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Mill Turn Centre Installed at Shepherd Engineering

Mill Turn Centre Installed at Shepherd Engineering

Added to MTDCNC by MTDCNC on 08 March 2013

Such has been the effect of Citizen’s machine tool development programme on Shepherd Engineering that the installation of the latest Citizen A32-VII CNC sliding head turn-mill centre has enabled the high precision subcontract machinist to cut into existing well-proven sliding head cycle times by an average of 20 per cent.

This level of increased productivity is even being achieved against work previously produced on a four year old top-of-the-range Citizen M32.  And, as a result of investing in the A32 in mid-2012, Shepherd Engineering has been able to secure new contracts for year 2013 worth £250,000 from one customer and been able to break into the demanding F1 and aerospace sectors.

According to production director Craig Sargent, the A32 has great rigidity due to its centre-rib bed construction and while it has less versatility and tool carrying capability of the M32, running at the same well-trusted speeds and feeds to preserve tool life and process predictability what makes the difference on certain types of work is the machine’s capability to effectively overlap axis sequences, the use of 45 m/min rapid traverse rates, its drive system acceleration rates and the ability of the control to manipulate data through its higher speed processing.

Based in Great Yarmouth, Shepherd Engineering resides in a 5,000 ft2 machine shop it moved to mid-way through 2012.  The move was forced due to the success of the business following the installation of two Citizen machines, the M32 in 2008 and a K16 in 2010, which totally turned around the firm.  The decision to install the A32 meant the existing 3,000 ft2 facility occupied for 22 years would no longer accommodate the production demands.

The turn-around of the business and recent successes where the three Citizen machines now contribute some 60 per cent to turnover is attributed by director Keith Wood to the combination of productivity, precision, flexibility and versatility of sliding head technology.  He is a firm believer that had the company not made the decision to purchase the M32 during MACH 2008, it would no longer be competitive in today’s market.  

Prior to MACH, having a machine shop based on fixed head lathes and machining centres, second operation work was crippling the business in costs, low-efficiency and in particular extended lead times for the delivery of parts to customers.  Mr Wood said:  “We were rapidly losing out to the single operation competition on turned and milled parts so it was the decision to invest in what was the most flexible small turned part machine at the MACH show that suited our purpose to tackle and expand the opportunities available in high precision work we were producing for the subsea and valve industry.”

Within just one year of the Citizen M32 being installed the effect on the business was significant.   Not only providing a new working capability in being very competitive for instance, being able to combine four previous operations on parts to just one the production potential also opened the order books for new work from existing customers to rapidly fill machining schedules.

Indeed, the instant transition from having an almost hand-to-mouth order book of two weeks to one of a couple of months, including certain call-off contracts that spanned 12 months, breathed a totally new level of confidence into the company.

This was reinforced by the fact that the firm ran out of spindle capacity which led to the installation of the Citizen K16 to accommodate smaller work and free up capacity for higher value, larger components on the M32.  With this 16mm capacity machine, Mr Sargent redesigned a component for a customer to suit the production capability around hole configurations and as a result significantly reduced the price per part.  To his amazement, the customer’s reaction to the cost reduction was to place another contract that worked out to a 28,000 part requirement a year.

Far from standing still, with the two Citizen machines running 12 hour days and through the night on selected parts and being the main source of growth (of over 18 per cent a year) over the last three years, when compared with the output of fixed head lathes and vertical machining centres, the added capability of the A32 has once again enabled the pace of growth to be further increased.  As important is the improvement in margins and profitability that will facilitate future investment.

Shepherd Engineering was set up 30 years ago by Peter Shepherd with Keith Wood working for the business for 23 years and becoming a partner 12 years ago.  At that time conventional machines served the customer base producing the likes of connectors and valves for subsea and the fluid power sector.  Manual machines were progressively replaced with CNC in supplying customers throughout the UK.

Today high precision components are produced mainly involving materials such as difficult to machine alloy steels, a wide variety of stainless and aluminium bronze, PEEK and a certain ultra-exotic free issue US specification MP35N steel – that is even more demanding than inconel.  Batches overall vary between 100 and 5,000 and tolerances are typically down to 0.01 mm which, says Mr Sargent, the Citizen’s maintain with an “almost ease”.  Cycle times vary between short 32 secs bursts to 20 mins – the latter reflecting complexity and material type.

A further benefit to Shepherd’s business is that Citizen’s technology input to its growth over the last three years means that headcount has been maintained at 15 people, four of whom are ex-apprentices and one of these is currently being trained to set the A32.

It was the high rigidity of the 7-axis, 23 tool capacity Citizen A32 that has brought in further work, for the USA, including two deep sea valve parts made from MP35N.  The customer had great difficulty before finding Shepherd Engineering to engage a subcontractor to produce the parts without significant rejection rates.  The turned and grooved high tolerance part is some 10 mm diameter by 10 mm long with a 0.95 mm hole drilled through which is counterbored to 1.2 mm diameter by 0.5 mm deep each end.  Such is the achievement of Shepherd’s setters that the customer acceptance rate has never fallen below 97 per cent.


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