Turn-mill benefits at Unicut Precision

Twin-spindle twin-turret lathes prove to be the ideal solution for machining hydraulic components

Posted on 04 Nov 2019 and read 1192 times
Turn-mill benefits at Unicut PrecisionTwo more Miyano BNE-51MSY turn-mill centres from Citizen Machinery UK have been installed at the sub-contract machinist Unicut Precision, which is based in 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 are now producing complex components for the hydraulics industry, which accounts for a large proportion of Unicut’s business.

Established in 1990 by Jason Nicholson (then 24 years old) 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 sub-contractor for most of its existence, progressing to CNC turning in 1993.

However, the company diversified into prismatic machining in 2017 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 by the company — 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 2,000psi coolant pressure), as well as eight Miyano machines (deploying up to 72 cutters).

They are usually replaced every five to seven years to take advantage of their high residual value at that age.

While the turning machines have been sourced mainly from Bushey-based Citizen Machinery UK Ltd (www.citizenmachinery.com), each purchase is rigorously analysed by Mr Nicholson with regard to machine cost and achievable cycle times to ensure the lowest cost per part produced and the fastest return on investment.

Ease of machine integration and use is also a paramount consideration, alongside the required component quality.

Additionally, prompt provision of service is an important factor.

Unicut’s first Cincom sliding-head lathe — a 12mm bar auto — was installed in 1999. Within a year, three more had been installed — followed three months later by a 32mm model. The first Miyano was bought 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 components and unattended running — including overnight — leading to much higher profitability.

Business model

To distinguish Unicut from other sub-contractors, Mr Nicholson decided early on to adopt a different business model.

Turn-mill 3This was based on approaching OEMs, analysing their main cost drivers, investigating the possibility of re-engineering components for more-efficient production, establishing desired cycle times, identifying the 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% of the company’s throughput is produced on this basis.

For machining larger-diameter parts, a 51mm-capacity Miyano is used.

This costs about the same as a top-end 32mm Cincom sliding-head machine, but unless a high component length-to-diameter ratio dictates otherwise, Mr Nicholson prefers the fixed-head option for a number of reasons.

These include rigidity, thermal stability, value for money and speed.

Moreover, the bar capacity is greater (offering more flexibility), the 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 (this allows three tools to be in cut at the same time — a facility regularly used by Unicut for optimised levels of productivity).

Mr Nicolson says that once a BNE-51MSY is set, it will produce a run of — say — 1,000 components to very high accuracy without the machine being touched; he includes macros in the program to offset tools automatically after a predetermined number of parts have been produced.

Tolerances down to ± 2µm can be held, and surface finish is described as “impeccable”.

Mr Nicholson highlights the Mitsubishi CNC system fitted to Miyano and Cincom machines, referring to its flexibility and ease of operation (with drop-down menus and comprehensive graphical support).

“Citizen’s off-line Alkart Wizard software helps to ensure jobs that are quickly into production.

“However, for larger production runs, time can generally be cut from a cycle by tweaking the program at the control.”

Swarf control

Citizen’s operating system in the CNC fitted to one of Unicut’s Cincom sliding-head machines features the manufacturer’s patented LFV (low-frequency vibration) software, which operates in two CNC axes simultaneously, allowing stringy swarf to be broken into shorter chips that suit the material being cut and the swarf conveyor.

Turn-mill 2This feature is popular with operators, as it enables uninterrupted production without having to stop the lathe due to ‘bird nests’ clogging the workpiece and tools.

Mr Nicholson highlights the example of a type 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.

He 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 easily adjusted.

“It is especially good for processing plastics unattended, as well as other difficult-to-machine metals such as duplex stainless steel and titanium. It just works.”

Sharing his thoughts on the current buoyancy of the sub-contract machining sector due to the weakness of the pound against overseas currencies, Mr Nicholson says it has cut 20% off the price of components that Unicut exports and has boosted turnover, despite raw material and the equipment on which to machine it costing more to buy.

His company’s first order from China was delivered in August this year, and exports overall currently account for 40% of turnover — up from 10-30% in previous years.

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