EDM specialist expands milling capacity with Hurco 5-axis machines

EDM (electric discharge machining) subcontractor RST Engineering (www.rsteng.co.uk) decided 20 years ago that a manual-tool-change Hurco Hawk, due to the ease of shop floor programming on its twin-screen control system, was the best CNC milling machine to take over from hand-operated mills for manufacturing copper electrodes, jigs and fixtures. A 10-minute demonstration on the Hurco (www.hurco.co.uk) stand at the MACH 1998 machine tool show was enough to convince RST's management that the power and simplicity of the software made it an obvious choice for this type of work.

The machine proved so fit for purpose that RST had no hesitation in replacing it in 2002 with an automatic-tool-change, 3-axis Hurco VM2 machining centre, which was equipped with a similar proprietary Ultimax twin-screen control as well as a 4th axis Nikken table.

Over the next decade, the subcontractor milled and drilled more and more of its customers' components on the machine, work that it was previously having to put out to another firm, thereby saving money and enjoying more control over production scheduling and delivery lead-times. The VM2 is now dedicated again to machining only electrodes, however, and is sited in the EDM shop alongside four wire erosion machines, the same number of die sinkers and a pair of EDM hole drilling machines.

New milling shop

In an adjacent unit, three additional Hurco machining centres, a larger three-axis machine and two 5-axis models, have taken over production of RST's mainly aluminium, stainless steel and titanium prismatic components. All machines are fitted with Hurco's latest WinMax twin-screen control, which provides much greater functionality for conversational shop floor programming and even generates 3+2-axis cycles. The machines have helped propel the milling side of the subcontractor's business to account for more than one-third of turnover.

RST was established in 1986 by Robert and Maureen Taylor and is now run by their three sons, Sean, Jason and Paul. It produces components for a wide range of industries including communications, aerospace, medical and scientific research as well as for more unusual customers making bespoke clocks and shotguns, for example.

Jason Taylor commented, "Around 40 per cent of our business is in aerospace, involving wiring, sparking and milling satellite communications components like waveguides and diplexers plus some second-tier work producing components such as gimbals and joints for military aircraft.

"Last December (2017) we gained AS9100 aerospace quality management accreditation and are looking to expand in the sector by taking on long-term commercial aircraft contracts, hopefully building them to account for a quarter of our business in a few years' time."

The initiative had been in the company's sights for several years and so also was relocation, which took place in August 2016 to new, 7100 sq ft premises on the Young's Industrial Estate in Leighton Buzzard, two and a half times larger than RST's previous unit.

The move entailed a £300,000 investment that included the purchase of a coordinate measuring machine and a Hurco VMX60SRTi 5-axis machining centre of B-axis spindle design and 1,524 x 660 x 610 mm capacity. It joined a smaller 5-axis Hurco VMX30Ui of swivelling trunnion design purchased two years earlier and a larger 3-axis Hurco VM30i installed the year before to cope with a wider variety of component sizes.

In the previous factory the VMX30Ui worked alongside a similar VMX30U 5-axis machine installed five years previously, in 2009, fitted with older technology drives and control. Mr Taylor was able to benchmark one 5-axis model against the other and was astonished at the improved performance of the more modern machine.

He said, "Cycle times were considerably reduced using the same program, for instance when machining a shotgun trigger guard, and the improvement in surface finish was very apparent, especially when milling surfaces and transitions.

"The gains were so great that it prompted us to part-exchange the older 5-axis trunnion model and buy the bigger B-axis machine, which has similarly improved drives and control system."

Only a small proportion of RST's 5-axis machining is fully interpolative, programming of these parts of cycles being done off-line at a VISI CADCAM station. 3+2-axis programming is shared between VISI and Hurco's WinMax control software on the shop floor using the latter's Transform Plane facility (www.youtube.com/watch?v=EcysJ_plqN0), while 3-axis routines are produced entirely in WinMax.

Another feature of the software that all RST staff appreciates is NC Merge (http://blog.hurco.com/blog/bid/194602/Hurco-s-NC-Merge-the-best-of-both-worlds), which allows 3-axis parts of a cycle to be prepared at the control and merged with 5-axis sections programmed in VISI. The load on the offline CADCAM station is reduced and in any case, 3-axis programming is more efficiently completed conversationally in WinMax, according to Mr Taylor. It is even possible to program on the shop floor and start running 3-axis/2D blocks of code on a machine and tack on 5-axis/3D blocks downloaded from VISI afterwards, saving time when proving out jobs.

Mr Taylor added, "The latest Hurco B-axis machine is very versatile and well suited to subcontracting, as it is able to produce 5-axis parts up to 600 mm diameter on the rotary table and a second, 3- or 4-axis part on the fixed table to the side, giving Op1/Op2 possibilities.

"Alternatively, one large component up to 1.5 metres in X by 660 mm in Y can be 3-axis milled and drilled.

"The machine holds very tight positional and dimensional tolerances down to ±10 microns in 5-axis working and half that when interpolating three axes, with excellent repeatability.

"Together with our trunnion-type 5-axis VMX30Ui and the other 3-axis Hurco, which also have 12,000 rpm spindles, it places us in a good position to enter the civil aerospace supply chain now that we have AS9100."