypes to production runs of more than two million and the versatility of the Cincoms suits this activity perfectly.
“The lathes operate minimally attended or lights-out, 24 hours a day, seven days a week, yet scrap rate is vanishingly small at less than a quarter of one percent, despite having to hold tolerances down to four microns total.
“The low power consumption is also important for us to keep electricity bills down and Citizen has taken this to the next level with the latest eco features built into its lathes.”
About the energy-saving characteristics of modern Citizen lathes
Eco II is Citizen Machinery’s proprietary suite of intelligent energy-saving technologies integrated into its Cincom lathes, as well as its Miyano fixed-head turning centres. Acting as an environmental management dashboard and utility regulator integrated into the Mitsubishi control, the embedded software automatically reduces the consumption of electrical power and compressed air when the machine is idling, rather than allowing the servo motors to remain continuously powered up.
The software monitors the lathe’s operating status in real time. If a standby state with no programmed movement is detected, power to the servos is cut automatically and auxiliary systems are put to sleep, with both waking up instantly when a cycle resumes. In respect of compressed air consumption, one of the most expensive utilities on a factory floor, Eco II tackles waste in two ways.
First, as a continuous blast of full-pressure air is not always needed, the machine uses a smart pulsed air delivery system that works in targeted intervals, maintaining full effectiveness for part ejection, collet or tool taper cleaning, parts catching and other functions, while lowering compressed air consumption by up to 60 percent.
Second, the machine’s internal air purge system is automatically shut down after a preset time whenever the lathe falls into standby mode. Additionally, the base level pneumatic demand has been reduced from 0.5 MPa to 0.4 MPa, yielding a reduction in general factory air consumption of up to 20 percent, without sacrificing actuation power.
An operator is able to access a live touchscreen graphical interface with real-time displays of active electrical power consumption versus peak maximum thresholds, cumulative carbon dioxide emission, historical utilisation graphs tracking the ratio of cutting time compared with setup times and alarm stops, and how much kinetic energy is captured and regenerated into electricity as the spindles decelerate and the axes undergo braking.
Eco Balance is the lathe manufacturer’s branding and certification standard for its green initiatives. It encompasses several pillars, not only the above-mentioned energy reduction measures, as well as the elimination of power-hungry hydraulics, but also further electricity-saving strategies like shutting down internal cabinet lighting, screen backlights and auxiliary fans alongside servo motor sleep cycles when the machine stops moving.
For a Citizen lathe to be designated an official Eco Balance Machine, it must prove it balances high productivity with a reduced environmental footprint, verified by measurement of reductions in electrical power and compressed air usage compared to previous machine generations. This overarching philosophy forms the basis for ESG (environmental, social and governance) auditing, an anti-greenwashing process that verifies a machine manufacturer’s claims of environmental protection.
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