Whether it is a difficult-to-machine Hastelloy component for a petrochemical customer, or a heavy cast iron part for a full-size replica of a steam-driven crane engine, subcontractor Richard Scourfield and his wife, Kay, invariably produce them on their Hurco machining centre and lathes. Their company, Bartlett Engineering, is in Tenby on the Pembrokeshire peninsula, half an hour’s drive from one of Europe’s largest oil and gas ports, Milford Haven, where two terminals are currently being built for liquefied natural gas.
Petrochemical work accounts for 75 per cent of Bartlett’s turnover when the industry is prospering, as it is at present. A lot of high-grade stainless steel is machined as well as a mix of other materials including boiler plate. Some of the alloys are difficult to machine, not only the tough, nickel-based materials and stainless steel but also other ferrous alloys such as EN26W steel hardened to 350 BH (Brinell hardness).
A component produced from the latter material in medium size batches on one of two Hurco TM10 lathes is a washer that requires a 30 mm diameter, indexable-insert drill rotating at 800 rpm to be fed at 80 m/min down the centre of the bar. The steel is hardened to 380 BH in the process. A Hurco sales engineer who happened to be present on one occasion when machining started jumped out of his chair when he heard the sound for the first time. Even he had not seen such a rigorous machining operation carried out on one of their lathes.
It was agreed during that visit that Bartlett is probably the heaviest user of Hurco machines in the whole of the UK. The lathes are constantly pulling 80 per cent of available power and 22,000 components have been produced by the two TM10s in the last 12 months.
One is a bar-fed model for producing components up to 75 mm diameter, while the other is used as a chucker for parts up to 254 mm (10 inches) diameter. Installed in June 2007 and January 2008 respectively, they have an 18.7 kW spindle with a maximum torque of 312 Nm and through-coolant.
Mr Scourfield, who served a 5-year apprenticeship at the former Central Electricity Generating Board, has been turning parts since he was 11 years old. He says that Hurco’s CNC lathes are 12 times more productive than the manually operated lathes that Bartlett has used since the company started in 1966. He has one word to describe the TM10s: “excellent”.
The company moved into CNC as recently as 2005 by purchasing entry-level lathes and machining centres from another supplier. It was a good introduction, but Mr Scourfield soon found that he needed higher power for the type of work that Bartlett traditionally receives.
This was true not only of turning but also of prismatic machining, so a Hurco VMX60 vertical machining centre with 1524 x 660 x 610 mm travels and 24-position tool magazine was installed in September 2007.
One of the first components to be machined was larger than the X-axis, so after suitable safety measures had been put in place, the side door was opened to allow the 2.5 metre long part to protrude so that it could be clamped on the table. The job involved milling slots in the steel cross members, which were sawn from a 203 x 133 mm H-beam. They formed part of a 20 metre underframe chassis that Bartlett was fabricating for the Isle of Wight Railway.
Another early component that was longer than the VMX60’s width was a superheater element for a boiler. Made from 220 mm diameter seamless carbon steel pipe, the two metre long element contained rows of holes that had been machined manually at Tenby for some years, production time being around 24 hours. Cycle time on the Hurco is just nine hours.
Half of the contracts received by Bartlett require reverse engineering, such as replacement parts for petrochemical plant that has been manufactured overseas. Measurements taken from component samples are used to create drawings from which the CNC machines are programmed by manual data input on the shop floor.
All of the subcontractor’s programming is done this way, as finding staff in Pembrokeshire with G- and M-code skills is very difficult.
What Mr Scourfield and his operators particularly like about the Hurco machines is the proprietary conversational control system. He says it is easy to produce machining cycles using the Windows interface and touch screen commands, and as programming is so quick, it is ideal for Bartlett’s one-offs and small batch runs. The company has no need at all for off-line programming.
Whereas Windows software was available on Hurco lathes from the time that they were introduced, this was not the case with the machining centres. Following the launch last year of the updated Windows-based software, Winmax, the control on Bartlett’s VMX60 has been upgraded, with significant benefits. According to Mr Scourfield, programming is simplified and 20 per cent quicker using the Windows interface, and 3D colour graphics are improved. Advances in data smoothing have increased contouring speeds and there are many additional features that will be useful for future jobs, such as the ability to select the quality of surface finish.
In June this year, a Hurco H320 – the largest in the company’s range of rotary tables – was added to the VMX60. Conversational 4th-axis programming is standard on all WinMax controls, meaning that Bartlett was able to start programming rotary parts immediately, with only a couple of hours’ additional instruction.
Mr Scourfield concluded, “We pride ourselves on machining parts that no-one else can or wants to produce, but we are only able to do that if our machines are of top quality and back-up is reliable."
“Our location in west Wales is perfect for ports and refineries, but relatively inaccessible for machine tool vendors. When we installed the first Hurco lathe, we were promised prompt service and that is exactly what we have received on the few occasions we have needed to call the supplier out.”