Current best practice in press tools, mould tools and stamping dies relies heavily on the choice of machine.
Conventionally described as a ‘black art’, modern toolmaking leans as heavily on the latest machining technologies, such as milling and EDM, as it does on skills and knowledge. The machines used by toolmakers share common attributes; namely precision, rigidity and speed. However, the choice of machine can still play a hugely significant role in achieving competitive gain.
This thought was uppermost in the minds of Mark Wingfield and Arthur Watts, managing partners at Smethwick, UK-based A&M EDM, when the pair wanted a large new machining centre to help produce automotive press tools. The decision: a Hurco twin-column, bridge-type DCX22 with 2,200 x 1,700 x 750mm axis travels.
Tooling manufacture at A&M spans single-stage press tools, progression and extrusion tools. Investing in the Hurco machine allows this type of work to be performed efficiently and often unmanned owing to the long prismatic machining cycles.
A&M also produces parts such as trim dies for Jaguar car body panels. Indeed, buoyancy within the UK automotive industry and a requirement for ever-larger press tooling plates was the driving reason behind the investment in the DCX22, along with a large, fourth axis indexing head.
Less than two miles from the door of A&M can be found Cube Precision, another toolmaker investing in Hurco technology, this time the slightly larger (3,200 x 2,100 x 920mm) DCX32 machining centre. Recent work here involved completing tools for pressing the door outer panels that go into the all-aluminium Range Rover L405. Other press tools machined on the DCX include those for producing wheel arches on the new Jaguar F-Type.
“Despite its size, the machine easily achieves general tolerances of 0.03mm and regularly goes down to 0.02mm, with excellent surface finish,” says Neil Clifton, one of three director-owners of Cube Precision. “We also like that the machine comes with a 40-position magazine and automatic toolchanger for BT50 cutters as standard. Such equipment normally costs extra on a machining centre of this size.”
Moving away from press tools, stamping dies are widely acknowledged to be one of the most time-consuming, hard-to-machine components in the automotive industry. A typical strategy for surface contouring is to use ball-type cutters that can remove material at varying depths of cut. However, long overhangs from the spindle nose often put excessive load on the tool and machine spindle.
With this in mind, the choice of a Mikron HSM800 CNC milling centre with pallet changer from Agie Charmilles at Klaus Baier, proved crucial. The Pfronten, Gemany-based company is a specialist in stamping dies for auto parts such as heat exchanger components, seat holders and levers.
According to Klaus Baier, the Mikron HSM800 demonstrates high spindle speeds (54,000rpm), high feed rates and excellent acceleration, which is especially important when working with small cutter diameters. Furthermore, in comparison with other production techniques, the effort for post-processing is considerably reduced, says the firm.
Of course, the development of new features for machining centres used in toolmaking activities continues unabated as each vendor vies for market share. Haas Automation, for example, has recently redesigned its VM Series of mould machining centres. Haas engineers reviewed all aspects of the VM machines, including motion control, coolant containment, chip evacuation, ergonomics and serviceability, then made improvements and put everything into a new package.
Among other new mould-making machining centres are the Hwacheon Sirius UM, the Hurco VMXHSi and the Hyundai Wia Hi-Mold, to name but a few.
The Hi-Mold from Hyundai Wia is a high-speed machining centre suited to precision machining due to the bridge design’s high rigidity and the generation of low heat. The head of the main axis moves up, down, left and right on the cross beam, while the table moves front to rear. All ballscrews are connected directly to the servo-drive motors without gears or belts, to eliminate backlash. Rapid high-speed axis movement is achieved by the use of linear motion guideways that reduce non-cutting time.
According to Hyundai Wia, more and more toolmakers are investing in equipment engineered specifically for the machining of moulds. So, while in the past a basic vertical machining centre might have been purchased to machine moulds, today that’s simply not practical. To remain competitive in the global marketplace, tool shops must invest in technology better suited for mould making. This includes moving away from typical C-frame vertical machining centres accessorised for making moulds, to bridge-type VMC’s with spindle speeds to 40,000 rpm, through-spindle coolant and simultaneous five-axis capability.
While milling is a core toolmaking competency, no toolroom is complete without EDM technology. Here too, investing in the latest and greatest machines can pay real dividends. Take WH Smith & Sons, for instance, where the first Sodick AG100L CNC die sink EDM in Europe has now been installed at the company’s Sutton Coldfield, UK premises. The company says the machine can spark large tools such as automotive radiator grille cavities in about a week (100- 150 hours), whereas before it could take four weeks using machines of smaller capacity.
“In terms of pure speed I would estimate it’s around 30% faster than our existing machines,” says toolroom manager, Stephen Hunt. “Functionality such as linear drives, which give high-speed movement of the head, along with deep-rib and deep-machining capability, provide genuine marketplace differentiation.”
Working every day since installation, the acquisition has proved extremely successful. Thanks to the machine’s large work tank the company can accommodate workpieces up to two metres in length, weighing up to five tonnes. This has helped the firm meet rising demand for large automotive injection mould tools, such as radiator grilles, bumper support brackets and number plate plinths.
“Increasing numbers of automotive customers are coming to us for several reasons,” says Hunt. “Yes, they prefer a single source for both parts and tooling, but they can also see the tools, something not possible if using a resource in the Far East. Additionally, the ability to offer a quick response to modifications is highly valued by customers.”
Regardless of the issues surrounding offshoring and re-shoring, when it comes to toolmaking, there is only one way to achieve genuine competitive advantage – always invest in the best machine that budget will allow.