Fast CNC programming small batches economically

When asked about Hurco CNC machine tools, a subcontractor's operators said they like the MAX conversational control system as programming is so quick for one-offs and small batch runs.

When asked about Hurco CNC machine tools, a subcontractor's operators said they like the MAX conversational control system as programming is so quick for one-offs and small batch runs.

Half of the contracts received by UK subcontractor Bartlett Engineering, in Tenby, Pembrokeshire, require reverse engineering.

Examples include replacement parts for petrochemical plant that has been manufactured overseas.

Measurements taken from component samples are used to make 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, said Bartlett.

Bartlett operates Hurco Europe CNC lathes and vertical machining centre (VMC).

Owner Richard Scourfield said that what the machine operators particularly like about the Hurco machines is the proprietary MAX conversational control system.

He said 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 said it had 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 MAX control on Bartlett's VMX60 VMC has been upgraded, with significant benefits.

According to Scourfield, programming is simplified and 20% 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, said Scourfield, such as the ability to select the quality of surface finish.

The work at bartlett can range from a difficult-to-machine Hastelloy component for a petrochemical customer to a heavy cast iron part for a full-size replica of a steam-driven crane engine.

Scourfield, and his wife, Kay, said that they invariably machine them on their Hurco machining centre and lathes.

With petrochemical plants in the vicinity, some 75% of Bartlett's turnover is in components for that industry.

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, such as the tough, nickel-based materials and stainless steel and other ferrous alloys such as EN26W steel hardened to 350 BH (Brinell hardness).

Made from EN26W in medium size batches on one of two Hurco TM10 lathes is a washer that requires a 30mm diameter, indexable-insert drill rotating at 800 rev/min to be fed at 80m/min down the centre of the bar.

The steel is hardened to 380 BH in the process.

Apparently, a Hurco sales engineer was startled when the machining began.

Even he had not seen such a rigorous machining operation carried out on one of their lathes, said Scourfield.

Bartlett is probably the heaviest user of Hurco machines in the whole of the UK.

The lathes are constantly pulling 80% of available power and 22,000 components have been produced by the two TM10s in the last 12 months, said Hurco.

One TM10 is bar-fed for producing components up to 75mm diameter.

The other TM10 is used as a chucker for parts up to 254mm (10in) diameter.

Installed in June 2007 and January 2008 respectively, they have an 18.7kW spindle with a maximum torque of 312Nm and a through-coolant cutting facility.

Scourfield had served a five-year apprenticeship at the UK's former Central Electricity Generating Board and has been turning parts since he was 11 years old.

He said 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 in 2005 by purchasing 'entry-level' lathes and machining centres from another supplier.

It was a good introduction, but Scourfield soon found that he needed higher power for the type of work that Bartlett traditionally received.

This was true not only of turning but also of prismatic machining, so a Hurco VMX60 vertical machining centre with 1524 x 660 x 610mm travels and 24-position tool magazine was installed in September 2007.

* Machining large part on the VMC - one of the first components to be machined was larger than the VMC's X-axis, so after suitable safety measures had been put in place, the VMC's side door was opened to allow the 2.5m long part to protrude so that it could be clamped on the table.

The job involved milling slots in the steel cross members, which had been sawn from a 203 x 133mm H-beam.

They formed part of a 20m long underframe chassis that Bartlett was fabricating for the preserved Isle of Wight Railway.

Another early component that was longer than the VMX60's table was a superheater element for a boiler.

Made from 220mm diameter seamless carbon steel pipe, the 2m long element contained rows of holes that had been machined manually at Tenby for some years andproduction time was around 24h.

Cycle time on the Hurco is just 9h.

* Expanding VMC usefulness - in June, 2008, Bartlett had fitted Hurco's H320 rotary tables to the VMX60.

As conversational 4-axis programming is standard on all WinMax controls, Bartlett was able to start programming rotary parts immediately, with only a couple of hours' additional instruction.

Scourfield said that Bartlett prides itself on machining parts that no-one else can do or wants to produce, but the machines have to be top quality and back-up must be reliable.

He concluded: "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.".

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