Longing for more lathes
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Subcontractors rarely know what type of work will be coming through the door from one day to the next, so versatility is a necessity to produce a wide variety of components. The diversity of work is particularly large in the case of Repro Engineering with 80% of its turnover deriving from turn-milled parts in the 19 to 51mm diameter range produced from a variety of different plastics, mild and stainless steels.
A large proportion of the turned parts are manufactured on Miyano fixed-head CNC turning centres and Cincom sliding-head models from Citizen Machinery. The first Miyano to be installed was a BND42S twin-spindle lathe with live tooling in 1997 and it departed after 23 years of service, having produced more than 2 million components primarily in one hit lights-out operation. The second Miyano, a BND51S, was bought in 1998 and sold in mid-2022 after an even longer period on the shop floor.
Repro Engineering’s Owner and Managing Director Richard Palmer said: “We have a policy of regularly reviewing our capacity and keeping plant up to date. In the case of the Miyanos, earlier exchange simply wasn’t necessary, as the machines continued to hold tolerance. Not having to spend money on replacing them earlier helps to keep costs down for our customers and makes us more competitive.”
The replacement for the BND51S was a more capable BNJ-51SY, which arrived in May 2022. Featuring two turrets and Y-axis main turret movement, it allows complex machining to be carried out at the main and sub spindles simultaneously. The turning centre also sports many more tool positions than the older model, so fewer tool changes are needed.
Nine Miyano machines have been purchased over the years and many have been replaced by newer models. The subcontractor’s current tally of Miyano bar-fed lathes is five, accounting for nearly half of its fixed-head lathes. Three of the Miyanos have Y-axis function and all are fitted with short bar magazines for feeding one-metre stock up to 51mm diameter. Additionally, the subcontractor operates a Miyano LZ-01R chucker for billet work, especially components that need hard turning.
Regarding Repro Engineering’s sliding-head capacity, the subcontractor operates three Cincom lathes for parts up to 32mm diameter. Impressed with the quality and longevity of the Miyano machines, Mr Palmer decided to approach Citizen for larger Swiss-type lathes capable of producing bigger diameter shaft-type components. He purchased a Cincom A32-VII in 2009, followed by a more highly specified M32-VIII with a B-axis in 2013, and another A32-VII two years later.
Repro Engineering also operates four machining centres, which generate the other 20% of turnover. One machine is part of an automated cell with robot loading and some are equipped with a fourth CNC axis for indexing.
Mr Palmer points out that, in this respect, a twin-spindle bar-fed turning centre is the ideal platform for unattended production in one hit of complex components, even prismatic parts requiring all six sides to be accessed. Cycle times tend to be longer on mill-turn centres, which in any case normally require an operator to be present. He does not hesitate to put parts onto his lathes that require no turning operations at all except parting off.
Mr Palmer concluded: “All Citizen lathes are real workhorses. They are robust and compact and some have hand-scraped guideways, which leads to excellent machining quality. The Miyanos are so heavily built, they are almost over-engineered. They just keep going and going, maintaining their accuracy and repeatability for decades. Consequently, for machining parts up to 51mm, they are our preferred lathes. Likewise, for turning and milling in sliding-head mode, we have standardised on Cincom when machining parts from larger diameter bars up to 32mm.”
Founded by Mr Palmer’s father in 1967 and now operating 24/7 from a 12,000sq/ft premises in Waterlooville, Hampshire; Repro Engineering produces batch sizes typically in the range of 1,000 to 50,000, although prototype batches down to 100 are not infrequent. Some parts are machined to very tight tolerances down to 10 microns.
